Hasil untuk "physics.plasm-ph"

J. Rousk, J. Rousk, E. Bååth et al.

K. Caldeira, M. Wickett

E. O. Mclean

Gero Miesenböck, D. A. D. Angelis, J. Rothman

Boeun Lee, Hyoree Seo, Hae Ri Lee et al.

L. Giordano, B. Han, M. Risch et al.

E. A. Miller, D. Beasley, R. Dunn et al.

The human vaginal microbiome is dominated by bacteria from the genus Lactobacillus, which create an acidic environment thought to protect women against sexually transmitted pathogens and opportunistic infections. Strikingly, lactobacilli dominance appears to be unique to humans; while the relative abundance of lactobacilli in the human vagina is typically >70%, in other mammals lactobacilli rarely comprise more than 1% of vaginal microbiota. Several hypotheses have been proposed to explain humans' unique vaginal microbiota, including humans' distinct reproductive physiology, high risk of STDs, and high risk of microbial complications linked to pregnancy and birth. Here, we test these hypotheses using comparative data on vaginal pH and the relative abundance of lactobacilli in 26 mammalian species and 50 studies (N = 21 mammals for pH and 14 mammals for lactobacilli relative abundance). We found that non-human mammals, like humans, exhibit the lowest vaginal pH during the period of highest estrogen. However, the vaginal pH of non-human mammals is never as low as is typical for humans (median vaginal pH in humans = 4.5; range of pH across all 21 non-human mammals = 5.4–7.8). Contrary to disease and obstetric risk hypotheses, we found no significant relationship between vaginal pH or lactobacilli relative abundance and multiple metrics of STD or birth injury risk (P-values ranged from 0.13 to 0.99). Given the lack of evidence for these hypotheses, we discuss two alternative explanations: the common function hypothesis and a novel hypothesis related to the diet of agricultural humans. Specifically, with regard to diet we propose that high levels of starch in human diets have led to increased levels of glycogen in the vaginal tract, which, in turn, promotes the proliferation of lactobacilli. If true, human diet may have paved the way for a novel, protective microbiome in human vaginal tracts. Overall, our results highlight the need for continuing research on non-human vaginal microbial communities and the importance of investigating both the physiological mechanisms and the broad evolutionary processes underlying human lactobacilli dominance.

Yirui Cheng, Qingyu Zeng, Qing Han et al.

Exosomes are cup-shaped small (30–150 nm) extracellular vesicles with the structure of lipid bilayer membrane (Tkach and Thery, 2016) containing proteins, mRNAs and microRNAs that mediate intercellular communication (Valadi et al., 2007). Unlike other extracellular vesicles, exosomes are released into the extracellular space when the multivesicular bodies (MVBs) fuse with the plasma membrane (Colombo et al., 2014). Almost all cell types can secret exosomes and exosomes exist in diverse biological fluids, such as blood, urine, saliva, hydrothorax and breast milk (Thery et al., 2006). Up to now, a number of studies have demonstrated the functions of exosomes in disease development and the potential clinical applications in diagnosis and therapy (Shao et al., 2016). To conduct reproducible studies on exosomal content and function, storage conditions need to have minimal impact on exosomes. There have been a few studies providing partial confirmation of the effect of different storage conditions on exosomes currently. Using exosomes from urine (Zhou et al., 2006) and conditioned medium (Lee et al., 2016) respectively to investigate the influence of storage temperature on exosomes as measured by Western blot, both groups have concluded that storage below −70 °C for a long time is the best temperature for the recovery of exosomes. On the other hand, Sokolova et al. (2011) applied nanoparticle tracking analysis (NTA) to measure the size changes of exosomes at different temperatures, revealing that storage at 37 °C led to more reduction in exosome sizes than that at 4 °C. However, in this study no information about changes in the particle concentration was reported. Some other studies revealed the effect of pH, storage temperature and cycles of freezing and thawing only on the yield of exosome isolation, but not on quantity changes during storage (Akers et al., 2016; Ban et al., 2015; Zhao et al., 2017). Therefore, the standard criterion of exosomal preservation condition is still undefined. Herein, we used HEK 293T cells and ExtraPEG method (Rider et al., 2016) to investigate the influence of multiple storage conditions (temperature, cycles of freezing and thawing, pH) on the quantity changes and cellular uptake of exosomes. ExtraPEG is a new polyethylene glycol (PEG) precipitation method for the purification exosomes without affecting their biological activity. Generally, ultracentrifugation (UC) (Mincheva-Nilsson et al., 2016) is most reliable but time-consuming; and precipitation methods such as ExoQuick (patent number: US20130337440 A1) and ExtraPEG can obtain higher yields of exosomes but with impurity of coprecipitated proteins. First, exosomes from the conditioned medium were extracted by ExtraPEG or UC method. After isolation, transmission electron microscope (TEM), NTA and Western blot were performed to analyze exosomes. Exosomes extracted by UC or ExtraPEG were similar in cupshaped structure (Fig. S1A and S1B), size distribution (Fig. S1C and S1D). And as representative exosome biomarkers, ALG-2-interacting protein X (ALIX), heat shock protein 70 (HSP70) and tumor susceptibility gene 101 (TSG101) were detected in exosomal protein while β-tubulin, widely used as an internal reference to analyze intracellular protein levels, was not detected in exosome samples (Fig. S1E and S1F). These data indicated exosomes were successfully isolated by ExtraPEG method and suitable for the following experiments. After isolation, the exosome pellets were divided equally into several portions and each portion was stored at different temperatures (−80 °C, −20 °C, 4 °C, 37 °C and 60 °C), or through 1–5 cycles of freezing to −80 °C and thawing, or at different pH levels (pH 4, pH 7 and pH 10). After 24 h, NTA and Western blot were performed to measure the remaining quantity of exosomes. Regarding temperatures, the exosomes stored at 4 °C had the highest concentration (Fig. 1A). Consistent with the NTA results, the exosomes stored at 4 °C showed higher levels of representative exosome markers ALIX, HSP70 and TSG101 (Fig. 1B). With the increasing cycles of freezing and thawing, the exosomal concentration and protein levels of ALIX, HSP70 and TSG101 all decreased (Fig. 1D and 1E). For different pH levels, the loss of exosomal concentration and three exosome markers ALIX, HSP70 and TSG101 at pH 4 and pH 10 was more than that at pH 7 (Fig. 1E and 1F). Interestingly, exosomes stored at pH 4 decreased more sharply than that at pH 10 (Fig. 1F and 1G), suggesting that acidic

Xiaorong Fan, Zhong Tang, Yawen Tan et al.

Sandeep J. Sonawane, Rahul S. Kalhapure, T. Govender

M. Karimi, M. Eslami, Parham Sahandi-Zangabad et al.

N. Barrow

Jingfang Shangguan, Dinggeng He, Xiaoxiao He et al.

Measuring pH in living cells is of great importance for better understanding cellular functions as well as providing pivotal assistance for early diagnosis of diseases. In this work, we report the first use of a novel kind of label-free carbon dots for intracellular ratiometric fluorescence pH sensing. By simple one-pot hydrothermal treatment of citric acid and basic fuchsin, the carbon dots showing dual emission bands at 475 and 545 nm under single-wavelength excitation were synthesized. It is demonstrated that the fluorescence intensities of the as-synthesized carbon dots at the two emissions are pH-sensitive simultaneously. The intensity ratio (I475 nm/I545 nm) is linear against pH values from 5.2 to 8.8 in buffer solution, affording the capability as ratiometric probes for intracellular pH sensing. It also displays that the carbon dots show excellent reversibility and photostability in pH measurements. With this nanoprobe, quantitative fluorescence imaging using the ratio of two emissions (I475 nm/I545 nm) for the detection of intracellular pH were successfully applied in HeLa cells. In contrast to most of the reported nanomaterials-based ratiometric pH sensors which rely on the attachment of additional dyes, these carbon-dots-based ratiometric probes are low in toxicity, easy to synthesize, and free from labels.

Xin Pang, Yue Jiang, Qicai Xiao et al.

Haoran Wei, Eric P. Vejerano, Weinan Leng et al.

Significance Aerosols with high water content (aerosol droplets) are ubiquitous and play a significant role in atmospheric chemistry and meteorology. However, directly measuring the pH of an individual aerosol droplet remains challenging due to its inaccessibility to pH electrodes. In this study, nanometer-sized pH probes were dispersed in droplets to report pH via surface-enhanced Raman spectroscopy. The droplet core exhibits higher pH than the bulk solution, suggesting the presence of a stable pH gradient. This in situ technique extends pH characterization to confined water environments and deepens our understanding of aerosol chemistry and the air/water interface. Suspended aqueous aerosol droplets (<50 µm) are microreactors for many important atmospheric reactions. In droplets and other aquatic environments, pH is arguably the key parameter dictating chemical and biological processes. The nature of the droplet air/water interface has the potential to significantly alter droplet pH relative to bulk water. Historically, it has been challenging to measure the pH of individual droplets because of their inaccessibility to conventional pH probes. In this study, we scanned droplets containing 4-mercaptobenzoic acid–functionalized gold nanoparticle pH nanoprobes by 2D and 3D laser confocal Raman microscopy. Using surface-enhanced Raman scattering, we acquired the pH distribution inside approximately 20-µm-diameter phosphate-buffered aerosol droplets and found that the pH in the core of a droplet is higher than that of bulk solution by up to 3.6 pH units. This finding suggests the accumulation of protons at the air/water interface and is consistent with recent thermodynamic model results. The existence of this pH shift was corroborated by the observation that a catalytic reaction that occurs only under basic conditions (i.e., dimerization of 4-aminothiophenol to produce dimercaptoazobenzene) occurs within the high pH core of a droplet, but not in bulk solution. Our nanoparticle probe enables pH quantification through the cross-section of an aerosol droplet, revealing a spatial gradient that has implications for acid-base–catalyzed atmospheric chemistry.

A. Reddy, Don F. Norris, S. Momeni et al.

M. Kosmulski

B. Cerozi, K. Fitzsimmons

Y. Zou, Zhen Hu, Jian Zhang et al.

P. Salvo, B. Melai, N. Calisi et al.