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The objective of this study was to develop a conceptual framework to study soil aggregate dynamics through the integration of aggregation, disruption, stabilization and destabilization processes of soil constituent units. We used aggregate‐size distribution and water stability of macroaggregates to evaluate changes in soil aggregates in two ecosystems where one is the ‘reference’ state and the other is the ‘new’ state. The framework was validated with data from (a) a non‐buffered annual row crop (ARC) system, (b) a no‐till (NT) system and (c) a bare fallow (BF) system. The dynamics of soil aggregates in the ARC were dominated by the disruption of aggregates (the aggregation–disruption index (ADI) was −0.08), in NT they were dominated by the aggregation process (ADI = 0.03) and in BF dominated by the disruption of aggregates (ADI = −0.20). Three pathways were observed: (a) expression of the aggregation process, which is essential in reestablishing soil structure and functionality, (b) expression of the disruption process, which is critical in the destruction of soil structure and (c) prevalence of mixed behaviour, where the dominant process depended on the relative rate of aggregation and disruption. The proposed framework and study of the carbon associated with aggregates could pave the way for the development of a methodology for the quantitative study of soil organic carbon (SOC) dynamics, carbon inputs (outputs), soil carbon fractions, and edaphic and biotic conditions that regulate SOC dynamics. HIGHLIGHTS: Soil aggregate dynamics were assessed within multiple management systems. A new methodology is proposed for the quantitative study of soil aggregate dynamics. Provided an understanding of aggregation, disruption, stabilization and destabilization in aggregate dynamics. Aggregate dynamic pathways of value in land management can minimize deterioration of the environment.

Although in vitro fertilization (IVF) is associated with adverse perinatal outcomes, there is increasing concern about the long-term and sex-specific health implications. Augmenting our IVF mouse model to longitudinally investigate metabolic outcomes in offspring from optimal neonatal litter sizes, we found sex-specific metabolic outcomes in IVF offspring. IVF-conceived females had higher body weight and cholesterol levels compared to naturally conceived females, whereas IVF-conceived males had higher levels of triglycerides and insulin, and increased body fat composition. Through adult liver transcriptomics and proteomics, we identified sexually dimorphic dysregulation of the sterol regulatory element-binding protein (SREBP) pathways that are associated with the sex-specific phenotypes. We also found that global loss of DNA methylation in placenta was linked to higher cholesterol levels in IVF-conceived females. Our findings indicate that IVF procedures have long-lasting sex-specific effects on metabolic health of offspring and lay the foundation to utilize the placenta as a predictor of long-term outcomes.

Although in vitro fertilization (IVF) is associated with adverse perinatal outcomes, an increasing concern is the long-term health implications. We augmented our IVF mouse model to longitudinally investigate cardiometabolic outcomes in offspring from optimal neonatal litter sizes. We found that IVF-conceived females had higher body weight and cholesterol levels compared to naturally-conceived females, whereas IVF-conceived males had higher levels of triglycerides and insulin, and increased body fat composition. Through transcriptomics and proteomics of adult liver, we identified sexually-dimorphic dysregulation of the sterol regulatory element binding protein (SREBP) pathways that are associated with the sex-specfic phenotypes. We also found that global loss of DNA methylation in placenta was linked to higher cholesterol levels in IVF-conceived females. Our findings indicate that IVF procedures have long-lasting sex-specific effects on metabolic health of offspring and lay the foundation to utilize the placenta as a predictor of long-term outcomes.

Riparian buffers are a conservation practice that increases vegetation diversity on the agricultural landscape while providing environmental benefits. This study specifically focused on the ability of riparian buffers to remove nitrate from shallow groundwater. There are many studies that assessed nitrate removal within buffers, but not many have a long-term, continuous data set that can analyze for variation in nitrate removal rates over time. Here we report on 21 years of nitrate well data, from 1996 through 2017, for three buffers in the Bear Creek watershed in central Iowa. These buffers are named using abbreviations to help keep landowners anonymous (e.g. RN, RS, and ST). Studied buffers RS and ST showed greater nitrate reduction (or removal) after 10 and 6 years of its establishment, respectively. Buffer RN did not experience a significant nitrate removal increase with time, but instead had higher nitrate removal rates when compared to buffers RS and ST of 10.3 g NO3−-N m−1 day−1 from the start of this study. From this data, we suggest that past land management played a major role in the responses observed. RN had previously been established in cool-season grasses for grazing before being converted to a buffer, while RS and ST had been managed in a corn and soybean rotation. RN was thought to have higher denitrification immediately with increased labile soil carbon input and enhanced soil aggregation due to the grassland perennials, while buffer vegetation establishment increased soil carbon inputs and soil aggregation over time for RS and ST. These nitrate removal trends would not have been observed without access to long-term, continuous data. This study highlighted the importance of long-term data sets and the need to assess conservation practices over time to determine their longevity and efficiency with time.

Summary Agriculture in the temperate zone of the Midwestern USA has removed most riparian buffer zones from the landscape, which impairs the soil functioning of the soil in these ecosystems. The objective of this study was to assess soil degradation in a non-buffered riparian zone with an annual row crop (ARC) and in a longer established (more than 85 years) riparian cool season grass (CSG) buffer in central Iowa, USA. To achieve our objective, we compared the functioning of the target system, ARC, with a system that has been undisturbed since 1990, CSG. We measured the aggregate size distribution and stability of macroaggregrates, aggregate-associated soil organic carbon and particulate organic matter (POM). The categorization of aggregates by size and water stability (slaking resistance) showed a significantly larger (P 250 µm) under CSG (53%) than under ARC (26.3%). On the other hand, soil under ARC had the larger proportion of large and small water-unstable macroaggregates. The results indicate that the concentration of organic C associated with the total water-stable aggregates is 1.9 times greater under CSG (23.9 mg C g−1) than for the ARC (12.4 mg C g−1). The concentration of carbon in light particulate organic matter (LPOM-C) under CSG accounted for 12% of total soil organic carbon (TSOC), but only 6% under ARC management. The chemical composition of LPOM in the ARC soil had a large alkyl-C/O-alkyl C ratio, which suggests more organic matter decomposition than with the CSG. Electronic micrographs showed evidence that under CSG roots and fungal hyphae form an extensive network around the large macroaggregates (> 2000 µm), and thus maintain the stability of the macroaggregates. Preserving the CSG buffer reduces soil erosion and the processes associated with nonpoint source pollutants, which improves water quality in an intensively managed agricultural system. Highlights How do soil aggregation and POM change after conversion of CSG buffer to continuous cultivation? Improved understanding of soil degradation through water-stable and -unstable aggregates and SOC. Lack of disturbance of CSG buffer favours formation of macroaggregates and SOC stabilization. Preserving CSG buffer improves water quality in an intensively managed agricultural system.

Transport and fate of dissolved nitrous oxide (N2O) in groundwater and its significance to nitrogen dynamics within agro-ecosystems are poorly known in spite of significant potential of N2O to global warming and ozone depletion. Increasing denitrification in riparian buffers may trade a reduction in nitrate (NO3−) transport to surface waters for increased N2O emissions resulting from denitrification-produced N2O dissolved in groundwater being emitted into the air when groundwater flows into a stream or a river. This study quantifies the transport and fate of NO3− and dissolved N2O moving from crop fields through riparian buffers, assesses whether groundwater exported from crop fields and riparian buffers is a significant source of dissolved N2O emissions, and evaluates the Intergovernmental Panel on Climate Change (IPCC) methodology to estimate dissolved N2O emission. We measured concentrations of NO3−; chloride (Cl−); pH; dissolved N2O, dissolved oxygen (DO), and organic carbon (DOC) in groundwater under a multi-species riparian buffer, a cool-season grass filter, and adjacent crop fields located in the Bear Creek watershed in central Iowa, USA. In both the multi-species riparian buffer and the cool-season grass filter, concentrations of dissolved N2O in the groundwater did not change as it passed through the sites, even when the concentrations of groundwater NO3− were decreased by 50% and 59%, respectively, over the same periods. The fraction of N lost to leaching and runoff (0.05) and the modified N2O emission factor, [ratio of dissolved N2O flux to N input (0.00002)] determined for the cropped fields indicate that the current IPCC methodology overestimates dissolved N2O flux in the sites. A low ratio between dissolved N2O flux and soil N2O emission (0.0003) was estimated in the cropped fields. These results suggest that the riparian buffers established adjacent to crop fields for water quality functions (enhanced denitrification) decreased NO3− and were not a source of dissolved N2O. Also, the flux of dissolved N2O from the cropped field was negligible in comparison to soil N2O emission in the crop fields.

Streambank erosion may represent a significant source of sediment and phosphorus (P) to overall watershed loads; however, watershed-scale quantification of contributions is rare. In addition, streambanks are often comprised of highly variable stratigraphic source materials (e.g., alluvial deposits), which may differentially impact in-channel P dynamics once eroded. The objective of this study was to quantify sediment and total phosphorus (TP) losses from four materials comprising streambanks within a 5218 ha watershed in Iowa, USA. Streambank-face surveys, erosion pins, and soil analyses were used to quantify surface area representation, recession, and losses of sediment and TP over a two-year period. Cumulative, whole-bank gross mean recession totaled 18.6 cm over two years, and material-specific gross mean recession ranged from 15.5 to 64.1 cm. Cumulative, whole-bank mean gross mass losses totaled 0.28 Mg sediment and 0.7 × 10−5 Mg TP per meter channel length. Annual sediment losses equated to 4–44% of historic suspended sediment loads. Stratigraphy was significant in gross material erosion and losses, with lower materials (i.e., bank toe region) exhibiting the greatest recession rates and cumulative recession. Weathered/colluvial material dominated total bank face surface area (88.3%), and contributed the greatest proportion of sediment and TP mass loss (66, 68%, respectively) versus other streambank materials.

Double-stranded RNA (dsRNA) induces sequence-specific mRNA degradation in most eukaryotic organisms via a conserved pathway known as RNA interference (RNAi). Post-transcriptional gene silencing by RNAi is also connected with transcriptional silencing of cognate sequences. In plants, this transcriptional silencing is associated with sequence-specific DNA methylation. To address whether this mechanism operates in mammalian cells, we used bisulfite sequencing to analyze DNA in mouse oocytes constitutively expressing long dsRNA against the Mos gene. Our data show that long dsRNA induces efficient Mos mRNA knockdown but not CpG and non-CpG DNA methylation of the endogenous Mos sequence in oocytes and early embryos. These data demonstrate that dsRNA does not directly induce DNA methylation in the trans form of this sequence in these mammalian cells.

The restoration of riparian zones has been an important issue in many regions for the recovery of ecosystem functions. The objective of this study was to assess soil aggradation in a 7-year established riparian switchgrass buffer (SGB) and in a non-buffered riparian zone with an annual row crop (ARC). We measured the aggregate size distribution and stability of macroaggregates, aggregate-associated soil organic carbon, soil organic matter fractions and the chemical composition of light particulate organic matter to monitor soil aggregation in a riparian soil following the conversion of agricultural row crops to switchgrass filters. Aggregate size fractions were separated by wet sieving using the aggregate size-stability protocol. The proportion of soil and total organic C was quantified for each aggregate size class. Soil organic matter fractions were isolated by size and density into light particulate organic matter and heavy particulate organic matter and mineral fraction organic matter. The categorization of aggregates by size and water stability (slaking resistance) showed a significantly larger (p < 0.001) proportion of water-unstable large macroaggregates (>2000 µm) under SGB (34%) compared to that under ARC (29%), while the proportion of water-unstable small macroaggregates (250–2000 µm) was significantly higher under ARC (14%) than under SGB (10%). Our results showed that the amounts of light and heavy particulate organic matter did not change in the short-term (7 years) after SGB establishment. It appears that the lower soil stabilization and soil organic C storage under SGB is related to (i) the large number of coarse roots; (ii) lower inputs of light and heavy particulate organic matter; (iii) no changes in the alkyl-C/O-alkyl-C ratio over time; and (iv) light particulate organic matter with a high C/N ratio.

Removal of poly(A) tail is an important mechanism controlling eukaryotic mRNA turnover. The major eukaryotic deadenylase complex CCR4-NOT contains two deadenylase components, CCR4 and CAF1, for which mammalian CCR4 is encoded by Cnot6 or Cnot6l paralogs. We show that Cnot6l apparently supplies the majority of CCR4 in the maternal CCR4-NOT in mouse, hamster, and bovine oocytes. Deletion of Cnot6l yielded viable mice, but Cnot6l−/− females exhibited ∼40% smaller litter size. The main onset of the phenotype was post-zygotic: fertilized Cnot6l−/− eggs developed slower and arrested more frequently than Cnot6l+/− eggs, suggesting that maternal CNOT6L is necessary for accurate oocyte-to-embryo transition. Transcriptome analysis revealed major transcriptome changes in Cnot6l−/− ovulated eggs and one-cell zygotes. In contrast, minimal transcriptome changes in preovulatory Cnot6l−/− oocytes were consistent with reported Cnot6l mRNA dormancy. A minimal overlap between transcripts sensitive to decapping inhibition and Cnot6l loss suggests that decapping and CNOT6L-mediated deadenylation selectively target distinct subsets of mRNAs during oocyte-to-embryo transition in mouse.

Livestock grazing in the Midwestern United States can result in significant levels of runoff sediment and nutrient losses to surface water resources. Some of these contaminants can increase stream eutrophication and are suspected of contributing to hypoxic conditions in the Gulf of Mexico. This research quantified effects of livestock grazing management practices and vegetative filter strip buffers on runoff depth and mass losses of total solids, nitrate-nitrogen (NO3-N), and ortho-phosphorus (PO4-P) under natural hydrologic conditions. Runoff data were collected from 12 rainfall events during 2001 to 2003 at an Iowa State University research farm in central Iowa, United States. Three vegetative buffers (paddock area:vegetative buffer area ratios of 1:0.2, 1:0.1, and 1:0 no buffer [control]) and three grazing management practices (continuous, rotational, and no grazing [control]) comprised nine treatment combinations (vegetative buffer ratio/grazing management practice) replicated in three 1.35 ha (3.34 ac) plot areas. The total 4.05 ha (10.02 ac) study area also included nine 0.4 ha (1.0 ac) paddocks and 27 vegetative buffer runoff collection units distributed in a randomized complete block design. The study site was established on uneven terrain with a maximum of 15% slopes and consisted of approximately 100% cool-season smooth bromegrass. Average paddock and vegetative buffer plant tiller densities estimated during the 2003 project season were approximately 62 million and 93 million tillers ha−1 (153 million and 230 million tillers ac−1), respectively. Runoff sample collection pipe leakage discovered and corrected during 2001 possibly reduced runoff depth and affected runoff contaminant mass losses data values. Consequently, 2001 runoff analysis results were limited to treatment comparisons within the 2001 season and were not compared with 2002 and 2003 data. Analysis results from 2001 showed no significant differences in average losses of runoff, total solids, NO3-N, and PO4-P among the nine vegetative buffer/grazing practice treatment combinations. Results from 2002 indicated significantly higher losses of runoff and total solids from 1:0 no buffer/rotational grazing and 1:0 no buffer/continuous grazing treatment combination plots, respectively, compared among other 2002 season treatment combinations. The 2003 results showed significantly higher runoff and total solids losses from 1:0 no buffer/no grazing treatment combination plots compared among all 2003 treatment combinations and from 1:0.1 vegetative buffer/no grazing treatment combination plots compared among all 2003 treatment combinations and with respective 2002 treatment combinations. However, the 2003 results indicated effective vegetative buffer performance with significantly lower runoff, total solids, and NO3-N losses from the larger 1:0.2 buffer area compared among the smaller 1:0.1 buffer area and 1:0 no buffer treatment combinations. The 2003 results also indicated a highly significant increase in losses of NO3-N from 1:0.1 buffer/no grazing treatment combination plots compared among other 2003 season treatment combinations and with respective 2002 treatment combinations. Overall results from this study suggest a shift from significantly higher 2002 season plot losses of continuous and rotational grazing treatment combinations to significantly higher 2003 season losses of no grazing treatment combinations. We speculate this shift to significantly higher runoff and contaminant losses from no grazing treatment combination plots during 2003 reflects the variability inherent to a complex and dynamic soil-water environment of livestock grazing areas. However, we also hypothesize the environmental conditions that largely consisted of a dense perennial cool-season grass type, high-relief landscape, and relatively high total rainfall depth may not necessarily include livestock grazing activities.

Advanced maternal age is unequivocally associated with increased aneuploidy in human eggs and infertility, but the molecular basis for this phenomenon is unknown. An age-dependent deterioration of the spindle assembly checkpoint (SAC) has been proposed as a probable cause of aneuploidy. Accurate chromosome segregation depends on correct chromosome attachment to spindle microtubules, and the SAC provides time for this process by delaying anaphase onset until all chromosomes are stably attached. If SAC function decreases with age, oocytes from reproductively old mice would enter anaphase of meiosis I (AI) prematurely, leading to chromosome segregation errors and aneuploid eggs. Although intuitively appealing, this hypothesis is largely untested. We used a natural reproductive aging mouse model to determine if a defective SAC is the primary cause of aneuploidy in eggs. We tracked the progress of individual oocytes from young and old mice through meiosis I by time-lapse microscopy and counted chromosomes in the resulting eggs. This data set allowed us to correlate the timing of AI onset with aneuploidy in individual oocytes. We found that oocytes from old mice do not enter AI prematurely compared to young counterparts despite a 4-fold increase in the incidence of aneuploidy. Moreover, we did not observe a correlation between the timing of AI onset and aneuploidy in individual oocytes. When SAC function was challenged with a low concentration of the spindle toxin nocodazole, oocytes from both young and old mice arrested at meiosis I, which is indicative of a functional checkpoint. These findings indicate that a defective SAC is unlikely the primary cause of aneuploidy associated with maternal age.

The elevated incidence of aneuploidy in human oocytes warrants study of the molecular mechanisms regulating proper chromosome segregation. The Aurora kinases are a well-conserved family of serine/threonine kinases that are involved in proper chromosome segregation during mitosis and meiosis. Here we report the expression and localization of all three Aurora kinase homologs, AURKA, AURKB, and AURKC, during meiotic maturation of mouse oocytes. AURKA, the most abundantly expressed homolog, localizes to the spindle poles during meiosis I (MI) and meiosis II (MII), whereas AURKB is concentrated at kinetochores, specifically at metaphase of MI (Met I). The germ cell-specific homolog, AURKC, is found along the entire length of chromosomes during both meiotic divisions. Maturing oocytes in the presence of the small molecule pan-Aurora kinase inhibitor, ZM447439 results in defects in meiotic progression and chromosome alignment at both Met I and Met II. Over-expression of AURKB, but not AURKA or AURKC, rescues the chromosome alignment defect suggesting that AURKB is the primary Aurora kinase responsible for regulating chromosome dynamics during meiosis in mouse oocytes.

Subsurface lithology plays an important role in many riparian zone processes, but few studies have examined how sediment nutrient concentrations vary with depth. In this study, we evaluated concentrations of nutrients (N, C and P) with depth in a riparian zone of the glaciated Midwest. A total of 146 sediment samples were collected from 24 cores that extended to a maximum depth of 3.6 m at eight sites in the riparian zone of Walnut Creek. Subsurface deposits were predominantly silt loam, becoming coarser and more variable with depth. Nitrogen and carbon content ranged from

A nonapeptide Ac-His-Phe-Gly-Cys-D-Phe-Ser-Gly-Glu-Cys-NH2 (XI) cyclized through the cysteines at positions 4 and 9 is synthesized as a model active site for the enzyme alpha-chymotrypsin. A CPK model of XI indicates that the peptide will have a high probability of folding into a conformation in which the two beta-phenyls interact to form a hydrophobic site to one side of the cyclohexyl structure, and the Ser-His-Glu side chains form a hydrogen bonded triad over the plane of cyclopeptidyl structure. Substrates can then bind at the hydrophobic pocket formed by the beta-phenyls and be acted upon by the Ser-His-Glu catalytic triad, as in the enzyme. 1H. n.m.r. shows: (i) multiplet peaks for the phenyl protons in D2O that condense to a singlet in DMSO-d6, (ii) a perturbation of the phenyl protons chemical shift on proflavin association to XI, and (iii) perturbation of the His pKa to a higher value on association of proflavin to XI. These data support the existence of a hydrophobic site and a Glu-His interaction in the peptide. Furthermore, the greater than 10(2) better affinity of proflavin to XI than to AcTrp supports the existence of a hydrophobic site. However, no acceleration of p-nitrophenyl acetate or trans-cinnamoyl imidazole hydrolysis over that of imidazole is observed. The possible reasons for a lack of esterase activity in XI and other peptidyl models of serine protease active sites are discussed.

Phosphorus and sediment are major nonpoint source pollutants that degrade water quality. Streambank erosion can contribute a significant percentage of the phosphorus and sediment load in streams. Riparian land-uses can heavily influence streambank erosion. The objective of this study was to compare streambank erosion along reaches of row-cropped fields, continuous, rotational and intensive rotational grazed pastures, pastures where cattle were fenced out of the stream, grass filters and riparian forest buffers, in three physiographic regions of Iowa. Streambank erosion was measured by surveying the extent of severely eroding banks within each riparian land-use reach and randomly establishing pin plots on subsets of those eroding banks. Based on these measurements, streambank erosion rate, erosion activity, maximum pin plot erosion rate, percentage of streambank length with severely eroding banks, and soil and phosphorus losses per unit length of stream reach were compared among the riparian land-uses. Riparian forest buffers had the lowest streambank erosion rate (15-46 mm/year) and contributed the least soil (5-18 tonne/km/year) and phosphorus (2-6 kg/km/year) to stream channels. Riparian forest buffers were followed by grass filters (erosion rates 41-106 mm/year, soil losses 22-47 tonne/km/year, phosphorus losses 9-14 kg/km/year) and pastures where cattle were fenced out of the stream (erosion rates 22-58 mm/year, soil losses 6-61 tonne/km/year, phosphorus losses 3-34 kg/km/year). The streambank erosion rates for the continuous, rotational, and intensive rotational pastures were 101-171, 104-122, and 94-170 mm/year, respectively. The soil losses for the continuous, rotational, and intensive rotational pastures were 197-264, 94-266, and 124-153 tonne/km/year, respectively, while the phosphorus losses were 71-123, 37-122, and 66 kg/km/year, respectively. The only significant differences for these pasture practices were found among the percentage of severely eroding bank lengths with intensive rotational grazed pastures having the least compared to the continuous and rotational grazed pastures. Row-cropped fields had the highest streambank erosion rates (239 mm/year) and soil losses (304 tonne/km/year) and very high phosphorus losses (108 kg/km/year).

Inositol 1,4,5-trisphosphate generated by the action of a phospholipase C (PLC) mediates release of intracellular Ca2+ that is essential for sperm-induced activation of mammalian eggs. Much attention currently focuses on the role of sperm-derived PLCzeta in generating changes in egg intracellular Ca2+ despite the fact that PLCzeta constitutes a very small fraction of the total amount of PLC in a fertilized egg. Eggs express several isoforms of PLC, but a role for an egg-derived PLC in sperm-induced Ca2+ oscillations has not been examined. Reducing egg PLCbeta1 by a transgenic RNAi approach resulted in a significant decrease in Ca2+ transient amplitude, but not duration or frequency, following insemination. Furthermore, overexpressing PLCbeta1 by microinjecting a Plcb1 cRNA significantly perturbed the duration and frequency of Ca2+ transients and disrupted the characteristic shape of the first transient. These results provide the first evidence for a role of an egg-derived PLC acting in conjunction with a sperm-derived PLCzeta in egg activation.

Time-resolved infrared absorption spectroscopy is used to investigate the kinetics of the linkage isomerization reaction M(CO)5(η1-L) → M(CO)5(η2-L), where M = Cr, Mo, or W, and L = 2-methyl-2,3-dihydrofuran or 2,3-dihydropyran. Photolysis of M(CO)6 in cyclohexane in the presence of excess L produces the η1 (O-bound) isomer as the sole kinetic product. The kinetic product subsequently reacts intramolecularly to form an equilibrium mixture of the η1 and η2 (CC bound) isomers. Activation and equilibrium parameters are derived for the reactions and compared with previous results for linkage isomerization of the M(CO)5(dihydrofuran) complexes. The results of the experimental study, supported by DFT calculations, indicate that for M = W the kinetics of the η1 → η2 isomerization depend primarily on how close the double bond is to the metal atom in the η1 isomer, while the thermodynamics of the η1 ⇄ η2 equilibrium are determined primarily by electronic factors. In contrast, for M = Cr and Mo, both steric and ele...

Time-resolved step-scan Fourier transform infrared spectroscopy is used to observe, for the first time in room-temperature solution, the coordinatively unsaturated species Co(CO)4 and Co2(CO)7, the products of UV flash photolysis of Co2(CO)8. There appears to be minimal interaction between Co(CO)4 and the solvent, but significant solvation of ‘Co2(CO)7’. The Co2(CO)7:Co(CO)4 ratio depends very strongly on the photolysis wavelength: photolysis in n-heptane at 266 nm or 308 nm produces [Co2(CO)7] and [Co(CO)4] in a ratio of ∼2:1, but the ratio following 355 nm photolysis is ∼1:4. The wavelength dependence of the branching ratio is discussed in terms of the electronic spectrum of Co2(CO)8.

We report the design and discovery of a 2-aminobenzimidazole-based series of potent and highly selective p38alphainhibitors. The lead compound 1 had low-nanomolar activity in both ATP competitive enzyme binding and inhibition of TNFalpha release in macrophages. Compound 18 showed excellent pharmacokinetics properties and oral activity in the rat collagen induced arthritis model compared with other p38 reference compounds. A SAR strategy to address CyP3A4 liability is also described.

The transient species W(CO)5(CyH) (CyH = cyclohexane) is prepared by laser photolysis of a CyH solution of W(CO)6. Time-resolved infrared spectroscopy is used to probe the ligand substitution reactions of W(CO)5(CyH) with thiophene and tetrahydrothiophene (THT). From the temperature dependence of the second-order rate constants derived from the kinetic study, we obtain for reaction with thiophene ΔH⧧ = 5.7 ± 0.1 kcal mol-1 and ΔS⧧ = −11.2 ± 1.1 eu, while for reaction with THT, ΔH⧧ = 2.6 ± 0.1 kcal mol-1 and ΔS⧧ = −15.5 ± 0.8 eu. As expected, THT, the stronger electron donor, is the more reactive ligand of the two. THT is much more reactive than would be expected based on its strength as an electron donor, however. We show that the relative reactivities of O-, N-, and S-containing five-membered heterocycles toward ligand substitution at W(CO)5(CyH) can be accounted for by a model that takes into account the attacking ligand's polarizability in addition to its electron-donating ability.

The synthesis of novel aza-1,7-annulated indoles was achieved and these were converted to indolocarbazoles that proved to be potent kinase inhibitors. These compounds were also evaluated in a human colon carcinoma cell line and proved to be good antiproliferative agents.

The synthesis and kinase inhibitory activity of a series of novel 1,7-annulated indolocarbazoles 6 and 16 is described. These compounds exhibited potent inhibitory activity against cyclin-dependent kinase 4 and good antiproliferative activity in a human colon carcinoma cell line.

Substitution of the weakly-coordinated solvent molecule at a solvated transition-metal intermediate is frequently investigated by “fast kinetic” methods. In typical experiments, the kinetics of the reaction are determined by following the time dependence of the changes in the reaction mixture's UV-visible or infrared spectrum following photolytic creation of the intermediate. We consider the two limiting mechanisms (associative and dissociative), as well as the case of competition between them, and show that under typical “fast kinetics” experimental conditions, the different mechanisms are kinetically indistinguishable. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 427–433, 2004

Time-resolved IR absorption spectroscopy was used to investigate the photolysis of Vaska's Complex (VC), trans -(PPh 3 ) 2 Ir(CO)(Cl). Upon 308 nm photolysis, an intermediate was formed that regenerated VC on a millisecond timescale. This intermediate was not formed at the laser flash, but was generated over the course of ∼10 μs. Most unusually, there was no evidence for prompt bleach of the C–O stretch of VC upon photolysis. Evidence was presented that the intermediate from which regeneration of VC occurred was a dimeric species. Possible pathways for the generation of the dimeric intermediate are discussed.

A series of indolo[2,3-a]pyrrolo[3,4-c]carbazoles and their bis-indolylmaleimides precursors have been prepared in order to compare their activity as D1-CDK4 inhibitors. Both enzymatic and antiproliferative assays have shown that the structurally more constrained indolo[2,3-a]pyrrolo[3,4-c]carbazoles are consistently more active (8-42-fold) in head-to-head comparison with their bis-indolylmaleimides counterparts. Cell-cycle analysis using flow cytometry have also shown that the indolocarbazoles are selective G1 blockers while the bis-indolylmaleimides arrest cells in the G2/M phase.

The synthesis of new analogues of Arcyriaflavin A in which one indole ring is replaced by an aryl or heteroaryl ring is described. These new series of aryl[a]pyrrolo[3,4-c]carbazoles were evaluated as inhibitors of Cyclin D1-CDK4. A potent and selective D1-CDK4 inhibitor, 7a (D1-CDK4 IC(50)=45 nM), has been identified. The potency, selectivity profile against other kinases, and structure-activity relationship (SAR) trends of this class of compounds are discussed.

Cryptophycin 52 is a synthetic derivative of Cryptophycin 1, a potent antimicrotubule agent isolated from cyanobacteria. In an effort to increase the potency and water solubility of the molecule, a structure-activity relationship study (SAR) was initiated around the phenyl ring of fragment A. These Cryptophycin 52 analogues were accessed using a Wittig olefination reaction between various triphenylphosphonium salts and a key intermediate aldehyde prepared from Cryptophycin 53. Substitution on the phenyl ring of fragment A was well tolerated, and several of these analogues were equally or more potent than Cryptophycin 52 when evaluated in vitro in the CCRF-CEM leukemia cell line and in vivo against a murine pancreatic adenocarcinoma.

Time-resolved infrared spectroscopy is used to examine the reactions of the transient intermediate W(CO) 5 (CyH) (CyH = cyclohexane), formed by photolysis of a cyclohexane solution of W(CO) 6 , with L = pyrrole and pyrrolidine. Time- and temperature-dependent rate constants for the ligand substitution reaction to form W(CO) 5 (L) are determined. These reactions appear to go through an associative interchange mechanism. Eyring activation parameters for the ligand exchange are derived. For L = pyrrolidine, ΔH = 1.8 ′ 0.1 kcal mol - 1 and ΔS = -18.9 ′ 0.4 eu; for L = pyrrole, ΔH = 5.1 ′ 0.2 kcal mol - 1 and ΔS = -11.6 ′ 1.2 eu. Most unusually, the observed pseudo-first-order rate constant for reaction with pyrrole is not a linear function of pyrrole concentration. This deviation from simple first-order behavior is explained in terms of association of pyrrole in solution to form dimers and higher clusters that lower the ligand's effective concentration. The enthalpy of dimerization of pyrrole is estimated from the kinetic data to be approximately 4 kcal mol - 1 . The results of reaction of W(CO) 5 (CyH) with pyrrole and pyrrolidine are discussed in terms of the behavior of this intermediate with other ligands.

A novel series of pyrrolo[3,4-c] carbazoles fused with a quinolinyl/isoquinolinyl moiety were synthesized and their D1/CDK4 inhibitory and antiproliferative activity were evaluated. Compound 8H, 14H-isoquinolinyl[6,5-a]-pyrrolo[3,4-c]carbazole-7,9-dione (1d) was found to be a highly potent D1/CDK4 inhibitor with an IC50 of 69 nM. Compound 1d also inhibited tumor cell growth, arrested tumor cells in G1 phase and inhibited pRb phosphorylation.

Photolysis of a cyclohexane (CyH) solution of M(CO)6 (M = Cr, Mo, W) in the presence of excess 2,3- or 2,5-dihydrofuran (DHF) yields the complex M(CO)5(DHF). The solvated complex M(CO)5(CyH) formed...

In this study, butyrolactone I (BL I), a potent and specific inhibitor of cyclin-depen- dent kinases (cdk), is shown to inhibit germinal vesicle breakdown (GVBD) in pig oocytes. Oocytes treated with 100 mM BL I were arrested in the germinal vesicle (GV)-stage and displayed low activity of cdc2 kinase and MAP kinase. Nevertheless, chromosome conden- sation occurred and highly condensed bivalents were seen within an intact GV after a 24-hr culture in the presence of BL I. The inhibitory effect of BL I on MAP kinase activation during culture was likely mediated through a cdk-dependent pathway, since MAP kinase activity present in extracts derived from metaphase II eggs was not inhibited by BL I. The block of GVBD could be released by treating oocytes with okadaic acid (OA), an inhibitor of type 1 and 2A phosphatases; 82% of the oocytes treated with the combination of OA/BL I underwent GVBD, and MAP kinase became activated, while cdc2 kinase remained inhibited. These results suggest that both chromosome condensation and GVBD could occur without activation of cdc2 kinase, whereas an increase in MAP kinase activity may be a requisite for GVBD in pig oocytes in conditions when cdc2 kinase activation is blocked by BL I. Mol. Reprod. Dev. 63: 110-118, 2002. 2002 Wiley-Liss, Inc.

The signaling connection between mitogen-activated protein kinases(MAPKs) and nuclear steroid receptors is complex and remains mostly unexplored. Here we report that stress-activated protein kinases p38 and JNK trans-activate nuclear steroid vitamin D receptor (VDR) gene and increase vitamin D(3)-dependent growth inhibition in human breast cancer cells. Activation of p38 and JNK by an active MAPK kinase 6 stimulates VDR promoter activity independently of the ligand vitamin D(3) and estrogen receptor expression. Moreover, stimulation of the endogenous stress pathways by adenovirus-mediated delivery of recombinant MAPK kinase 6 also activates VDR and sensitizes MCF-7 cells to vitamin D(3)-dependent growth inhibition. Both the p38 and JNK MAPK pathways and the downstream transcription factor c-Jun/AP-1 are required for the VDR stimulation, as revealed by application of their dominant negatives, the specific p38 inhibitor SB203580, and site-directed mutagenesis of the AP-1 element in the VDR promoter. The essential role of the p38 and JNK stress pathways in up-regulation of VDR expression is further confirmed by using the chemical stimulator arsenite. These results establish a signaling connection between the stress MAPK pathways and steroid hormone receptor VDR expression and thereby offer new insights into regulation of cell growth by the MAPK pathways through regulation of vitamin D(3)/VDR activity.

Time-resolved infrared absorption spectroscopy is used to study the reactions of the solvated transient intermediate W(CO)5(cyclohexane) with the molecules (L) 2-methyltetrahydrofuran (MeTHF), 2,5-dimethyltetrahydrofuran (Me2THF), 2-methylfuran (MeFur), and 2,5-dimethylfuran (Me2Fur). In all four cases, the only reaction observed on the microsecond to millisecond time scale is substitution of the cyclohexane molecule to form W(CO)5(L). From the temperature dependence of the reaction rate constant, measured over the range 15−60 °C, we determine the following activation parameters: for L = MeTHF, ΔH⧧ = 4.0 ± 0.3 kcal mol-1, ΔS⧧ = −14.1 ± 1.0 eu; for L = Me2THF, ΔH⧧ = 4.3 ± 0.3 kcal mol-1, ΔS⧧ = −14.8 ± 1.2 eu; for L = MeFur, ΔH⧧ = 6.0 ± 0.2 kcal mol-1, ΔS⧧ = −10.2 ± 1.2 eu; and for L = Me2Fur, ΔH⧧ = 6.3 ± 0.4 kcal mol-1, ΔS⧧ = −9.8 ± 1.0 eu. We find that the relative rates of reaction of MeTHF and Me2THF can be explained solely in terms of a steric effect, while for MeFur and Me2Fur, the inductive effect o...

Superimposed on the activation of the embryonic genome in the preimplantation mouse embryo is the formation of a transcriptionally repressive state during the two-cell stage. This repression appears mediated at the level of chromatin structure, because it is reversed by inducing histone hyperacetylation or inhibiting the second round of DNA replication. We report that of more than 200 amplicons analyzed by mRNA differential display, about 45% of them are repressed between the two-cell and four-cell stages. This repression is scored as either a decrease in amplicon expression that occurs between the two-cell and four-cell stages or on the ability of either trichostatin A (an inhibitor of histone deacetylases) or aphidicolin (an inhibitor of replicative DNA polymerases) to increase the level of amplicon expression. Results of this study also indicate that about 16% of the amplicons analyzed likely are novel genes whose sequence doesn't correspond to sequences in the current databases, whereas about 20% of the sequences expressed during this transition likely are repetitive sequences. Lastly, inducing histone hyperacetylation in the two-cell embryos inhibits cleavage to the four-cell stage. These results suggest that genome activation is global and relatively promiscuous and that a function of the transcriptionally repressive state is to dictate the appropriate profile of gene expression that is compatible with further development.

Bcl-2 has been described as a factor that can protect from apoptosis. The protective effect of Bcl-2 may be lost if the protein is phosphorylated. Bcl-2 phosphorylation can be induced by agents that affect microtubule depolymerization or prevent microtubule assembly. In 13 human tumor cell lines there was a high degree of heterogeneity in Bcl-2 protein expression. Human H460 non-small-cell lung carcinoma (NSCLC) cells expressed high levels of Bcl-2 and were selected for study. Western blot analysis for Bcl-2 phosphorylation was carried out after 4 h and 24 h of exposure to cryptophycin 52, cryptophycin 55, paclitaxel or vinblastine. Cryptophycin 52 and cryptophycin 55 were very potent inducers of Bcl-2 phosphorylation. After 4 h of exposure, Bcl-2 phosphorylation was evident with 0.05 nM cryptophycin 52, 0.25 nM cryptophycin 55, 5 nM vinblastine and 50 nM paclitaxel. The hyperphosphorylated form of Bcl-2 was evident after 24 h exposure of H460 cells to 0.25 nM cryptophycin 52 or cryptophycin 55 and 50 nM vinblastine or paclitaxel. The effects of the compounds on the cell cycle paralleled those on Bcl-2 phosphorylation. In H460 cells 90% cell killing was obtained with 0.13 nM cryptophycin 52, 0.2 nM cryptophycin 55, 20 nM paclitaxel and > 100 nM vinblastine after 24 h of exposure as determined by colony formation. In Bcl-2-negative Calu-6 NSCLC cells, 90% cell killing was obtained with 0.03 nM cryptophycin 52, 0.1 nM cryptophycin 55, 11 nM paclitaxel and 0.5 nM vinblastine using the same experimental design. Thus, cryptophycins are potent inducers of Bcl-2 phosphorylation. The cryptophycins were more potent cytotoxic agents in Bcl-2-negative Calu-6 cells than in Bcl-2-positive H460 cells indicating that pathways triggered by Bcl-2 phosphorylation are involved in cryptophycin-induced lethality.

A study was conducted to evaluate the ability of a multispecies riparian buffer (MRB) to remove sediment, nitrogen, and phosphorus from cropland runoff. Simulated rainfall was applied to 4.1- by 22.1-m bare cropland source areas paired with either no buffer, a 7.1-m-wide switchgrass (Panicum virgatum L. cv. Cave-n-Rock) buffer, or a 16.3-m-wide switchgrass-woody plant buffer. Each treatment plot combination had three replicates. The switchgrass buffer trapped 70% of the incoming sediment, while the switchgrass-woody buffer trapped more than 92%. In general, these buffers retained 93% of sand and silt particles and 52% of clay particles. During a 2-h rainfall simulation at 25 mm h -1 , the switchgrass buffer removed 64, 61, 72, and 44% of the incoming total N, NO 3 -N, total P, and PO 4 -P, respectively. The switchgrass-woody buffer removed 80, 92, 93, and 85% of the incoming total N, NO 3 -N, total P, and PO 4 -P, respectively. During a 1-h rainfall simulation at 69 mm h -1 , the switchgrass buffer removed 50, 41, 46, and 28% of the incoming total N, NO 3 -N, total P, and PO 4 -P, respectively. The switchgrass-woody plant buffer removed 73, 68, 81, and 35% of the incoming total N, NO 3 -N, total P, and PO 4 -P, respectively. The switchgrass buffer was effective in trapping coarse sediment and sediment-bound nutrients. But the additional buffer width with high infiltration capacity provided by the deep-rooted woody plant zone was effective in trapping the clay and soluble nutrients.

Time- and temperature-resolved infrared absorption spectroscopy is used to probe the reaction of THF with W(CO)5(solv) (solv = cyclohexane, cyclohexane-d12) to form W(CO)5(THF). In cyclohexane-d0, ΔH⧧ for the reaction is determined to be 3.6 ± 0.2 kcal mol-1 (15.2 ± 0.9 kJ mol-1) and ΔS⧧ = −13.7 ± 2.5 eu (−57.3 ± 10.5 J mol-1 K-1). In cyclohexane-d12, ΔH⧧ = 2.4 ± 0.6 kcal mol-1 (10.2 ± 2.5 kJ mol-1) and ΔS⧧ = −18.3 ± 3.5 eu (−76.6 ± 14.6 J mol-1 K-1). The low activation enthalpy in comparison to the (CO)5W−cyclohexane bond dissociation energy, the negative entropy of activation, and comparison with other spectroscopic experiments involving reactions of W(CO)5(cyclohexane) indicate that the reaction proceeds by an associative interchange reaction mechanism. An unusual isotope effect, in which reaction proceeds more slowly in cyclohexane-d12 even though ΔH⧧ is lower, is explained in terms of relative populations of low-frequency vibrations and the relative C−H and C−D bond strengths in the solvent molecule ...

A general synthetic approach to novel cryptophycin analogues 6 is described. N-Hydroxysuccinimide active ester 15, a key common intermediate, was converted to beta-epoxide 6 in three steps, via initial coupling with unprotected amino acid 9, followed by deprotection/macrolactamization of acyclic precursor 16, and final oxidation of styrene 7 to install the C7-C8 beta-epoxide. Cryptophycin styrenes 7 and beta-epoxides 6, bearing diverse side chains in fragment "B", were evaluated for cytotoxic activity. beta-Epoxides 6, in general, were significantly more potent than the corresponding alpha-epoxides 17 and styrenes 7. A benzyl side chain was required for potent activity, with beta-epoxide 6u, possessing a 3-Cl,4-(dimethylamino)benzyl moiety, as the most potent cytotoxic agent prepared, with an IC(50) = 54 pM, only 2-fold less than that of Cryptophycin-52 (3).

Temporal and spatial distribution of the sites of DNA replication were examined in 1-cell mouse embryos. Embryos were labelled with bromodeoxyuridine (BrdU) at hourly intervals after fertilisation, and the incorporation of BrdU was examined by laser-scanning confocal microscopy following immunostaining with an anti-BrdU antibody. DNA replication first started uniformly in both the male and female pronuclei in the intranuclear region and then was observed in the peripheral regions of nucleus and nucleolus. These changes, however, occurred asynchronously in that the female pronucleus required a longer time to complete replication in the intranuclear region but not in the peripheral regions. Inhibiting transcription with α-amanitin had no effect on the temporal and spatial patterns of DNA replication. Treatment of the embryos with trapoxin, a specific inhibitor of histone deacetylase, accelerated the completion of replication in the peripheral regions but not in the intranuclear region. These results suggest that DNA replication is temporally and spatially regulated in the 1-cell embryos and that acetylation of histones, but not transcription, is involved in the regulation of DNA replication.

Ras activates a multitude of downstream activities with roles in cellular proliferation, invasion and metastasis, differentiation, and programmed cell death. In this work we have evaluated the requirement of extracellular signal-regulated protein kinase (ERK), c-Jun NH2-terminal kinase kinase (JNKK), and c-Jun/AP-1 activities in transformation and extracellular matrix invasion of ras oncogene expressing NIH 3T3 fibroblasts by expressing stable mutant genes that constitutively inhibit these activities. Whereas the inhibition of ERK activity reverts the transformed and invasive phenotype, the inhibition of the JNK pathway and AP-1 trans-activating activities by JNKK[K129R] and c-Jun(TAM67) had no effect on the ability of the ras oncogene-expressing cells to grow in soft agar or invade Matrigel basement membrane. Thus an elevated JNK activity and/or c-Jun/AP-1 trans-activating activity are not absolute requirements for ras transformation or invasion through basement membrane, and the dependence on AP-1 activity for transformation is cell-specific. However, inhibition of JNK kinase (JNKK) in ras-transformed cells with normally elevated JNK activity switches the protease-dependent invasive phenotype from a urokinase plasminogen activator (uPA)-dependent to a cathepsin L (CL)-dependent invasive phenotype. Conversely, treatment of ras-transformed cells of low constitutive JNK activity with the JNK stimulator, anisomycin, converts the protease mRNA levels from those characteristic of a CL-dependent to a uPA-dependent phenotype. These protease phenotypes can be duplicated in untransformed NIH 3T3 cells that express platelet-derived growth factor receptors and m1 muscarinic receptors that selectively stimulate the ERK or JNK pathways, respectively. It is concluded that high ERK activity is required for both protease phenotypes, whereas the JNK pathway and c-Jun/AP-1 activity are not required for transformation but regulate a switch between uPA and CL protease phenotypes in both transformed and untransformed cells. In ras-transformed NIH 3T3 fibroblasts, the uPA- and CL-dependent protease phenotypes are redundant in their ability to invade through basement membrane.

Structure modification of the beta-alanine region (fragment C) of the potent antimitotic agent cryptophycin was investigated. This includes: (1) introduction of substituents at the previously unsubstituted C7 position of the macrolide ring and (2) replacement of the (2R)-3-amino-2-methyl-propanoic acid (beta-alanine) with various (1)-amino acids to give the corresponding 15-membered unnatural cryptophycin analogs.

Exocytosis of cortical granules in mouse eggs is required to produce the zona pellucida block to polyspermy. In this study, we examined the role of microfilaments and microtubules in the regulation of cortical granule movement toward the cortex during oocyte maturation and anchoring of cortical granules in the cortex. Fluorescently labeled cortical granules, microfilaments, and microtubules were visualized using laser-scanning confocal microscopy. It was observed that cortical granules migrate to the periphery of the oocyte during oocyte maturation. This movement is blocked by the treatment of oocytes with cytochalasin D, an inhibitor of microfilament polymerization, but not with nocodazole or colchicine, inhibitors of microtubule polymerization. Cortical granules, once anchored at the cortex, remained in the cortex following treatment of metaphase II-arrested eggs with each of these inhibitors; i.e., there was neither inward movement nor precocious exocytosis. Finally, the single cortical granule-free domain that normally becomes localized over the metaphase II spindle was not observed when the chromosomes become scattered following microtubule disruption with nocodazole or colchicine. In these instances a cortical granule-free domain was observed over each individual chromosome, suggesting that the chromosome or chromosome-associated material, and not the spindle, dictates the localization of the cortical granule-free domain.

Extensive biochemical and pharmacological evidence indicates that LY231514 is a novel antifolate antimetabolite. LY231514 is transported into cells mainly through the reduced folate carrier system and extensively metabolized to polyglutamated forms. The polyglutamates of LY231514 inhibit at least three key folate enzymes: TS, DHFR, and GARFT, and to a lesser extent AICARFT and C1-tetrahydrofolate synthase. The combined effects of the inhibition exerted by LY231514 at each target give rise to an unusual end-product reversal pattern at the cellular level that is distinct from those of other inhibitors such as methotrexate and the quinazoline antifolates. The metabolic effects exerted by LY231514 on the folate and nucleotide pools are also quite distinct from those of MTX and LY309887. The efficient polyglutamation, longer cellular retention and the multiple folate enzyme inhibition mechanism may all have contributed directly to the exciting antitumor responses now observed in Phase I and II studies. The multitargeted inhibition mechanism of LY231514 is particularly intriguing. This new level of mechanistic insight, which has evolved from the study of LY231514, challenges the traditional concept and paradigm of antifolate drug discovery and development which focused on developing very potent and selective inhibitors of single folate enzyme targets, such as DHFR, TS or one of the enzymes along the de novo purine biosynthetic pathway. Given the complex nature of folate metabolism and the critical role of folates in maintaining the physiological functions of living systems, it is completely reasonable to suspect that agents which can interfere at multiple sites in the folate pathway may trigger and cause more biochemical imbalance in the cellular DNA and RNA synthesis of malignant cells than agents that act on a single point (Fig. 5). In conclusion, LY231514 (MTA) is a new generation antifolate antimetabolite demonstrating inhibitory activity against multiple folate enzymes including TS, DHFR and GARFT. In current phase II studies, MTA is broadly active as a single agent and is showing very encouraging antitumor activity in multiple solid tumors including colorectal, breast and non-small cell lung cancers (38-43). The every three week dosing schedule has proven to be convenient and easy to administer and the clinical toxicities of LY231514 seem to be well tolerated. More advanced and extensive clinical trials of LY231514 are currently in progress.

A multispecies riparian buffer strip (MRB) was established along Bear Creek in central Iowa by the Agroecology Issues Team at Iowa State University (ISU) in order to assess the ability of the MRB to positively impact soil erosion and process non-point source pollutants to improve water quality. Soil organic matter (SOM), and especially biologically-active soil organic matter, is considered to be an important soil quality indicator variable because of it has relationship to critical soil functions like erodibility and the capacity of the soil to act as an environmental buffer. The objectives of this study were to examine trends in SOM C accrual and to quantify intra-seasonal changes in SOM C and particulate organic matter (POM) C for each vegetation zone of a MRBS seven years after establishment on previously cultivated or heavily grazed soil. Total SOM C and POM C in soil under perennial vegetation (poplar, switch- grass and cool season grass) were significantly higher than under cropped soil. Total POM C changed within vegetation type over the four month study period, whereas total SOM C did not. After six growing seasons, SOM C increased 8.5% under poplar grown in association with cool season grass, and 8.6% under switchgrass. The results are very promising and suggest that changes in SOM C can occur in a relatively short time after the establishment of perennial vegetation in a MRB. These changes should increase the ability of MRB soil to process non- point source pollutants.

By influencing belowground processes, streamside vegetation affects soil processes important to surface water quality. We conducted this study to compare root distributions and dynamics, and total soil respiration among six sites comprising an agricultural buffer system: poplar (Populus × euroamericana‘ Eugenei), switchgrass, cool-season pasture grasses, corn (Zea mays L.), and soybean (Glycine max (L.) Merr.). The dynamics of fine (0--2 mm) and small roots (2--5 mm) were assessed by sequentially collecting 35 cm deep, 5.4 cm diameter cores from April through November. Coarse roots were described by excavating 1 × 1 × 2 m pits and collecting all roots in 20 cm depth increments. Root distributions within the soil profile were determined by counting roots that intersected the walls of the excavated pits. Soil respiration was measured monthly from July to October using the soda-lime technique. Over the sampling period, live fine-root biomass in the top 35 cm of soil averaged over 6 Mg ha-1 for the cool-season grass, poplar, and switchgrass sites while root biomass in the crop fields was < 2.3 Mg ha-1 at its maximum. Roots of trees, cool-season grasses, and switchgrass extended to more than 1.5 m in depth, with switchgrass roots being more widely distributed in deeper horizons. Root density was significantly greater under switchgrass and cool-season grasses than under corn or soybean. Soil respiration rates, which ranged from 1.4--7.2 g C m-2 day-1, were up to twice as high under the poplar, switchgrass and cool-season grasses as in the cropped fields. Abundant fine roots, deep rooting depths, and high soil respiration rates in the multispecies riparian buffer zones suggest that these buffer systems added more organic matter to the soil profile, and therefore provided better conditions for nutrient sequestration within the riparian buffers.

A practical, total synthesis of seco-(+)-oxaduocarmycin 3a, an analogue of the highly cytotoxic natural product, duocarmycin SA (1), is described. The 13-step synthesis features a novel and efficient intramolecular aryl radical cyclization onto a vinyl chloride as a direct entry to the (chloromethyl)indoline alkylating subunit 14. Subsequent resolution, utilizing a preparative Chiralpak AD column, provided enantiomerically pure alkylating subunits 14a and 14b which were elaborated to seco-(+) and ent-(−)-oxaduocarmycins, 3a and 3b, respectively. The natural enantiomer 3a was active at pM concentrations and exhibited 7−50-fold higher potentcy than its enantiomer 3b in in vitro cytotoxicity assays.

With increasing time after ovulation, mammalian eggs become more sensitive to agonists of activation in vitro or may undergo spontaneous activation in vivo. We have tested the hypothesis that postovulatory eggs undergo time-dependent cell cycle and cytoplasmic changes that result in a partially activated state, accounting for their time-dependent susceptibility to activate. In vivo changes in key activation markers in mouse eggs were quantified at 13, 16, and 22 h post-hCG (1, 4, and 10 h postovulation). Spontaneous activation was first detected at 16 h, with a 20-25% decrease in the activities of histone H1 and mitogen-activated protein (MAP) kinases and with 3% of eggs undergoing both anaphase onset and a partial loss of cortical granules. By 22 h, more than 60% of eggs were in anaphase, H1 and MAP kinase activities had decreased 40-50%, the extent of zona pellucida modification had increased, and proteins normally synthesized after fertilization had appeared. Pronuclear formation in response to inositol 1,4,5-trisphosphate injection increased dramatically from 10% at 13 h to about 40% and 90% at 16 h and 22 h, respectively. The partial decreases (less than those after fertilization) in H1 and MAP kinase activities provide a likely biochemical basis for the increased sensitivity of eggs to agonists, seen over time, that results in pronuclear formation. Also, all of these time-dependent changes caution against the use of mouse eggs > 16 h after hCG administration in studying the mechanism of normal fertilization and have implications for animal and human in vitro fertilization.