Assessment of nematode community structure as a bioindicator in river monitoring.

Nematode communities from river water and sediments were assessed for the abundance, feeding types, maturity indices and nematode channel ratio (NCR). The sampling sites studied included different levels of pollution and contamination from agricultural, industrial and sewage sources. The nematode abundance found in the sediment samples was more than that in the water samples. The lowest nematode abundance in sediment samples and the lowest NCR in water samples were both found at the industrial pollution site. Water samples showed positive correlation between the NCR and river pollution index (RPI). Mean maturity indices in sediment samples were inversely correlated with RPI. The pollutant source determined the relationship between NCR and pollution level, while maturity index always showed negative correlation with pollutant level regardless of the pollutant sources. The nematode abundance and its community structure were both reliable bioindicators for monitoring long-term river pollution in both qualitative and quantitative aspects.

Effect of Crop Rotation on Meloidogyne spp. and Pratylenchus spp. Populations in Strawberry Fields in Taiwan.

Changes in population levels of Meloidogyne hapla, M. incognita, Pratylenchus coffeae, and P. penetrans were studied in 12 strawberry fields in the Dahu region of Taiwan. Ten potential rotation crops and two cultural practices were evaluated for their effect on nematode populations and influence on strawberry yield. Rotation with rice or taro and the cultural practice of flooding and bare fallowing for four months were found to reduce nematode soil populations to two or fewer nematodes per 100 ml soil. Average strawberry yields increased between 2.4% to 6.3% following taro compared to the bare fallow treatment. Corn suppressed M. incognita and M. hapla populations and resulted in an increased in strawberry yield compared to bare fallow. Other phytopathogens also present in these fields limited taro as the rotation choice for nematode management. Results of this research and economic analysis of the input requirements for various rotation crops, corn and bare fallow were recommended as the most appropriate rotation strategies for nematode management in strawberry in this region.

Evaluation of Asteraceae Plants for Control of Meloidogyne incognita.

Of the 56 species and 43 genera of Asteraceae tested, 9 were highly resistant or immune to Meloidogyne incognita and did not form root galls. Twenty-six species and six cultivars had 25% or fewer roots galled and were considered moderately resistant to M. incognita. Pre-planting Cosmos bipinnatus (F190), Gaillardia pulchella, Tagetes erecta, Tithonia diversifolia, or Zinnia elegans (F645) reduced root galling and M. incognita J2 in and around Ipomoea reptans. Amendment of soils with roots, stems, or leaves of G. pulchella was effective in controlling M. incognita on I. reptans. Tissue extracts of G. pulchella were lethal to various plant-parasitic nematodes but were innocuous to free-living nematodes. Root exudates of G. pulchella were lethal to J2 of M. incognita and were inhibitory to the hatch of eggs at the concentration of 250 ppm or higher. Gaillardia pulchella could be used to manage M. incognita as a rotation crop, a co-planted crop, or a soil amendment for control of root-knot nematode.

Deep cervical lymph flow following the infusion of mannitol in rabbits.

Jugular lymph flow of anesthetized rabbits in response to infusion of mannitol solutions differing in osmolarity were measured. Either an isotonic (310 mosmol), hypotonic (100 mosmol), or hypertonic (605 mosmol) mannitol solution was infused into either the internal carotid artery (ICA) or the right lateral ventricle (RLV). Lymph was collected continuously and measured over a 60 min preinfusion period, as well as during mannitol infusion and intermittent recovery periods. The mean peak flow rates of hypertonic infusion for the first 30 min via ICA and RLV were 2.2 +/- 0.4 (12% decrease) and 5.0 +/- 1.0 microliter/min (72% increase), over those of isotonic infusates which were 2.5 +/- 0.3 microliters/min (via ICA) and 2.9 +/- 0.5 microliters/min (via RLV), respectively. In contrast, lymph flow rates of hypotonic infusate for the first 30 min via ICA and RLV were 3.9 +/- 0.8 microliters/min and 2.3 +/- 0.4 microliters/min, respectively. A decrease both in intracranial pressure and in lymph flow following hypertonic mannitol infusion via ICA were observed. However, intracranial pressure and lymph formation were increased following hypertonic infusion via RLV. The results indicate that the changes in jugular lymph flow could be affected by the changing in osmolarity of mannitol infusate.

Boundary conditions for the diffusion equation in radiative transfer.

Using the method of images, we examine the three boundary conditions commonly applied to the surface of a semi-infinite turbid medium. We find that the image-charge configurations of the partial-current and extrapolated-boundary conditions have the same dipole and quadrupole moments and that the two corresponding solutions to the diffusion equation are approximately equal. In the application of diffusion theory to frequency-domain photon-migration (FDPM) data, these two approaches yield values for the scattering and absorption coefficients that are equal to within 3%. Moreover, the two boundary conditions can be combined to yield a remarkably simple, accurate, and computationally fast method for extracting values for optical parameters from FDPM data. FDPM data were taken both at the surface and deep inside tissue phantoms, and the difference in data between the two geometries is striking. If one analyzes the surface data without accounting for the boundary, values deduced for the optical coefficients are in error by 50% or more. As expected, when aluminum foil was placed on the surface of a tissue phantom, phase and modulation data were closer to the results for an infinite-medium geometry. Raising the reflectivity of a tissue surface can, in principle, eliminate the effect of the boundary. However, we find that phase and modulation data are highly sensitive to the reflectivity in the range of 80-100%, and a minimum value of 98% is needed to mimic an infinite-medium geometry reliably. We conclude that noninvasive measurements of optically thick tissue require a rigorous treatment of the tissue boundary, and we suggest a unified partial-current--extrapolated boundary approach.

Properties of photon density waves in multiple-scattering media.

Amplitude-modulated light launched into multiple-scattering media, e.g., tissue, results in the propagation of density waves of diffuse photons. Photon density wave characteristics in turn depend on modulation frequency (omega) and media optical properties. The damped spherical wave solutions to the homogeneous form of the diffusion equation suggest two distinct regimes of behavior: (1) a high-frequency dispersion regime where density wave phase velocity V(p) has a radicalomega dependence and (2) a low-frequency domain where V(p), is frequency independent. Optical properties are determined for various tissue phantoms by fitting the recorded phase (?) and modulation (m) response to simple relations for theappropriate regime. Our results indicate that reliable estimates of tissue like optical properties can be obtained, particularly when multiple modulation frequencies are employed.

Changes of deep cervical lymph flow following the infusion of isotonic, hypotonic, and hypertonic NaCl in rabbit.

Isotonic, hypotonic, or hypertonic saline was infused in anesthetized rabbits in order to test the effects of osmolality in cerebral vessels on lymph flow. The jugular lymph trunk was cannulated by PE tubing in a headward direction. Either a hypo-(100 mosmol), iso-(310 mosmol), or hypertonic (605 mosmol) NaCl solution was infused into the internal carotid artery (ICA) or the right lateral ventricle (RIV). Lymph was continuously collected at slight negative pressure, and measured over a 90 min preinfusion period, as well as during saline infusion and intermittent recovery periods. Mean peak flow rates for the first 30 min infusion of hypertonic saline via ICA and RLV were 5.1 +/- 1.2 and 6.7 +/- 1.6 microliters/min, respectively, or a significant increase of 38% and 40% over those of isotonic saline (3.7 +/- 0.9 microliters/min via ICA; 4.8 +/- 1.0 microliters/min via RLV). Conversely, for hypotonic saline, lymph flow rates were significantly reduced by 19% (2.9 +/- 0.6 microliters/min) and 23% (3.7 +/- 0.7 microliters/min) for the first 30 min infusion via ICA and RLV, respectively. Increases in arterial and intracranial pressures, as well as an enhancement of respiratory movements following hypertonic saline infusion, augmented lymph formation. The results suggest that the observed changes in jugular lymph flow following saline infusion can be correlated to the resulting increase in intracranial pressure and respiratory movements, and changes in the osmolality and blood pressure of cerebral vessels.

Spatial Fourier analysis of video photobleaching measurements. Principles and optimization.

The major use of the fluorescence recovery after photobleaching (FRAP) technique is to measure the translational motion of the molecular components in various condensed media. In a conventional laser spot photobleaching experiment, a photomultiplier is used to measure the total brightness levels of the bleached region in the sample, so no spatial information can be directly obtained. In video-FRAP, a series of images after photobleaching is acquired, allowing the spatial character of the recovery to be determined; this permits direct detection of both anisotropic diffusion and flow. To utilize all of the available image data to determine the transport coefficients, a two-dimensional spatial Fourier transform analysis of the images after photobleaching was employed. The change in the transform between two time points reflects the action of diffusion during the interim. An important advantage of this method, which involves taking the ratio of image transforms at different time points, is that it does not require a specific initial condition to be created by laser photobleaching. The ability of the analysis to extract transport coefficients from computer-simulated diffusional recovery is assessed in the presence of increasing amounts of noise. Experimental data analysis from the diffusion of proteins in viscous solutions and from the diffusion of protein receptors on cell surfaces demonstrate the feasibility of the Fourier analysis to obtain transport coefficients from the video FRAP measurement.

Fluorescence recovery after photobleaching techniques to measure translational mobility in microscopic samples.

The scope of photobleaching applications and the method itself are briefly reviewed. Two current applications in this laboratory are then outlined. First, the use of spatial Fourier transforms to analyze video photobleaching measurements is presented. This method extracts diffusion coefficients using all the image data and it does not require that the initial condition created by photobleaching be known. Second, the use of genetic engineering methods coupled with photobleaching analysis is discussed as means to uncover the structural determinants of membrane protein lateral mobility.

Characterization of low-light-level cameras for digitized video microscopy.

The use of low-light-level video cameras and solid-state image detectors in conjunction with image digitizers for optical microscopy is increasing dramatically as more people learn about such systems, and as they become more powerful, less expensive, and easier to use. However, there is currently little information available allowing comparison between cameras, or for determining camera suitability for a given experiment. In this paper, we describe a series of tests designed to characterize the performance of low-light-level cameras. The results of these tests should assist in the selection of appropriate cameras for given video microscopy applications.