mm-wave Rydberg-Rydberg transitions gauge intermolecular coupling in a molecular ultracold plasma.

Out-of-equilibrium, strong correlation in a many-body system can trigger emergent properties that act to constrain the natural dissipation of energy and matter. Signs of such self-organization appear in the avalanche, bifurcation, and quench of a state-selected Rydberg gas of nitric oxide to form an ultracold, strongly correlated ultracold plasma. Work reported here focuses on the initial stages of avalanche and quench and uses the mm-wave spectroscopy of an embedded quantum probe to characterize the intermolecular interaction dynamics associated with the evolution to plasma. Double-resonance excitation prepares a Rydberg gas of nitric oxide composed of a single selected state of principal quantum number, n0. Penning ionization, followed by an avalanche of electron-Rydberg collisions, forms a plasma of NO+ ions and weakly bound electrons, in which a residual population of n0 Rydberg molecules evolves to a state of high orbital angular momentum, ℓ. Predissociation depletes the plasma of low-ℓ molecules. Relaxation ceases and n0ℓ(2) molecules with ℓ ≥ 4 persist for very long times. At short times, varying excitation spectra of mm-wave Rydberg-Rydberg transitions mark the rate of electron-collisional ℓ-mixing. Deep depletion resonances that persist for long times signal energy redistribution in the basis of central-field Rydberg states. The widths and asymmetries of Fano line shapes witness the degree to which coupling in the arrested bath (i) broadens the allowed transition and (ii) mixes the local network of levels in the ensemble.

The painful truth: work-related musculoskeletal disorders in Australian surgeons.

BACKGROUND: Work-related musculoskeletal disorder (WRMD) is a collective term for preventable work-related disorders that cause musculoskeletal symptoms. The growing prevalence of these disorders amongst surgeons has been labelled an 'impending epidemic' and currently there is a lack of awareness and no existing intervention programme. AIMS: To estimate prevalence and identify risk factors for developing work related neck, shoulder and upper back pain in surgeons. METHODS: Cross-sectional questionnaire survey of surgeons and surgical trainees across Australia. We collected data on demographics, nature of regular operative work, hours working/operating per week, and prevalence and severity of musculoskeletal disorders based on the Nordic Musculoskeletal Questionnaire [1]. We assessed associations between categorical predictors and pain over 7 days and 12 months using Pearson's chi-square test. We assessed associations involving continuous variables using Student's t-test. Tests were two-tailed and assessed at the 5% alpha level. RESULTS: From ~2058 recipients, 329 (16%) responded; 137 (42%) surgeons reported shoulder, neck or upper back pain in a 7-day period, 245 (75%) reported pain and 101 (31%) had pain preventing normal work in a 12-month period. Significant predictors of increased prevalence included female sex (P < 0.001), decreasing age (P < 0.01) and fewer years working (P < 0.01). Body mass index (BMI) and mode of practise did not significantly affect prevalence of WRMDs. CONCLUSIONS: The prevalence of WRMDs amongst surgeons is high, females and younger surgeons reporting increased rates. There is a need to build awareness and educate surgical trainees about WRMDs.

Penultimate deglacial warming across the Mediterranean Sea revealed by clumped isotopes in foraminifera.

The variability of seawater temperature through time is a critical measure of climate change, yet its reconstruction remains problematic in many regions. Mg/Ca and oxygen isotope (δ 18OC) measurements in foraminiferal carbonate shells can be combined to reconstruct seawater temperature and δ 18O (δ 18OSW). The latter is a measure of changes in local hydrology (e.g., precipitation/evaporation, freshwater inputs) and global ice volume. But diagenetic processes may affect foraminiferal Mg/Ca. This restricts its potential in many places, including the Mediterranean Sea, a strategic region for deciphering global climate and sea-level changes. High alkalinity/salinity conditions especially bias Mg/Ca temperatures in the eastern Mediterranean (eMed). Here we advance the understanding of both western Mediterranean (wMed) and eMed hydrographic variability through the penultimate glacial termination (TII) and last interglacial, by applying the clumped isotope (Δ 47) paleothermometer to planktic foraminifera with a novel data-processing approach. Results suggest that North Atlantic cooling during Heinrich stadial 11 (HS11) affected surface-water temperatures much more in the wMed (during winter/spring) than in the eMed (during summer). The method's paired Δ 47 and δ 18OC data also portray δ 18OSW. These records reveal a clear HS11 freshwater signal, which attenuated toward the eMed, and also that last interglacial surface warming in the eMed was strongly amplified by water-column stratification during the deposition of the organic-rich (sapropel) interval known as S5.

Bipolar seesaw control on last interglacial sea level.

Our current understanding of ocean-atmosphere-cryosphere interactions at ice-age terminations relies largely on assessments of the most recent (last) glacial-interglacial transition, Termination I (T-I). But the extent to which T-I is representative of previous terminations remains unclear. Testing the consistency of termination processes requires comparison of time series of critical climate parameters with detailed absolute and relative age control. However, such age control has been lacking for even the penultimate glacial termination (T-II), which culminated in a sea-level highstand during the last interglacial period that was several metres above present. Here we show that Heinrich Stadial 11 (HS11), a prominent North Atlantic cold episode, occurred between 135 ± 1 and 130 ± 2 thousand years ago and was linked with rapid sea-level rise during T-II. Our conclusions are based on new and existing data for T-II and the last interglacial that we collate onto a single, radiometrically constrained chronology. The HS11 cold episode punctuated T-II and coincided directly with a major deglacial meltwater pulse, which predominantly entered the North Atlantic Ocean and accounted for about 70 per cent of the glacial-interglacial sea-level rise. We conclude that, possibly in response to stronger insolation and CO2 forcing earlier in T-II, the relationship between climate and ice-volume changes differed fundamentally from that of T-I. In T-I, the major sea-level rise clearly post-dates Heinrich Stadial 1. We also find that HS11 coincided with sustained Antarctic warming, probably through a bipolar seesaw temperature response, and propose that this heat gain at high southern latitudes promoted Antarctic ice-sheet melting that fuelled the last interglacial sea-level peak.

Sea-level variability over five glacial cycles.

Research on global ice-volume changes during Pleistocene glacial cycles is hindered by a lack of detailed sea-level records for time intervals older than the last interglacial. Here we present the first robustly dated, continuous and highly resolved records of Red Sea sea level and rates of sea-level change over the last 500,000 years, based on tight synchronization to an Asian monsoon record. We observe maximum 'natural' (pre-anthropogenic forcing) sea-level rise rates below 2 m per century following periods with up to twice present-day ice volumes, and substantially higher rise rates for greater ice volumes. We also find that maximum sea-level rise rates were attained within 2 kyr of the onset of deglaciations, for 85% of such events. Finally, multivariate regressions of orbital parameters, sea-level and monsoon records suggest that major meltwater pulses account for millennial-scale variability and insolation-lagged responses in Asian monsoon records.

Sea-level and deep-sea-temperature variability over the past 5.3 million years.

Ice volume (and hence sea level) and deep-sea temperature are key measures of global climate change. Sea level has been documented using several independent methods over the past 0.5 million years (Myr). Older periods, however, lack such independent validation; all existing records are related to deep-sea oxygen isotope (δ(18)O) data that are influenced by processes unrelated to sea level. For deep-sea temperature, only one continuous high-resolution (Mg/Ca-based) record exists, with related sea-level estimates, spanning the past 1.5 Myr. Here we present a novel sea-level reconstruction, with associated estimates of deep-sea temperature, which independently validates the previous 0-1.5 Myr reconstruction and extends it back to 5.3 Myr ago. We find that deep-sea temperature and sea level generally decreased through time, but distinctly out of synchrony, which is remarkable given the importance of ice-albedo feedbacks on the radiative forcing of climate. In particular, we observe a large temporal offset during the onset of Plio-Pleistocene ice ages, between a marked cooling step at 2.73 Myr ago and the first major glaciation at 2.15 Myr ago. Last, we tentatively infer that ice sheets may have grown largest during glacials with more modest reductions in deep-sea temperature.

Rapid coupling between ice volume and polar temperature over the past 150,000 years.

Current global warming necessitates a detailed understanding of the relationships between climate and global ice volume. Highly resolved and continuous sea-level records are essential for quantifying ice-volume changes. However, an unbiased study of the timing of past ice-volume changes, relative to polar climate change, has so far been impossible because available sea-level records either were dated by using orbital tuning or ice-core timescales, or were discontinuous in time. Here we present an independent dating of a continuous, high-resolution sea-level record in millennial-scale detail throughout the past 150,000 years. We find that the timing of ice-volume fluctuations agrees well with that of variations in Antarctic climate and especially Greenland climate. Amplitudes of ice-volume fluctuations more closely match Antarctic (rather than Greenland) climate changes. Polar climate and ice-volume changes, and their rates of change, are found to covary within centennial response times. Finally, rates of sea-level rise reached at least 1.2 m per century during all major episodes of ice-volume reduction.

Leishmania mexicana: expression; characterization and activity assessment of E. coli-expressed recombinant CRK3.

OBJECTIVES AND METHODS: Previous studies have shown that CRK3 protein kinase of Leishmania mexicana is a potential drug target. Therefore, the aim of this study was to provide an active protein kinase for chemical inhibitors testing. A system was developed to express and affinity-purify recombinant L. mexicana CRK3 protein from Escherichia coli. RESULTS: Biochemical analysis has confirmed the expression of the pure kinase. The bacterial-expressed kinase was found to be inactive as a monomer. The mutated CRK3-E178 protein kinase was also found to be inactive. CONCLUSION: This study suggests that cyclin binding and phosphorylation status are both important for reconstituting protein kinase activity. Work presented by this paper has confirmed the usefulness of the prokaryotic system for production of pure homogenous recombinant protein kinase of Leishmania parasite, though this system is unable to produce active CRK3 protein kinase  

Apoptosis-like death as a feature of malaria infection in mosquitoes.

Malaria parasites of the genus Plasmodium make a hazardous journey through their mosquito vectors. The majority die in the process, many as a result of the action of mosquito defence mechanisms. The mosquito too is not unscathed by the encounter with these parasites. Tissue damage occurs as a result of mid-gut invasion and reproductive fitness is lost when many developing ovarian follicles are resorbed. Here we discuss some of the mechanisms that are involved in killing the parasite and in the self-defence mechanisms employed by the mosquito to repair the mid-gut epithelium and to manipulate resources altering the trade-off position that balances reproduction and survival. In all cases, cells die by apoptotic-like mechanisms. In the midgut cells, apoptosis-induction pathways are being elucidated, the molecules involved in apoptosis are being recognised and Drosophila homologues sought. The death of ookinetes in the mosquito mid-gut lumen is associated with caspase-like activity and, although homologues of mammalian caspases are not present in the malaria genome, other cysteine proteases that are potential candidates have been discussed. In the ovary, apoptosis of patches of follicular epithelial cells is followed by resorption of the developing follicle and a subsequent loss of egg production in that follicle.

The CRK3 protein kinase is essential for cell cycle progression of Leishmania mexicana.

The Leishmania mexicana CRK3 gene encodes a cdc2-related protein kinase with activity towards histone H1. Attempts to disrupt both alleles of CRK3 in the promastigote life-cycle stage resulted in changes in cell ploidy, which were avoided only when an extra copy of CRK3 was expressed from an episome. This provides strong evidence that CRK3 is essential to L. mexicana. The cyclin-dependent kinase specific inhibitor flavopiridol inhibited affinity purified histidine tagged CRK3 (CRK3his) with an IC(50) value of 100 nM and inhibited in vitro growth of L. mexicana promastigotes. Incubation of promastigotes with 2.5 microM flavopiridol for 24 h led to cell cycle arrest with an accumulation of 95% of cells in G2 or early mitosis (G2/M). Release from cell cycle arrest resulted in a semi-synchronous re-entry into the cell cycle; samples taken at 2, 4, and 6 h after release from the block were enriched for cells in G1 (68%), S-phase (70%), and G2/M phase (61%), respectively. This method of synchronisation was used to show that the majority of CRK3his activity towards the substrate histone H1 was present at G2/M. These data suggest that CRK3 has an essential role in controlling cell cycle progression at the G2/M-phase transition in L. mexicana promastigotes.

The crk3 gene of Leishmania mexicana encodes a stage-regulated cdc2-related histone H1 kinase that associates with p12.

A cdc2-related protein kinase gene, crk3, has been isolated from the parasitic protozoan Leishmania mexicana. Data presented here suggests that crk3 is a good candidate to be the leishmanial cdc2 homologue but that the parasite protein has some characteristics which distinguish it from mammalian cdc2. crk3 is predicted to encode a 35.6-kDa protein with 54% sequence identity with the human cyclin-dependent kinase cdc2 and 78% identity with the Trypanosoma brucei CRK3. The trypanosomatid CRK3 proteins have an unusual, poorly conserved 19-amino acid N-terminal extension not present in human cdc2. crk3 is single copy, and there is 5-fold higher mRNA in the replicative promastigote life-cycle stage than in the non-dividing metacyclic form or mammalian amastigote form. A leishmanial suc-binding cdc2-related kinase (SBCRK) histone H1 kinase, has previously been described which binds the yeast protein, p13(suc1), and that has stage-regulated activity (Mottram J. C., Kinnaird, J., Shiels, B. R., Tait, A., and Barry, J. D. (1993) J. Biol. Chem. 268, 21044-21051). CRK3 from cell extracts of the three life-cycle stages was found to bind p13(suc1) and the leishmanial homologue p12(cks1). CRK3 fused with six histidines at the C terminus was expressed in L. mexicana and shown to have SBCRK histone H1 kinase activity. Depletion of histidine-tagged CRK3 from L. mexicana cell extracts, by Ni-nitrilotriacetic acid agarose selection, reduced histone H1 kinase activity binding to p13(suc1). These data imply that crk3 encodes the kinase subunit of SBCRK. SBCRK and histidine-tagged CRK3 activities were inhibited by the purine analogue olomoucine with an IC50 of 28 and 42 microM, respectively, 5-6-fold higher than human p34(cdc2)/cyclinB.

Gene disruptions indicate an essential function for the LmmCRK1 cdc2-related kinase of Leishmania mexicana.

The generation of homozygous null mutants for the crk1 Cdc2-Related Kinase of Leishmania mexicana was attempted using targeted gene disruption. Promastigote mutants heterozygous for crk1 were readily isolated with a hyg-targeting fragment, but attempts to create null mutants by second-round transfections with a bie-targeting fragment yielded two classes of mutant, neither of which was null. First, the transfected fragment formed an episome; second, the cloned transfectants were found to contain wild-type crk1 alleles as well as hyg and ble integrations. DNA-content analysis revealed that these mutants were triploid or tetraploid. Plasticity in chromosome number following targeting has been proposed as a means by which Leishmania avoids deletion of essential genes. These data support this theory and implicate crk1 as an essential gene, validating CRK1 as a potential drug target. L mexicana transfected with a Trypanosoma brucel homologue, tbcrk1, was shown to be viable in an immcrk1 null background, thus showing complementation of function between these trypanosomatid genes. The expression of crk1 was further manipulated by engineering a six-histidine tag at the C-terminus of the kinase, allowing purification of the active complex by affinity selection on Nl(2+)-nitriloacetic acid (NTA) agarose.

Leishmania mexicana p12cks1, a homologue of fission yeast p13suc1, associates with a stage-regulated histone H1 kinase.

We have isolated a Leishmania mexicana homologue of the fission yeast suc1 gene using PCR with oligonucleotides designed to conserved regions of cdc2 kinase subunits (cks). The product of cks1 is a 12 kDa polypeptide, which has 70% identity with human p9cks1 and 44% identity with fission yeast p13suc1.p12cks1 was detected in the three life-cycle stages of L. mexicana by immunoblotting. Recombinant p12cks1 (p12cks1his) bound to agarose beads was used as a matrix to affinity-select histone H1 kinase complexes from Leishmania, yeast and bovine extracts. Immunoblotting showed that yeast and bovine cdc2 kinase bound to p12cks1his, thus demonstrating functional homology between L. mexicana p12cks1 and yeast p13suc1. Histone H1 kinase activity was found at a high level in the proliferative promastigote and amastigote forms of L. mexicana, but at a low level in the non-dividing metacyclic form. These activities are likely to be the same as the leishmanial p13suc1 binding kinase (SBCRK) described previously [Mottram, Kinnaird, Shiels, Tait and Barry (1993) J. Biol. Chem. 268, 21044-21051]. A distinct cdc2-related kinase, L. mexicana CRK1, was also found to associate with p12cks1his but affinity-depletion experiments showed that CRK1 was not responsible for the histone H1 kinase activity associating with p12cks1his in promastigote cell extracts. The finding that p12cks1 associates with at least two cdc2-related kinases, SBCRK and CRK1, is consistent with the presence of a large gene family of cdc2-related kinases in trypanosomatids, a situation thought to be more similar to higher eukaryotes than yeast.

Non-Hodgkin's lymphoma in a population with or at risk for acquired immunodeficiency syndrome: indications for intensive chemotherapy.

PURPOSE: An increased risk of malignancies, including Kaposi's sarcoma and non-Hodgkin's lymphoma, is found in patients infected with the human immunodeficiency virus type 1 (HIV-1). Treatment of such patients may be complicated by their underlying immunodeficiency, especially when aggressive regimens are used. Clinical presentation and treatment outcomes were assessed in 31 patients with non-Hodgkin's lymphoma who had or were at risk for infection with HIV-1 at a single community institution. PATIENTS AND METHODS: Lymphomas presented in advanced stages and involved extranodal sites. Twenty-six patients received therapy (two radiation, one surgery), and a total of 23 patients received chemotherapy. RESULTS: A 52 percent response rate was seen with the use of chemotherapy. A history of opportunistic infections, or Kaposi's sarcoma, or both impacted negatively on the ability to achieve a complete response. Sixty-four percent of the 11 patients who received an intensive chemotherapeutic regimen, MACOP-B (methotrexate, Adriamycin, cyclophosphamide, vincristine, prednisone, bleomycin) had complete remissions. Overall median survival for 23 patients who received chemotherapy was seven months. Patients achieving complete responses had a median survival of 20 months. CONCLUSION: Our results support intensive chemotherapy for patients with lymphoma and HIV-1 infection.