Out of the frying pan into the fire: Predicted warming in alpine streams suggests hidden consequences for aquatic ectotherms.

Thermal regimes of aquatic ecosystems are predicted to change as climate warming progresses over the next century, with high-latitude and high-elevation regions predicted to be particularly impacted. Here, we have modelled alpine stream water temperatures from air temperature data and used future predicted air temperature trajectories (representative concentration pathway [rcp] 4.5 and 8.5) to predict future water temperatures. Modelled stream water temperatures have been used to calculate cumulative degree days (CDDs) under current and future climate conditions. These calculations show that degree days will accumulate more rapidly under the future climate scenarios, and with a stronger effect for higher CDD values (e.g., rcp 4.5: 18-28 days earlier [CDD = 500]; 42-55 days earlier [CDD = 2000]). Changes to the time to achieve specific CDDs may have profound and unexpected consequences for alpine ecosystems. Our calculations show that while the effect of increased CDDs may be relatively small for organisms that emerge in spring-summer, the effects for organisms emerging in late summer-autumn may be substantial. For these organisms, the air temperatures experienced upon emergence could reach 9°C (rcp 4.5) or 12°C (rcp 8.5) higher than under current climate conditions, likely impacting on the metabolism of adults, the availability of resources, including food and suitable oviposition habitat, and reproductive success. Given that the movement of aquatic fauna to the terrestrial environment represents an important flux of energy and nutrients, differential changes in the time periods to achieve CDDs for aquatic and terrestrial fauna may de-couple existing predator-prey interactions.

Morphological analysis of chiral rod clusters from a coarse-grained single-site chiral potential.

We present a coarse-grained single-site potential for simulating chiral interactions, with adjustable strength, handedness, and preferred twist angle. As an application, we perform basin-hopping global optimisation to predict the favoured geometries for clusters of chiral rods. The morphology phase diagram based upon these predictions has four distinct families, including previously reported structures for potentials that introduce chirality based on shape, such as membranes and helices. The transition between these two configurations reproduces some key features of experimental results for fd bacteriophage. The potential is computationally inexpensive, intuitive, and versatile; we expect it will be useful for large scale simulations of chiral molecules. For chiral particles confined in a cylindrical container we reproduce the behaviour observed for fusilli pasta in a jar. Hence this chiropole potential has the capability to provide insight into structures on both macroscopic and molecular length scales.

Dynamical properties of two- and three-dimensional colloidal clusters of six particles.

Colloidal clusters are important systems for studying self-assembly. Clusters of six colloidal particles attracting each other via short-ranged interactions have been recently studied both theoretically and experimentally. Here we present a computer modelling study of the thermodynamics and dynamics of these clusters using a short-ranged Morse potential in two and three dimensions. We combine energy landscape methods with comprehensive sampling, both of configurations using Markov chain Monte Carlo and also of trajectories using Langevin molecular dynamics propagation. We show that the interaction energies between the particles are probably greater than previously assumed. The rates predicted by transition state theory using harmonic vibrational densities of states are off by four orders of magnitude, since the effects of viscosity are not accounted for. In contrast, sampling short trajectories using an appropriate friction constant and discrete relaxation path sampling produces reasonable agreement with the experimental rates.

Validation of cDNA microarray gene expression data obtained from linearly amplified RNA.

BACKGROUND: DNA microarray technology has permitted the analysis of global gene expression profiles for several diseases, including cancer. However, standard hybridisation and detection protocols require micrograms of mRNA for microarray analysis, limiting broader application of this technology to small excisional biopsies, needle biopsies, and/or microdissected tissue samples. Therefore, linear amplification protocols to increase the amount of RNA have been developed. The correlation between the results of microarray experiments derived from non-amplified RNA and amplified samples needs to be evaluated in detail. METHODS: Total RNA was amplified and replicate hybridisation experiments were performed with linearly amplified (aRNA) and non-amplified mRNA from tonsillar B cells and the SUDHL-6 cell line using cDNA microarrays containing approximately 4500 genes. The results of microarray differential expression using either source of RNA (mRNA or aRNA) were also compared with those found using real time quantitative reverse transcription polymerase chain reaction (QRT-PCR). RESULTS: Microarray experiments using aRNA generated reproducible data displaying only small differences to data obtained from non-amplified mRNA. The quality of the starting total RNA template and the concentration of the promoter primer used to synthesise cDNA were crucial components of the linear amplification reaction. Approximately 80% of selected upregulated and downregulated genes identified by microarray analysis using linearly amplified RNA were confirmed by QRT-PCR using non-amplified mRNA as the starting template. CONCLUSIONS: Linear RNA amplification methods can be used to generate high fidelity microarray expression data of comparable quality to data generated by microarray methods that use non-amplified mRNA samples.

Vitamin D-mediated gene regulation in phenotypically defined human B cell subpopulations.

Isolation of distinct subpopulations of density-fractionated normal human B lymphocytes reveals that the requirements for up-regulation of the vitamin D receptor (VDR) and initiation of 1alpha,25-dihydroxyvitamin D3 [1alpha,25-(OH)2D3]-mediated genomic trans-activation are dependent upon the state of cellular activation. The kinetics of the response differ widely among these B cell subpopulations. However, these density-fractionated B cell subpopulations are phenotypically diverse and therefore are not representative of distinct stages of B cell maturation and differentiation. To examine the role of B cell differentiation on the induction and maintenance of biological receptivity to 1,25-(OH)2D3, we purified naive, germinal center, and memory B cells based on their expression of CD38 and CD44 surface antigens and surface Ig isotype. These phenotypically defined B cell subpopulations were all found to constitutively express VDR, and all exhibited similar activation requirements and kinetics for initiation of 1,25(OH)2D3-mediated genomic trans-activation. Taken together, these results suggest that defined stages of differentiation in normal B cells are not significant predicators of VDR expression or receptivity to 1,25-(OH)2D3. Rather, the degree of cellular activation, regardless of maturation stage, determines whether the effects of this immunoregulatory hormone will influence a mature B lymphocyte.

The human B cell response to IL-13 is dependent on cellular phenotype as well as mode of activation.

Normal mature quiescent human B lymphocytes, isolated as a function of buoyant density, require activation for up-regulation of IL-13R constituents. Cell activation through a combination of surface Ig and CD40 receptor ligation leads to the most substantial message production for IL-13Ralpha1. Functional consequences of this receptor variation, in initially quiescent cells, includes demonstrable effects on cellular proliferation in response to ligand exposure. Variations in the method of surface activation, with particular emphasis on the CD40 receptor, reveals that immobilized CD40 ligand may be sufficient, in and of itself, to up-regulate IL-13Ralpha1, which may bear significance for B-lymphocyte bystander proliferation. Regulation of the IL-13Ralpha1 protein and message also differs as a function of cellular phenotype. Although values are greater in memory than naive B cells, as they are initially isolated from extirpated tonsils, variations in the magnitude of message and protein, as a function of surface stimulation, are more substantial in the naive subset. The magnitude of variation in message production in naive cells is associated with a more vigorous proliferative response to IL-13 than seen in memory lymphocytes. The cellular response to IL-13, as a function of activation and phenotype, is the converse of that demonstrated for IL-2. Evaluation of proliferation, receptor message, ligand binding protein production, and the response to putatively synergistic cytokines reveals that IL-2 is the predominant lymphokine utilized by memory cells. This is in contradistinction to IL-13, which along with IL-4, are the predominant moieties for naive lymphocytes.

Differential regulation of gene transcription in subpopulations of human B lymphocytes by vitamin D3.

We have previously shown that freshly extirpated normal human tonsil B cells, which are phenotypically diverse, representing different stages of cellular activation and differentiation, are refractory to the effects of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and require specific activation signals for induction of responsiveness. To determine whether these diversely activated B cell populations respond to 1,25-(OH)2D3, human tonsil B cells were density fractionated and evaluated biochemically and functionally. Low density tonsil B cells, representing the centroblastic fraction, were observed to constitutively express vitamin D receptor message and protein. In contrast, high density quiescent tonsillar B cells had no detectable vitamin D receptor message or protein and required stimulation in vitro for their up-regulation. Biological responsiveness to 1,25-(OH)2D3 was assessed by messenger RNA (mRNA) expression of the vitamin D-dependent enzyme, 25-hydroxyvitamin D3 24-hydroxylase. Low density centroblastic B cells did not require exogenous surface activation for expression of 24-hydroxylase mRNA, which was detectable after 6 h of culture in the presence of 1,25-(OH)2D3. In contrast, high density tonsil B cells required in vitro activation for induction of 24-hydroxylase mRNA, and expression was not detectable for up to 48 h of culture. These observations suggest that reactivity of normal B cell populations to vitamin D is dependent upon their specific stage of activation.

Regulation of interleukin-13 receptor constituents on mature human B lymphocytes.

Human B cells stimulated through both their immunoglobulin and CD40 receptors up-regulate 745 +/- 51 interleukin (IL)-13 ligand binding sites with an affinity of 0.91 +/- 0.08 nM within 24 h. IL-13 binds primarily to the IL-13Ralpha1 with subsequent sequestration of the IL-4Ralpha into the complex. IL-13Ralpha1 may also be found in those receptors capable of binding IL-4. gamma chain (gammac) participates in receptors capable of binding IL-4 but is not found in association with bound IL-13. Dimeric receptors composed of the IL-4Ralpha complexed with either the IL-13Ralpha1 or gammac occur simultaneously within defined B cell populations. mRNAs for all receptor constituents are increased subsequent to immunoglobulin stimulation alone, while maximal expression of IL-13Ralpha1 is more dependent upon co-stimulation of immunoglobulin and CD40 receptors. mRNA levels for IL-13Ralpha1 vary over a wider range subsequent to surface stimulation than other receptor components. Although gammac is not bound to IL-13 in B cells under the conditions evaluated, it may influence IL-13 binding by competing with IL-13Ralpha1 for association/sequestration with the IL-4Ralpha chain. IL-13Ralpha2 does not participate in the IL-13 receptor that is up-regulated upon activation of quiescent tonsillar B lymphocytes, although mRNA for the protein may be found in the centroblastic fraction of tonsillar cells.

Requirements for induction of vitamin D-mediated gene regulation in normal human B lymphocytes.

Mature human lymphocytes are unique targets of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3) in that vitamin D receptors (VDR) are not constitutively expressed, and specific cellular activation signals are required for both the up-regulation of VDR and establishment of reactivity to the lipophilic ligand. Treatment of B lymphocytes with the cytokine IL-4 (IL-4), in the absence of prior activation, induces a weak up-regulation of VDR expression but fails to generate vitamin D-responsive element (VDRE)-reactive nuclear protein complexes or to initiate the genomic transcription of 25-hydroxyvitamin D3 24-hydroxylase. Stimulation of B lymphocytes by either ligation of CD40 Ag or cross-linking the Ig receptor is also insufficient to render B lymphocytes responsive to 1 alpha,25(OH)2D3. However, this apparent lack of response to the secosterol can be overcome by stimulation of B lymphocytes with a combination of these cellular activation signals, which are sufficient to lead to G1 cell cycle progression. In the presence of 1 alpha,25(OH)2D3, cellular activation associated with stimulation of such a progression appears to be sufficient for the up-regulation of VDR message and protein and necessary for the establishment of VDRE binding complexes and the induction of 24-hydroxylase message. Furthermore, biologic functions are modulated, in that the hormone inhibits proliferation in a subset of the activated B cells. These observations suggest that reactivity to 1 alpha,25(OH)2D3 is tightly regulated in B lymphocytes, requiring specific signals for its initiation.

Differential regulation of vitamin D receptors in clonal populations of a chronic myelogenous leukemia cell line.

RWLeu4 is a chronic myelogenous leukemia cell line that is sensitive to the antiproliferative and differentiation-inducing actions of 1alpha,25(OH)2-vitamin D3 (VD3). The JMRD3 cell line is a VD3-resistant variant of RWLeu4 that was selected by continuous passage of RWLeu4 in the presence of VD3. The isolation of a spontaneous VD3-resistant variant suggests that phenotypically different cells exist within the RWLeu4 cell population. Therefore, single-cell clones of RWLeu4 cells were isolated and characterized. Four clonal cell populations that fall into three groups differing in response to the antiproliferative and differentiation-inducing actions of VD3 were examined. Surprisingly, the extent of response of the clones to VD3 does not show a correlation with the basal level of the vitamin D receptor (VDR). RWLeu4-3 and RWLeu4-4 are the clones most sensitive to the antiproliferative actions of VD3 (ED50 approximately equal to 1 nM); however, RWLeu4-3 expresses basal levels of VDRs similar to those found in the parental cells and the RWLeu4-2 clone, while in RWLeu4-4, VD3 binding and VDR protein are below the limits of detection. Furthermore, RWLeu4-10 expresses the highest basal level of VDR protein but is relatively resistant to the antiproliferative actions of VD3 (ED50 > or = 30 nM). Like JMRD3, RWLeu4-10 is still capable of differentiating in response to VD3, as judged by the induction of biochemical processes and cell-surface antigen expression. Although VD3 treatment increases VDR protein levels and DNA-binding activity in all clones, altered DNA-protein complexes are detected in RWLeu4-4. Our results suggest that sensitivity to the antiproliferative and differentiation-inducing actions of VD3 is not dependent solely upon the level of VDR expressed, but may also require posttranslational modification of the VDR or complex interactions with other nuclear transcription factors.

Osmium-187 enrichment in some plumes: evidence for core-mantle interaction?

Calculations with data for asteroidal cores indicate that Earth's outer core may have a rhenium/osmium ratio at least 20 percent greater than that of the chondritic upper mantle, potentially leading to an outer core with an osmium-187/osmium-188 ratio at least 8 percent greater than that of chondrites. Because of the much greater abundance of osmium in the outer core relative to the mantle, even a small addition of metal to a plume ascending from the D" layer would transfer the enriched isotopic signature to the mixture. Sources of certain plume-derived systems seem to have osmium-187/osmium-l88 ratios 5 to 20 percent greater than that for chondrites, consistent with the ascent of a plume from the core-mantle boundary.

Diet, body mass index, and colonic epithelial cell proliferation in a healthy population.

Using 63 healthy subjects, we conducted an observational study to assess associations between colonic epithelial cell proliferation and dietary intake of selected nutrients. Study subjects exhibited no personal or family history of colon carcinoma, familial polyposis coli, sporadic adenomas, or chronic inflammatory bowel diseases. In this study population, a negative association between the tritiated thymidine-labeling index and dietary intake of calcium (p < 0.003) was found after the effects of age, sex, body mass index (kg/m2), dietary fat, and total energy were controlled in a linear regression model. The association for calcium indicated that a daily calcium intake of 1,200 mg was associated with a predicted thymidine-labeling index of 6%. In the same model, a positive association with the thymidine-labeling index was found for body mass index (p < 0.002) and was suggested for female gender (p < 0.09). No association was found between the thymidine-labeling index and intake of fat, protein, carbohydrate, retinol, ascorbic acid, phosphorus, or iron. Repeat measures of diet in this investigation were used to estimate a subject's daily intake of selected nutrients.

Functional block for 1 alpha,25-dihydroxyvitamin D3-mediated gene regulation in human B lymphocytes.

Elements necessary for the steroid hormone 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3) to induce a biological response include the presence of specific intracellular receptors (vitamin D3 receptors (VDR)) and modulation of gene expression via hormone-activated receptor binding to regulatory regions of target genes. These parameters were examined in normal and Epstein-Barr virus-immortalized human B cells and compared with 1 alpha,25-(OH)2D3-responsive cells of the T and monocytic lineages. Although resting tonsillar B cells did not express VDR mRNA, activation of these cells with interleukin-4 induced VDR in the absence of exogenously supplemented 1 alpha,25-(OH)2D3. As indicators of hormone-mediated gene regulation we analyzed modulation of CD23, a common B cell/monocyte surface antigen, and 24-hydroxylase. 1 alpha,25-(OH)2D3 inhibited CD23 expression in U937 cells, yet failed to modulate CD23 expression in B cells. Furthermore, 1 alpha,25-(OH)2D3 induced 24-hydroxylase mRNA expression and metabolic activity in both U937 cells and lectin-activated T cells, yet failed to induce 24-hydroxylase mRNA or its metabolic activity in B cells. These findings suggest that although human B lymphocytes can express VDR mRNA and protein, they exhibit a functional block for vitamin D-dependent gene regulation.

Unilateral parathyroidectomy: the value of the localizing scan.

Surgery for correction of primary hyperparathyroidism utilizing a standard bilateral neck exploration has a success rate of approximately 90 to 95%. With the inception of pre-operative localization studies that were 90% accurate in localizing the diseased gland, the concept arose that a unilateral exploration could be as successful as a bilateral exploration. Bilateral exploration of the neck for hyperparathyroidism exposes the patient to a greater potential of morbidity for hypoparathyroidism and recurrent laryngeal nerve injury. It is our feeling based on personal experience that unilateral parathyroidectomy in selective cases can be as successful as the bilateral operation and be more cost effective, saving over $1,100 (U.S.) per case.

Severity of illness classification for infection control departments: a study in nosocomial pneumonia.

BACKGROUND: A subjective severity of illness classification was evaluated in a study of nosocomial pneumonia. This is a 5-category system based on the determination of the control of underlying illness and the risk of death during current hospital admission. METHODS: A case-control study was performed with 128 cases of nosocomial pneumonia and 252 control patients. An additional 60 case and 90 control patients were used to compare this classification with APACHE II scoring in intensive care unit patients. RESULTS: In univariate analysis, the severity illness classification was significantly associated with nosocomial pneumonia risk (p < 0.01). APACHE II adequately predicted mortality rate but was not statistically significantly associated with nosocomial pneumonia risk among intensive care unit patients. In logistic regression analysis, the severity of illness classification, surgery, age, nasogastric tube placement, and histamine blockers each showed significant independent association with nosocomial pneumonia. CONCLUSIONS: The role of the severity of illness classification for risk stratification in nosocomial pneumonia is valid. Its roles in the evaluation of surgical wound infection, nosocomial bacteremia, and quality of care remain to be determined in subsequent studies.

Rhenium-osmium isotope constraints on the age of iron meteorites.

Rhenium and osmium concentrations and the osmium isotopic compositions of iron meteorites were determined by negative thermal ionization mass spectrometry. Data for the IIA iron meteorites define an isochron with an uncertainty of approximately +/-31 million years for meteorites approximately 4500 million years old. Although an absolute rheniumosmium closure age for this iron group cannot be as precisely constrained because of uncertainty in the decay constant of (187)Re, an age of 4460 million years ago is the minimum permitted by combined uncertainties. These age constraints imply that the parent body of the IIAB magmatic irons melted and subsequently cooled within 100 million years after the formation of the oldest portions of chondrites. Other iron meteorites plot above the IIA isocbron, indicating that the planetary bodies represented by these iron groups may have cooled significantly later than the parent body of the IIA irons.

Methods for the separation of rhenium, osmium and molybdenum applicable to isotope geochemistry.

Effective methods are described for the chemical separation of rhenium, osmium and molybdenum. The methods are based on distillation and anion-exchange chromatography, and have been the basis for rhenium-osmium isotope studies of ore deposits and meteorites. Successful anion-exchange separation of osmium requires both recognition and careful control of the osmium species in solution; thus, distillation of osmium tetroxide from a mixture of sulfuric acid and hydrogen peroxide is preferred to anion-exchange. Distribution coefficients measured for perrhenate in sulfuric acid media are sufficiently high (K(d) > 500) for rhenium to be directly loaded onto an ion-exchange column from a distillation residue and subsequently eluted with nitric acid. Polymerization of molybdenum species during elution is prevented by use of a solution that is 1M in hydrochloric acid and 1M in sodium chloride.

Distribution of skeletal metastases in prostatic and lung cancer. Mechanisms of skeletal metastases.

The distribution of skeletal metastases in prostatic and lung cancer was examined to test the hypothesis that prostatic carcinoma spreads by a unique hematogenous route. Abnormal technetium-99m methylene diphosphonate bone scans were retrospectively reviewed in 71 patients with prostatic carcinoma and 41 patients with lung cancer comparing patterns of osseous involvement. Differences in the distribution of lesions were not significant. It is concluded that prostatic carcinoma does not metastasize to specific skeletal sites by a singular hematogenous pathway.

Rhenium-osmium and samarium-neodymium isotopic systematics of the stillwater complex.

Isotopic data for the Stillwater Complex, Montana, which formed about 2700 Ma (million years ago), were obtained to evaluate the role of magma mixing in the formation of strategic platinum-group element (PGE) ore deposits. Neodymium and osmium isotopic data indicate that the intrusion formed from at least two geochemically distinct magmas. Ultramafic affinity (U-type) magmas had initial epsilon(Nd) of -0.8 to -3.2 and a chondritic initial (187)Os/(186)Os ratio of approximately 0.88, whereas anorthositic affinity (A-type) magmas had epsilon(Nd) of -0.7 to +1.7 and an initial (187)Os/(186)Os ratio of approximately -1.13. These data suggest that U-type magmas were derived from a lithospheric mantle source containing recycled crustal materials whereas A-type magmas originated either by crustal contamination of basaltic magmas or by partial melting of basalt in the lower crust. The Nd and Os isotopic data also suggest that Os, and probably the other PGEs in ore horizons such as the J-M Reef, was derived from A-type magmas. The Nd and Os isotopic heterogeneity observed in rocks below the J-M Reef also suggests that A-type magmas were injected into the Stillwater U-type magma chamber at several stages during the development of the Ultramafic series.

Rhenium-osmium isotope systematics of carbonaceous chondrites.

Rhenium and osmium concentrations and Os isotopic compositions of eight carbonaceous chondrites, one LL3 ordinary chondrite, and two iron meteorites were determined by resonance ionization mass spectrometry. Iron meteorite (187)Re/(186)Os and (l87)Os/(l86)Os ratios plot on the previously determined iron meteorite isochron, but most chondrite data plot 1 to 2 percent above this meteorite isochron. This suggests either that irons have significantly younger Re-Os closure ages than chondrites or that chondrites were formed from precursor materials with different chemical histories from the precursors of irons. Some samples of Semarkona (LL3) and Murray (C2M) meteorites plot 4 to 6 percent above the iron meteorite isochron, well above the field delineated by other chondrites. Murray may have lost Re by aqueous leaching during its preterrestrial history. Semarkona could have experienced a similar loss of Re, but only slight aqueous alteration is evident in the meteorite. Therefore, the isotopic composition of Semarkona could reflect assembly of isotopically heterogeneous components subsequent to 4.55 billion years ago or Os isotopic heterogeneities in the primordial solar nebula.