Constructed Crevasses and Land Gain in the Mississippi River Delta

Extensive land loss, which is mostly wetland loss, has taken place during this century in the Mississippi River delta and other river deltas. Our purpose was to evaluate the effectiveness of constructing “artificial” crevasses, or cuts in the natural levee, made by the U.S. Fish and Wildlife Service in the Delta National Wildlife Refuge (DNWR) to slow or reverse this type of land loss. Land growth of the crevasses was determined from aerial photographs and was related to crevasse-site characteristics. The newly constructed crevasses create emergent wetlands after 2 years of subaqueous growth at about 4.7 ha/year and an average cost of $21,377 per crevasse. The present total cost per hectare declines with age as new land builds, and it will equal $48 per hectare if all the open water in the receiving ponds fills in. At these rates, the net land loss rates in the DNWR measured from 1958 to 1978 would be compensated for by the building of 63 crevasses, 24 of which are already in place.     

Nutrient stoichiometry,freshwater residence time,and nutrient retention in a river-dominated estuary in the Mississippi Delta

A 3-month field study was conducted to examine the effects of Atchafalaya River discharge on nitrogen and phosphorus concentrations in the Fourleague Bay system, to document patterns with salinity variation, to evaluate stoichiometric nutrient ratios of nitrogen and phosphorus in the river and bay, and to examine the relationship between estuarine freshwater residence time and export of total nitrogen (TN) and total phosphorus (TP) to the Gulf of Mexico. During spring peak discharge of the Atchafalaya River, nutrient ratios in lower Fourleague Bay indicate potential phosphorus limitation with an average dissolved inorganic nitrogen (DIN) to dissolved inorganic phosphorus (DIP) ratio of 32:1, primarily a result of high concentrations of nitrogen entering the northern bay from the Atchafalaya River and of fairly stable phosphorus concentrations. Ratios of DIN to phosphorus in the river were much higher (54:1), indicating a significant loss of nitrogen within the Fourleague Bay system. Freshwater residence time averaged approximately 7 days during the study and ranged from 2 to 100 days. TN export averaged 57% over the study and ranged from less than 3% at long residence times to greater than 80% at short residence times. TN export to the coastal ocean with respect to residence time is considerably less than has been shown in other studies. Nitrate + nitrite export averaged 49% for the 3-month study. Percentages of TP export were greater than TN, averaging 82% for the study period. By examining the Atchafalaya River delta as a natural analog for controlled river diversions, which are currently being used as coastal restoration tools, this study shows that discharging river water into highly productive shallow coastal estuarine and wetland systems can significantly reduce the amount of nitrogen exported to the Gulf of Mexico.     

Lipid Metabolism During Early Stages of Wallerian Degeneration in the Rat Sciatic Nerve

We examined changes in biosynthetic capacity of sciatic nerve during the early stages of Wallerian degeneration, utilizing a model that permits exclusion of nonresident cells from degenerating nerve. Sciatic nerve segments were placed in either 5-microns pore (allowing infiltration of nonresident cells) or 0.22-microns pore (excluding nonresident cells) Millipore diffusion chambers and then implanted in the peritoneal cavity of the same 32-34-day-old rat. At times up to 7 days postsurgery, nerve segments from the chambers, as well as control segments from the contralateral sciatic nerve, were removed and their capacity to incorporate radioactive precursors into lipids and proteins assayed in vitro. In nerve segments from both the 0.22- and 5-microns pore chambers, incorporation of [14C]acetate into total lipids was decreased relative to control by 50% at 12 h postsurgery and by 85% at day 3. This decreased incorporation of [14C]acetate reflects primarily decreased de novo synthesis of cholesterol and of fatty acyl residues incorporated into glycerolipids and sphingolipids. There was a preferentially decreased synthesis of cerebrosides and cholesterol (components enriched in myelin) relative to other lipids, while cholesterol esters and free fatty acids (products of membrane degradation) accounted for a greater proportion of the greatly reduced levels of total lipid label. In contrast to [14C]acetate, incorporation of [3H]glycerol into lipids was increased up to fourfold, relative to control, 1 day after nerve transection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Common carp in the Upper Mississippi River

Since its escapement into the Upper Mississippi River (UMR) and rapid expansion in the late 1900's, the common carp, Cyprinus carpio, has become a major component of the river fishery. Mean annual harvest value for this species was $270000 between 1953 and 1977. Recent evidence suggests that common carp may not be as abundant in the river as they have been in the past. We summarized historical commerical information on common carp in the UMR to put its current harvest levels in perspective. A major factor responsible for recent low annual harvests has been PCB contamination of the river in the Lake Pepin area. Market and biological factors probably have also contributed to declining harvests. To help explain why common carp populations in the UMR may be declining, we reviewed literature pertaining to the ecology of the species, particularly that from the river, its tributaries, or midwestern lakes. We included information on how common carp are controlled by environmental factors, and how they interact with other biota. Most aspects of carp ecology in the UMR and other areas are similar. Exceptions relate primarily to their response to annual water level regimes of the river. We postulate that population declines and absent year classes in the UMR may be related to poor recruitment during high- or variable-water years.     

Mobilization of Reserve Proteins During Early Stages of Seed Germination in Fagopyrum Esculentum

Hydrolysis of 13S globulin, the main storage protein in grains of common buckwheat (Fagopyrum esculentum Moench), proceeds in at least two phases during germination. The first stage, involving a limited proteolytic cleavage of the protein, is associated with increased activity of proteases having maximum activity at pH 7.6. The second stage, involving further hydrolysis of the partially cleaved protein, starts after 12 h of imbibition. During this phase, activity of proteases increased and activity maximum shifted to pH 5.6. Nevertheless, 13S globulin retains its antigenic identity till the emergence of radicle and plumule. Thus, it may not be the major source of amino acids utilized by the germinating seed during the initial stages of imbibition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Trace Metal Concentrations in Marsh Profiles Under the Influence of an Emerging Delta (Atchafalaya River and Wax Lake Delta) Overlying a Several Thousand Year Old (Former)Mississippi River Delta Lobe

There are concerns over the increasing concentrations of trace metals being found in the environment. Deltas are essentially integrators of watershed contamination as they are the repositories of sediment transported from and through the watershed. In order to assess changes in trace metal concentrations transported by the Mississippi River–Atchafalaya River systems, vibracores were collected from three coastal freshwater marsh sites under the influence of the Atchafalaya River and emerging Wax Lake Delta (WLD). The cores extended to a depth of 4 m which included deposits of an earlier Mississippi River Delta lobe. C-14 dating showed an age at the lower depth corresponding to approximately 3500 years ago. Vertical profile distribution of metals and metalloids were measured and comparisons between older deposits and concentrations in recent deposits were made. Concentrations of As, Cr, Cu, Ni, Zn, Mo, V, Co, and Hg metals were measured in the profiles along with Fe, Mn, and Al. There was no significant increase in heavy metals or metalloids in recent years as compared to more than 3000-year-old sediment associated with an earlier Mississippi River Delta lobe. Results show that sediment diversion through the Wax Lake Outlet did not increase concentrations of these metals in surface marsh soils. The metal concentrations in the marsh profile were compared to ERL (effects range low) and ERM (effects range medium) values to allow an ecotoxicological assessment. Arsenic was below the ERM values but was greater than the ERL which indicate a potential toxicity under certain conditions. All other metal/metalloids measured were below ERL limits. This study suggests that planned Mississippi River sediment diversions designed to slow the rate of coastal land loss are not likely to lead to trace metals contamination.     

Phosphorylated LIM Kinases Colocalize with Gamma-Tubulin in Centrosomes During Early Stages of Mitosis

LIM kinases (LIMK1 and LIMK2) are LIM domain containing serine/threonine kinases that modulate reorganization of actin cytoskeleton through inactivating phosphorylation of cofilin. The Rho family of small GTPases regulates the catalytic activity of LIMK1 and LIMK2 through activating phosphorylation by ROCK or by p21 kinase. Recent studies have suggested that LIMK1 could play a role in modulation of cellular growth by alteration of the cell cycle in breast and prostate tumor cells; however, the direct mitogenic effects of LIMK1 in these tumor cells is yet to be elucidated. Via immunofluorescence, in this study, we show that phosphorylated LIM kinases (pLIMK1/2) are colocalized with γ-tubulin in the centrosomes during the early mitotic phases of human breast and prostate cancer cells (MDA-MB-231 and DU145); apparent colocalization begins in the centrosomes in prophase. As shown by both bright field (MDA-MB-231) and fluorescent immunohistochemistry (MDA-MB-231 and DU145), pLIMK1/2 does not localize to centrosomes during interphase. By bright field immunohistochemistry, the largest area of the centrosome that is stained with pLIMK1/2 occurs at anaphase. In early telophase, reduced staining of pLIMK1/2 at the spindle poles and concomitant accumulation of pLIMK1/2 at the cleavage furrow begins to occur. In late telophase, loss of staining of pLIMK1/2 and of colocalization with γ-tubulin occurs at the poles and pLIMK1/2 became further concentrated at the junction between the two daughter cells. Co-immunoprecipitation studies indicated that γ-tubulin associates with phosphorylated LIMK1 and LIMK2 but not with dephosphorylated LIMK1 or LIMK2. The results suggest that activated LIMK1/2 may associate with γ-tubulin and play a role in mitotic spindle assembly.     

Acrylamide Gel Electrophoresis of Intracellular Proteins During Early Stages of Sporulation in Bacillus subtilis

Acrylamide gel electrophoresis of unfractionated cellular extracts of Bacillus subtilis is shown to be an effective method for characterizing many of the changes in protein composition, when coupled with specific histological-type staining reactions. The results obtained here by using extracts from cells at different stages of growth and sporulation are consistent with observations from other laboratories where extensively purified and highly characterized enzymes have been studied. In several instances, the histochemical reactions can be associated with a specific enzymatic function and appear to indicate the presence of multiple molecular forms. In other instances, the data cannot be evaluated in terms of known enzyme function because the specificity of the histochemical analysis is not certain. However, the assays described permit monitoring of electrophoretic changes at the level of individual proteins within sporulating cultures. The results suggest that B. subtilis may contain two "hexokinase-like" enzymes which cease to function before sporulation is initiated. Aldolase and alanine dehydrogenase are detectable as single bands of enzyme activity during vegetative growth but as multiple molecular forms once sporulation has been initiated. Reduced nicotinamide adenine dinucleotide dehydrogenase activity is represented by an entire family of reactive species in these crude extracts, which undergo multiple changes during the early stages of sporulation. Tricarboxylic acid cycle dehydrogenase enzymes and those bands having esterase activity on alpha-naphthyl acetate show detectable changes in specific activity after cessation of exponential growth. Glucose dehydrogenase is not detectable until the sequence of changes leading to spore formation has progressed for 4 or 5 hr.     

赤水河四川华吸鳅的早期发育

四川华吸鳅Sinogastromyzon szechuanensis为长江上游特有鱼类.为了积累其生物学资料,为相关的保护措施提供参考,于2009年通过人工授精获得四川华吸鳅受精卵,对其胚胎和仔鱼的发育过程进行了观察和描述.四川华吸鳅的受精卵呈浅黄色,卵膜径较小(1.85 mm±0.23 mm),具粘性.在水温26.3~27.8℃下,胚体经历22 h 34 min发育成仔鱼出膜;初孵仔鱼全长4.39 mm±0.21 mm,肌节37对;日龄4 d时,卵黄囊吸收完毕,进入外营养期;日龄65 d时,鳞片长齐,进入幼鱼期.整个早期发育过程历时65 d 22 h 34 min.     

Factors Regulating Nitrogen Retention During the Early Stages of Recovery from Fire in Coastal Chaparral Ecosystems

Fire is a fundamental reorganizing force in chaparral and other Mediterranean-type ecosystems. Postfire nutrient redistribution and cycling are frequently invoked as drivers of ecosystem recovery. The extent to which N is transported from slopes to streams following fire is a function of the balance between the rate at which soil microbes retain and metabolize N into forms that readily dissolve or leach, and how rapidly recovering plants sequester this mobilized N. To better understand how fire impacts this balance, we sampled soil and plant N dynamics in 17 plots distributed across two burned, chaparral-dominated watersheds in Santa Barbara County, California. We measured a variety of ecosystem properties in both burned and unburned plots on a periodic basis for 2 years, including soil water content, pH, soil and plant carbon and nitrogen, extractable inorganic nitrogen, dissolved organic nitrogen, and microbial biomass. In burned plots, nitrification was significantly enhanced relative to rates measured in unburned plots. Ephemeral herbs established quickly following the first postfire rain events. Aboveground plant biomass assimilated N commensurate with soil net mineralization, implying tight N cycling during the early stages of recovery. Microbial biomass N, on the other hand, remained low throughout the study. These findings highlight the importance of herbaceous species in conserving ecosystem nutrients as shrubs gradually recover.     

A short-term physical activity randomized trial in the Lower Mississippi Delta

Background

The purpose of this study was to determine if a short-term pedometer-based intervention results in immediate increases in time spent in moderate-to-vigorous physical activity (MVPA) compared to a minimal educational intervention.

Methods

A sample of 43 overweight adults 35 to 64 years of age participated in a one week pedometer-based feasibility trial monitored by accelerometry. Participants were randomized into a one-week education-only group or a group that also wore a pedometer. Accelerometer-measured MVPA was measured over 7 days at baseline and again for 7 days immediately post-intervention.

Results

Minutes of MVPA increased significantly in the overall sample (p = 0.02); however, the effect of adding the pedometer to the education program was not significant (p = 0.89). Mean (±SE) MVPA increased from 12.7±2.4 min/day to 16.2±3.6 min/day in the education-only group and from 13.2±3.3 min/day to 16.3±3.9 min/day in the education+pedometer group. The correlation between change in steps/day and change in MVPA was 0.69 (p<0.0001).

Conclusions

The results of this study suggest that the addition of a pedometer to a short-term education program does not produce added benefits with respect to increasing physical activity in the Lower Mississippi Delta.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01264757","term_id":"NCT01264757"}}NCT01264757     

Southern Trauma: Revisiting Caste and Class in the Mississippi Delta

Two classic ethnographies, Hortense Powdermaker's After Freedom: A Cultural Study in the Deep South and John Dollard's Caste and Class in a Southern Town , contributed to a "master narrative" of the Mississippi Delta and the South that viewed class largely through the lens of race. Their work contributed to the community studies and culture and personality traditions and became part of the public discourse of race in the United States. This article examines the institutional and theoretical frameworks within which they worked. We focus on three aspects of their work: (1) their definition of class that left race as the only salient social divide; (2) their portrayal of middle- and upper-class statements as normative; and (3) their uncritical use of data from elsewhere in the South to interpret their Indianola data. We report the events at the Yale Institute of Human Relations that led Dollard to publish before Powdermaker.     

Thermotolerance of Pearl Millet and Maize at Early Growth Stages: Growth and Nutrient Relations

Thermotolerance of pearl millet (Pennisetum glaucum cv. ICMV-94133) and maize (Zea mays cv. Golden) was assessed at germination and vegetative stage. Final percentage of germinated seeds and rate of germination (number of days to 50 % germination) decreased due to high temperature (45 °C) similarly in the both species. In contrast, at the vegetative stage, high temperature (38/27 °C) caused a significant reduction in shoot dry mass of maize, whereas this attribute remained almost unchanged in pearl millet. Relative growth rate and net assimilation rate (NAR) increased significantly in pearl millet due to high temperature, but in contrast, in maize NAR was slightly reduced. Concentrations of N, P, and K in the shoots of both species increased at high temperature, but N accumulation was more pronounced in pearl millet than in maize. High temperature caused a marked increase in both shoot and root Ca²⁺ concentration in maize, but it did not affect that of pearl millet. S concentration in the shoots of maize decreased significantly due to high temperature, whereas that in pearl millet remained unaffected. Shoot Na⁺ concentration of both species was not significantly affected by high temperature. High temperature caused a significant increase in uptake of N, P, and K⁺ in pearl millet, but the uptake of Ca²⁺, Mg²⁺, Na⁺ and S remained unaffected in this species. In contrast, in maize, a significant increase in uptake of K⁺ and Ca²⁺, and a decrease in uptake of N, S, Mg²⁺, and Na⁺ were found at high temperature. Overall, maize showed lower tolerance to high temperature compared with pearl millet.     

Nitrate-nitrogen retention in wetlands in the Mississippi River Basin

Nitrate-nitrogen retention as a result of river water diversions is compared in experimental wetland basins in Ohio for 18 wetland-years (9 years × 2 wetland basins) and a large wetland complex in Louisiana (1 wetland basin × 4 years). The Ohio wetlands had an average nitrate-nitrogen retention of 39 g-N m⁻² year⁻¹, while the Louisiana wetland had a slightly higher retention of 46 g-N m⁻² year⁻¹ for a similar loading rate area. When annual nitrate retention data from these sites are combined with 26 additional wetland-years of data from other wetland sites in the Basin Mississippi River (Ohio, Illinois, and Louisiana), a robust regression model of nitrate retention versus nitrate loading is developed. The model provides an estimate of 22,000 km² of wetland creation and restoration needed in the Mississippi River Basin to remove 40% of the nitrogen estimated to discharge into the Gulf of Mexico from the river basin. This estimated wetland restoration is 65 times the published net gain of wetlands in the entire USA over the past 10 years as enforced by the Clean Water Act and is four times the cumulative total of the USDA Wetland Reserve Program wetland protection and restoration activity for the entire USA.     

Seasonal succession of the phytoplankton in the upper Mississippi River

Species composition and seasonal succession of the phytoplankton were investigated on the upper Mississippi River at Prairie Island, Minnesota, U.S.A. Both the numbers and volume of individual species were enumerated based on cell counts with an inverted microscope. A succession similar to algal succession in the local lakes occurred. The diatoms were dominant during the spring and fall and blue-green algae were dominant during the summer. The algal concentrations have increased up to 40 fold the concentrations of the 1920's, since the installation of locks and dams. The maximum freshweight standing crop was 4 mg · l^–1 in 1928 (Reinhard 1931), 13 mg · l^–1 in 1975 a wet year, and 47 mg · l^–1 in 1976, a relatively dry year with minimal current discharge. The diatoms varied from 36–99%, the blue-green algae from 0–44% and the cryptómonads from 0–50% of the total standing crop. The green algae were always present but never above 21% of the biomass. The dominant diatoms in recent years were centric -Stephanodiscus andCyclotella spp. (maximum 50,000 ml^–1). The dominant blue-green algae wereAphanizomenon flos-aquae (L.) Ralfsex Born.et Flahault andOscillatoria agardhii Gomont (maximum 800 ml^–1). These algal species are also present in local lakes. Shannon diversity values indicated greatest diversity of algae during the summer months.     

On Some Features of Early Embryonic Development Stages of Cnidaria

Division of the life cycle of Cnidaria (except for Anthozoa) into two independent generations, polypoid and medusoid, i.e., metagenesis, is considered to be unjustified. Like other Metazoa, their life cycle can be divided into three periods: embryonic, postembryonic, and definitive, i.e., according to the age [9, 10]. An important feature of Cnidaria is the transition of some postembryonic stages to the sedentary mode of life. As in other animals, this change results in a substantial reduction in organismic integrity and an anarchical type of cell division. Some researchers [3, 5, 7] regard this type of cell division as original. However, the anarchical type of cell division itself is secondary and, for this reason, cannot be ancestral to other types. The statement that the spiral type of cell division originated from the pseudo-spiral type also arouses serious criticism. The spiral type is caused by a change in the structure of the blastomere ooplasm rather than the appropriate arrangement of blastomeres.     

水稻胚胎发生与萌发早期分离胚中内源激素的变化

以酶联免疫吸附检测技术分析了水稻(Oryza sativa ssp. japonica)分离胚不同发育时期及萌发早期的内源激素含量的动态变化.GA1含量是所测激素中含量最高的.GA1的变化趋势基本上与ABA相反.花后4 d的胚中GA1和ABA的含量最高;花后8 d到18 d,GA1的含量下降,而ABA含量增加.在早期萌发过程中,种子吸涨后2 d的胚中GA1含量迅速上升,而ABA下降.GA1/ABA的最高比值也出现在吸涨后2 d的胚中.iPAs和ZRs的最高含量也出现在开花后4 d的胚中,但随后含量均下降到相当低的水平,并几乎没有变化.研究结果进一步证实了GA1在早期胚胎发生和萌发过程中起重要的作用;推测iPAs和ZRs可能仅在胚胎发生的早期起作用;GA1与ABA含量之间的相对平衡控制着胚胎发育的过程.用分离胚作为测试材料可以避免胚乳等其他组织成分的干扰,从而比较准确地反映了胚的内源激素变化.此外,本研究是首次用4 d的水稻幼胚作为激素含量测定的起始材料.