Rapid Kinetic Interactions of Sugar and Sugar Alcohol with Sweet Taste Receptors on Live Cells Using Stopped-Flow Spectroscopy.

The subjective measurement of the dynamic perception of sweetness is a problem in food science. Herein, the rapid interactions of sugars and sugar alcohols with sweet taste receptors on living cells on a millisecond timescale were studied via stopped-flow fluorescence spectroscopy. According to the rapid-kinetic parameters, sweeteners were divided into two groups. Sweeteners in group I disrupted the hydrogen bond network structure of water, and the apparent rate constant (kobs) was in the range of 0.45-0.6 s-1. Sweeteners in group II promoted the hydrogen bond formation of water, and the kobs was mostly in the range of 0.6-0.75 s-1. For most sweeteners, the kobs of cell responses was negatively correlated with the apparent specific volume of sweeteners. The differences in the cellular responses may be attributed to the disturbance in the water structure. Experimental results showed that the kinetic parameters of sweet cell responses reflected the dynamic perception of sweetness. Rapid kinetics, solution thermodynamic analysis, and water structure analysis enriched the physicochemical study of the sweetness mechanism and can be used to objectively evaluate the dynamic perception of sweetness.

[Application of digital dynamic smile aesthetic simulation teaching method in orthodontic practicum].

PURPOSE: To integrate digital dynamic smile aesthetic simulation (DSAS) cognitive education in orthodontic practicum and evaluate the teaching effects. METHODS: A total of 32 dental students during orthodontic practicum were randomly divided into two groups. One group received traditional teaching method to draft treatment plan, and another group was implemented with DSAS teaching method. Then two groups exchanged. Students were asked to grade both teaching methods and statistical analysis was performed on the scoring results with SPSS 24.0 software package. RESULTS: The scores of the DSAS teaching method was much higher than traditional method, and the difference was statistically significant(P=0.012). Students considered that DSAS teaching method was more "novel and fascinating", and also "convenient for comprehending of orthodontic treatment". Students hoped to popularize the DSAS teaching method in future orthodontic practicum. CONCLUSIONS: As a novel teaching method, DSAS is more intuitive and vivid to stimulate students' interest in learning, and it is helpful to improve the effect of orthodontic practical teaching.

Activation of the Extracellular Signal-Regulated Kinase Signaling Is Critical for Human Umbilical Cord Mesenchymal Stem Cell Osteogenic Differentiation.

Human umbilical cord mesenchymal stem cells (hUCMSCs) are recognized as candidate progenitor cells for bone regeneration. However, the mechanism of hUCMSC osteogenesis remains unclear. In this study, we revealed that mitogen-activated protein kinases (MAPKs) signaling is involved in hUCMSC osteogenic differentiation in vitro. Particularly, the activation of c-Jun N-terminal kinases (JNK) and p38 signaling pathways maintained a consistent level in hUCMSCs through the entire 21-day osteogenic differentiation period. At the same time, the activation of extracellular signal-regulated kinases (ERK) signaling significantly increased from day 5, peaked at day 9, and declined thereafter. Moreover, gene profiling of osteogenic markers, alkaline phosphatase (ALP) activity measurement, and alizarin red staining demonstrated that the application of U0126, a specific inhibitor for ERK activation, completely prohibited hUCMSC osteogenic differentiation. However, when U0126 was removed from the culture at day 9, ERK activation and osteogenic differentiation of hUCMSCs were partially recovered. Together, these findings demonstrate that the activation of ERK signaling is essential for hUCMSC osteogenic differentiation, which points out the significance of ERK signaling pathway to regulate the osteogenic differentiation of hUCMSCs as an alternative cell source for bone tissue engineering.

Bone regeneration by nanohydroxyapatite/chitosan/poly(lactide-co-glycolide) scaffolds seeded with human umbilical cord mesenchymal stem cells in the calvarial defects of the nude mice.

In the preliminary study, we have found an excellent osteogenic property of nanohydroxyapatite/chitosan/poly(lactide-co-glycolide) (nHA/CS/PLGA) scaffolds seeded with human umbilical cord mesenchymal stem cells (hUCMSCs) in vitro and subcutaneously in the nude mice. The aim of this study was to further evaluate the osteogenic capacity of nHA/CS/PLGA scaffolds seeded with hUCMSCs in the calvarial defects of the nude mice. Totally 108 nude mice were included and divided into 6 groups: PLGA scaffolds + hUCMSCs; nHA/PLGA scaffolds + hUCMSCs; CS/PLGA scaffolds + hUCMSCs; nHA/CS/PLGA scaffolds + hUCMSCs; nHA/CS/PLGA scaffolds without seeding; the control group (no scaffolds) (n = 18). The scaffolds were implanted into the calvarial defects of nude mice. The amount of new bones was evaluated by fluorescence labeling, H&E staining, and Van Gieson staining at 4 and 8 weeks, respectively. The results demonstrated that the amount of new bones was significantly increased in the group of nHA/CS/PLGA scaffolds seeded with hUCMSCs (p < 0.01). On the basis of previous studies in vitro and in subcutaneous implantation of the nude mice, the results revealed that the nHA and CS also enhanced the bone regeneration by nHA/CS/PLGA scaffolds seeded with hUCMSCs in the calvarial defects of the nude mice at early stage.

Evaluation of in vitro and in vivo osteogenic differentiation of nano-hydroxyapatite/chitosan/poly(lactide-co-glycolide) scaffolds with human umbilical cord mesenchymal stem cells.

We aimed to evaluate the feasibility of the application of the nano-hydroxyapatite/chitosan/poly(lactide-co-glycolide) (nHA/CS/PLGA) scaffold seeded with human umbilical cord mesenchymal stem cells (hUCMSCs) in bone tissue engineering. We prepared the nHA/CS/PLGA, nHA/PLGA, CS/PLGA, and PLGA scaffolds, and tested their mechanical strength. We analyzed the surface antigen markers of hUCMSCs to determine their capability to differentiate into osteoblasts, chondrocytes, and adipocytes. The growth of hUCMSCs on the four types of scaffold was assayed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT assay) and observed using scanning electron microscopy (SEM). Quantitative analysis of alkaline phosphatase (ALP) activity and osteocalcin (OCN) content, as well as the semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was performed. After 21 days, the subcutaneous implantations of the scaffolds samples seeded with hUCMSCs into nude mice were analyzed using immunohistochemical staining. The results showed that the mechanical strength of the nHA/CS/PLGA scaffold was enhanced. Furthermore, the nHA/CS/PLGA scaffolds were the most suitable for the adhesion, proliferation, and osteogenic differentiation of hUCMSCs in vitro and nude mouse subcutaneous implantation. The enhanced osteogenic inductivity of the nHA/CS/PLGA scaffolds for hUCMSCs might result from the addition of nHA and CS.

Molecular recognition of melamine by vesicles spontaneously formed from orotic acid derived bolaamphiphiles.

Molecular recognition by means of multiple hydrogen bonds is of great importance in biological functions. In this paper, an orotic acid derived bolaamphiphile 1,12-diaminododecane diorotate (DDO) with molecular recognition function moieties was designed. Both self-aggregation behavior and molecular recognition with melamine were extensively examined. This bolaamphiphile itself can form vesicles easily in aqueous solutions at 25 °C. Steady-state fluorescence was used to characterize the detailed molecular recognition process. The fluorescence of melamine was quenched more effectively by the spontaneously formed vesicles than by the monomers of the surfactant. Two mechanisms were involved in the fluorescence quench process. At lower concentration, the fluorescence of melamine was found to be quenched by static complex formation. While at higher concentration, both static and dynamic quenching mechanisms coexisted in interaction process. Thermodynamic parameters measured by isothermal titration calorimetry showed that the free energy (ΔG) is negative, indicating that binding of DDO molecules with melamine is favorable energetically. Hydrogen-bonded interactions contribute comparatively a lot for the DDO monomer binding with melamine; at the higher concentration above its critical aggregation concentration, the dissociation of the aggregates take place and lead to an entropically driven molecular recognition process. As complicated binding sites can be constructed through self-assembly at the vesicle interface rather than simple molecular modules, this bolaamphiphile with the molecular recognition functional group may make it possible to generate well-defined recognition sites to mimic biomolecular receptors. Moreover, the present research will give a guide to design chemosensors for melamine detection based on molecular recognition.

Characterization of tomato zonate spot virus, a new tospovirus in China.

An isolate of a new tospovirus species, causing concentric zoned ringspots on fruits and necrotic lesions on leaves of infected plants, was characterised based on particle morphology, host range and serological properties. The complete nucleotide sequences of large (L), medium (M), and small (S) RNAs of this virus were found to contain 8919, 4945, and 3279 nts respectively. The L RNA encoded the RNA-dependent RNA polymerase (RdRp) (2885 aa, 332.7 kDa). The M RNA encoded a non-structural (NSm) protein (309 aa, 34.4 kDa) and a viral glycoprotein precursor (Gn/Gc) (1122 aa, 127.4 kDa). The S RNA encoded a non-structural protein (NSs) (459 aa, 51.9 kDa) and the nucleocapsid (N) protein (278 aa, 30.6 kDa). This N protein shared amino acid identities of 80.9% with those of calla lily chlorotic spot virus. Our results suggest that the virus studied here belongs to a new tospovirus species, for which the name tomato zonate spot virus is proposed.