Biomedical subjects

Huihui Xu

Publications and source records attributed to Huihui Xu.

6 recordsLinked to original sources

PubMed2026

Potato Black Scurf and Stem Canker: Pathogen Biology, Global Distribution, and Traditional and Modern Diagnostics.

Rhizoctonia solani is a soil- and seed-borne fungal pathogen of potatoes. It is a persistent threat to potato production worldwide. The symptoms appear as black scurf on tubers and stem canker, causing severe yield and quality losses of potatoes. The pathogen reproduces asexually via hyphae and sclerotia. Its genetic diversity is organized into anastomosis groups (AGs), with AG3-PT being the predominant group on potato. The global trade of seed potatoes is very important for agricultural development; however, it has facilitated the dissemination of the pathogen across regions. Moreover, disease development is affected by environmental and agronomic factors, causing variable symptom severity and differential economic impacts. Given the pathogen's genetic complexity, accurate diagnosis is very important, necessitating a transition from traditional culture-based and biochemical methods toward molecular, genomic, and emerging digital technologies. Methods such as PCR, isothermal amplification, sequencing, sensor-based biosensing, and artificial intelligence-driven imaging have improved the detection, quantification, and noninvasive monitoring of the pathogen. Combining these diagnostic methods into a tiered framework will be helpful for precision disease surveillance, informed disease management decision-making, and the development of sustainable potato production systems.

black scurf↗

PubMed2006

Error propagation model for microscopic magnetic resonance elastography shear-wave images.

Microscopic magnetic resonance elastography is a high-resolution method for visualizing shear waves and assessing the biomechanical viscoelastic properties of small biological samples. In this work, we used error propagation to develop a simple analytical model that relates the signal-to-noise ratio of MR magnitude images to the variance in shear-wave maps collected using gradient-echo and spin-echo phase-contrast pulse sequences. Our model predicts results for shear-wave images in phantoms, which match the experimentally observed phase variance within 8%. This model can be used to optimize MR pulse sequences for elastography studies, as well as other phase-difference techniques in MRI.

Biomechanical Phenomena↗

PubMed2006

Magnetic resonance microscopy for monitoring osteogenesis in tissue-engineered construct in vitro.

Magnetic resonance microscopy (MRM) is used to monitor osteogenesis in tissue-engineered constructs. Measurements of the developing tissue's MR relaxation times (T(1) and T(2)), apparent diffusion coefficient (ADC) and elastic shear modulus were conducted over a 4-week growth period using an 11.74 T Bruker spectrometer with an imaging probe adapted for MR elastography (MRE). Both the relaxation times and the ADC show a statistically significant decrease after only one week of tissue development while the tissue stiffness increases progressively during the first two weeks of in vitro growth. The measured MR parameters are correlated with histologically monitored osteogenic tissue development. This study shows that MRM can provide quantitative data with which to characterize the growth and development of tissue-engineered bone.

Alkaline Phosphatase↗

PubMed2006

Nondestructive evaluation of osteogenic differentiation in tissue-engineered constructs.

Conventional measurements of osteogenesis in tissue-engineered constructs are destructive to living cells and incapable to provide three-dimensional information. In the present study, noninvasive magnetic resonance (MR) microscopy was used to evaluate osteogenic differentiation in vitro in human mesenchymal stem cell-based tissue-engineered constructs. The constructs were prepared by seeding the cells (10(6)cells/ml) on 4 x 4 x 4 mm gelatin sponge cubes and subsequently exposing them to osteogenic differentiation or basic medium. During the 4-week experiment, alkaline phosphatase (ALP) activity and calcium content of differentiated constructs were significantly increased compared to the basic medium controls. The T1, T2, and apparent diffusion coefficient (ADC) of differentiated constructs were significantly lower than those of the control group at each time point (p < 0.05). The MR parameters of constructs were significantly correlated to their ALP activities (r to T1, T2, and ADC = -0.57, -0.78, and -0.81, respectively) and calcium content (r to T1, T2, and ADC = 0.48, 0.90, and 0.92, respectively) measured by biochemical techniques. MR microscopy can be a promising tool for noninvasive assessment of osteogenic differentiation and to provide three-dimensional information about tissue-engineered constructs.

Alkaline Phosphatase↗

PubMed2006

MR assessment of osteogenic differentiation in tissue-engineered constructs.

Bone marrow stromal cells (MSC) are a promising source of osteoprogenitor cells for bone tissue engineering. However, the population of the osteoprogenitor cells and their differentiation potentials change with the gender, age, and health of the donor. Development of a noninvasive method to assess osteogenic progression is critical for successful bone tissue regeneration. High-resolution magnetic resonance imaging (MRI) (at 11.7 T, with spatial resolution of 62.5 x 62.5 microm in 500 microm slices) is used in the present study to monitor osteogenic differentiation of tissue-engineered constructs prepared by seeding human bone MSCs on gelatin sponge scaffolds. Quantitative measurements of the MR relaxation times (T1, T2) and the apparent diffusion coefficient (ADC) were performed for four successive weeks on control tissue constructs and constructs exposed to osteogenic differentiation medium. The T1 and T2 relaxation times and ADC were found to decrease as osteogenic progression proceeded in samples exposed to osteogenic differentiation medium. At week 4, the T1, T2, and ADC of TE constructs were 1.81 +/- 0.11 s, 19.5 +/- 11.02 ms, and 1.01 +/- 0.47 x 10(3) mm(2)/s, respectively, for osteogenic differentiated constructs, significantly different from control constructs 2.22 +/- 0.08 s, 50.39 +/- 5.57 ms, and 1.86 +/- 0.18 x 107(3) mm(2)/s (p < 0.05). The MR parameters were also highly correlated with the cell seeding densities and alkaline phosphatase (ALP) activities of the osteogenic constructs. In conclusion, periodic measurements of MR parameters (T1, T2, and ADC) provide a promising method for noninvasive monitoring of the status of tissue-engineered bone growth and differentiation.

Alkaline Phosphatase↗

PubMed2005

Microscopic magnetic resonance elastography (microMRE).

Magnetic resonance elastography (MRE) was extended to the microscopic scale to image low-frequency acoustic shear waves (typically less than 1 kHz) in soft gels and soft biological tissues with high spatial resolution (34 micromx34 micromx500 microm). Microscopic MRE (microMRE) was applied to agarose gel phantoms, frog oocytes, and tissue-engineered adipogenic and osteogenic constructs. Analysis of the low-amplitude shear wave pattern in the samples allowed the material stiffness and viscous loss properties (complex shear stiffness) to be identified with high spatial resolution. microMRE experiments were conducted at 11.74 T in a 56-mm vertical bore magnet with a 10 mm diameterx75 mm length cylindrical space available for the elastography imaging system. The acoustic signals were generated at 550-585 Hz using a piezoelectric transducer and high capacitive loading amplifier. Shear wave motion was applied in synchrony with the MR pulse sequence. The field of view (FOV) ranged from 4 to 14 mm for a typical slice thickness of 0.5 mm. Increasing the agarose gel concentration resulted in an increase in shear elasticity and shear viscosity. Shear wave motion propagated through the frog oocyte nucleus, enabling the measurement of its shear stiffness, and in vitro shear wave images displayed contrast between adipogenic and osteogenic tissue-engineered constructs. Further development of microMRE should enable its use in characterizing stiffer materials (e.g., polymers, composites, articular cartilage) and assessing with high resolution the mechanical properties of developing tissues.

Adipose Tissue↗