Testing quantum electrodynamics in extreme fields using helium-like uranium.

Quantum electrodynamics (QED), the quantum field theory that describes the interaction between light and matter, is commonly regarded as the best-tested quantum theory in modern physics. However, this claim is mostly based on extremely precise studies performed in the domain of relatively low field strengths and light atoms and ions1-6. In the realm of very strong electromagnetic fields such as in the heaviest highly charged ions (with nuclear charge Z ≫ 1), QED calculations enter a qualitatively different, non-perturbative regime. Yet, the corresponding experimental studies are very challenging, and theoretical predictions are only partially tested. Here we present an experiment sensitive to higher-order QED effects and electron-electron interactions in the high-Z regime. This is achieved by using a multi-reference method based on Doppler-tuned X-ray emission from stored relativistic uranium ions with different charge states. The energy of the 1s1/22p3/2 J = 2 → 1s1/22s1/2 J = 1 intrashell transition in the heaviest two-electron ion (U90+) is obtained with an accuracy of 37 ppm. Furthermore, a comparison of uranium ions with different numbers of bound electrons enables us to disentangle and to test separately the one-electron higher-order QED effects and the bound electron-electron interaction terms without the uncertainty related to the nuclear radius. Moreover, our experimental result can discriminate between several state-of-the-art theoretical approaches and provides an important benchmark for calculations in the strong-field domain.

Proton-Capture Rates on Carbon Isotopes and Their Impact on the Astrophysical

The ^{12}C/^{13}C ratio is a significant indicator of nucleosynthesis and mixing processes during hydrogen burning in stars. Its value mainly depends on the relative rates of the ^{12}C(p,γ)^{13}N and ^{13}C(p,γ)^{14}N reactions. Both reactions have been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy down to the lowest energies to date (E_{c.m.}=60 keV) reaching for the first time the high energy tail of hydrogen burning in the shell of giant stars. Our cross sections, obtained with both prompt γ-ray detection and activation measurements, are the most precise to date with overall systematic uncertainties of 7%-8%. Compared with most of the literature, our results are systematically lower, by 25% for the ^{12}C(p,γ)^{13}N reaction and by 30% for ^{13}C(p,γ)^{14}N. We provide the most precise value up to now of 3.6±0.4 in the 20-140 MK range for the lowest possible ^{12}C/^{13}C ratio that can be produced during H burning in giant stars.

Tumor necrosis factor activities and cancer therapy--a perspective.

Tumor necrosis factor (TNF) is a multifunctional cytokine which has excited and fascinated numerous investigators and commercial entities due to its promise as a therapeutic agent against cancer and as a target for drugs treating septic shock. TNF is a protein having cytotoxic, cytostatic, immunomodulatory as well as several other activities and is also involved in septic shock. This review covers the structure of TNF and its receptors, various in vitro activities and in vivo activities based on studies in animal model systems. The role of TNF as an anticancer therapeutic agent, based on various phase I and phase II clinical studies, has also been considered. The review concludes with several considerations for increasing the therapeutic utility of TNF in terms of targeting, toxicity and half-life.

Analysis of alpha-factor secretion signals by fusing with acid phosphatase of yeast.

In yeast, Saccharomyces cerevisiae, the PHO5 gene encodes the repressible acid phosphatase (APase) whose activity can be easily monitored by either the staining of colonies or by colorimetric assay. Therefore, gene fusions to PHO5 provide a convenient system for structural and functional analysis of yeast genes. We have constructed fusions of the PHO5 gene with a MF alpha 1 gene of yeast to delineate the secretion signal(s) in the alpha-factor leader peptide. Gene fusion between MF alpha 1 and PHO5 codes for a hybrid protein in which the alpha-factor leader peptide of 89 amino acids (aa) directed the export of APase, a periplasmic protein, into the medium. Since the hybrid gene is transcribed from the alpha-factor promoter, expression of the APase activity from these hybrid genes showed cell type-specific regulation. Further analyses of another MF alpha 1-PHO5 fusion showed that only the first 22 aa of the 89-aa alpha-factor leader peptide contained sufficient information for the secretion of APase into the medium. This shows that, in addition to the analysis of gene regulation, PHO5 fusions can be used to study signals involved in the proper localization of proteins.

Selection of secretory protein-encoding genes by fusion with PHO5 in Saccharomyces cerevisiae.

Secretory protein-encoding genes of Saccharomyces cerevisiae have been cloned by a novel procedure that is based on the functional selection of their fusions with acid phosphatase (APase) at the DNA level. DNA fragments that functionally replace the promoter and signal sequence-encoding regions of the PHO5 gene (encoding APase) have been obtained by positive selection from a pool of cloned random DNA fragments. Five unique DNA sequences containing the promoter, and encoding signal sequences have been isolated. We have also isolated the complete gene, SSP120, encoding one of these S. cerevisiae secretory proteins, SSP120. Gene disruption studies have shown that the SSP120 gene is not essential for viability and growth. The SSP120 amino acid (aa) sequence has 13.5% identity with the middle 88-250 aa residues of the chicken glycosylation site-binding protein. However, SSP120 disruption did not affect protein glycosylation in yeast. The present study provides an alternative approach for the isolation of genes encoding secretory proteins, in contrast to classical genetic approaches that require isolation of functionally defective mutations followed by gene isolation by functional complementation. The present procedure should contribute to our understanding of protein sorting by permitting the cloning of genes encoding proteins targeted to different organelles in the secretory pathway.

Cloning of the HIS5 gene of Saccharomyces cerevisiae by yeast transformation.

A yeast DNA fragment complementing a yeast his5 mutation was cloned on a shuttle vector, YRp7, by transformation of the yeast host with plasmid DNA prepared from a gene bank constructed in the Escherichia coli host. That the DNA fragment contains the yeast HIS5 gene was confirmed by the integration of the cloned plasmid into the his5 region of the yeast chromosome. The cloned yeast HIS5 gene weakly complemented the E. coli hisC mutation and gave rise to a slow-growing E. coli transformant without addition of histidine. From the slow-growing culture, rapidly growing variants of E. coli were easily obtained by mutations either in the bacterial chromosome or in the plasmid.

Accuracy of computer-assisted semen analysis in prefreeze and post-thaw specimens with high and low sperm counts and motility.

OBJECTIVES: We evaluated the accuracy and precision of computer-assisted semen analysis (CASAs) to determine whether variations in the CASA results were related to the type of analyzer or to the type of specimens analyzed. METHODS: Semen specimens were analyzed manually and by CASA before freezing and after thawing. Multiple ejaculates (220 semen specimens) from normal healthy donors (n = 8) and 131 semen specimens from 57 patients with cancer were assessed. RESULTS: The differences between CASA and manual sperm counts and percent motility were higher in prefreeze and post-thaw specimens at sperm concentrations of less than 20 x 10(6)/mL. The differences between CASA and manual results were significant for cancer patients, compared with normal donors (P <0.01). CONCLUSIONS: CASA results are unreliable at sperm counts of less than 20 x 10(6)/mL and post-thaw motility is generally underestimated by CASAs.

Effect of cryopreservation on semen quality in patients with testicular cancer.

OBJECTIVES: Current techniques in cryopreservation of human semen substantially decrease sperm quality. In addition, the pregnancy rate using cryopreserved sperm obtained from testicular cancer patients is lower than when sperm from normal fertile men is used. However, it is still unclear whether cryopreserved sperm from these patients is inherently defective or if the sperm loses its motility after thawing. This study was undertaken to assess the effect of cryopreservation on the quality and motion characteristics of semen from patients with testicular cancer before definitive therapy compared with semen from normal volunteers. METHODS: We compared the sperm quality before and after cryopreservation in samples from 34 patients with testicular cancer and 30 normal volunteers who were referred for sperm banking over a 7-year period. The effects of cancer stage and histologic type on various semen parameters were also examined. A computer-assisted semen analysis was performed before and after cryopreservation on each specimen. The nitrogen vapor technique using Test yolk buffer with glycerol as a cryoprotective agent was used for cryopreservation. The motile sperm count and motion characteristics (motility, velocity, linearity, amplitude of the lateral head movement, motility index) were analyzed before and after cryopreservation and compared between the groups. RESULTS: Semen quality did not significantly differ among patients with Stage I, II, or III cancer. However, semen quality tended to be poorer at higher cancer stages. In general, semen quality was better among patients with pure seminomas than with pure embryonal tumors; quality was worst among patients with mixed germ cell tumors. However, 71.4% of patients with mixed tumors presented with Stage III disease, whereas all patients with seminomas presented with Stage I disease. Significant differences were also seen in prefreeze motility (median, 42% [interquartile range, 24 to 51] versus 60.5% [range, 49 to 73]; P = 0.0004) and motile sperm count (6.7 x 10(6)/mL [range, 3.4 to 14.4] versus 50.0 [range, 24.6 to 72.0]; P = 0.0001) in patients compared with controls, respectively. The motile sperm count and percent motility significantly decreased in both patients and controls after cryopreservation (P = 0.0001). However, the percentage decline in motile sperm count and motion characteristics after cryopreservation did not differ significantly between patients and controls (P > 0.01). CONCLUSIONS: We conclude that the effect of cryopreservation on sperm quality in patients with testicular cancer is identical to its effect on sperm from normal fertile men. Differences in values after preservation are explained by poor semen characteristics before freezing; semen quality declines with more extensive disease. Stage I patients also had poorer quality than control subjects. Thus, we recommend that routine sperm banking be encouraged among all patients with testicular cancer before the initiation of specific medical treatment. We also recommend that future efforts be focused on improving the technique of sperm banking.

Nuclear condensation and fragmentation following cerebral hypoxia-ischemia occurs more frequently in immature than older rats.

Apoptotic cell death is associated with condensation and fragmentation of the nuclear chromatin into apoptotic bodies. Such nuclei occur frequently following cerebral hypoxia-ischemia in 1 week old rats but seem sparse in older animals. We investigated the age dependence by counting pyknotic or punctate chromatin containing cells in the cerebral cortex of 1,2 and 4 week old animals subjected to cerebral hypoxia-ischemia. In 1 week old animals the majority of injured neurons in the cortex had nuclei with punctate condensed chromatin but few were pyknotic. In the 2 and 4 week old animals the majority of injured cells were pyknotic (P < 0.002). Electron microscopic studies demonstrated the presence of apoptotic bodies. The results suggest that immature brain retains a part of the developmental cell death "program' that is activated following hypoxia-ischemia.

Tumor necrosis factor analogs: identification of functional domains.

Truncated tumor necrosis factor analogs were produced by making in vitro deletions of the coding sequence of the human TNF gene. One of these analogs, TNF-desA7, lacked seven amino terminal residues of the mature TNF protein and the other two analogs, TNF-desC7 and TNF-desC2, had deletions of seven and two carboxy terminal amino acids, respectively. While the deletion of the first seven amino acid residues did not affect the biological activity of the protein, the deletions of carboxy terminal residues in both analogs resulted in the complete loss of biological activity. A direct correlation of the biological activity of the TNF protein and its binding to neutralizing monoclonal antibodies was observed. The carboxy terminal-deleted TNF analogs, with no biological activity, did not bind to neutralizing monoclonal antibodies while the amino terminal-deleted analog, which retained complete biological activity, did bind. These results indicate that the carboxy terminal amino acids of the TNF protein are essential for TNF biological activity and are part of an epitope recognized by neutralizing monoclonal antibodies.

Seimatoantlerium tepuiense gen. nov., a unique epiphytic fungus producing taxol from the Venezuelan Guyana.

Seimatoantlerium gen. nov., type species, S. tepuiense sp. nov. is proposed for an acervular fungus producing 4-septate, holoblastic conidia with 6-8 unbranched, apical appendages that dehisce as an appendage apparatus and also commonly possessing one or two exogenous basal appendages as well as a pedicel. It is compared with Seimatosporium, Seimatosporiopsis, and other genera. It is epiphytic on Maguireothamnus speciosus, a rubiaceous plant endemic to the tepuis of southeastern Venezuela. It produces the anti-oomycetous anticancer compound, taxol, as shown by immunological and spectroscopic methods. Taxol production is discussed relative to the ability of this fungus to exist in an extremely moist ecosystem, as well as to its relationship to other plant associated fungi.

Glyphosate-tolerant corn: the composition and feeding value of grain from glyphosate-tolerant corn is equivalent to that of conventional corn (Zea mays L.).

Glyphosate-tolerant (Roundup Ready) corn line GA21 has been developed by genetic modification to tolerate glyphosate, the active ingredient in Roundup herbicide. The purpose of this study was to evaluate the compositional and nutritional safety of corn line GA21 compared to that of conventional corn. Compositional analyses were conducted to measure proximate, fiber, amino acid, fatty acid, and mineral contents of grain and proximate, fiber, and mineral contents of forage collected from 16 field sites over two growing seasons. The nutritional safety of corn line GA21 was evaluated in a poultry feeding study conducted with 2-day old, rapidly growing broiler chickens, at a dietary concentration of 50-60% w/w. Compositional analysis results showed that, except for a few minor differences that are unlikely to be of biological significance, the grain and forage of GA21 corn were comparable in their composition to that of the control corn line and to conventional corn. Results from the poultry feeding study showed that there were no differences in growth, feed efficiency, adjusted feed efficiency, and fat pad weights between chickens fed with GA21 grain or with parental control grain. These data taken together demonstrate that Roundup Ready corn is as safe and nutritious as conventional corn for food and feed use.

Relationship between creatine kinase activity and semen characteristics in subfertile men.

OBJECTIVE: Creatine kinase is an indicator of sperm maturity. We studied whether sperm creatine kinase levels differ between normal healthy donors and subfertile patients and determined the correlation between sperm creatine kinase level and semen quality in subfertile men. MATERIAL AND METHODS: Semen samples were obtained from 76 subfertile and 15 healthy normal donors after 48 to 72 hours of sexual abstinence. Sperm characteristics were assessed with a computer-assisted semen analyzer. Morphology was evaluated by Kruger's strict criteria and World Health Organization methods. The thiobarbituric acid assay was used to measure lipid peroxidation; sperm creatine kinase activity was measured using a commercial kit after detergent extraction (Triton X-100). RESULTS: Creatine kinase levels were significantly higher (P < .001) in subfertile men (median = 0.197 U/10(8) sperm) compared with donors (median = 0.061 U/10(8) sperm). In subfertile men, creatine kinase levels correlated significantly with lipid peroxidation levels (r = .49; P = 0.03) and sperm concentration (r = -.70; P < .001), and with normal sperm forms by Kruger's (r = -.30; P = 0.01) and WHO methods (r = -.32; P < .005). Creatine kinase levels and spermatozoal characteristics did not correlate significantly in donors. Compared with subfertile normospermic men, creatine kinase activity was significantly higher in oligospermic and asthenospermic men (P <.001). CONCLUSIONS: The inverse relationship between creatine kinase level and sperm concentration and morphological forms suggests that creatine kinase levels can be a reliable marker for semen quality in subfertile men. An elevated creatine kinase level and its correlation with lipid peroxidation levels may reflect biochemically immature spermatozoa.

Dependence of yeast sporulation on mitochondrial protein synthesis.

Sporulation in diploid Saccharomyces cerevisiae is not dependent on continued protein synthesis in the mitochondria. Using chloramphenicol, it is shown that proteins essential for respiration and sporulation are synthesized in mitochondria early during growth in a presporulation medium.

Two-dimensional electrophoretic analyses of proteins synthesized during differentiation of 3T3-L1 preadipocytes.

The changes in protein composition and cell surface proteins that occur during the adipocyte conversion of 3T3-L1 preadipocytes were monitored by two-dimensional polyacrylamide gel electrophoresis folowing incubation of cells with [35S]methionine for periods of 3 and 24 h. Alterations in the biosynthesis of more than 30 cytoplasmic proteins, 9 non-histone, chromosome-associated proteins, and 24 membrane proteins, were detected. Although the methodological limitations of the electrophoretic systems employed result in an underestimate of the total number of differences, the alterations observed exceed the enzyme changes known to occur during differentiation of these cells. One major alteration occurring during differentiation is a decrease in the content of a protein whose position following two-dimensional electrophoresis tentatively identified it as actin. A fall in actin content accompanying adipocyte conversion was confirmed by direct analysis of the DNase 1 inhibitory activity in homogenates prepared from cells during the course of differentiation. Studies of cell surface proteins by lactoperoxidase-catalyzed iodination reveal a number of changes during differentiation including an increase in a polypeptide(s) in the molecular weight range of 16,500 to 18,500, a decrease in at least four proteins of molecular weights greater than 100,000, and in a protein of molecular weight 95,000.

Resident continuity of care experience in a Canadian general surgery training program.

OBJECTIVES: To provide baseline data on resident continuity of care experience, to describe the effect of ambulatory centre surgery on continuity of care, to analyse continuity of care by level of resident training and to assess a resident-run preadmission clinic's effect on continuity of care. DESIGN: Data were prospectively collected for 4 weeks. All patients who underwent a general surgical procedure were included if a resident was present at operation. SETTING: The Division of General Surgery, Queen's University, Kingston, Ont. OUTCOME MEASURES: Preoperative, operative and inhospital postoperative involvement of each resident with each case was recorded. RESULTS: Residents assessed preoperatively (before entering the operating room) 52% of patients overall, 20% of patients at the ambulatory centre and 83% of patients who required emergency surgery. Of patients assessed by the chief resident, 94% were assessed preoperatively compared with 32% of patients assessed by other residents (p < 0.001). Of the admitted patients, 40% had complete resident continuity of care (preoperative, operative and postoperative). There was no statistical difference between this rate and that for emergency, chief-resident and non-chief-resident subgroups. Of the eligible patients, 58% were seen preoperatively by the resident on the preadmission clinic service compared with 54% on other services (p < 0.1). CONCLUSIONS: This study serves as a reference for the continuity of care experience in Canadian surgical programs. Residents assessed only 52% of patients preoperatively, and only 40% of patients had complete continuity of care. Factors such as ambulatory surgery and junior level of training negatively affected continuity experience. Such factors must be taken into account in planning surgical education.

The action of chelating agents on human liver aldehyde dehydrogenase.

Human liver aldehyde dehydrogenase was inhibited by aromatic chelating agents. However, structurally related compounds with much lower metal-complexing ability displayed affinities for enzyme essentially equal to those of their respective chelating analogues. Inhibition was competitive with respect to the coenzyme. It is suggested that hydrophobic interactions between the inhibitors and the coenzyme-binding site of the enzyme are responsible for the observed effects on activity.