Nutrient distribution in a Swedish tree species experiment

The influence of four tree species on the distribution of nutrients between different compartments of the ecosystem was examined. In a randomized block (n=3) experiment in south-western Sweden, Ca, Mg and K were determined as exchangeable amounts in the mineral soil and as total amounts in the O+A₁ horizons (topsoil) and in the aboveground tree biomass. N contents were determined in all compartments as well as P contents of the aboveground tree biomass and the topsoil. The four tree species planted were: silver fir [Abies alba Mill.] (AA), grand fir [Abies grandis Lindl.] (AG), Norway spruce [Picea abies L. Karst.] (PA) and Japanese larch [Larix leptolepis (Sieb. och Zucc.) Endl.] (LL). At the age of 35–36 years, the total stemwood production of the most productive species, AG, was estimated at 471 m³ ha⁻¹. In relation to AG, LL had produced 80%, PA 73% and AA 37%. The system totals [aboveground tree biomass total + topsoil total + exchangeable (Ca, Mg, K) or total (N) in the mineral soil] of Ca, K and N did not differ significantly at the 5% level between the investigated species. For Mg, the system total in LL was significantly higher than for the other species. There was an indication that LL and AA contained higher amounts of Ca, Mg, K and N in the topsoil but less in the biomass than did AG and PA (partly significant). In the mineral soil, there were no significant differences in the exchangeable pools of Ca and K, nor in the total amounts of N. The biomass nutrient concentrations generally decreased in the order: AA > PA > AG > LL. At stem or whole-tree harvest, the Ca export per biomass unit would more than double in the case of PA compared to LL. LL also contained less N in the biomass than the other species. However, the N content in the biomass did not differ between the most (AG) and the least (AA) productive species, although the production of dry weight biomass (standing + harvested) of AG had been twice that of AA. It is concluded that the nutrient budget of a managed forest may vary considerably depending on the choice of tree species.     

Micropropagation of Cowania subintegra and Cowania stansburiana

Both Cowania subintegra Kearney and C. stansburiana Torr. were successfully propagated in vitro. Shoot proliferation occurred from shoot tips of green-house grown C. subintegra using a modified Murashige and Skoog medium supplemented with 4.4 M 6-benzyladenine and 0.5 M indole butyric acid. Excised microshoots (1.5–3.0 cm long) of both species were rooted using a two-step process in which they were cultured for 3 days in a root initiation medium with 2.7 M naphthaleneacetic acid and then transferred to a low nitrogen root elongation medium without auxin. Plantlets were successfully transferred to soilless potting mix.     

Effect of hepatocyte growth factor/scatter factor and other growth factors on motility and morphology of non-tumorigenic and tumor cells

Summary Using an automated cell analyzer system, the effect of hepatocyte growth factor/scatter factor (HGF/SF), epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), endothelial acidic fibroblast growth factor (a-FGF), platelet derived growth factor (PDGF), and recombinant human insulinlike growth factor (IGF) on the motility and morphology of Madin-Darby canine kidney (MDCK), rat hepatomas, C₂, and H_5–6 and murine mammary carcinoma (EMT-6) cells was investigated. Treatment of MDCK cells with HGF/SF, bFGF, EGF, and a-FGF resulted in an increase in average cell velocity and in the fraction of moving cells. Cells treated with the PDGF and IGF did not show significant alterations in velocity. MDCK cells treated with each growth factor were classified into groups of “fast” and “slow” moving cells based on their average velocities, and the average morphologic features of the two groups were quantitated. Fast-moving cells had larger average area, circularity, and flatness as compared to slow-moving cells. Factors that stimulated cell movement also induced alterations in cell morphologic parameters including spreading, flatness, area, and circularity. HGF/SF also scattered and stimulated motility of C₂ and H_5–6 hepatoma cells. In contrast to MDCK cells, there was no significant difference between the morphology of the fast moving and slow moving C₂ and H_5–6 cells. These studies suggest that growth factor cytokines have specific effects on motility of normal and tumor cells.     

Some results in graph theory and their application to abstract relational biology

It has been shown in earlier work that one approach to what Rashevsky has called “abstract biology” is through the study of the class of ( )-systems that can be formed in an arbitrary subcategory of the category of sets. The concept of the ( )-system, however, depends on the availability of mappings that contain other mappings in their range. It is shown that, by introducing an appropriate measure for this property, the problem of characterizing those categories suitable for a rich theory of ( )-systems reduces to a problem familiar from the general theory of graphs. Some new results in these directions are obtained, and it is then shown that any category with mappings that possess properties we might expect to hold in the physical world will also admit a rich theory of ( )-systems. In particular, it is shown that a sufficiently large family of mappings drawn at random from such a category will with overwhelming probability contain an ( )-system. This research was supported by the United States Air Force through the Air Force Office of Scientific Research of the Air Research and Development Command, under Grant No. AF-AFOSR-9-63.     

Dual mode of energy coupling by the oxyanion-translocating ArsB protein.

The arsA and arsB genes of the ars operon of R-factor R773 confer arsenite resistance in Escherichia coli by coding for an anion-translocating ATPase. Arsenite resistance and the in vivo energetics of arsenite transport were compared in cells expressing the arsA and arsB genes and those expressing just the arsB gene. Cells expressing the arsB gene exhibited intermediate arsenite resistance compared with cells expressing both the arsA and arsB genes. Both types of cells exhibited energy-dependent arsenite exclusion. Exclusion of 73AsO2- from cells expressing only the arsB gene was coupled to electrochemical energy, while in cells expressing both genes, transport was coupled to chemical energy, most likely ATP. These results suggest that the Ars anion transport system can be either an obligatory ATP-coupled primary pump or a secondary carrier coupled to the proton motive force, depending on the subunit composition of the transport complex.     

The ars operon of Escherichia coli confers arsenical and antimonial resistance.

The chromosomally encoded arsenical resistance (ars) operon subcloned into a multicopy plasmid was found to confer a moderate level of resistance to arsenite and antimonite in Escherichia coli. When the operon was deleted from the chromosome, the cells exhibited hypersensitivity to arsenite, antimonite, and arsenate. Expression of the ars genes was inducible by arsenite. By Southern hybridization, the operon was found in all strains of E. coli examined but not in Salmonella typhimurium, Pseudomonas aeruginosa, or Bacillus subtilis.     

Independent changes in type I and type II receptors for transforming growth factor beta induced by bone morphogenetic protein 2 parallel expression of the osteoblast phenotype.

Transforming growth factor beta (TGF-beta), a potent regulator of bone formation, has bifunctional effects on osteoblast replication and biochemical activity that appear differentiation dependent. We now show that cell surface binding sites for TGF-beta vary markedly among fibroblasts, bone-derived cells, and highly differentiated osteosarcoma cultures from fetal rats. Expression of betaglycan and type II receptors decline relative to type I receptor expression in parallel with an increase in osteoblast-like activity, predicting that the ratio among various TGF-beta binding sites could influence how its signals are perceived. Bone morphogenetic protein 2 (BMP-2), which induces osteoblast function, does not alter TGF-beta binding or biochemical activity in fibroblasts and has only small effects in less differentiated bone cells. In contrast, BMP-2 rapidly reduces TGF-beta binding to betaglycan and type II receptors in osteoblast-enriched primary cell cultures and increases its relative binding to type I receptors in these cells and in ROS 17/2.8 cultures. Pretreatment with BMP-2 diminishes TGF-beta-induced DNA synthesis in osteoblast-enriched cultures but synergistically enhances its stimulatory effects on either collagen synthesis or alkaline phosphatase activity, depending on the present state of bone cell differentiation. Therefore, BMP-2 shifts the TGF-beta binding profile on bone cells in ways that are consistent with progressive expression of osteoblast phenotype, and these changes distinguish the biochemical effects mediated by each receptor. Our observations indicate specific stepwise actions by TGF-beta family members during osteoblast differentiation, developing in part from changes imprinted by BMP-2 on TGF-beta receptor stoichiometry.     

Secretion of unprocessed human surfactant protein B in milk of transgenic mice

Because of the apparent clinical importance of human pulmonary surfactant B (SP-B), the expression of SP-B was directed to the mammary gland of transgenic mice using previously characterized rat whey acidic protein (WAP) regulatory sequences. rWAP/SP-B mRNA was expressed specifically in the mammary gland, and ranged from 1 to 5% of the endogenous WAP mRNA levels. SP-B was detected immunologically in both tissue and milk. The transgene product had an apparent molecular weight of 40--45 kDa, corresponding to the predicted size of the SP-B proprotein. Incubation of an SP-B-enriched fraction of milk with cathepsin D in vitro produced 20--25 kDa species, consistent with cleavage of the amino terminal domain by cathepsin D. This was confirmed using antibodies specific to the carboxy-terminal domain of SP-B. However, the appearance of only the SP-B proprotein in milk suggests that cathepsin D is not involved in the in vivo processing of SP-B. The SP-B proprotein can be expressed in milk of transgenic mice without any observed effects on mammary gland morphology or lactation     

A conceptual model for the assessment of depressional wetlands in the prairie pothole region

The U.S. Environmental Protection Agency's (EPA's), Environmental Monitoring and Assessment Program (EMAP) is developing a landscape-level conceptual model to evaluate the condition of depressional (basin-type) wetlands in the prairie pothole region (PPR) of the United States. This effort is underway to determine the current condition of the Nation's wetlands and to track how it is improving or degrading over time, as well as to identify management priorities over major geographic areas. The depressional wetlands in the PPR were selected by EMAP both because of the importance of this region for waterfowl and because of the efforts currently being conducted by federal agencies and academic institutions in this region. The PPR provides nesting habitat for more than 15 species of ducks, and supports as much as half of the total production of dabbling and diving ducks in North America. Wetlands in this area became a vulnerable resource after extensive draineage in the 1800s. We propose a conceptual model that represents a framework for guiding the development of ecological indicators, research activities, and data collection for the evaluation of wetland conditions. In princple, this conceptual model is applicable to wetlands in any part of the world.