Estimation of complete mutual information exploiting nonlinear magnitude-phase dependence: Application to spatial FNC for complex-valued fMRI data.

BACKGROUND: Real-valued mutual information (MI) has been used in spatial functional network connectivity (FNC) to measure high-order and nonlinear dependence between spatial maps extracted from magnitude-only functional magnetic resonance imaging (fMRI). However, real-valued MI cannot fully capture the group differences in spatial FNC from complex-valued fMRI data with magnitude and phase dependence. METHODS: We propose a complete complex-valued MI method according to the chain rule of MI. We fully exploit the dependence among magnitudes and phases of two complex-valued signals using second and fourth-order joint entropies, and propose to use a Gaussian copula transformation with a lower bound property to avoid inaccurate estimation of joint probability density function when computing the joint entropies. RESULTS: The proposed method achieves more accurate MI estimates than the two histogram-based (normal and symbolic approaches) and kernel density estimation methods for simulated signals, and enhances group differences in spatial functional network connectivity for experimental complex-valued fMRI data. COMPARISON WITH EXISTING METHODS: Compared with the simplified complex-valued MI and real-valued MI, the proposed method yields higher MI estimation accuracy, leading to 17.4 % and 145.5 % wider MI ranges, and more significant connectivity differences between healthy controls and schizophrenia patients. A unique connection between executive control network (EC) and right frontal parietal areas, and three additional connections mainly related to EC are detected than the simplified complex-valued MI. CONCLUSIONS: With capability in quantifying MI fully and accurately, the proposed complex-valued MI is promising in providing qualified FNC biomarkers for identifying mental disorders such as schizophrenia.

Dynamic functional network connectivity based on spatial source phase maps of complex-valued fMRI data: Application to schizophrenia.

BACKGROUND: Dynamic spatial functional network connectivity (dsFNC) has shown advantages in detecting functional alterations impacted by mental disorders using magnitude-only fMRI data. However, complete fMRI data are complex-valued with unique and useful phase information. METHODS: We propose dsFNC of spatial source phase (SSP) maps, derived from complex-valued fMRI data (named SSP-dsFNC), to capture the dynamics elicited by the phase. We compute mutual information for connectivity quantification, employ statistical analysis and Markov chains to assess dynamics, ultimately classifying schizophrenia patients (SZs) and healthy controls (HCs) based on connectivity variance and Markov chain state transitions across windows. RESULTS: SSP-dsFNC yielded greater dynamics and more significant HC-SZ differences, due to the use of complete brain information from complex-valued fMRI data. COMPARISON WITH EXISTING METHODS: Compared with magnitude-dsFNC, SSP-dsFNC detected additional and meaningful connections across windows (e.g., for right frontal parietal) and achieved 14.6% higher accuracy for classifying HCs and SZs. CONCLUSIONS: This work provides new evidence about how SSP-dsFNC could be impacted by schizophrenia, and this information could be used to identify potential imaging biomarkers for psychotic diagnosis.

Denoising brain networks using a fixed mathematical phase change in independent component analysis of magnitude-only fMRI data.

Brain networks extracted by independent component analysis (ICA) from magnitude-only fMRI data are usually denoised using various amplitude-based thresholds. By contrast, spatial source phase (SSP) or the phase information of ICA brain networks extracted from complex-valued fMRI data, has provided a simple yet effective way to perform the denoising using a fixed phase change. In this work, we extend the approach to magnitude-only fMRI data to avoid testing various amplitude thresholds for denoising magnitude maps extracted by ICA, as most studies do not save the complex-valued data. The main idea is to generate a mathematical SSP map for a magnitude map using a mapping framework, and the mapping framework is built using complex-valued fMRI data with a known SSP map. Here we leverage the fact that the phase map derived from phase fMRI data has similar phase information to the SSP map. After verifying the use of the magnitude data of complex-valued fMRI, this framework is generalized to work with magnitude-only data, allowing use of our approach even without the availability of the corresponding phase fMRI datasets. We test the proposed method using both simulated and experimental fMRI data including complex-valued data from University of New Mexico and magnitude-only data from Human Connectome Project. The results provide evidence that the mathematical SSP denoising with a fixed phase change is effective for denoising spatial maps from magnitude-only fMRI data in terms of retaining more BOLD-related activity and fewer unwanted voxels, compared with amplitude-based thresholding. The proposed method provides a unified and efficient SSP approach to denoise ICA brain networks in fMRI data.

Influence of coal gangue mulching with various thicknesses and particle sizes on soil water characteristics.

Water availability seriously affects vegetation restoration in arid mining areas, and mulching is an effective way to improve soil water conditions. Coal gangue occupies large swathes of land resources, resulting in ecological fragility and various environmental problems. Despite coal gangue having mineral elements similar to those in soil, its potential function as a mulch for soil water conservation has been unclear. Herein, mulching on the surfaces of soil columns with 30 cm height and 15 cm inner diameter was conducted using coal gangue with four particle size ranges (0-0.5, 0.5-1, 1-2, and 2-4 cm) and four thicknesses (4, 8, 12, and 16 cm) under laboratory conditions to investigate water infiltration and evaporation under different conditions. The cumulative infiltration of the treatments with mulching thicknesses of 4 cm (T1), 8 cm (T2), 12 cm (T3), and 16 cm (T4) was 16.1%, 22.9%, 28.6%, and 41.6% greater than that of the control, respectively. The cumulative evaporation of the treatments with particle size ranges of 0-0.5 cm (P1), 0.5-1 cm (P2), 1-2 cm (P3), and 2-4 cm (P4) was 6.5%, 28.6%, 22.9%, and 18.6% lower than the control, respectively. Overall, to enhance the soil water storage capacity in mining areas, the results suggest that coal gangue mulching with a thickness of 8-16 cm and particle size range of 0.5-2 cm is suitable.

Sparse representation of complex-valued fMRI data based on spatiotemporal concatenation of real and imaginary parts.

BACKGROUND: Spatial sparsity has been found to be in line with the intrinsic characteristic of brain activation. However, identifying a sparse representation of complex-valued fMRI data is challenging due to high noise within the phase data. NEW METHODS: We propose to reduce the noise by combining real and imaginary parts of complex-valued fMRI data along spatial and temporal dimensions to form a real-valued spatiotemporal concatenation model. This model not only enables flexible usage of existing real-valued sparse representation algorithms but also allows for the reconstruction of complex-valued spatial and temporal components from their real and imaginary estimates. We propose to select components from both real and imaginary estimates to reconstruct the complex-valued component, using phase denoising to recover weak brain activity from high-amplitude noise. RESULTS: The K-SVD algorithm was used to obtain a sparse representation within the spatiotemporal concatenation model. The results from simulated and experimental complex-valued fMRI datasets validated the efficacy of our method. COMPARISON WITH EXISTING METHODS: Compared to a magnitude-only approach, the proposed method detected additional voxels manifest within several specific regions expected to be involved but likely missing from the magnitude-only data, e.g., in the anterior cingulate cortex region. Simulation results showed that the additional voxels were accurate and unique information from the phase data. Compared to a complex-valued dictionary learning algorithm, our method exhibited lower noise for both magnitude and phase maps. CONCLUSIONS: The proposed method is robust to noise and effective for identifying a sparse representation of the natively complex-valued fMRI data.

An Elevated Platelet-to-Lymphocyte Ratio Predicts Poor Prognosis and Clinicopathological Characteristics in Patients with Colorectal Cancer: A Meta-Analysis.

Background. The aims of this study were to evaluate the clinicopathological and prognostic values of platelet-to-lymphocyte ratio (PLR) in colorectal cancer (CRC). Methods. The PubMed and Embase databases and the references of relevant studies were systematically searched. This study was performed with hazard ratios (HRs) and odd ratios (ORs) with corresponding 95% confidence intervals (CIs) as effect measures. Results. Our results indicated that elevated PLR was associated with poor overall survival (HR = 1.46, 95% CI = 1.23-1.73), disease-free survival (HR = 1.64, 95% CI = 1.17-2.30), cancer-specific survival (HR = 1.30, 95% CI = 1.12-1.51), and recurrence-free survival (HR = 1.38, 95% CI = 1.09-1.74) in CRC. For the clinicopathological characteristics, our results indicated that there were differences in the rate of elevated PLR between stages III/IV and I/II groups (OR = 1.38, 95% CI = 1.01-1.88), pT3/T4 and pT1/T2 groups (OR = 1.82, 95% CI = 1.03-3.20), and poor differentiation and moderate/well differentiation (OR = 2.59, 95% CI = 1.38-4.84). Conclusions. Our results indicated that elevated PLR predicted poor prognosis and clinicopathological characteristics in CRC and PLR is a convenient and low-cost blood-derived prognostic marker for CRC.

Effect of radiotherapy after breast-conserving surgery in older patients with early breast cancer and breast ductal carcinoma in situ: a meta-analysis.

BACKGROUND: There are no consistent agreements on whether radiotherapy after breast-conserving surgery (BCS) could provide local control and survival benefit for older patients with early breast cancer or breast ductal carcinoma in situ (DCIS). The present study aimed to evaluate the efficacy of radiotherapy after BCS in older patients with early breast cancer or DCIS. RESULTS: Radiotherapy could reduce the risk of local relapse in older patients with early breast cancer. The 5-year AR of local relapse was 2.2% and 6.2% for radiotherapy and non-radiotherapy group, respectively, with low 5-year ARD of 4.0% and high NNT of 25. The 10-year AR of local relapse was 5.3% and 10.5% for radiotherapy and non-radiotherapy group, respectively, with the 10-year ARD of 5.2% and NNT of 20. However, radiotherapy could not improve survival benefits, including overall survival, cancer-specific survival, breast-cancer-specific survival, and distant relapse. Moreover, radiotherapy could reduce the risk of ipsilateral breast events in older patients with DCIS. MATERIALS AND METHODS: PubMed and Embase database were searched for relevant studies. Hazard ratios (HRs), risk ratios (RRs), absolute risk (AR), absolute risk difference (ARD), and number needed to treat (NNT) were used as effect measures to evaluate the efficacy of radiotherapy in older patients. CONCLUSIONS: Our study indicates that radiotherapy could slightly reduce the risk of local relapse in older patients with favorable early breast cancer. However, radiotherapy cannot translate into significant survival benefits.

Aspirin and non-steroidal anti-inflammatory drugs use reduce gastric cancer risk: A dose-response meta-analysis.

BACKGROUND: The association between non-steroidal anti-inflammatory drugs (NSAIDs) and gastric cancer (GC) risk is controversial. The aim of this study is to evaluate the chemopreventive effect of NSAIDs for GC. METHODS: A literature search was performed for relevant studies using the PubMed and Embase database (up to March 2016). Risk ratios (RRs) and 95% confidence intervals (CIs) were used as the effect measures. The dose-response analysis and subgroup analysis were also performed. RESULTS: Twenty-four studies were included. Our results indicated that NSAIDs could reduce GC risk (any NSAIDs: RR=0.78, 96%CI=0.72-0.85; aspirin: RR=0.70, 95%CI=0.62-0.80; non-aspirin NSAIDs: RR=0.86, 95%CI=0.80-0.94), especially for non-cardia GC risk. Moreover, the dose-response analysis indicated the risk of GC decreased by 11% and 5% for 2 years increment of any NSAIDs and aspirin use, respectively. There were nonlinear relationships between the frequency of any NSAIDs use and aspirin use and GC risk (P for non-linearity<0.01), with a threshold effect of 5 times/week. A monotonically decreasing trend was observed only for the frequency of less than 5 times/week. CONCLUSIONS: Our results indicate that NSAIDs is inversely associated with GC risk, especially for non-cardia GC risk. NSAIDs use may become a feasible approach to prevent GC.

Phenolic alkaloids from Menispermum dauricum inhibits BxPC-3 pancreatic cancer cells by blocking of Hedgehog signaling pathway.

BACKGROUND: The Hedgehog (Hh) signaling pathway plays an important role in pancreatic cancer (PC) cells. Phenolic alkaloids from Menispermum dauricum (PAMD), a traditional Chinese medicine used for the treatment of immune disorders, have been reported to have antitumor activity recently. OBJECTIVE: To investigate the efficacy and mechanism of PAMD against PC cell BxPC-3. MATERIALS AND METHODS: F assay was used to assess cell proliferation inhibition of PAMD; the apoptotic induction and cell cycle arrest was detected by flow cytometry; the BxPC-3 xenograft was established to evaluate the tumor growth inhibition of PAMD; hematoxylin-eosin staining was applied to analyze the pathological morphology of tumor tissues; immunohistochemistry (IHC) and Western blot was adopted to detect the protein levels; quantitative real-time polymerase chain reaction was used to determine the mRNA expressions. RESULTS: PAMD shows time-and dose-dependent proliferation inhibition on the BxPC-3 cell, induced G0/G1 phase arrest and cell apoptosis in vitro. PAMD also showed better inhibition of tumor growth and a preferable safety profile compared with chemotherapeutic regimen 5-fluoro-2, 4 (1 H, 3 H) pyrimidinedione in BxPC-3 xenograft in vivo. Furthermore, PAMD directly decreases the protein and mRNA levels of Sonic Hedgehog (Shh) and its downstream transcription factor Gli-1 in the BxPC-3 tumor tissues. CONCLUSION: The treatment of PAMD displayed Hh signaling pathway blockade through decreasing the protein and mRNA levels of Shh and its downstream transcription factor Gli-1, suggesting a promising strategy in treating human PC.

Hydrogen sulfide suppresses the expression of MMP-8, MMP-13, and TIMP-1 in left ventricles of rats with cardiac volume overload.

AIM: To study the effects of hydrogen sulfide (H2S) on the left ventricular expression of MMP-8, MMP-13, and TIMP-1 in a rat model of congenital heart disease. METHODS: Male SD rats underwent abdominal aorta-inferior vena cava shunt operation. H2S donor NaHS (56 µmol·kg(-1)·d(-1), ip) was injected from the next day for 8 weeks. At 8 weeks, the hemodynamic parameters, including the left ventricular systolic pressure (LVSP), the left ventricular peak rate of contraction and relaxation (LV ± dp/dtmax) and the left ventricular end diastolic pressure (LVEDP) were measured. The left ventricular tissues were dissected out, and hydroxyproline and collagen I contents were detected with ELISA. The expression of MMP-8, MMP-13, and a tissue inhibitor of metalloproteinase-1 (TIMP-1) in the tissues was measured using real-time PCR, Western blotting, and immunohistochemistry, respectively. RESULTS: The shunt operation markedly reduced LVSP and LV ± dp/dtmax, increased LVEDP, hydroxyproline and collagen I contents, as well as the mRNA and protein levels of MMP-8, MMP-13, and TIMP-1 in the left ventricles. Chronic treatment of the shunt operation rats with NaHS effectively prevented the abnormalities in the hemodynamic parameters, hydroxyproline and collagen I contents, and the mRNA and protein levels of MMP-13 and TIMP-1 in the left ventricles. NaHS also prevented the increase of MMP-8 protein expression, but did not affect the increase of mRNA level of MMP-8 in the shunt operation rats. CONCLUSION: H2S suppresses protein and mRNA expression of MMP-8, MMP-13, and TIMP-1 in rats with cardiac volume overload, which may be contributed to the amelioration of ventricular structural remodeling and cardiac function.

Hydrogen sulfide upregulates heme oxygenase-1 expression in rats with volume overload-induced heart failure.

The present study investigated the role of hydrogen sulfide (H2S), a novel gaseous transmitter, in chronic heart failure (CHF) induced by left-to-right shunt, leading to volume overload. Thirty male Sprague-Dawley rats were randomly divided into four groups: the shunt group, the sham group, the shunt + sodium hydrosulfide (NaHS) group and the sham + NaHS group. CHF was induced in the rats by abdominal aorta-inferior vena cava shunt operation. Rats in the shunt + NaHS and sham + NaHS groups were injected intraperitoneally with NaHS (H2S donor). Haemodynamic parameters were measured 8 weeks after surgery. In addition, left ventricular heme oxygenase (HO)-1 mRNA expression was measured by real-time PCR. Protein expression of HO-1 was evaluated by western blot analysis. Eight weeks after surgery, compared to the sham group, the left ventricular systolic pressure (LVSP) and left ventricular peak rate of contraction and relaxation (LV±dp/dtmax) were significantly reduced; the left ventricular end-diastolic pressure (LVEDP) was significantly increased in the shunt group (all P<0.05). However, NaHS increased LVSP and LV±dp/dtmax (all P<0.05) and decreased LVEDP (P<0.05). Protein expression of HO-1 was significantly decreased in the shunt group compared to that in the sham group (P<0.05). NaHS increased protein expression of HO-1 compared to that in the shunt group (P<0.05). HO-1 mRNA expression was significantly increased in the shunt + NaHS group compared to that in the shunt group (P<0.01). The present study demonstrated that H2S may play a protective role in volume overload-induced CHF by upregulating protein and mRNA expression of HO-1.

Cytocompatibility of electrospun nanofiber tubular scaffolds for small diameter tissue engineering blood vessels.

A tubular scaffold was fabricated by using electrospun polymer solution blends of pNSR32 (recombinant spider silk protein), PCL (polycaprolactone) and Gt (gelatin). The physicochemical properties and cytocompatibility of these scaffolds were investigated. Afterwards, the pNSR32/PCL/Gt tubular scaffold (inner diameter=3mm) showed high porosity of 86.2 ± 2.9%, pore size of 2423 ± 979nm and average fibre diameter of 166 ± 85nm. Water uptake and contact angle of the scaffolds reached 112.0 ± 4.4% and 45.7 ± 13.7°, respectively. SDRAECs (Sprague Dawley Rat Aortic Endothelial Cells) grew and proliferated well and phenotype could be maintained on the composite scaffolds after they had been cultured on the composite scaffolds for 7 days. Compared with pure PCL scaffolds a greater density of viable cells was seen on the composites, especially the pNSR32/PCL/Gt scaffolds.

Changes in plasma hydrogen sulfide and nitric oxide levels and their clinical significance in children with Kawasaki disease.

BACKGROUND: Cardiac involvement is the most common complication of Kawasaki disease (KD); however, the underlying mechanisms are not understood. The present study was designed to investigate changes in plasma hydrogen sulfide (H(2)S) and nitric oxide (NO) levels in the acute and recovery stages of KD children and to examine their clinical significance. METHODS: Thirty-five KD patients and 32 healthy children were enrolled in the study. KD patients were divided into two subgroups: a non-cardiac involvement group and a cardiac involvement group. Plasma H(2)S levels were measured using the sulfur-sensitive electrode method and plasma NO levels and NO synthase activity were determined using the nitrate reductase method both before and after intravenous immune globulin (IVIG) therapy. RESULTS: Plasma H(2)S levels significantly decreased in KD patients during the acute phase of the disease and NO levels were significantly increased, compared with the control group (P < 0.01). After treatment with IVIG, both plasma H(2)S and NO levels significantly increased (P < 0.01). The plasma levels of H(2)S were significantly lower in the cardiac involvement group compared with the non-cardiac involvement group (P < 0.05). CONCLUSION: H(2)S and NO may play a role in the pathophysiological process of inflammation during the acute phase of KD. Endogenous H(2)S may exert protective effects with respect to cardiac complications in KD.

[Sodium hydrosulfide improves cardiac functions and structures in rats with chronic heart failure].

OBJECTIVE: To explore the effects of sodium hydrosulfide (NaHS), a hydrogen sulphide (H(2)S) donor, on cardiac functions and structures in rats with chronic heart failure induced by volume overload and examine its influence on cardiac remodelling. METHODS: A total of 47 SD rats (120 - 140 g) were randomly divided into 5 groups:shunt group (n = 11), sham group (n = 8), shunt + NaHS group (n = 10), sham + NaHS group (n = 8) and shunt + phentolamine group (n = 10). The rat model of chronic heart failure was induced by abdominal aorta-inferior vena cava puncture. At Week 8 post-operation, hemodynamic parameters, microstructures and ultrastructures of myocardial tissues were analyzed. Extracellular collagen content in myocardial tissues was analyzed after Sirius red staining. Right ventricular hydroxyproline concentration was determined and compared. RESULTS: At Week 8 post-operation, compared with the sham operation and shunt + NaHS groups, the shunt group showed significantly increased right ventricular systolic pressure (RVSP) and right ventricular end diastolic pressure (RVEDP) (mm Hg: 35.2 ± 3.9 vs 21.4 ± 3.7 and 28.1 ± 2.7, 32 ± 5 vs 21 ± 4 and 26 ± 4, all P < 0.05, 1 mm Hg = 0.133 kPa). The RV peak rate of contraction and relaxation markedly decreased (RV ± dp/dt max) (mm Hg/s: 1528 ± 113 vs 2336 ± 185 and 1835 ± 132, 1331 ± 107 vs 2213 ± 212 and 1768 ± 116, all P < 0.05). It was found microscopically that myocardial fibers in the shunt group were irregularly arranged, partially cytolysis and infiltrated by inflammatory cells. Electron microscopy revealed that myocardial fibers thickened non-uniformly in the shunt group, some fiber mitochondria were highly swollen and contained vacuoles. And sarcoplasmic reticulum appeared slightly dilated. Polarized microscopy indicated that, collagen content (particularly type-I collagen) increased in the shunt group compared with the sham operation group. Additionally, compared with the shunt group, the shunt and NaHS treatment groups showed an amelioration of myocardial damage, an alleviation of myocardial fiber changes and a decrease in myocardial collagen content (particularly type-I collagen). Compared with the sham operation and shunt + NaHS groups, the shunt group displayed increased right ventricular hydroxyproline (mg×g(-1)·pro: 1.32 ± 0.25 vs 0.89 ± 0.18 and 0.83 ± 0.19, all P < 0.05). CONCLUSION: H(2)S may improve cardiac functions and ameliorate cardiac structures in rats with chronic heart failure probably through dilating the blood vessels and affecting the extracellular collagen metabolism.

[Toxic effects of Hg2+, Cd2+ and Cu2+ on cell membrane system of Cabomba caroliniana A. Gray].

By the observation with electron- and confocal laser scanning microscopy and the determination of physiological and biochemical reactions, the toxic effects of Hg2+, Cd2+ and Cu2+ on the cell membrane system of Cabomba caroliniana A. Gray were investigated. The results showed that under the actions of the three heavy metal ions, the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) in C. caroliniana leaf cells increased, activities of protective enzymes were in disorder, and lipid peroxidation happened. The cell membrane was damaged, membrane permeability increased, and plasmolysis occurred. Meanwhile, the chloroplast swelled or even disintegrated. The excitement of photosynthetic pigments on thylakoids membrane by light was inhibited, and the auto-fluoresent intensity was decreased. The cristae of mitochondria swelled and decreased, mitochondria membrane was damaged, and nuclear membrane was broken. The effects of Hg2+, Cd2+ and Cu2+ on the cell membrane system of C. caroliniana showed a definite dose-effect correlation, and the stability of membrane system played a key role in the resistance of C. caroliniana to the toxic effects of heavy metals. C. caroliniana was sensitive to Hg2+, and the lethal concentration of Hg2+ was ranged from 0.3 to 0.5 mg L(-1). C. caroliniana had relatively higher endurance to Cd2+ and Cu2+, and could be used as the resistant plant for biological control.

[Statistical analysis of articles, citations and authors in Chinese Journal of Burns from 2003 to 2005].

OBJECTIVE: To study the characteristics of articles, citations and authors in Chinese Journal of Burns (Chin J Burns). METHODS: The date concerning articles, citations and authors of Chin J Burns from 2003 to 2005 were collected and analyzed in terms of bibliographic parameters. RESULTS: There were 741 papers published in Chin J Burns during these 3 years, and papers with funded projects accounted for 19.7%. The average number of articles per issue was 41,with paper density of 0.59, and publication date were 15 months in average after submission. Among these papers, 87.9% of which were shared with co-authors, with a corporation rate of 3.94. The papers with citation accounted for 78.7%, and 90.6% of all the citations came from journals, especially English journals. The Price's indicator was 65.6%. CONCLUSION: Chinese Journal of Burns, an academic journal of high quality, with strong influence, pushes the discipline of Burns medicine in China forward.

[Location and relative quantity of coumarins in the stem of Dendrobium thyrsiflorum].

AIM: To determine the location and relative quantity of coumarins in the stem of Dendrobium thyrsiflorum Rchb. f. , and to provide a scientific basis for evaluating and utilizing the famous medicinal plant. METHODS: The stems of one, two and three years old, separately, were collected in February. Location and relative quantity of coumarins in the top, middle and basal parts of each stem sample were determined by using laser scanning confocal microscopy (LSCM). ANOVA and Tukey's test were employed in the statistical analysis. RESULTS: The coumarins located mainly in vascular bundles, especially on the walls of the outer fiber cells. There was significant difference or great significant difference exist in every part of the stem from different ages. The values of significant difference were as follows: basal part P = 0.004 (< 0.01); middle part P = 0.009 (< 0.01); top part P = 0.036( < 0.05). CONCLUSION: Two years old stem could be the best choice when collecting Dendrobium thyrsiflorum in Feburary.