Acute upregulation of interleukin-1 receptor by ligand.

In this study we have investigated the effect that interleukin 1 (IL-1) has on cell surface IL-1 receptor expression in the murine thymoma cell line, EL4 6.1. These cells express IL-1 receptors with both high affinity (Kd = 65 pM, 986 receptors/cell) and low affinity (Kd = 14.5 nM, 10,417 receptors/cell). The high- and low-affinity receptors are indistinguishable by crosslinking studies performed at both high and low ligand concentrations. However, the two affinity states could be functionally distinguished on the basis of their internalization of ligand. Receptor-mediated endocytosis was dependent upon the concentration of ligand bound to the cells. In the presence of low IL-1 concentrations receptor-mediated endocytosis was slow, whereas at high IL-1 concentrations, endocytosis was more rapid. Furthermore, receptor-mediated endocytosis of IL-1 did not result in downregulation of surface IL-1 receptors. Indeed, both kinetic and equilibrium binding studies revealed that pre-incubation of cells with IL-1 alpha resulted in an acute upregulation of 125IL-1 alpha binding to high affinity surface receptors in a time and energy dependent manner. Examination of the association kinetics suggested that increased binding was not attributable to positive co-operativity of the high affinity IL-1 receptor, but was due to increasing IL-1 receptor number. This observation was confirmed by equilibrium binding studies. Moreover, receptor numbers were not enhanced by de novo synthesis, nor release of receptors from an intracellular pool. The observed increases in surface ligand binding were most probably due to conversion of the surface pool of low affinity receptors into high affinity receptors.     

Leap frog in slow motion: Divergent responses of tree species and life stages to climatic warming in Great Basin subalpine forests

In response to climate warming, subalpine treelines are expected to move up in elevation since treelines are generally controlled by growing season temperature. Where treeline is advancing, dispersal differences and early life stage environmental tolerances are likely to affect how species expand their ranges. Species with an establishment advantage will colonize newly available habitat first, potentially excluding species that have slower establishment rates. Using a network of plots across five mountain ranges, we described patterns of upslope elevational range shift for the two dominant Great Basin subalpine species, limber pine and Great Basin bristlecone pine. We found that the Great Basin treeline for these species is expanding upslope with a mean vertical elevation shift of 19.1 m since 1950, which is lower than what we might expect based on temperature increases alone. The largest advances were on limber pine‐dominated granitic soils, on west aspects, and at lower latitudes. Bristlecone pine juveniles establishing above treeline share some environmental associations with bristlecone adults. Limber pine above‐treeline juveniles, in contrast, are prevalent across environmental conditions and share few environmental associations with limber pine adults. Strikingly, limber pine is establishing above treeline throughout the region without regard to site characteristic such as soil type, slope, aspect, or soil texture. Although limber pine is often rare at treeline where it coexists with bristlecone pine, limber pine juveniles dominate above treeline even on calcareous soils that are core bristlecone pine habitat. Limber pine is successfully “leap‐frogging” over bristlecone pine, probably because of its strong dispersal advantage and broader tolerances for establishment. This early‐stage dominance indicates the potential for the species composition of treeline to change in response to climate change. More broadly, it shows how species differences in dispersal and establishment may result in future communities with very different specific composition.     

Calcium pools,calcium entry,and cell growth

The Ca²⁺ pump and Ca²⁺ release functions of intracellular Ca²⁺ pools have been well characterized. However, the nature and identity of Ca²⁺ pools as well as the physiological implications of Ca²⁺levels within them, have remained elusive. Ca²⁺ pools appear to be contained within the endoplasmic reticulum (ER); however, ER is a heterogeneous and widely distributed organelle, with numerous other functions than Ca²⁺ regulation. Studies described here center on trying to determine more about subcellular distribution of Ca²⁺ pools, the levels of Ca²⁺ within Ca²⁺ pools, and how these intraluminal Ca²⁺ levels may be physiologically related to ER function. Experiments utilizingin situ high resolution subcellular morphological analysis of ER loaded with ratiometric fluroescent Ca²⁺ dyes, indicate a wide distribution of inositol 1,4,5-trisphosphate (InsP₃)-sensitive Ca²⁺ pools within cells, and large changes in the levels of Ca²⁺ within pools following InsP₃-mediated Ca²⁺ release. Such changes in Ca²⁺ may be of great significance to the translation, translocation, and folding of proteins in ER, in particular with respect to the function of the now numerously described luminal Ca²⁺-sensitive chaperonin proteins. Studies have also focussed on the physiological role of pool Ca²⁺ changes with respect to cell growth. Emptying of pools using Ca²⁺ pump blockers can result in cells entering a stable quiescent G₀-like growth state. After treatment with the irreversible pump blocker, thapsigargin, cells remain in this state until they are stimulated with essential fatty acids whereupon new pump protein is synthesized, functional Ca²⁺ pools return, and cells reenter the cell cycle. During the Ca²⁺ pool-depleted growth-arrested state, cells express a Ca²⁺ influx channel that is distinct from the store-operated Ca²⁺ influx channels activated after short-term depletion of Ca²⁺ pools. Overall, these studies indicate that significant changes in intraluminal ER Ca²⁺ do occur and that such changes appear linked to alteration of essential ER functions as well as to the cell cycle-state and the growth of cells.     

Diel variability in nitrogenous nutrient uptake at photic and subphotic depths

Diel patterns in nitrogen uptake were investigated at threepositions along an offshore orientated transect in the SouthernBenguela Upwelling System. Both photic and sub-photic depthswere targeted in the ¹⁵N tracer experiments. An appreciableproportion of nitrogen uptake was found to occur at sub-photicdepths during both the day and the night. The importance ofsub-photic uptake decreased offshore but remained non-trivialat all locations. Although NH₄ dominated this uptake, NO₃ removalat depth did account for an important fraction of the totalwater column NO₃ uptake, particularly over the shelf at night.For example, sub-photic NO₃ uptake at night for the inshorestations averaged 68% of the total for the water column decliningto 3% offshore. The impact of sub-photic NO₄ uptake on new productionwill depend on whether the NO₃ is incorporated into primaryassimilation pathways or is transported to the sediments ininorganic form. Whereas sub-photic/photic uptake decreased offshore,night/day uptake ratios increased with distance from the coast,approaching unity at the offshore location. This effect wasmost obvious for the photic communities This finding supportsthe belief that dark nitrogen uptake assumes increased importanceas nutrients become less available. Photic zone f-ratios weresmaller at night (mean = 0.14) than during the day (mean = 0.28)indicating a greater importance of reduced nitrogen uptake duringthe dark hours This emphasis on NH₄ utilization at night canbe explained purely in terms of energy efficiency. Such die1phasing in f-ratios needs to be accounted for in scaling totalproduction to new proifudon.     

Milk-derived growth factors as serum supplements for the growth of fibroblast and epithelial cells

Summary We have investigated the response of several epithelial and fibroblastic cells to a mitogenic extract of bovine milk. Cation exchange chromatography was used to produce a mitogen-rich fraction from an industrial whey source that, although comprising only 0.5% of total whey protein, contained the bulk of the growth factor activity. This fraction was a source of potent growth promoting activity for all mesodermal-derived cells tested, including human skin and embryonic lung fibroblasts, Balb/c 3T3 fibroblasts, and rat L6 myoblasts. Maximal growth of all these cell types exceeded that observed in 10% fetal bovine serum. Feline kidney and baby hamster fibroblasts and Chinese hamster ovary cells were less responsive, achieving a maximal growth response of 50–75% that observed in 10% fetal bovine serum. Maximal growth achieved in whey-extract-supplemented cultures of Balb/c 3T3 and human skin fibroblasts, and L6 myoblast cultures exceeded that seen in response to recombinant acidic or basic fibroblast growth factor, platelet-derived growth factor, insulin-like growth factor, or epidermal growth factor. Importantly, addition of low concentrations of fetal bovine serum to the whey-derived mitogenic fraction produced an additive response. However, concentrated milk-derived factors were found to be inhibitory to the growth of all epithelial lines tested, including rat intestinal epithelial cells, canine kidney epithelial cells, and mink lung cells. It is concluded that industrial whey extracted in this form constitutes an important source of potent growth-promoting agents for the supplementation of mesodermal-derived cell cultures.     

An Aspergillus niger esterase (ferulic acid esterase III) and a recombinant Pseudomonas fluorescens subsp. cellulosa esterase (Xy1D) release a 5-5' ferulic dehydrodimer (diferulic acid) from barley and wheat cell walls.

Diferulate esters strengthen and cross-link primary plant cell walls and help to defend the plant from invading microbes. Phenolics also limit the degradation of plant cell walls by saprophytic microbes and by anaerobic microorganisms in the rumen. We show that incubation of wheat and barley cell walls with ferulic acid esterase from Aspergillus niger (FAE-III) or Pseudomonas fluorescens (Xy1D), together with either xylanase I from Aspergillus niger, Trichoderma viride xylanase, or xylanase from Pseudomonas fluorescens (XylA), leads to release of the ferulate dimer 5-5' diFA [(E,E)-4,4'-dihydroxy-5,5'-dimethoxy-3,3'-bicinnamic acid]. Direct saponification of the cell walls without enzyme treatment released the following five identifiable ferulate dimers (in order of abundance): (Z)-beta-(4-[(E)-2-carboxyvinyl]-2-methoxyphenoxy)-4-hydroxy-3-methoxycinnamic acid, trans-5-[(E)-2-carboxyvinyl]-2-(4-hydroxy-3-methoxy-phenyl) -7-methoxy-2, 3-dihydrobenzofuran-3-carboxylic acid, 5-5' diFA, (E,E)-4, 4'-dihydroxy-3, 5'-dimethoxy-beta, 3'-bicinnamic acid, and trans-7-hydroxy-1-(4-hydroxy-3-methoxyphenyl) -6-methoxy-1, 2-dihydronaphthalene-2, 3-dicarboxylic acid. Incubation of the wheat or barley cell walls with xylanase, followed by saponification of the solubilized fraction, yielded 5-5'diFA and, in some cases, certain of the above dimers, depending on the xylanase used. These experiments demonstrate that FAE-III and XYLD specifically release only esters of 5-5'diFA from either xylanase-treated or insoluble fractions of cell walls, even though other esterified dimers were solubilized by preincubation with xylanase. It is also concluded that the esterified dimer content of the xylanase-solubilized fraction depends on the source of the xylanase.     

Diel Surface Temperature Range Scales with Lake Size

Ecological and biogeochemical processes in lakes are strongly dependent upon water temperature. Long-term surface warming of many lakes is unequivocal, but little is known about the comparative magnitude of temperature variation at diel timescales, due to a lack of appropriately resolved data. Here we quantify the pattern and magnitude of diel temperature variability of surface waters using high-frequency data from 100 lakes. We show that the near-surface diel temperature range can be substantial in summer relative to long-term change and, for lakes smaller than 3 km², increases sharply and predictably with decreasing lake area. Most small lakes included in this study experience average summer diel ranges in their near-surface temperatures of between 4 and 7°C. Large diel temperature fluctuations in the majority of lakes undoubtedly influence their structure, function and role in biogeochemical cycles, but the full implications remain largely unexplored.     

The effects of immune rhesus monkey serum on schistosomula of Schistosoma mansoni during cultivation in vitro

Clegg J. A. and Smithers S. R., 1972. The effect of immune rhesus monkey serum on schistosomula of Schistosoma mansoni during cultivation in vitro. International journal for Parasitology2: 79–98. The sera of rhesus monkeys hyperimmunized by 2–4 exposures to S. mansoni cercariae contain an antibody lethal to schistosomula cultivated in vitro. The antibody (IgG) is dependent on labile factors in fresh monkey serum. It can be absorbed by adult worms cultivated in vitro and it is not the antibody responsible for CHR or COP reactions. A titre of lethal antibody sufficient to kill all schistosomula in vitro is maintained for 2–3 months following challenge: it then falls to a moderate level which may be retained for several years. After inactivation, hyperimmune serum inhibits the growth of cultured schistosomula but does not kill them. Following a small primary infection rhesus serum develops a marked growth-inhibiting property and a low titre of lethal antibody at about 4 months, i.e. the time when resistance to reinfection can first be reliably demonstrated.     

Nononcogenic deletion mutants of herpesvirus saimiri are defective for in vitro immortalization.

Herpesvirus saimiri L-DNA sequences between 0.0 and 4.0 map units (4.5 kilobase pairs) are required for oncogenicity; these sequences are not required for replication of the virus. To investigate the basis for the lack of oncogenicity of mutants with deletions in this region and to study the function of this region, we developed a reliable system for in vitro immortalization by herpesvirus saimiri. In contrast to peripheral blood lymphocytes from cotton-top tamarins (Saguinus oedipus) and owl monkeys (Aotus sp.), infection of peripheral blood lymphocytes from common marmosets (Callithrix jacchus) in vitro with herpesvirus saimiri consistently yielded continuously growing lymphoblastoid cell lines. Such cell lines were established using strains of herpesvirus saimiri from group A and group non-A, non-B; however, repeated attempts to immortalize common marmoset peripheral blood lymphocytes using strains from group B were not successful. Common marmoset cell lines immortalized by herpesvirus saimiri were T12+, T8+, T4-, and B1-, indicating that they were derived from suppressor/cytotoxic T lymphocytes. Cell lines could not be established using the nononcogenic mutants 11att and S4, both of which were derived from the group A strain 11 virus. Strain 11att has a spontaneous deletion and S4 has a constructed deletion in the 0.0 to 4.0 map unit region. Constructed strains which had these deleted sequences restored did immortalize common marmoset peripheral blood lymphocytes. Thus, the nononcogenic deletion mutants are defective for immortalization. This system should facilitate attempts to define the sequences responsible for immortalization and to determine their function.