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Tropopause‐penetrating convection is a frequent seasonal feature of the Central United States climate. This convection presents the potential for consistent transport of water vapor into the upper troposphere and lower stratosphere (UTLS) through the lofting of ice, which then sublimates. Water vapor enhancements associated with convective ice lofting have been observed in both in situ and satellite measurements. These water vapor enhancements can increase the probability of sulfate aerosol‐catalyzed heterogeneous reactions that convert reservoir chlorine (HCl and ClONO2) to free radical chlorine (Cl and ClO) that leads to catalytic ozone loss. In addition to water vapor transport, lofted ice may also scavenge nitric acid and further impact the chlorine activation chemistry of the UTLS. We present a photochemical model that resolves the vertical chemical structure of the UTLS to explore the effect of water vapor enhancements and potential additional nitric acid removal. The model is used to define the response of stratospheric column ozone to the range of convective water vapor transported and the temperature variability of the lower stratosphere currently observed over the Central United States in conjunction with potential nitric acid removal and to scenarios of elevated sulfate aerosol surface area density representative of possible future volcanic eruptions or solar radiation management. We find that the effect of HNO3removal is dependent on the magnitude of nitric acid removal and has the greatest potential to increase chlorine activation and ozone loss under UTLS conditions that weakly favor the chlorine activation heterogeneous reactions by reducing NOxsources. Some summertime storms in the Central United States are strong enough to transport water uniquely deep into the atmosphere and up into the normally very dry stratosphere, which houses the ozone layer. Moistening the stratosphere changes its chemical balance. The additional moisture results in the transformation of normally inert halogen compounds, including chlorine and bromine, into chemically highly reactive forms that destroy ozone. This activation of inert halogen compounds and ozone loss is dependent on the amount of water added to the stratosphere and the temperature of the stratosphere. Not every storm that transports water into the stratosphere will result in halogen activation and ozone loss, only those that transport significant amounts of water and/or those that overlap with the coldest parts of the stratosphere. The influence of storms on the chemistry of the stratosphere, however, may not be limited to only water. Nitric acid, which plays a role in slowing the activation of inert halogen compounds, may also be removed. We simulate the chemical effects of a range of potential nitric acid removal in conjunction with moistening of the stratosphere. We find that nitric acid removal has the potential to most exacerbate halogen compound activation and ozone loss when the moistening would normally only have mild effects on the stratosphere. Should nitric acid removal be a common occurrence during these stratosphere‐moistening storms, the fraction of storms that can lead to halogen activation and ozone loss is larger than previously thought. Photochemical box model defines the vertically resolved response of the stratosphere chemical composition to convective perturbationEffect of nitric acid removal on column ozone loss is dependent on favorability of initial conditions to heterogeneous chlorine activationNitric acid removal has the most impact on column ozone loss under conditions of mild favorability to chlorine activation

Presents several letters to the editor referencing articles and topics discussed in previous issues. Comments on the state of education in the U.S.; Discussion on European University; Comments on the Geneva award.

Presents several letters to the editor regarding various issue and articles published in previous issues of the journal. Criticism of influence of the Liberal party in Virginia; Refusal for building agnostic churches; Difficulties faced in implementing discipline in colleges in the U.S.

Slickspot soils are saline, and knowledge of their humic chemistry would contribute to our limited understanding how salinity affects soil C and N stocks. We characterized humic acids (HA) from slickspot soils with solid-state 13C nuclear magnetic resonance (NMR). Expanding on previous use of cross polarization/magic angle spinning (CP/MAS) NMR, we used direct polarization (DP) and yet more advanced spectral editing techniques to identify specific functional groups, detect the connectivities of different functional groups, and selectively observe fused ring carbons. A series of soil HA was extracted from soil layers having different physical properties silt texture, vesicular structure, and clay texture. They were compared with HA from corresponding depths in soils adjacent to the slickspots. All HA consisted of five main structural components aliphatic chains, peptides, sugar rings, lignin residues, and aromatics/olefinics. For all soils, except one outside slickspots, the HA from the vesicular and clay layers contained less nonpolar alkyls and more aromatics than those from surface silt layers, but their spectral proportions differed when the 13C NMR was performed using CP/MAS instead of DP. Humic acids from the surface layers inside the slickspots had lower aromaticity than those from outside the slickspots. Advanced spectral editing techniques allowed for the selection of nonprotonated carbons and mobile groups, alkyls, CH, and CH2groups, which would otherwise be buried in the heavily overlapped spectrum. They provided more structural information than was obtained by routine 13C CP/MAS or DP.

Slickspot peppergrass (Lepidium papilliferum) is a biennial, or possibly perennial, endemic plant growing in the Southern Idaho high desert in visually distinct small-scale depressions in soils that collect water (so-called slickspots). Lepidium papilliferumestablishes seed banks not germinating the first year but remaining dormant and viable for several years. Humic acids (HA) are universally considered to be the most important, abundant, and biologically and chemically active fractions of soil organic matter and are known to affect plant growth by various mechanisms, depending on their origin, nature, and concentration. The effects of HA in slickspot soils and how they relate to the possibility of being a factor in restoring native plants is only partially known. Thus, the objective of this study was to identify and evaluate the effects of HA isolated from three different layers within the soil profile (silt, vesicular, and clay) from inside a representative slickspot on the germination and early growth of slickspot peppergrass. Furthermore, these effects were tentatively related to the chemical, physicochemical, compositional, structural, and functional characteristics of the HA. Results of statistical analysis showed that both the type and concentration of the three HA examined exert a highly significant or significant effect on the germination and early growth of slickspot peppergrass as a function of the soil depth from which the HA originated in the slickspot. In particular, germination seemed to be enhanced, especially at higher concentrations, by the less hydrophobic HA, rich in oxygen and total sugars, present in the bottom clay soil layer, whereas root growth and shoot growth were positively influenced by the more hydrophobic and probably more polycondensed HA, rich in C, H, N, and phenolic OH present in the top layer rich in silt.

The use of organic residues as soil additives is increasing, but, depending on their composition and application methods, these organic amendments can stimulate the emissions of CO2and N2O. The objective of this study was to quantify the effects of management practices in irrigated sweet corn (Zea maysL.) on CO2and N2O emissions and to relate emissions to environmental factors. In a 3‐yr study, corn residues (CR) and pasteurized chicken manure (PCM) were used as soil amendments compared with no residue (NR) under three management practices: shallow tillage (ST) and no tillage (NT) under consecutive corn crops and ST without crop. Tillage significantly increased (P< 0.05) CO2and N2O fluxes in residue‐amended plots and in NR plots. Carbon dioxide and N2O fluxes were correlated with soil NH4concentrations and with days since tillage and days since seeding. Fluxes of CO2were correlated with soil water content, whereas N2O fluxes had higher correlation with air temperature. Annual CO2emissions were higher with PCM than with CR and NR (9.7, 2.9, and 2.3 Mg C ha−1, respectively). Fluxes of N2O were 34.4, 0.94, and 0.77 kg N ha−1yr−1with PCM, CR, and NR, respectively. Annual amounts of CO2–C and N2O–N emissions from the PCM treatments were 64 and 3% of the applied C and N, respectively. Regardless of cultivation practices, elevated N2O emissions were recorded in the PCM treatment. These emissions could negate some of the beneficial effects of PCM on soil properties.

Naturally occurring humic substances in soils hold promise as a factor related to restoring native plants. We have characterized the humic acids (HA) from inside and outside slickspots of two sites in the Juniper Butte Range soils on the Snake River Plain in Southwest Idaho. These HA may promote the establishment of native slickspot peppergrass (Lepidium papilliferum) seedlings. The HA were extracted from the silt, vesicular, and clay layers using a modified International Humic Substances Society method, and isolated by membrane filtration, precipitation, dialysis, and freeze-drying. Elemental analyses showed minor differences between HA; the inside surface silt samples had higher C and N values than the outside or the deeper samples. Differences were also noted between sample sites and between the samples for carbohydrates, amino acids, and acidity functionalities. Fourier transform infrared and fluorescence, and especially cross-polarization magic angle spinning 13C-nuclear magnetic resonance spectroscopies, provided compositional information and highlighted differences between the samples.

Organic matter (OM)-based amendments offered to farmers vary greatly in their source, properties, and effectiveness. Some of these are produced from natural organic resources, whereas others originate from recycled organic waste, in part as an environment-friendly low-cost alternative to waste disposal. Stimulatory effects of OM on plant growth have been noticed in many systems, but a few reports have indicated negative effects. Many factors and interactions dictate plant response to these materials, and not all are well understood. Procedures that can be used to evaluate OM composition and characteristics that might affect plant growth are complicated and expensive. Deleterious effects of OM additions are frequently associated with a nonmature status of the decomposing material, but maturity is difficult to define. Evaluation of humic substances (HS)-based products is even more complex and needs improvement of the available methodologies. This article presents two simple versatile bioassay methods carried out in microplates or pouches for screening and evaluating soluble organic products for agronomic and horticultural use. To illustrate the two methods, we present microplate experiments with creeping bentgrass (Agrostis palustrisHuds.) that provide an evaluation of plant response to N rates spanning from deficient to excessive levels (0.9-57.6 mg N L−1) and to 11 different soluble HS products. The pouch method is presented by soybean (Glycine maxL.) and corn (Zea maysL.) experiments that evaluate plant response to two HS and determine whether it is related to Fe or Zn mediation by the tested substances. The two methods are shown to be sensitive for nutritional factors and could effectively rank various OM materials frombeing deleterious to stimulatory to plant growth.

The 13C natural abundance approach for determining soil organic C (SOC) stability and turnover has been used to determine SOC mineralization kinetics. These calculations generally assume that 13C fractionation during relic SOC and unharvested biomass mineralization is insignificant. The objective of this study was to determine the impact of this assumption on calculated relic SOC half‐lives. Study sites were located in Minnesota and South Dakota. At the Minnesota site, SOC contained in the surface 30 cm of soil in a fallowed area decreased from 90.8 to 73.2 Mg ha−1during a 22‐yr period. Associated with this decrease was a 0.72‰ increase in the soil δ13C values (from −18.97 to −18.25‰). Based on these values, the Rayleigh fractionation constant (ε) of relic SOC was −3.45‰. At the South Dakota site, SOC decreased 10% (2.8 ± 1.8 g kg−1) and δ13C increased 3.2% (0.548 ± 0.332‰) during a 5‐yr period. The Rayleigh fractionation constant for this experiment was −6.94‰ (±4.74‰). In a separate experiment, the δ13C value of corn (Zea maysL.) and soybean [Glycine max(L.) Merr.] residue remained unchanged after 4 mo. The impact of 13C enrichment during relic C mineralization on calculated C budgets depends on the type of residue returned to the soil. A simulation study showed that for systems where C4residues are returned to soil derived from C3and C4plants, not considering 13C enrichment during relic SOC mineralization will result in underestimating relic SOC half‐lives and overestimating the contribution of fresh C4biomass in the SOC. The effect of 13C enrichment during relic SOC and unharvested biomass mineralization had cumulative impacts on C budgets and did not cancel each other out. The reverse was true for C3biomass. To minimize these errors, SOC maintenance rate experiments should measure 13C enrichment during relic SOC and unharvested biomass mineralization.

Soil organic carbon (SOC) in agroecosystems is regulated by crop rotation and soil disturbance. We assessed crop sequence and tillage effects on SOC dynamics and storage using natural 13C abundance of corn (Zea maysL.) and soybean [Glycine max(L.), Merr.]. Treatments consisted of tillage: moldboard plow (MP), chisel plow (CP), and no‐tillage (NT); and crop sequence: continuous corn (CC), continuous soybean (SS), and alternating corn–soybean (CS). Soil samples were collected after 14 yr in each treatment and in fallow alley‐ways and were analyzed for SOC, δ13C, bulk density, and pH. Tillage by crop sequence interactions occurred as treatments with MP and SS as well as fallow averaged 135 Mg SOC ha−1(0‐ to 45‐cm depth), while CP treatments with corn (CC and CS) and NT with CC averaged 164 Mg SOC ha−1Crop sequence effects on SOC (0‐ to 45‐cm depth) occurred when tillage was reduced with CP and NT averaging 15% greater SOC in CC than SS. In addition to less C inputs than CC, SS accelerated rates of SOC decomposition. Tillage effects on SOC were greatest in CC where CP had 26% and NT 20% more SOC than MP, whereas SOC in SS was similar across tillage treatments. Up to 33% of the greater SOC under CC for CP and NT, compared with MP, occurred below tillage operating depths. Substantial losses of SOC were estimated (1.6 Mg SOC ha−1yr−1) despite lowering SOC decay rates with reduced tillage and high levels of C inputs with CC.

Two classical articles were selected to represent the topic "Milestones in Soil Organic Matter Studies" for the special issue to celebrate the 90th anniversary of Soil Science.The first article, "Comparative Study of Decomposition Rates of Organic Matter in Temperate and Tropical Regions," was authored by H. Jenny, S.P. Gessel, and F.T. Bingham and published in Soil Sci.68419-423, 1949. This article, which compared nitrogen and organic matter production and decomposition in temperate and tropical soils, has already been cited in more than 350 journal articles. The citing authors have used the Jenny et al. data to explain their own results in several ways including soil organic carbon increases, litter decomposition rates, dynamic modeling of soil organic matter formation, and ecological and forest ecosystem modeling. The second article, "Turnover of Soil Organic Matter in Some Rothamsted Classical Experiments," was authored by D.S. Jenkinson and J.H. Rayner, Soil Sci.123298-305, 1977. This article has had a huge impact on considerations of soil organic matter turnover and has already been cited in upwards of 500 journal articles. The data were fundamental in the progression to the ROTHC model and has led to comparisons of other models such as CANDY, CENTURY, DAISY, and NCSOIL. Without a doubt, the articles by Jenny et al. and by Jenkinson and Rayner on organic amendments to soils, on biomass in soil from plant and microbial sources, and on the turnover of organic matter have contributed enormously to our abilities to predict the long-term stabilities of organic matter in the soil environment. But, there is much work still to be done. At last, we have the technologies that will enable us to understand the compositions and aspects of the structures of the plant and microbial tissues transformed to soil organic components that have degrees of resistance to degradation in the soil environment. Then, when we know better how the compositions/structures of these components are influenced by different soil properties, we will be in a better position to predict more accurately the behavior of organic matter in different soil types under different management regimes.

The apoptosis of chondrocytes plays an important role in endochondral bone formation and in cartilage degradation during aging and disease. Prolactin (PRL) is produced in chondrocytes and is known to promote the survival of various cell types. Here we show that articular chondrocytes from rat postpubescent and adult cartilage express the long form of the PRL receptor as revealed by immunohistochemistry of cartilage sections and by RT-PCR and Western blot analyses of the isolated chondrocytes. Furthermore, we demonstrate that PRL inhibits the apoptosis of these same chondrocytes cultured in low-serum. Chondrocyte apoptosis was measured by hypodiploid DNA content determined by flow cytometry and by DNA fragmentation evaluated by the ELISA and the TUNEL methods. The anti-apoptotic effect of PRL was dose-dependent and was prevented by heat inactivation. These data demonstrate that PRL can act as a survival factor for chondrocytes and that it has potential preventive and therapeutic value in arthropathies characterized by cartilage degradation.

Carbon dioxide (CO2) production is a more desirable indicator of soil carbon (C) dynamics than CO2flux at the soil-air interface, which is significantly influenced by the gas-transport condition of the soil. Production of CO2can be computed from CO2concentrations if high-temporal measurements are made. Our objective was to design, implement, and test an automated CO2measurement system that requires low maintenance but provides high-temporal resolution of CO2concentrations in soil. The CO2sensors were located at different soil depths from 10 to 60 cm, with and without roots, to measure the effect of corn (Zea mays, L.) root activities on CO2concentrations over time. A direct comparison indicates that soil CO2measured with the automated measurement system represents CO2of soil surrounding the sensor. Computed CO2production was highest in the soils above 20 cm. A peak of soil CO2concentration occurred after each of the major rain events. The amplitude of the peaks decreased with depth. Differences between the CO2concentrations in the root and root-excluded soils were small between rainfall events and large at and after rain. Soil CO2concentration showed diurnal variations at the 10-, 20-, and 40-cm depths, whereas it was hardly detectable at the 60-cm depth. The automated CO2measurement system is a useful tool for gaining knowledge of CO2production in soils over time and across depth and of contributions from roots and bulk soil to total CO2production in soils.

A better understanding of C turnover, with estimates of root‐derived C, is needed to manage soil C sequestration. The objective was to evaluate the long‐term treatment and environmental effects on unharvestable soil C components. Two N fertilizer treatments and a control were imposed during 29 yr of continuous corn (Zea maysL.) with stover removal as silage vs. stover return during grain harvest with moldboard plow (MB) tillage. Soil organic carbon (SOC) declined and natural 13C abundance (δ13C) increased during the 29‐yr period. Field averages of SOC and δ13C (0–30 cm) were 96.4 Mg ha−1and −17.3‰ in 1965; respective values in 1995 were 78.9 Mg ha−1and −16.6‰. Loss of SOC was greater with stover removed or no fertilization, but δ13C increased for all treatments. Stover yield (SY), SOC, and δ13C data were applied to a model to estimate unharvestable C and predict total source C (SC) input from corn. The SC for 29 yr totaled 172 to 189 Mg ha−1when stover was harvested and 268 to 284 Mg ha−1when stover was returned. The SC input from unharvestable sources was 1.8 times more than SC from aboveground stover when N was added and 1.7 when N was not added. The root‐to‐shoot ratio was 1.1 when N was added and 1.2 with no N. Only 5.3% of the SC was retained as SOC. Unharvestable C contributions to rhizodeposition are much larger than suggested from controlled studies including C‐enriched CO2followed by soil respiration or CO2efflux measurements.

Soil organic carbon (SOC) is sensitive to management of tillage, residue (stover) harvest, and N fertilization in corn (Zea maysL.), but little is known about associated root biomass including rhizodeposition. Natural C isotope abundance (δ13C) and total C content, measured in paired plots of stover harvest and return were used to estimate corn‐derived SOC (cdSOC) and the contribution of nonharvestable biomass (crown, roots, and rhizodeposits) to the SOC pool. Rhizodeposition was estimated for each treatment in a factorial of three tillage treatments (moldboard, MB; chisel, CH; and no‐till, NT), two N fertilizer rates (200 and 0 kg N ha−1), and two corn residue managements. Treatments influenced cdSOC across a wide range (6.8–17.8 Mg C ha−1). Nitrogen fertilization increased stover C by 20%, cdSOC by only 1.9 Mg C ha−1, and increased rhizodeposition by at least 110% compared with that with no N fertilizer. Stover harvest vs. stover return reduced total source carbon (SC) by 20%, cdSOC by 35%, and total SOC. The amount of stover source carbon (SSC) responded to tillage (MB > CH > NT), but tillage affected the amount of cdSOC differently (NT > CH > MB). Total SOC was maintained only by both N fertilization and stover return during the 13‐yr period. The ratio of SC in the nonharvestable biomass to SSC ranged from 1.01 to 3.49; a ratio of 0.6 conforms to a root‐to‐shoot ratio of 0.4 when the root biomass includes 50% rhizodeposits. Tillage controlled the fraction of SC retained as cdSOC (i.e., humified; 0.26 for NT and 0.11 for MB and CH), even though N fertilization, stover harvest, and tillage all significantly influenced SC. Decomposition of labile rhizodeposits was a major component of the nonhumified fraction. Rhizodeposition was as much as three times greater than suggested by laboratory and other controlled studies. To understand and manage the entire C cycle, roots and rhizodeposition must be included in the analysis at the field level.

The amino-terminal 16 kDa fragment of prolactin (16K PRL) promotes the expression of the inducible isoform of nitric oxide synthase (iNOS) accompanied by the production of nitric oxide (NO) by rat pulmonary fibroblasts. The present study was designed to elucidate whether the mechanism by which 16K PRL promotes iNOS expression involves the activation of nuclear factor-kappa B (NF-kappaB), a key transcription factor for iNOS induction. 16K PRL stimulated DNA-binding activity of NF-kappaB in pulmonary fibroblasts as demonstrated by gel shift assays. Likewise, fluorescence immunocytochemistry showed that 16K PRL promotes nuclear translocation of the p65 subunit of NF-kappaB. Finally, treatment with 16K PRL induced the degradation of the NF-kappaB inhibitor kappaB-beta (IkappaB-beta), and such degradation was prevented by blocking IkappaB-beta phosphorylation. Altogether, these results show that 16K PRL activates NF-kappaB nuclear translocation via the phosphorylation and degradation of IkappaB-beta. These findings are consistent with NF-kappaB being part of the signal transduction pathway activated by 16K PRL to induce iNOS expression.

The role of agricultural practices on soil carbon (C) dynamics is critical to improved soil management. Our main objective was to examine the C interactions resulting from crop changes under different tillage and residue treatments. Tillage choices were no-till (NT), moldboard plow (MB), and chisel plow (CH); residue options were residue harvested (h) and residue returned (r); and N fertilization rates were 0 and 200 kg N ha−1, applied annually only during the corn (Zea maysL.) (C4plant) years. Soil samples were taken from a long-term experiment representing 13 years of continuous corn followed by 4 years of soybean Glycine max(L.) Merr. (C3plant). Samples taken at 5-cm depth increments to either 45 cm (yr-13) or 30 cm (yr-17) and at 15-cm depth increments thereafter, down to 90 cm, were analyzed for C and natural abundance 13C (δ13C). Specific objectives were to show (i) differences in soil organic carbon (SOC) and δ13C caused by crop change; (ii) distributions of SOC and δ13C with depth at yr-13 and yr-17; and (iii) how much of the SOC, after 4 years of soybean, was current C (soybean-derived) and how much was relic C (after 13 yr of corn and earlier grass crops). There were three depth zones 0 to 20, 20 to 40, and 40 to 90 cm. SOC decreased with depth, but in the 20- to 40-cm zone the decrease was relatively rapid. Values of δ13C increased with depth, except at depths greater than 40 cm when δ13C tended to decrease. Differences in SOC and δ13C caused by crop change generally occurred in the upper 20 cm. Decreases in SOC and δ13C under NT and CH as a result of crop change occurred at the very surface, whereas under MB, the decrease occurred down to 25 cm. The contribution of soybean to SOC ranged from −6 to 27. When residues were returned, SOC in the 0- to 5-cm depth increased under NT (about 26) and CH (about 19). Under MB, the measured contribution of soybean at any 5-cm increment within the upper 25 cm was less than 8; however, at the 25- to 30-cm depth with residue harvested, the contribution was greater than 14. Except for the very surface of NTr and CHr and at the 25- to 30-cm depth under MBh, the SOC within the profile was predominantly relic C. A positive interaction between N application and corn residues returned showed that N could not sustain SOC without residue return. This interaction carried a residual through the soybean period, yet no N was applied to soybean. An overall relation between yr-13 and yr-17 suggested a 24 reduced SOC after soybean.

Prolactin, growth hormone and placental lactogen are members of a family of polypeptide hormones which share structural similarities and biological activities. Numerous functions have been attributed to these hormones, among which stand out their recently discovered effects on angiogenesis, the process by which new blood vessels are formed from the pre-existing microvasculature. Prolactin, growth hormone and placental lactogen, along with two non-classical members of the family, proliferin and proliferin-related protein, can act both as circulating hormones and as paracrine/autocrine factors to either stimulate or inhibit various stages of the formation and remodeling of new blood vessels, including endothelial cell proliferation, migration, protease production and apoptosis. Such opposing actions can reside in similar but independent molecules, as is the case of proliferin and proliferin-related protein, which stimulate and inhibit angiogenesis respectively. The potential to exert opposing effects on angiogenesis can also reside within the same molecule as the parent protein can promote angiogenesis (i.e. prolactin, growth hormone and placental lactogen), but after proteolytic processing the resulting peptide fragment acquires anti-angiogenic properties (i.e. 16 kDa prolactin, 16 kDa growth hormone and 16 kDa placental lactogen). The unique properties of the peptide fragments versus the full-length molecules, the regulation of the protease responsible for specific protein cleavage, the selective expression of specific receptors and their associated signal transduction pathways are issues that are being investigated to further establish the precise contribution of these hormones to angiogenesis under both physiological and pathological situations. In this review article, we summarize the known and speculative issues underlying the effects of the prolactin, growth hormone and placental lactogen family of proteins on angiogenesis, and address important remaining enigmas in this field of research.

Humic substances (HS) are the major components of the mixture of materials that comprise soil organic matter, and these substances, which are by far the most abundant organic materials in the environment, are themselves complicated mixtures of biologically transformed organic debris. However, it is likely that many of the solubilization properties of the mixtures arise from the presence of nonhumic components that are intimately associated with the HS and that cannot be separated effectively from these components. Separation and fractionation techniques are improving, and most of the instruments needed to advance awareness of the composition and aspects of structures are now in place. There is a need, however, to review the operational definitions that now apply and to put in place a classification system that will take into account origins and some compositional characteristics. The broad based definition of humin is especially unsatisfactory. This umbrella term covers a mixture of materials that are insoluble in aqueous systems and that contain nonhumic components such as long chain hydrocarbons, esters, acids, and even relatively polar structures of microbial origin, such as polysaccharides and glomalin, that can be associated with the nonpolar moieties and with soil minerals, as well as plant components that are highly resistant to decomposition. Advances in the humic sciences in recent times have been impressive, and the questioning of ‘ingrained’ theories and concepts is opening vistas through which we are seeing new concepts of size, shape, and association; the remarkable developments in nuclear magnetic resonance are also allowing better interpretations of compositions and of aspects of structures. From these advances will emerge a more fundamental understanding of HS functions in such important roles as the stabilization of soil aggregates, the binding of anthropogenic organic chemicals, and the sequestration of C from atmospheric CO2. The latter function is especially important at this time because we need to know why some soils sequester more C than others and why the qualities (or composition and structure) of HS in some soils are different from those in others.

Members of the prolactin (PRL) hormonal family have direct effects on endothelial cell proliferation, migration and tube formation. Moreover, isoforms of PRL may function as autocrine regulators of endothelial cells. Bovine brain capillary endothelial cells (BBCEC) express the PRL gene, while anti-PRL antibodies inhibit BBCEC proliferation. Here, we show the expression of the PRL gene into various PRL isoforms in endothelial cells from the human umbilical vein. Reverse transcription-polymerase chain reaction of total RNA from human umbilical vein endothelial cells (HUVEC) detected the full-length PRL mRNA as well as a 100 bp smaller PRL transcript similar to the one previously reported in BBCEC. HUVEC were positive to PRL immunocytochemistry. In addition, various PRL immunoreactive proteins were detected in HUVEC extracts and HUVEC conditioned media by metabolic labelling immunoprecipitation analysis. These PRL immunorelated proteins had apparent molecular masses of 60, 23, 21, 16 and 14 kDa. In contrast to previous findings in BBCEC, HUVEC conditioned media contained very little PRL bioactivity as determined by the selective bioassay of Nb2 cell proliferation. Moreover, some polyclonal or monoclonal antibodies directed against PRL stimulated HUVEC proliferation, in contrast to the inhibitory effect seen in BBCEC. The present findings extend the previous observations about the expression of PRL gene in endothelial cells from bovine brain capillaries to human cells of the umbilical vein, implicating that endothelium from different types of vessels and species share the expression of PRL gene but may differ in the putative autocrine role of the PRL isoforms expressed.

Prolactin (PRL), originally associated with milk secretion, is now known to possess a wide variety of biological actions and diverse sites of production beyond the pituitary. Proteolytic cleavage is a common post-translational modification that can either activate precursor proteins or confer upon the peptide fragment unique biological actions not exerted by the parent molecule. Recent studies have demonstrated that the 16-kDa N-terminal proteolytic cleavage product of PRL (16K-PRL) acts as a potent inhibitor of angiogenesis. Despite previous demonstrations of 16K-PRL production in vivo, biological functions beyond its antiangiogenic actions remain unknown. Here we show that 16K-PRL, but not full-length PRL, acts to promote the expression of the inducible isoform of nitric oxide synthase (iNOS) and nitric oxide (*NO) production by pulmonary fibroblasts and alveolar type II cells with potency comparable with the proinflammatory cytokines interleukin-1beta, interferon gamma, and tumor necrosis factor alpha. The differential effect of 16K-PRL versus PRL occurs through a receptor distinct from known PRL receptors. Additionally, pulmonary fibroblasts express the PRL gene and endogenously produce 16K-PRL, suggesting that this pathway may serve both autocrine and paracrine roles in the regulation of *NO production. These results reveal that proteolytic cleavage of PRL confers upon this classical hormone potent iNOS inducing activity, suggesting its role in inflammatory/immune processes.

Tetramethylammonium hydroxide (TMAH) thermochemolysis–gas chromatography/mass spectrometry (GC/MS) was employed to study the chemical structure of soil organic matter sampled from a soil plot in which corn (Zea maysL.) was farmed continuously for 15 yr. The chromatograms exhibited peaks related to compounds derived from lignin, fatty acid methyl esters (FAMEs), non‐lignin aromatic structures, and heterocyclic N compounds. The dominant lignin‐derived peaks in the TMAH thermochemolysis–GC/MS chromatograms were mainly derivatives of p‐hydroxyphenyl and guaiacyl structures, suggesting a non‐woody (grass) lignin type. With depth, the ratio of syringyl to guaiacyl compounds (S/G) decreased, suggesting a preferential degradation of the syringyl units by microorganisms. Fatty acid methyl esters of varying C‐chain length (C7to C27) were identified in the soil chromatograms. Both TMAH–GC/MS and 13C‐NMR (nuclear magnetic resonance) data suggested a relative increase of long‐chain fatty acids with soil depth (or degree of humification), suggesting a refractory nature for these compounds. The heterocyclic N compounds yielded from the TMAH thermochemolysis were mainly pyrroles, pyridines, and pyrazoles. In addition, low levels of methylated amino acids (phenylalanine, leucine, and valine) were detected. The presence of the amino acids in the bottom layer of the soil suggests a preservation mechanism. The changes identified in the chemical components provide clues as to the nature of the humification processes in the soil profile and also yield information on the nature of the sources of soil organic matter.

This series of papers focuses on considerations of the sizes and shapes of humic macromolecules. The initiative arose because of the divergent views held by participants at a symposium/workshop held under the auspices of the Soil Science Society of America and the International Humic Substances Society in Anaheim, CA in October 1997. Three different viewpoints were expressed, and each satisfied its proponent. One suggested that humic substances (HS) are macromolecular and assume random coil conformations in solution; a second proposed that HS are molecular associations of relatively small molecules held together by weak interaction forces; a third considered that HS are in solution as micelle or "pseudomicellar" structures. Viewpoints two and three could be broadly considered to be under the same umbrella. We have considered the experimental procedures that led the proponents to their points of view, and we do not consider it to be our brief to side with one or another of the concepts. Much work remains to be done before a definitive answer is found. We understand that the various concepts arose from studies of different soils using different experimental techniques, and we share the view that the matter/controversy can best be resolved when data are available from applications of the same advanced techniques and procedures to a variety of HS from different sources. We are convinced that awareness of the sizes and shapes of humic molecules is of fundamental importance for an understanding of the many basic reactions and interactions that take place in the soil environment and that have considerable environmental significance. It is our hope that this series of papers will stimulate researchers to pool their views, skills, and instrumentation and set about finding a solution to this fundamental aspect of humic structures.

In a small-plot field study on a Waukegan silt loam soil, annual applications of 20 g N m−2were made each May for 8 years before planting corn (Zea maysL.). Subplots were fertilized with 0.8 g 15N m−2. Soil treatment in the fall either incorporated the chopped corn stover after grain harvest, using a rototiller, or the stover was removed from the plots. Soil samples taken in the fall were ultrasonicated, separated into clay- and silt-sized fractions, and extracted exhaustively with 0.1 mol L−1sodium pyrophosphate (Na4P2O7) + 0.1 mol L−1NaOH (pH 12.6). Humic (HA) and fulvic (FA) acids were isolated using the International Humic Substances Society (IHSS) procedures. A variety of analytical methods were employed. The most useful information was obtained from amino acid (AA) and neutral sugar (NS) analyses, and from cross polarization magic angle spinning (CPMAS) 13C-NMR and δ13C data. Overall, the corn residue amendments did not have a large effect on the composition of the humic substances (HS) from the different sized separates, but there were differences in the relative abundance of some AA and NS in the HAs and FAs. The NMR and δ13C data provided evidence of some compositional differences and extent of humification between the HS from the clay- and silt-sized separates. The conclusion reached is, therefore, that the silt-sized particles were microaggregates of clay-sized particles, and the HS in these microaggregates were partially protected from bioalteration. These HS bore greater resemblance to the plants of origin than did those associated with the clays. The composition of the HAs and that of the FAs were similar to that of the Mollisol soil standard of the IHSS, but they were different from humic samples from other non-Mollisol soil types.

Estrogens are recognized regulators of the expression of neurohypophyseal hormones and of anterior pituitary prolactin (PRL). Here we have investigated whether the levels of PRL mRNA and of 23 and 14 kDa PRL variants present in the hypothalamo-neurohypophyseal system change during the estrous cycle or in response to estrogen treatment. The reverse transcription polymerase chain reaction (RT-PCR) was performed to examine PRL mRNA expression in isolated paraventricular (PVN) and supraoptic (SON) hypothalamic nuclei. In both nuclei PRL mRNA levels appeared higher in cycling females than in male rats, with the highest level occurring at estrus. This increase may involve estrogen action, since estrogen administration to ovariectomized rats was associated with apparently higher PRL mRNA levels in both the PVN and SON. Expression of the PRL gene at these sites may occur via both transcriptional factor Pit-1-dependent and -independent mechanisms. RT-PCR detected the mRNA for Pit-1 in the PVN but only at estrus. The concentration of the 23 kDa immunoreactive PRL determined in the neurohypophysis was significantly higher during estrus and after estrogen treatment. However, no difference was detected in the levels of the neurohypophyseal 14 kDa PRL-like fragment along the estrous cycle nor after estrogen administration. This lack of parallelism between neurohypophyseal PRLs could relate to an estrogen-induced inhibition of the proteolysis of 23 kDa PRL at this site, since estrogen treatment reduced the activity of neurohypophyseal proteolytic enzymes able to cleave PRL. Altogether our results are consistent with estrogens having a stimulatory effect on PRL gene expression in the hypothalamo-neurohypophyseal system and a concomitant inhibitory action on PRL proteolysis at this site.

Gives some practical advice on using pruning shears, loppers, and saws. Anvil pruning shears; Bypass pruning shears; Author's forester loppers; Bypass loppers; Pruning saws; Bow saw; How to prune; List of sources.

Municipal wastewater effluent studies have not evaluated perennial forage root growth at different effluent rates or cutting sequences. Our primary objective was to ascertain whether root length and mass of perennial grasses, that are tolerant of wastewater effluent, but that yield differently depending on frequency of cutting, are influenced by effluent application or cutting frequency. The two, three, or four‐time year−1cutting sequence had little effect on root length or dry weight, whereas wastewater treatment levels caused significant root differences. The high effluent (10 cm week−1) treatment produced less root length and root mass in all four species compared with the control and low effluent (5 cm week−1) treatments. When high levels of effluent were applied, reed canarygrass (Phalaris arundinaceaL.) had the greatest root length and mass, whereas orchardgrass (Dactylis glomerataL.) had the least; tall fescue (Festuca arundinaceaSchreb.) and Kentucky bluegrass (Poa pratensisL.) had intermediate root production. Although orchardgrass produced significantly fewer roots than did reed canarygrass, previous work had shown the aboveground yields of these species were comparable. Also, the high effluent treatment produced the greatest yield of aboveground dry matter, the finest roots, the least root dry matter, and lowest rooting density. We concluded that root mass or length were not primary determinants of forage production of adapted perennial grasses when ample water and nutrients were provided by wastewater effluent.

NCSWAP is a computer simulation model of N and C cycles in the soil‐water‐plant system. It integrates water flow dynamics, N solute transport, crop growth, N transformations, and tillage, residue and soil temperature effects. Experimental data were obtained from a nitrogen, tillage and residue management field study conducted at Rosemount, MN. The objectives of this study were to calibrate the potential rate of nitrification and to illustrate how the model could be used as a research tool to infer behavioral characteristics of the soil‐plant system. Significant differences in soil moisture, maize plant yield, and N uptake due to treatments were not detected either experimentally or by NCSWAP. A match between computed and observed tracer‐N uptake and NO‐3‐N and NH+4‐N in the surface (0‐to 15‐cm) soil depth was achieved when the potential rate of nitrification was set at 25 µg N g−1d−1at the beginning of the growing season, then reduced to 4 and 1 µg N g−1d−1from day 171 to 205 and from 206 on, respectively. NCSWAP showed that plant‐N uptake drew from fertilizer‐N during early plant development, but later from mineralized‐N, which diluted the plant tracer‐N content.

In this experiment we determined the residual nitrogen availability from sewage sludges applied to a Hubbard sandy loam soil. In Study I, three sludge types—anaerobically digested (119, 237, and 466 metric tons/ha), aerobically digested (244 metric tons/ha), and mixed primary‐settled and waste‐activated (493 metric tons/ha)—were applied over a 3‐year period. Soil samples were collected from the field experiment 2 years after the final sludge application. Study II samples were obtained from plots of a field experiment in which an anaerobically digested sludge had been applied (63, 125, and 200 metric tons/ha) 4 years earlier. Several biological and chemical characteristics were examined as indexes of N availability. Cumulative N mineralization during aerobic incubation was approximately linearly related to time1/2for all treatments. Index values for Study I samples varied widely, hut in general, reflected the quantity of sludge added: total soil C (1.05 to 4.66%), total soil N (0.092 to 0.608%), indigenous inorganic N (12 to 266 µg/g), N mineralized during 52 weeks of aerobic incubation (87 to 884 µg/g) and during 16 weeks of anaerobic incubation (14 to 525 µg/g), nitrogen mineralization potential, No(126 to 1,010 µg/g), and autoclave‐extractable N (76 to 441 µg/g). The sludge application rate was more important than the sludge type in affecting N mineralization. The sludge‐treated soils from Study II had lower and less varied index values than those from Study I. The evaluation of N‐availability indexes was based on the degree of correlation between the index values and N uptake by irrigated, field grown maize (Zea maysL.) (Study I) or sorghum‐sudangrass (Sorghum vulgare sudaneseL., var. ‘Trudan V’) grown in the greenhouse (Study II). Each index was useful in determining relative differences of N availability for this soil having received greatly differing organic N treatments from sewage sludge. Nitrogen mineralized during short and long periods of incubation correlated with plant N uptake equally well. The chemical indexes of N availability were as reliable as more time‐consuming incubation procedures for determining the N‐supplying capacity of soils.

A 2‐year field experiment was conducted to test the performance of reed canarygrass (Phalaris arundinaceaL.) and the removal of nitrogen from municipal waste‐water effluent under varying irrigation schedules. The effluent was obtained from an activated sludge treatment facility that served a domestic suburban population. The 1st‐year total application to the 12‐ by 12‐m plots was about 170 cm of effluent containing 320 kg/ha N, primarily in the ammonia form. The 2nd‐year application consisted of about 290 cm of effluent containing $30 kg/ha N. Treatments during both years were comprised of 1, 2, or 5 irrigations per week. Results indicated that there was no effect of varying the irrigation schedule on the reed canarygrass yields, which averaged 10.2 and 15.0 metric tons/ha during the 1st and 2nd year, respectively. There also was no effect on soil water N concentrations, which averaged 1.0 and 2.4 mg/liter during the 1st and 2nd year, respectively.

Land application of waste water when properly managed has the beneficial result of providing nutrients and water to crops without adverse environmental effects. Populations and activities of NH3‐oxidizing bacteria were studied during one growing season of corn (Zea maysL.) on soil irrigated with municipal waste‐water effluent. The method used to recover these bacteria from soil was shaking 1 hour in Soriano‐Walker medium. Soil populations of one serotype each of the genera Nitrosomonas, Nitrosolobus, and Nitrosospirawere enumerated by the fluorescent antibody (FA) technique. Populations of the three genera peaked at different times, with “total FA‐detectable” populations fluctuating only slightly over the entire season. Higher effluent (220 cm, 470 kg N/ha) treatments tended to have slightly lower populations than either fertilized control (336 kg N/ha) or low effluent (120 cm, 250 kg N/ha) treatments. Ammonia‐oxidation activity was significantly (5% level) higher for soils treated with high rates of effluent. Soil N levels showed NH4‐N decreasing sharply when the population of NH3‐oxidizers peaked in June, but accumulating in the fall when populations declined. Concentrations of NO3‐N in soil were directly related to effluent and fertilizer applications. Nitrate concentrations in soil water and ground water peaked approximately 1 month after the maximum NO3‐N concentrations occurred in the soil.

Rival hypotheses, the mineralization‐immobilization‐turnover (MIT) hypothesis and the direct hypothesis, contend that deamination of soluble, low‐molecular‐weight nitrogenous compounds in soil is mediated by either extracellular or intracellular enzymes, respectively. To test these hypotheses, two amino acids, glycine (C/N = 1.7) and leucine (C/N = 5.2), were added to an acid Hubbard loamy sand (sandy, mixed Udorthentic Haploboroll) and incubated for 7 d. Net mineralization of both C and N were S‐shaped functions of time, indicating that simple first‐order substrate‐dependent kinetics were not applicable. The net mineralization of C and N were strongly correlated with each other and reflect the C/N ratio of the substrate and the C/N ratio and microbial efficiency of the microbial biomass. Labeled 15N data, when analyzed using kinetic models reflecting either the direct or MIT hypotheses, reject the MIT hypothesis (α = 0.01) and show evidence of direct incorporation of amino acids into the microbial biomass.

Crop management effects on the renovation of municipal wastewater effluent were studied in a 6‐year field experiment. A randomized split‐plot block design was used, with corn (Zea maysL.) and forage grasses (reed canarygrass, Phalaris arundinaceaL.) as crops and effluent application rates of none, ∼0.05, and ∼0.10 m week−1. Nitrogen, phosphorus, potassium, sodium, and chloride were measured in percolating soil water during 5 years under corn and 3 years under forage grasses to assess the quality of renovated wastewater. Nitrogen concentrations were generally below 10 mg L−1, with total applications ranging between 200 and 970 kg N ha−1year−1. Nitrogen concentrations also were consistently lower under effluent treatments as compared with fertilized controls and lower under forage crops than under corn. Nitrogen levels increased significantly with increased application rates, especially under corn crops and only occasionally exceeded 10 mg L−1during early and late season when applications surpassed crop uptake demands. Low P concentrations (< 0.05 mg L−1) in percolate water verified nearly complete removal by the soilcrop system except during the final 2 years under corn when concentrations increased about fivefold to 0.7 mg L−1. Potassium levels suggested a continuing removal from the effluent. Sodium and chloride concentrations began at low levels and increased during the first 1 to 2 years of irrigation until they approached the concentrations of the effluent. These results indicate that high N demand crops such as forage grasses have the potential for better renovation of effluent than corn at high application rates, but at lower rates corn will renovate effluent to acceptable N concentrations.

Studies of municipal wastewater effluent utilization by perennial forages have not included alternative harvest schemes or long‐term measurements of species yields and persistence at high levels of effluent application. Our principal objective was to determine the persistence and yields of dry matter and feed nutrients of seven cool‐season perennial grasses and alfalfa (Medicago sativaL.) when they were harvested at each of three cutting schedules and received commercial fertilizer (control) or two levels of effluent over a 5‐year period. Four replications of three soil treatments (control that received well water and mineral fertilizer, and municipal wastewater effluent levels of either ≃ 5 or 10 cm/week) were established on a well‐drained soil having a water table at about 150 cm. Plots of alfalfa, smooth bromegrass (Bromus inermisLeyss.), orchardgrass (Dactylis glomerataL.), Kentucky bluegrass (Poa pratensisL.), tall fecue (Festuca arundinaceaSchreb.), timothy (Phleum pratenseL.), reed canarygrass (Phalaris arundinaceaL.), and quackgrass (Agropyron repensL.) were each harvested at schedules that ultimately included two, three, and four‐time cutting per season. Failure of alfalfa to persist well in any of the effluent‐treated plots was due primarily to a root‐rot complex that developed by the 2nd year. Vigorous smooth bromegrass stands were severely damaged in effluent‐receiving plots after the second harvest during year 1 (when all plots were cut three times) due to a failure of new tillers to develop; this grass did not recover well thereafter. Tall fescue and Kentucky bluegrass failed to persist well when they were cut twice annually in the presence of high N (control and high effluent level), but both had excellent persistence when they were cut four times annually. Timothy persisted poorly in all treatments, but its best persistence occurred when it was cut four times annually. The species having least variation in persistence among all cutting schedules and soil treatments was reed canarygrass. Alfalfa, timothy, and smooth bromegrass did not persist sufficiently well beyond the 2nd year to merit consideration as forages for livestock feed in wastewater effluent systems that utilize the levels of effluent we applied in this experiment. Reed canarygrass was either the highest yielding or among the highest yielding species at all cutting schedules in high effluent plots. When all species and cutting schedules during the first 3 years were averaged, high effluent plots yielded 10.5 metric tons/ha (100%), control plots yielded 10.0 (95%), and low effluent plots yielded 8.0 (76%), indicating that effluent applications of at least 10 cm/week during the growing season in temperate regions can lead to maximum yields of forage dry matter and feed nutrients by persistent species. Reed canarygrass always yielded the most crude protein per hectare, marking it as the best species for removing N from wastewater effluent at both low and high levels of application. If one assumes that the high effluent level is most likely to have practical application in wastewater renovation on grasslands, then reed canarygrass, orchardgrass, or tall fescue should be among the species of choice because they often outyielded the other persistent species (quackgrass and Kentucky bluegrass). if one assumes that the low effluent level is most likely to have practical application, then reed canarygrass or tall fescue should be the species of choice.

The objectives of this study were to determine if burrows produced by two species of earthworms (Aporrectodea tuberculataand Lumbricus rubellus) found in continuous corn (Zea maysL.) in Minnesota altered the infiltration rate and depth distribution of surface applied water. Each species was introduced (212 m−2) to in situ cylinders in plots initially void of worms that had been subjected to tillage with and without residue or no‐till with and without residue for 5 yr. Burrows produced by both species of worms during a 46‐d period increased average infiltration rates of 30 mm of water relative to controls after 46 d. Surface residues more than doubled the number of burrows open to the surface relative to incorporated residues (48 vs. 15 for L. rubellus, 37 vs. 15 for A. tuberculata). Cocoon production, an indicator of potential survivability, was present for both species in the no‐till‐surface residue treatment and for A. tuberculataalso in the till‐incorporated residue treatment. Bromide (Br‐) tracer and mass balance for Br‐in all treatments showed infiltration and Br‐movement in the upper 5 cm of the profile was fastest in tillage treatments with worms and residues and that Br‐movement beyond 19 cm was greatest for the no‐till treatments with worms and residues. Pore continuity and survival potential for worms in the no‐till‐residue treatment suggest that this treatment might increase populations of worms in cropland while altering the hydraulic status and erosion susceptibility of soils in the north central USA.

Changes in nitrogen, tillage, and residue management influence N dynamics, soil moisture availability, soil temperature, and corn (Zea maysL.) yields. The magnitude of the effect of these parameters on the soil/crop system is determined by initial soil and climatic conditions and can be described by field and simulation experiments. The objectives of this research were to determine the influence of depth to gravel and autoclave-extractable N on corn yields within a nitrogen-tillage-residue field experiment and to compare field data with simulated results. Several techniques were used to evaluate the corn/soil system including: a field experiment consisting of N rates, tillage and residue treatment combinations, spatial variability analysis of pertinent soil parameters, and computer simulation of the corn/soil system. Spatial variability analysis enabled weighting of initial parameter values on an area basis for each of the experimental units within the field experiment. These weighted values were then used to determine the influence of the initial conditions on corn production. This study showed that benefits derived for the corn plant from deeper soil depths depended on the interaction between available water, microbial activity, and the ability of the plant to avoid drought. Corn yields for the simulation system were comparable to observed yields, and the NCSWAP model predicted many of the observed responses.

ABSTRACTProlactin, the hormone originally associated with the secretion of milk, is known to represent a family of proteins with a striking variety of actions beyond the scope of reproduction. Current studies have further extended their area of influence by revealing that members of the prolactin family may act as regulators of angiogenesis.

Carbon flow in terrestrial ecosystems regulates partitioning between soil organic C (SOC) and atmospheric CO2. Our objectives were to assess SOC dynamics using natural 13C abundance in corn (Zea maysL., a C4species)‐soybean [Glycine max(L.) Merr., a C3species] sequences. Fifteen treatments of continuous corn, continuous soybean, various sequences of corn and soybean, and fallow were initiated in 1981 at Lamberton, MN, on a Webster clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll). In 1991, soil and aboveground shoot samples from all treatments were analyzed for total organic C and δ13C. Carbon inputs, δ13C, and SOC were integrated into a two‐pool model to evaluate C dynamics of corn and soybean. Total SOC was similar across all treatments after 10 yr; however, differences in soil δ13C occurred between continuous corn (δ13C = −17.2‰) and continuous soybean (δ13C = −18.2‰). Modeled C dynamics showed SOC decay rates of 0.011 yr−1for C4‐derived C and 0.007 yr−1for C3‐derived C, and humification rates of 0.16 yr−1for corn and 0.11 yr−1for soybean. Decay and humification rates were slightly lower than those found in other Corn Belt studies. Levels of SOC were predicted to decline an additional 7 to 18% with current C inputs from either corn or soybean, respectively. Annual C additions required for SOC maintenance averaged 5.6 Mg C ha−1, 1.4 to 2.1 times greater than previously reported estimates. Controlled variation in natural 13C abundance in corn‐soybean rotations during a 10‐yr period adequately traced C dynamics.

The decomposition of heterogeneous plant material could be described more generally if it were based on decomposition rates of defined materials. In this study, mineralization of 15N‐labeled wheat (Triticum aestivumL.) and 15N turnover linked with the decomposition of cellulose in soil were measured and compared with simulated kinetics computed by the model NCSOIL. Dried wheat shoots (2 g C kg−1) with a C/N ratio of 14.4, or cellulose with (15NH4)2SO4at the same C rate and C/N ratio, were added to two soils and incubated for 32 wk at 30 °C and 60% water‐holding capacity. Inorganic and Kjeldahl N and 15N were measured and compared with simulated data. Cellulose induced net immobilization of 70 mg N kg−1within 2 wk; thereafter, net N mineralization was greater than for untreated soils. The decomposition rate constant of cellulose, computed by optimization of the model, was 0.024 d−1. The model underestimated N immobilization, the subsequent rate of net N mineralization, and the isotopic dilution of inorganic N. These discrepancies probably resulted from slower turnover of microbial biomass than simulated. Wheat decomposition was divided into three stages, corresponding to soluble, cellulose‐like, and resistant fractions that decomposed with rate constants of 3.0, 0.024, and 4 × 10−8d−1and accounted for 19, 45, and 36%, respectively, of organic wheat N. The computed gross mineralization of wheat N after 32 wk totaled 64% of added organic N, whereas 15N recovery as inorganic N was 40 to 50%, depending on the soil. The difference was attributed to concurrent assimilation of labeled N by soil microbial biomass that depended partly on native soil N concentrations and should be considered in interpreting tracer experiments.

Factors that control immobilization of inorganic N in soils not amended with organic C‐rich materials have not been fully established. Different N flow schemes for N immobilization were tested by comparing the kinetics of CO2evolution, NH+4‐N, NO‐3‐N, inorganic 15N, and organic 15N excess, measured in soils incubated with 200 mg kg−1of 15N‐labeled NH+4‐N, with data simulated by the computer model NCSOIL structured to representseveral pathways of C and N turnover. Estimates of those parameters most likely to induce or enhance N immobilization, namely the mineralizable soil organic matter content, its C/N ratio, and the efficiency with which C is assimilated by the soil microbial biomass were obtained by optimization. Cumulative N immobilization was up to 10% of the N added and was greater when NH+4was added to dry soils than when added to preincubated soils. The immobilization was primarily due to the microbial biomass drawing N from the inorganic pool, rather than utilizing N directly from the decomposing soil organic matter. Nitrate formed by nitrification seemed to have also been immobilized. A microbial efficiency factor of 0.4 and a C/N ratio of 20 or more for mineralizable soil organic matter were needed to account for the observed rate of N immobilization.

Formation of new capillary blood vessels, termed angiogenesis, is essential for the growth and development of tissues and underlies a variety of diseases including tumor growth. Members of the prolactin hormonal family bind to endothelial cell receptors and have direct effects on cell proliferation, migration and tube formation. Because many angiogenic and antiangiogenic factors are produced by endothelial cells, we investigated whether endothelial cells expressed the prolactin gene. Here we show that bovine brain capillary endothelial cells (BBCEC) in culture express the full-length prolactin messenger RNA, in addition to a novel prolactin transcript, lacking the third exon of the gene. In addition cultures of BBCEC synthesize and secrete prolactin-like immunoreactive proteins with apparent molecular masses of 23, 21 and 14 kDa. The prolactin-like nature of these proteins in supported by the observation that Nb2-cells, a prolactin-responsive cell line, were stimulated to proliferate when co-cultured with endothelial cells and this stimulation was neutralized with prolactin-directed antibodies. Finally, consistent with a possible autocrine effect of endothelial-derived prolactins, polyclonal and monoclonal prolactin antibodies specifically inhibited basal and basis fibroblast growth-factor-stimulated growth of endothelial cells. Taken together, the present findings support the hypothesis of the prolactin gene being expressed in endothelial cells as proteins that could act in an autocrine fashion to regulate cell proliferation.

This 5‐year field study of phosphate (PO4) management was conducted on Waukegan silt loam (Typic Hapludoll) soil, which has a water table at about the 140‐ to 150‐cm depth. The results of municipal waste‐water irrigation, with annual application means of 0, 126, and 237 cm, indicates that in terms of PO4management, soils receiving comparable quantities of PO4from either waste water or mineral fertilizer (rates for good crop management) behaved in similar manner. Sharp increases in organic‐P were found in the surface horizon of soil receiving effluent, while increased levels of available‐P were observed to a depth of 60 cm in the high‐treatment area (mean annual P addition of 160 kg/ha). Phosphate‐adsorption studies, with the aid of the Langmuir equation, showed that the adsorption power of soil from the higher effluent application rates (237 cm/year) had been reduced. This was substantiated by higher P concentrations (0.01 vs. 0.07 mg/liter) observed in soil water at the 60‐cm depth of the high‐treatment areas. These observations were fitted into a simplified model that described the fate of effluent PO4applied to soil.

Milk yields were measured at 8-h intervals in rabbits during early (days 11–14) and late (days 31–34) lactation. A single injection of 1 mg bromocriptine given to rabbits 30 min before suckling on days 11 or 31 caused a significant reduction in milk yield after approximately 8 h. The depressant effect of the drug was then maintained over the next 24–36 h. Recovery of milk yield occurred in bromocriptine-treated rabbits during both early and late lactation 8-16 h after a single injection of 3 mg prolactin. The recovery accelerated more in the rabbits in the early lactating group. Attainment of the maximal stimulatory effect occurred by 24 h after prolactin injection during both early and late lactation although the improvement in milk yield lasted for a shorter period (8 h compared with 24 h) during late lactation compared with early lactation. These differences in response of the rabbit to prolactin during late lactation may contribute substantially to the declining milk yields characteristic of late lactation in this species.

We have described the expression of the prolactin (PRL) gene and the occurrence of PRL-like immunoreactive proteins in the hypothalamic-neurophypophyseal system of the rat. Here, we investigated the nature of neurohypophyseal PRL-like antigens, by studying the biological activity of medium conditioned by incubated neurohypophyses in specific bioassays for PRL and for the 16 kDa N-terminal fragment of PRL (16K PRL). Neurohypophyseal conditioned medium (NHCM) obtained after incubating neurohyphyseal lobes (1 h at 37°C) was enriched with proteins of 14 kDa and 23 kDa, that crossreacted with PRL-and 16K PRL-directed antisera. The NHCM stimulated in a dose-dependent fashion the proliferation of Nb2-lymphoma PRL-dependent cells. This effect paralleled that of PRL and 16K PRL standards and was neutralized by different dilutions of both PRL-and 16K PRL-antisera. Also, the NHCM inhibited the proliferation of endothelial cells in culture, an antiangiogenic-effect exerted by 16K PRL. The antiangiogenic effect of the NHCM was parallel to that of 16K PRL standard and neutralized by 16K PRL antiserum in a dose-dependent fashion. These results indicate that NHCM contains proteins that share receptor activation properties as well as antigenic determinants with both PRL and 16K PRL.

Small organic molecules, such as the commonly used herbicides napropamide [N,N‐diethyl‐2‐(1‐naphthyloxy) propionamide] and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine), complex with soluble humic acids (HAs), producing a marked effect on apparent solubility, availability, and mobility. The overall objective of the present paper is to propose a procedure by which the extent of complexation of small organic molecules with stable humic acids can be quantitatively estimated. Experiments were carried out to investigate the effects of HA and herbicide concentrations, pH, and ionic composition and strength on the extent and nature of complexation using an equilibrium dialysis procedure and 14C‐labeled herbicides. The relative strength of complexes of napropamide with a series of HAs from a wide range of sources, determined at a concentration of 2.0 mg HA mL−1, was in the order of soil > peat > water. Complexation of the herbicides with the soil HA was greater for napropamide than for atrazine (Kcat pH 6.5, 0.83 and 0.12 mL mg−1, respectively). As solubility of molecules in water increases, complex formation usually decreases. However, the complexation of napropamide and atrazine did not correlate inversely with their solubility. Environmental conditions, such as pH and ionic strength and composition, as well as the source of the HAs, had a strong effect on the complexation of the investigated pesticides. The relationship between complexation and the above factors suggests that it is their effect on coiling of the HA strands, which determines the extent of complexation.

Nitrogen availability and uptake from sewage sludge were studied in a field experiment during 1979 on a Hubbard sandy loam soil (Entic Haploboroll). Treatments of anaerobically digested (low, 6370; medium, 12 770; and high, 25 200 kg N ha−1), aerobically digested (12 540 kg N ha−1) and waste‐activated (24 500 kg N ha−1) sludge were applied between 1972 and 1974. By 1975, 50% more total N remained in plots receiving anaerobic sludge than in plots receiving equivalent N rates of waste‐activated or aerobic sludge. By 1979, only 12% of the 1975 level of potentially mineralizable N (N0) remained in the waste‐activated sludge plots, followed by anaerobic sludge (3, 11, and 9% in the low, medium, and high levels, respectively) and aerobic sludge (2%). In 1979, N uptake by maize (Zea maysL.) ranged from 67 kg N ha−1to 184 kg N ha−1on sludge‐treated plots and was 158 kg N ha−1on fertilized controls [250 kg N ha−1as (NH4)2SO4; 0 sludge]. Due to early depletion of N0in aerobic sludge and slow current rate of mineralization of N0in waste‐activated sludge, N uptake in 1979 from those sludge treatments was 51 and 58%, respectively, as high as from equivalent N application rates of anaerobic sludge. Maize grain and fodder yields reflected the uptake differences. In the 0‐ to 15‐cm soil depth, mineral N at planting time ranged from 23 kg N ha−1in aerobic and low anaerobic treatment plots to 31 kg N ha−1in medium and high anaerobic treatment plots. Multiple regression analysis indicated the effect of residual mineral N at planting time was more important than N mineralized during the season for both amount and efficiency of N uptake. Low residual NO3−‐N in the 0‐ to 15‐cm depth limited maize uptake of N mineralized during the season and of previously mineralized N present below the 45‐cm depth. The relative influence of residual mineral N on N uptake changed after sludge application. Therefore, combined N indexes and decay series should be used when estimating long‐term N supplying power of high sludge applications.

Two equations, a single exponential: Nt= No(1 − e‐kt) and a double exponential: Nt= NoS(1 − e‐kt) + No(1 − S)(1 − e‐kt), were used to compare mineralization potentials of soils, where Ntis the N mineralized in time (t), Nois the potentially mineralizable N, and Sand (1 − S) are the fractions of the labile and recalcitrant organic N compounds decomposing at specific rates hand k, respectively. Data were obtained from the published and unpublished incubation studies of Stanford and Smith (MD), Smith et al. (WA), Deans et al. (MN), El‐Haris et al. (US), and Griffin and Laine (CT). The double exponential equation provided the “best fit” of the N mineralization‐time (Nt/t) curve as determined by the estimated mean square error (MSE). With long‐term (>84 d) incubations, Nt/tcurves for the double exponential equation resulted in an avg MSE of 6 compared with the single exponential equation (avg MSE of 79) for CT, MN, and MD data sets (n= 20). For short‐term (≤84 d) incubations, Nt/tcurves were better estimated by the double exponential (avg MSE = 4, n= 21) than by the single exponential (avg MSE = 12, n= 13) for WA, US, and MN data.