Magnetic resonance image findings of placental lake: report of two cases

Two cases with a large cystic mass within the placenta are reported. By ultrasonography, it was found that both women had a subchorionic hypoechoic lesion (11.0 × 4.8 × 4.0 cm and 6.6 × 3.7 × 2.2 cm, respectively) at 24 and 35 weeks of gestation, respectively. In both cases, turbulent blood flow generated by a pulsatile jet flow (pulse rate; 40 to 60 beats per minute) into the cystic lesion seen on real-time imaging and lesions being low intensity on T1-weighted and isointensity on T2-weighted magnetic resonance image suggested that they contained fresh maternal blood. In both cases, the sonolucency of the lesions did not change until cesarean deliveries of females, both of whom were small-for-gestational-age infants (1940 g at 37 weeks and 2195 g at 37 weeks, respectively). Biochemical analysis of the fluid in the cystic lesion sampled during the cesarean section in the latter case confirmed that the fluid had originated from the maternal blood. These lesions histologically corresponded to large avillous areas surrounded by normal villi. Thus, a huge placental lake was diagnosed in both cases. Copyright © 2005 John Wiley & Sons, Ltd.     

A comparison of concentration ratios for technetium and nutrient uptake by three plant species

Technetium (Tc) is a non-essential element for which accumulation mechanisms in plants have recently been discussed, but only from the viewpoint of existence of anion transport proteins in plant cells. In this study, using three kinds of plants (Cucumis sativus L., Raphanus sativus L., and Brassica chinensis L.), uptake of Tc and Re (a chemical analogue of Tc) were observed. The results showed that Tc and Re uptake occurred not only with water mass flow or active nutrient uptake, but also with uptake of nutrient cations such as K+. It is suggested here that most stable chemical form under aerobic conditions, TcO4-, is used in cation transport as a substitute ions, such as Cl-. After TcO4- passes through a root surface, it moves through the xylem together with cations. Due to these uptake mechanisms, Tc is highly accumulated in plants.     

Effect of phosphate addition on the sorption-desorption reaction of selenium in Japanese agricultural soils

Desorption levels of soil-sorbed selenium (Se) were studied by adding phosphate to 22 typical Japanese agricultural soils. Soil-soil solution distribution coefficients of Se (Kd-Se) were measured using a batch process as an index of Se sorption level, adding 75Se as a tracer. After the Kd measurement, extraction of soil-sorbed 75Se with a 0.1 M or 1 M Na2HPO4 solution followed to determine the amount of 75Se desorbed by the phosphate. When the 0.1 M Na2HPO4 solution was used, 18-70% of soil-sorbed Se was extracted (average: 47%). However, when the 1 M Na2HPO4 solution was used, 27-83% of soil-sorbed Se was extracted (average: 57%). The observed 75Se desorption percentage indicated the maximum Se removability by phosphate addition. The desorption percentage of Se with 1 M Na2HPO4 correlated with Kd-Se values, suggesting that the soil sample with higher Kd-Se contained more reactive components for phosphate-sorption than the soil sample with lower Kd-Se. To evaluate the effect of phosphate concentration on the Se sorption, the Kd-Se was measured for two typical soils under different levels of phosphate (0.1-10 mM PO4). The Kd values were decreased by phosphate addition for both soils. The Kd decrease was observed even for just 1 mM PO4. The phosphate addition with 1 mM PO4 is the same level as in P fertilizer applied to paddy fields in Japan. Therefore, it was suggested that Se desorption should occur in Japanese soils due to the phosphate input.     

Reduced hypoosmoregulatory ability and alteration in gill chloride cell distribution in mature chum salmon (Oncorhynchus keta) migrating upstream for spawning

Osmoregulatory ability of mature chum salmon (Oncorhynchus keta) during spawning migration was examined by following the changes in gill Na⁺, K⁺-ATPase activity and in the distribution and morphology of chloride cells. Mature chum salmon caught in Otsuchi Bay, northern Honshu Island, Japan, died within 5 d in seawater (SW) in association with a marked increase in plasma osmolality, whereas the fish transferred to fresh water (FW) maintained plasma osmolality efficiently. Gill Na⁺, K⁺-ATPase activity decreased in both SW-maintained and FW-transferred fish. Well-developed chloride cells, identified by immunocytochemical staining specific for Na⁺, K⁺-ATPase, were present mainly in the filament epithelium of immature fish caught in the ocean. In mature fish caught in the bay, however, additional chloride cells were also found in the lamellar epithelium. The number of filament chloride cells decreased markedly in the mature fish both in SW and in FW, whereas the number of lamellar chloride cells was maintained. These results suggest that the loss of hypoosmoregulatory ability in mature chum salmon may be attributable to the decrease in filament chloride cells and associated decrease in gill Na⁺, K⁺-ATPase activity, and also that appearance of lamellar chloride cells may be preparatory to the forthcoming upstream migration. Received: 14 April 1997 / Accepted: 5 May 1997     

Use of X-ray absorption imaging to examine heterogeneous diffusion in fractured crystalline rocks

Heterogeneous diffusion in different regions of a fractured granodiorite from Japan has been observed and measured through the use of X-ray absorption imaging. These regions include gouge-filled fractures, recrystallized fracture-filling material and hydrothermally altered matrix. With the X-ray absorption imaging technique, porosity, relative concentration, and relative mass of an iodine tracer were imaged in two dimensions with a sub-millimeter pixel size. Because portions of the samples analyzed have relatively low porosity values, imaging errors can potentially impact the results. For this reason, efforts were made to better understand and quantify this error. Based on the X-ray data, pore diffusion coefficients (Dp) for the different regions were estimated assuming a single diffusion rate and a lognormal multirate distribution of Dp. Results show Dp for the gouge-filled fractures are over an order of magnitude greater than those of the recrystallized fracture-filling material, which in turn is approximately two times greater than those for the altered matrix. The recrystallized fracture-filling material was found to exhibit the greatest degree of variability. The results of these experiments also provide evidence that diffusion from advective zones in fractures through the gouge-filled fractures and recrystallized fracture-filling material could increase the pore space available for matrix diffusion. This evidence is important for understanding the performance of potential nuclear waste repositories in crystalline rocks as diffusion is thought to be an important retardation mechanism for radionuclides.     

Determination of bioavailable rhenium fraction in agricultural soils

Rhenium (Re) mobility in agricultural soils was studied in order to obtain information relevant to (99)Tc mobility in soil-to-plant systems. Since water soluble Tc and Re are highly bioavailable, extraction of Re with water was carried out in addition to a total Re determination in the soils. The geometric means of total Re for paddy field, upland field and other soils were 0.34, 0.23, and 0.28 ng g(-1), respectively, while those of water soluble Re (<0.45 microm membrane filterable) were 0.053, 0.015 and 0.008 ng g(-1), respectively. There were no differences for total Re among soil uses; however, the water soluble Re/total Re ratio was significantly higher in paddy field soils (16%) than in other soil uses (6% for upland fields and 3% for other uses). Rhenium mobility and plant availability were higher in paddy fields than in other agricultural fields, and similar phenomena would be expected for (99)Tc.     

Pressure cookers or pressure valves: Do roads lead to deforestation in China?

The effect of roads on forests is ambiguous. Many studies conclude that building and upgrading roads increases pressure on forests but some find that new and better roads may reduce the rate of deforestation. In this paper we use satellite remote sensing images of forest cover in Jiangxi Province, China, to test whether the existence and the size of roads (ranging from expressways to tertiary roads) in 1995 affected the level of forest cover in 2000 or the rate of change between 1995 and 2000. To account for road access for each of our 1 km² (“pixel”) units of forest cover we measure whether or not and what type of roads penetrate the “watershed” in which the pixel lies. These watersheds allow more plausible measures of accessibility than do traditional “crowfly” distance measures that ignore topography. To account for possible confounding we also use 12 additional covariates: geographic and climatic variables (e.g., elevation, slope, rainfall, temperature, soil properties); demographic and economic variables (e.g., local population and GDP per square kilometer); and distance variables (e.g., distance to the nearest provincial capital). Although simple univariate OLS regressions show that forest levels are lower and deforestation rates higher either when there is a road, or when there is a higher quality road, these results are not robust. Controlling for all of the covariates and also using recently developed covariate matching techniques to estimate treatment effects, we find that roads in China’s Jiangxi Province can most safely be described as having no impact on the level of forests and no impact on the rate of deforestation.