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.

Interpretation of three-dimensional structure from two-dimensional endovascular images: implications for educators in vascular surgery.

PURPOSE: Endovascular therapy has had a major effect on vascular surgery; surgeons perform tasks in three dimensions (3D) while viewing two-dimensional (2D) displays. This fundamental change in how surgeons perform operations has educational implications related to learning curves and patient safety. We studied the effects of experience, training, and visual-spatial ability on 3D perception of 2D angiographic images of abdominal aortic aneurysms (AAA). METHODS: A novel computer-based method was developed to produce 3D depth maps based on subjects' interpretations of 2D images. Seven experts (certified vascular surgeons) and 20 novices (medical or surgical trainees) were presented with a 2D AAA angiographic image. With software specifically designed for this study, a depth map representing each subject's 3D interpretation of the 2D angiogram was produced. The novices were then randomized into a control group and a treatment group, who received a 5-minute AAA anatomy educational session. All subjects repeated the exercise on a second AAA image. Finally, all novices were given tests of visual-spatial ability, including the Surface Development Test and the Mental Rotations Test. Comparisons between experts and novices were made with depth map comparison, a subject's perception of overall object contour. RESULTS: The depth maps were significantly different (depth map comparison, P <.001) between the expert and both novice groups for the first image. After the educational intervention, the control group and the treatment group exhibited significantly different depth maps (depth map comparison, P <.001), with treatment group depth maps more similar to those of the expert group. There were no significant correlations between the visual-spatial tests and the novice depth map comparison with the expert group. CONCLUSIONS: This is the first study to examine perception of endovascular images in an educational context. Perception of overall surface contour of 3D structures from 2D angiographic images is affected by experience and training. With application of methods of vision science to an important problem in surgery, this research represents a first step in understanding the nature of visual perceptual processes involved in execution of an increasingly common clinical task. These results have implications for understanding and studying the endovascular learning curve. CLINICAL RELEVANCE: This research represents a unique collaboration in an effort to understand and solve one of the greatest problems facing surgical educators and surgeons. This research uses applied tools in vision science to understand the perceptual constraints involved in minimally invasive surgery. Specifically, we examined the mental three-dimensional maps experts use when viewing two-dimensional displays. Furthermore, we compared experts with novices in an effort to assist surgical trainees.

Vascular surgery training in general surgery residency programs: the Canadian experience.

OBJECTIVES: Vascular surgery is traditionally considered a component of general surgery. There is growing evidence of improved patient outcome related to surgeon volume and vascular certification status. The American Board of Surgery in the United States, as well as until recently the Royal College of Physicians and Surgeons in Canada, requires that vascular surgery be considered an essential content area of general surgery training. This requirement is controversial. The purpose of this study was to describe experience and perceived competence in common vascular surgery procedures during general surgery residency training in Canada. METHODS: This web-based survey was conducted between January and June 2002. General surgery program directors (GSPDs), vascular surgeons involved in general surgery training programs (VSs), and senior general surgery residents (SRs) from the 13 English-speaking general surgery programs in Canada were surveyed. Questions were asked regarding which vascular surgery procedures are appropriate for general surgeons to perform, which procedures SRs are trained to perform, and which procedures SR intend to perform. RESULTS: The response rate was 62% for GSPDs, 57% for VSs, and 45% for SRs. Overall, 49% of SRs did not intend to perform any vascular procedures after training. GSPDs, VSs, and SRs indicated that most SRs should be and are trained to perform varicose vein surgery, leg amputation, and femoral embolectomy (P >.05). In addition, GSPDs, VSs, and SRs indicated that SRs should not be and are not trained to perform infrainguinal bypass grafting, carotid endarterectomy, or abdominal aortic aneurysm (AAA) repair (P >.05). There were significant differences with respect to ruptured AAA repair: 49% of SRs, 25% of PDs, and only 12% of VSs believe that general surgeons should be trained to perform ruptured AAA repair (P <.05). Overall, 76% of VSs believe SRs receive too little vascular training. CONCLUSION: There is similarity between GSPDs, VSs, and SRs with respect to vascular surgery training in Canadian general surgery programs. Vascular surgery training cannot be considered a component of general surgery. More rotations or fellowship training is required to become competent in management of common vascular surgery procedures. Perhaps this level of competence should not be an objective of general surgery training.

Aortic and iliac reconstruction after kidney transplantation: experience with an algorithm for renal protection.

Advances in renal transplantation have allowed for improved survival and an increased age of recipients. This has resulted in more aortoiliac lesions requiring intervention. The optimal approach for renal protection during aortoiliac surgery remains unknown. A retrospective review of transplant patients admitted to Toronto General Hospital for aortoiliac reconstruction between 1990 and 2000 was performed. A total of 20 aortic reconstructions were carried out in 18 patients: 5 patients with ascending aortic repairs and 15 patients with aortoiliac reconstructions. Of the five ascending repairs, all had cardiopulmonary bypass and four were performed under hypothermic arrest. There was one allograft loss in the postoperative period and one mortality. Of the 15 aortoiliac reconstructions 12 had protection: 10 temporary axillofemoral artery bypasses and 2 renal cold perfusion. In the 10 patients with temporary bypass protection, there were no graft losses. There was no graft loss in the hypothermic perfusion group. Of the three patients without protection, there was one graft loss. The postoperative rise in serum creatinine was significantly higher (p <0.05) in the no-protection group than in those receiving temporary bypass protection. Our algorithm of (1). temporary axillofemoral bypass, (2). cold perfusion if temporary bypass cannot be performed, and (3). clamp and sew if the patient is too unstable allows for surgery with excellent graft survival.

Rab3B in human platelet is membrane bound and interacts with Ca(2+)/calmodulin.

The subcellular distribution of Rab3B in fresh and aged platelets was determined and majority of the protein was localized with the particulate fraction with only a minor amount detected in the cytosol. Rab3B was pulled out from platelet particulate fraction with GST-RabGDI-alpha fusion protein. Using GST-Rab3B in in vitro pull-down experiments, the binding of calmodulin from platelet cytosol to Rab3B was demonstrated. In the reverse experiment, binding of Rab3B from platelet particulate and cytosolic fractions to Sepharose-CaM beads was also observed. The interaction between Rab3B and calmodulin was Ca(2+)-dependent but independent of the guanine nucleotide status of Rab3B. These findings provide evidence that Rab3B is primarily localized with the particulate fraction and that Ca(2+)/calmodulin could regulate function of this GTPase in the platelet.

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.

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.

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.

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

Seimatoantlerium gen. nov., type species, S.tepuiense sp. nov. is proposed for an acervular fungus producing 4-septate, holobastic 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. (AU)

Analysis of beta-tubulin cDNAs from taxol-resistant Pestalotiopsis microspora and taxol-sensitive Pythium ultimum and comparison of the taxol-binding properties of their products.

The anti-cancer drug taxol binds to beta-tubulin in assembled microtubules and causes cell cycle arrest in animal cells; in contrast, in fungi, the effect of taxol varies. For instance, the taxol-producer Pestalotiopsis microspora Ne32, an ascomycete, is resistant to taxol (IC50 greater than 11.7 microM), whereas Pythium ultimum, an oomycete, is sensitive to taxol (IC50 0.1 microM). In order to understand the differential fungal response to taxol, we isolated cDNAs encoding beta-tubulin from both P. microspora and P. ultimum. The deduced amino acid sequence of beta-tubulin from P. microspora is very similar to those from other Ascomycetes, many of which are resistant to taxol. The sequence of beta-tubulin from P. ultimum is very similar to those from Oomycetes and non-fungal organisms, many of which are sensitive to taxol. To examine the interaction between taxol and fungal microtubules, binding studies were performed with fungal cells, using [3H]taxol. The labeled taxol was found to bind specifically to P. ultimum, but not to P. microspora. In addition, the amount of [3H]taxol specifically bound to P. ultimum was reduced by the microtubule-depolymerizing drug thiabendazole, in a dose-dependent manner. These results suggest efficient binding of taxol to microtubules in P. ultimum, but not in P. microspora, and are consistent with the differential taxol sensitivity of these two organisms. Finally a comparison of previously characterized taxol binding sites in various beta-tubulin sequences showed that beta-tubulins of taxol-sensitive organisms, including P. ultimum, contain Thr219, but beta-tubulins of resistant organisms, including P. microspora, contain Asn or Gln at this position, suggesting an important role for residue 219 in the interaction between taxol and beta-tubulin.

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.

Relationship between creatine kinase levels and clinical diagnosis of infertility.

PURPOSE: The creatine kinase level indicates sperm maturity and correlates with the spermatozoal fertilizing potential. The relationship between creatine kinase levels in subfertile men and their clinical diagnosis was examined. METHODS: Patients with unexplained infertility (n = 34), varicocele (n = 20), postvasectomy reversal (n = 7), or cancer (n = 22) were included in this prospective clinical study. The control group consisted of healthy normal donors (n = 15). RESULTS: The median and interquartile range values of creatine kinase for each group were as follows: normal donors, 0.061 U/10(8) sperm (0.056 to 0.076 U/10(8) sperm); idiopathic male factor, 0.119 U/10(8) sperm (0.061 to 0.190 U/10(8) sperm); varicocele, 0.392 U/10(8) sperm (0.209 to 1.494 U/10(8) sperm); postvasectomy reversal, 0.589 U/10(8) sperm (0.425 to 4.043 U/10(8) sperm); and cancer, 0.068 U/10(8) sperm (0.047 to 0.168 U/10(8) sperm). Sperm creatine kinase levels were significantly higher in patients with varicocele compared to normal donors (P = 0.0001), cancer patients (P = 0.0002), and men with idiopathic infertility (P = 0.0009). Sperm concentration and creatine kinase level were inversely correlated in patients (r = -0.7, P < 0.001) but not in normal donors. CONCLUSIONS: Semen quality is poorer in subfertile patients with clinical varicocele and postvasectomy reversal than in cancer patients and patients with idiopathic male infertility. That the creatine kinase levels in cancer patients were similar to those of normal donors suggests that the final phase of spermatogenesis may not be altered in men with cancer; thus semen from these patients should be banked to ensure fertility after cancer treatment.

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.

Creatine kinase level and lipid peroxidation rate in human spermatozoa from patients with cancer.

PURPOSE: The present study assessed whether the poor semen quality in patients with cancer results from the inhibition of sperm maturation as indicated by creatine kinase or from increased oxidative stress as assessed by lipid peroxidation of the sperm membrane. METHODS: Cryopreserved semen specimens from patients with testicular (n = 10) and nontesticular (n = 12) cancer and normal healthy donors (n = 14) were analyzed for lipid peroxidation and creatine kinase levels. RESULTS: The levels of creatine kinase and malonaldehyde did not differ among testicular or nontesticular patients with cancer or normal healthy donors. CONCLUSIONS: Poor semen quality in testicular and nontesticular patients with cancer is not related to creatine kinase or lipid peroxidation levels; it may be related to other factors.

Effects of cryopreserved semen quality and timed intrauterine insemination on pregnancy rate and gender of offspring in a donor insemination program.

PURPOSE: Our purpose was to study the relationship among cryopreserved donor semen quality, pregnancy rates, and preconception sex selection after intrauterine insemination. METHODS: We reviewed the records of the 203 women in our donor insemination program from 1987 to 1994 who became pregnant after more than one insemination cycle and had no female-factor infertility. They were categorized according to the number of cycles required for pregnancy. Semen samples from 54 donors were analyzed before freezing and after thawing. Specimens resulting in pregnancy were compared to specimens from the same donor that did not. Semen characteristics were compared to gender of the child. RESULTS: Two hundred fifty two-women became pregnant of the 422 who were enrolled. The pregnancy rate per cycle was 13%. Semen quality was not related to pregnancy outcome or offspring gender. However, more male children (101 vs 83) were born. CONCLUSIONS: Semen characteristics in good-quality cryopreserved donor semen do not affect pregnancy rate or offspring gender.

Reasons for rejecting potential donors from a sperm bank program.

PURPOSE: Recruiting donors to a sperm bank program is difficult and slow because of high dropout rates and high rejection rates. The profile of successful and unsuccessful donors was determined at our sperm bank. METHODS: A total of 199 men was screened from 1986 to 1994 in the anonymous sperm bank donor programs; 174 (87%) men dropped out or did not meet minimum guidelines. The study included 25 accepted donors and 20 rejected men (of 52 rejected donors, only 20 donors who came for two consecutive semen analyses were selected). Sperm quality variables and demographic data were compared between the groups. RESULTS: Accepted donors had significantly better semen quality in motility, velocity, linearity, and ALH than did rejected donors (P < 0.01). More rejected donors than accepted donors were single (P < 0.01). A higher percentage of accepted donors consumed caffeine (P < 0.001), and they were more likely to have college degrees (P < 0.03). CONCLUSIONS: These results indicate that loss of interest and poor semen quality were the major reasons for rejection of donors in our anonymous donor sperm bank program.

Low-dose vigabatrin (gamma-vinyl GABA)-induced damage in the immature rat brain.

The antiepileptic drug, vigabatrin, inhibits GABA transaminase, thus elevating GABA levels in the brain. In adult animal experiments, high-dose (200 mg/kg/day) chronic vigabatrin administration is associated with potentially reversible myelin vacuolation, a phenomenon not documented in humans. We hypothesized that vigabatrin might adversely affect myelination in the developing brain. Rats were given vigabatrin in doses comparable to those used clinically (15-50 mg/kg/day), from age 12 to 16 days. The rats were killed at age 19-20 days. We observed decreased myelin staining in the external capsule, axonal degeneration in white matter, evidence of glial cell death in the white matter, and reactive astrogliosis in the frontal cortex. We did not detect myelin vacuolation. These findings indicate that vigabatrin can have adverse and potentially irreversible effects on the developing rat brain. The mechanism of damage could be direct toxicity of vigabatrin or an indirect effect mediated through elevated GABA levels. Vigabatrin has been recommended as a treatment for some forms of childhood epilepsy; therefore, further studies are needed to assess the risks in children.