Effects of habitat fragmentation on the genetic diversity and differentiation of Dendrolimus punctatus (Lepidoptera: Lasiocampidae) in Thousand Island Lake, China, based on mitochondrial COI gene sequences.

Thousand Island Lake (TIL) is a typical fragmented landscape and an ideal model to study ecological effects of fragmentation. Partial fragments of the mitochondrial cytochrome oxidase subunit I gene of 23 island populations of Dendrolimus punctatus in TIL were sequenced, 141 haplotypes being identified. The number of haplotypes increased significantly with the increase in island area and shape index, whereas no significant correlation was detected between three island attributes (area, shape and isolation) and haplotype diversity. However, the correlation with number of haplotypes was no longer significant when the 'outlier' island JSD (the largest island) was not included. Additionally, we found no significant relationship between geographic distance and genetic distance. Geographic isolation did not obstruct the gene flow among D. punctatus populations, which might be because of the high dispersal capacity of this pine moth. Fragmentation resulted in the conversion of large and continuous habitats into isolated, small and insular patches, which was the primary effect on the genetic diversity of D. punctatus in TIL. The conclusion to emphasize from our research is that habitat fragmentation reduced the biological genetic diversity to some extent, further demonstrating the importance of habitat continuity in biodiversity protection.

The association between biomarkers in cerebrospinal fluid and structural changes in the brain in patients with Alzheimer's disease.

BACKGROUND: Biochemical changes in the cerebrospinal fluid (CSF) could reflect pathophysiological processes in Alzheimer's disease (AD). However, it is still not clear how these processes correlate with grey matter (GM) volume and microstructural changes in the brain. OBJECTIVE: To assess the relationship between CSF biomarkers and structural brain changes in AD. DESIGN AND SETTING: Cross-sectional study in a memory clinic-based sample. SUBJECTS: A total of 78 subjects were included in the study: 22 with subjective cognitive impairment (SCI), 35 with mild cognitive impairment (MCI) and 21 with AD. MAIN OUTCOME MEASURES: Voxel-wise correlations between CSF biomarkers, including ß-amyloid42 (Aß42), tau phosphorylated at position threonine 181 and total tau protein, and GM volume, self-diffusion fractional anisotropy (FA) and mean diffusivity (MD) maps using voxel-based morphometry and tract-based spatial statistical analyses. FA and MD maps were obtained using diffusion tensor imaging. RESULTS: In the whole sample (patients with SCI, MCI and AD), there was positive correlation between GM volume and Aß42 concentration, and negative correlation with total tau protein. Higher FA was only related to higher concentration of Aß42. MD showed significant negative correlation with Aß42 and positive correlation with T-tau levels. The majority of brain regions with significant correlation with CSF biomarkers overlapped with the default mode network and extended to the adjacent white matter. CONCLUSIONS: Early AD pathological changes can be detected with voxel-based morphometric analysis and diffusion tensor imaging measurements. Furthermore, there was an association between CSF AD biomarkers and structural brain changes in areas related to the default mode network.

Effect of Hg, As and Pb on biomass production, photosynthetic rate, nutrients uptake and phytochelatin induction in Pfaffia glomerata.

Plantlets of Pfaffia glomerata (Spreng.) were exposed for 28 days to three different metal/metalloid (Hg, Pb and As) with different levels (Hg 1; As 25, 50, 100 and Pb 100 and 400 µM) to analyze the possible phytochelatin initiation and affects on growth and photosynthetic pigments vis-à-vis metal accumulation potential of plants. The plantlets showed significant Hg, As and Pb accumulation in roots (150, 1267.67 and 2129 µg g(-1) DW respectively); however, a low root to shoot metal translocation was observed. It was interesting to note that all tested macronutrient (Mg, K, Ca) was higher in shoots and just opposite in case of micronutrients (Cu, Fe, Zn), was recorded highest in roots. The growth of plantlets (analyzed in terms of length and dry weight) was negatively affected by various metal treatments. In addition, the level of photosynthetic pigments alters significantly in response to all metal/metalloid treatment. In response to all tested metal/metalloids in plants only As induced phytochelatins (PC2, PC3 and PC4) in roots, and in shoots, GSH was observed in all tested metal/metalloids. In conclusion, P. glomerata plantlets could not cooperatively induce phytochelatins under any of Hg and Pb levels.

[Research progress in biological characteristics and influencing factors of jaw bone marrow mesenchymal stem cell].

Jaw bone marrow mesenchymal stem cell (JBMMSC), which exists in the maxilla and mandible, is adult stem cells with strong proliferation ability and multiple differentiation potential. Pathological, physicochemical and biological factors can affect the biological characteristics of JBMMSC. Compared with bone marrow mesenchymal stem cells derived from long bone, the biological characteristics of JBMMSC are site-specific because of the different sources of tissue and osteogenesis of bone. The same influencing factors have different effects on these two kinds of cells. Besides, JBMMSC also has the advantages of easier access, less trauma and lower immunogenicity. It has broad application prospects in craniomaxillofacial defect repair, periodontal tissue regeneration, and improving the success rate after implantation and so on. It has attracted wide attention in the basic and clinical studies. However, the regulation mechanism of its proliferation and differentiation is not clear, which affects its application as seed cell. Therefore, this paper reviews the biological characteristics influencing factors of JBMMSC and application progress in clinical and basic research, aiming to provide reference for further research and clinical application.

Effects of pH, organic acids, and inorganic ions on lead desorption from soils.

The desorption characteristics of lead in two variable charge soils (one developed from Arenaceous rock (RAR) and the other derived from Quaternary red earths (REQ)) were studied, and the effects of pH value, organic acid, and competitive ions were examined. Desorption of Pb(2+) decreased from nearly 100.0 to 20.0% within pH 1.0-4.0 in both soils, and then the decrease diminished at pH > 4.0. Organic ligands at relatively low concentrations (< or =10(-3) mol L(-1)) slightly inhibited Pb(2+) desorption, but enhanced Pb(2+) desorption at higher concentrations. In this study, citric acid or acetic acid at higher concentrations (>10(-3) mol L(-1)) had the greatest improvement of Pb(2+) desorption, followed by malic acid; and the smallest was oxalic acid. Desorption of the adsorbed Pb(2+) increased greatly with increasing concentrations of added Cu(2+) or Zn(2+). Applied Cu(2+) increased Pb(2+) desorption more than Zn(2+) at the same loading.

Gender differences in cerebral blood flow and oxygenation response during focal physiologic neural activity.

Using functional magnetic resonance imaging techniques CBF and oxygenation changes were measured during sustained checkerboard stimulation in 38 right-handed healthy volunteers (18 men and 20 women). The average blood oxygenation level dependent (BOLD) contrast technique signal intensity change was 1.67 +/- 0.6% in the group of male volunteers and 2.15 +/- 0.6% in the group of female volunteers (P < .05). Baseline regional CBF (rCBF) values in activated gray matter areas within the visual cortex were 57 +/- 10 mL x 100 g(-1) x min(-1) in women and 50 +/- 12 mL x 100 g(-1) x min(-1) in men, respectively (P = .09). Despite a broad overlap between both groups the rCBF increase was significantly higher in women compared to men (33 +/- 5 mL x 100 g(-1) x min(-1) versus 28 +/- 4 mL x 100 g(-1) x min(-1), P < .01). The increase of rCBF was not correlated with the baseline rCBF (mL x 100 g(-1) x min(-1)) (r(s) = 0.01, P = .9). Moreover, changes of rCBF were not correlated with changes in BOLD signal intensities (r(s) = 0.1, P = .7). Enhanced rCBF response in women during visual stimulation could be related to gender differences in visual physiology or may reflect gender differences in the vascular response to focal neuronal activation. Gender differences must be considered when interpreting the results of functional magnetic resonance imaging studies.

Relationship between cerebral blood flow changes during visual stimulation and baseline flow levels investigated with functional MRI.

Using fMRI, the relationship between regional cerebral blood flow (rCBF) changes during visual stimulation and the prevailing baseline global and regional flow levels was evaluated in 22 volunteers. The absolute increase in rCBF was not correlated with baseline rCBF values (r = 0.01, p = 0.8); however, the percentage change in rCBF showed a negative correlation (r=-0.78, p<0.001). Both absolute and relative changes in rCBF were independent of baseline global CBF values. These results indicate that caution should be exercised when comparing relative flow changes during focal brain activation, especially in functional neuroimaging studies dealing with altered baseline flow values.

Condition number as a measure of noise performance of diffusion tensor data acquisition schemes with MRI.

Diffusion tensor mapping with MRI can noninvasively track neural connectivity and has great potential for neural scientific research and clinical applications. For each diffusion tensor imaging (DTI) data acquisition scheme, the diffusion tensor is related to the measured apparent diffusion coefficients (ADC) by a transformation matrix. With theoretical analysis we demonstrate that the noise performance of a DTI scheme is dependent on the condition number of the transformation matrix. To test the theoretical framework, we compared the noise performances of different DTI schemes using Monte-Carlo computer simulations and experimental DTI measurements. Both the simulation and the experimental results confirmed that the noise performances of different DTI schemes are significantly correlated with the condition number of the associated transformation matrices. We therefore applied numerical algorithms to optimize a DTI scheme by minimizing the condition number, hence improving the robustness to experimental noise. In the determination of anisotropic diffusion tensors with different orientations, MRI data acquisitions using a single optimum b value based on the mean diffusivity can produce ADC maps with regional differences in noise level. This will give rise to rotational variances of eigenvalues and anisotropy when diffusion tensor mapping is performed using a DTI scheme with a limited number of diffusion-weighting gradient directions. To reduce this type of artifact, a DTI scheme with not only a small condition number but also a large number of evenly distributed diffusion-weighting gradients in 3D is preferable.

Cerebral blood flow-related signal changes during breath-holding.

BACKGROUND AND PURPOSE: In the past, functional MR imaging techniques have been used successfully to determine cerebrovascular reactivity (CVR) to various stimuli, complementing the arsenal of functional brain investigations feasible with MR imaging. While previous studies have focused on blood oxygenation changes under vasodilatory stress, the aim of this study was to assess regional cerebral blood flow (rCBF) changes during breath-holding by using a flow-sensitive alternating inversion recovery (FAIR) imaging technique. METHODS: In six healthy volunteers, FAIR images were acquired during alternating periods of breath-holding and breathing at 40-second intervals after inspiration and at 30-second intervals after expiration, for a total dynamic scanning time of 10 minutes. To quantify the rCBF changes, we obtained 2.5-minute baseline samples during normal breathing. RESULTS: Repeated challenges of breath-holding induced an overall rise in rCBF. In general, rCBF changes were greatest in gray matter and were insignificant in white matter. Using the mean values of the baseline images collected before breath-holding to calculate the rCBF changes, we found that quantitative analysis yielded an rCBF increase of 47% to 87% after breath-holding. The rCBF changes clearly depended on the breath-holding duration and technique; however, for one given breath-holding paradigm the results showed relatively small interindividual variability. CONCLUSION: rCBF changes during a simple vascular challenge can be detected and quantified by means of functional MR imaging at 1.5 T. Noninvasive assessment of CVR could become a useful clinical tool to identify persons with impaired CVR.

Turbulent pipe flow studied by time-averaged NMR imaging: measurements of velocity profile and turbulent intensity.

A time-averaged method to obtain quantitative measurements in turbulent flow by phase flow encoding NMR imaging is introduced. With this method time-averaged velocity profiles and turbulence intensities can be determined. Time-averaged velocity profiles for pipe flow of water driven by a constant pressure gradient at Reynolds numbers from 1200 to 9400 were visualized. A precise correlation between the pixel intensity of the time-averaged NMR flow image and the local turbulence intensity of the flow is derived. The measured turbulence intensities are in agreement with published data obtained using other experimental methods.

[Hyperamylasemia in acute exacerbation of patients with chronic respiratory failure].

Serum amylase level was determined in 129 cases (225 episodes) of chronic respiratory failure at acute exacerbation and in 59 cases (62 episodes) of pneumonia without respiratory failure as control. Cases with accompanying diseases, such as acute pancreatitis, parotiditis, ileus and renal dysfunction, which were expected to develop hyperamylasemia were excluded. The 225 episodes were divided according to the causes of acute exacerbation into 4 groups: pneumonia, bronchitis, right heart failure without infection, and others (e. g. hemoptysis). Hyperamylasemia (greater than 400 S-U) was observed in groups of pneumonia (15/40 = 35.5%) and bronchitis (12/95 = 12.6%), respectively but not in those of right heart failure without infection (0/73 = 0%) and other causes (0/17 = 0%). As a result, hyperamylasemia was found only under conditions of inflammation of lung parenchyma and bronchi with acute exacerbation of respiratory failure. On the other hand no hyperamylasemia was observed in 62 episodes of pneumonia alone without respiratory failure. It was concluded that both respiratory tract infection and acute respiratory failure are necessary factors for development of hyperamylasemia originating from lung or bronchi.

[A heat transfer model for liquid cooling garment (LCG) and its analysis].

Objective. To establish the heat transfer model for liquid cooling garment (LCG) and, basing on this model, to find the relations between the design parameters and heat removing, as well as that between the design parameters and heat transfer efficiency. Method. Heat transfer process of the LCG was analyzed according to engineering facts. Result. The relations between the design parameters and heat removing, and also that between the design parameters and heat transfer efficiency were interelative and the optimal values of the parameters were essential to the design of LCG. Conclusion. The results might be useful in the design of LCG in extra vehicular activity (EVA) space suit.

[A study on physical characteristics of porous plates for water sublimator].

Objective. To investigate the development method of porous plate, the key part of water sublimator, and its main physical characteristics. Method. Technical parameters of porous plates used in water sublimator were analyzed. On the basis of this, porous plates made of different materials were developed by making use of sintered powder technology. A tester for testing the physical characteristics of porous plate was designed. All around physical characteristic tests for porous plates were conducted. Result. Main factors affecting performance of porous plates were tested. These provided basis for performance test of sublimator, established porous plate criterion and optimized porous plate. Conclusion. Porous plates developed by making use of sintered powder technology could meet requirements of performance of water sublimator.

[Appraisal and analysis of heat removing characteristic of liquid cooling garment using thermal manikin].

OBJECTIVE: To analyze the relation of the design parameters and appraise the heat removing characteristic of liquid cooling garment (LCG) using thermal manikin. METHOD: To appraise the design of LCG, the thermal manikin wearing LCG and heat insulation garment was put in the temperature cabin, then the inlet and outlet temperature of cooling liquid in the LCG were measured and the heat removed was calculated. RESULT: The relationship between the design parameters and heat removed, and also that between the design parameters and temperature ratio efficiency were found. And the heat removed was calculated. It provided a reasonable basis for appraisal of LCG. CONCLUSION: The design of the LCG for the EVA space suit was found to be reasonable. The flow rate regulation range was too narrow, and the change of heat removing capacity depended on the change of inlet temperature.

Diffusion-weighted MR imaging of acute cerebral ischemia.

Diffusion-weighted MR imaging has been used in studies on experimental animal models and on patients with acute cerebral ischemia. Compared with CT and conventional MR techniques, diffusion-weighted imaging can provide earlier and more precise detection of the location and the extent of an ischemic lesion during the critical first few hours after the onset of stroke. Quantitative apparent diffusion coefficient (ADC) mapping of the brain water can also be carried out by recording a series of diffusion-weighted images with different amplitudes of the displacement encoding gradients. ADC maps can provide important information about the extra- and intracellular water homeostasis. ADC reduction of the tissue water is one of the early signals of the pathophysiological cascade resulting from ischemic tissue injury. Diffusion MR imaging has become a valuable tool in stroke research. It may also prove a valuable tool in monitoring the efficiency of therapeutic effects in stroke patients. It is our intention to provide an overview of the recent development in this area with emphasis on the diffusion-weighted MR techniques, and to discuss the possible underlying biophysical mechanisms responsible for the contrast of diffusion-weighted imaging.

Image-based method for retrospective correction of physiological motion effects in fMRI: RETROICOR.

Respiration effects and cardiac pulsatility can induce signal modulations in functional MR image time series that increase noise and degrade the statistical significance of activation signals. A simple image-based correction method is described that does not have the limitations of k-space methods that preclude high spatial frequency correction. Low-order Fourier series are fit to the image data based on time of each image acquisition relative to the phase of the cardiac and respiratory cycles, monitored using a photoplethysmograph and pneumatic belt, respectively. The RETROICOR method is demonstrated using resting-state experiments on three subjects and compared with the k-space method. The method is found to perform well for both respiration- and cardiac-induced noise without imposing spatial filtering on the correction. Magn Reson Med 44:162-167, 2000.