Multi-GeV wakefield acceleration in a plasma-modulated plasma accelerator

We investigate the accelerator stage of a plasma-modulated plasma accelerator (P-MoPA) [Jakobsson et al., Phys. Rev. Lett. 127, 184801 (2021)0031-900710.1103/PhysRevLett.127.184801] using both the paraxial wave equation and particle-in-cell (PIC) simulations. We show that adjusting the laser and plasma parameters of the modulator stage of a P-MoPA allows the temporal profile of pulses within the pulse train to be controlled, which in turn allows the wake amplitude in the accelerator stage to be as much as 72% larger than that generated by a plasma beat-wave accelerator with the same total drive laser energy. Our analysis shows that Rosenbluth-Liu detuning is unimportant in a P-MoPA if the number of pulses in the train is less than ∼30, and that this detuning is also partially counteracted by increased red-shifting, and hence increased pulse spacing, towards the back of the train. An analysis of transverse mode oscillations of the driving pulse train is found to be in good agreement with 2D (Cartesian) PIC simulations. PIC simulations demonstrating energy gains of ∼1.5GeV (∼2.5GeV) for drive pulse energies of 2.4J (5.0J) are presented. Our results suggest that P-MoPAs driven by few-joule, picosecond pulses, such as those provided by high-repetition-rate thin-disk lasers, could accelerate electron bunches to multi-GeV energies at pulse repetition rates in the kilohertz range.

All-Optical GeV Electron Bunch Generation in a Laser-Plasma Accelerator via Truncated-Channel Injection

We describe a simple scheme, truncated-channel injection, to inject electrons directly into the wakefield driven by a high-intensity laser pulse guided in an all-optical plasma channel. We use this approach to generate dark-current-free 1.2 GeV, 4.5% relative energy spread electron bunches with 120 TW laser pulses guided in a 110 mm-long hydrodynamic optical-field-ionized plasma channel. Our experiments and particle-in-cell simulations show that high-quality electron bunches were only obtained when the drive pulse was closely aligned with the channel axis, and was focused close to the density down ramp formed at the channel entrance. Start-to-end simulations of the channel formation, and electron injection and acceleration show that increasing the channel length to 410 mm would yield 3.65 GeV bunches, with a slice energy spread ∼5×10^{-4}.

Measurement of the decay of laser-driven linear plasma wakefields

We present measurements of the temporal decay rate of one-dimensional (1D), linear Langmuir waves excited by an ultrashort laser pulse. Langmuir waves with relative amplitudes of approximately 6% were driven by 1.7J, 50fs laser pulses in hydrogen and deuterium plasmas of density n_{e0}=8.4×10^{17}cm^{-3}. The wakefield lifetimes were measured to be τ_{wf}^{H_{2}}=(9±2) ps and τ_{wf}^{D_{2}}=(16±8) ps, respectively, for hydrogen and deuterium. The experimental results were found to be in good agreement with 2D particle-in-cell simulations. In addition to being of fundamental interest, these results are particularly relevant to the development of laser wakefield accelerators and wakefield acceleration schemes using multiple pulses, such as multipulse laser wakefield accelerators.

Stability of the modulator in a plasma-modulated plasma accelerator

We explore the regime of operation of the modulator stage of a recently proposed laser-plasma accelerator scheme [Phys. Rev. Lett. 127, 184801 (2021)0031-900710.1103/PhysRevLett.127.184801], dubbed the plasma-modulated plasma accelerator (P-MoPA). The P-MoPA scheme offers a potential route to high-repetition-rate, GeV-scale plasma accelerators driven by picosecond-duration laser pulses from, for example, kilohertz thin-disk lasers. The first stage of the P-MoPA scheme is a plasma modulator in which a long, high-energy "drive" pulse is spectrally modulated by copropagating in a plasma channel with the low-amplitude plasma wave driven by a short, low-energy "seed" pulse. The spectrally modulated drive pulse is converted to a train of short pulses, by introducing dispersion, which can resonantly drive a large wakefield in a subsequent accelerator stage with the same on-axis plasma density as the modulator. In this paper we derive the 3D analytic theory for the evolution of the drive pulse in the plasma modulator and show that the spectral modulation is independent of transverse coordinate, which is ideal for compression into a pulse train. We then identify a transverse mode instability (TMI), similar to the TMI observed in optical fiber lasers, which sets limits on the energy of the drive pulse for a given set of laser-plasma parameters. We compare this analytic theory with particle-in-cell (PIC) simulations and find that even higher energy drive pulses can be modulated than those demonstrated in the original proposal.

Modulational instability in large-amplitude linear laser wakefields

We investigate the growth of ion density perturbations in large-amplitude linear laser wakefields via two-dimensional particle-in-cell simulations. Growth rates and wave numbers are found to be consistent with a longitudinal strong-field modulational instability. We examine the transverse dependence of the instability for a Gaussian wakefield envelope and show that growth rates and wave numbers can be maximized off axis. On-axis growth rates are found to decrease with increasing ion mass or electron temperature. These results are in close agreement with the dispersion relation of a Langmuir wave with an energy density that is large compared to the plasma thermal energy density. The implications for wakefield accelerators, in particular multipulse schemes, are discussed.

Use of Telemedicine Technology among General Practitioners during COVID-19: A Modified Technology Acceptance Model Study in Poland

During the COVID-19 pandemic, telehealth became a popular solution for the remote provision of primary care by General Practitioners (GPs) in Poland. This study aimed to assess the GPs' acceptance of telehealth during the COVID-19 pandemic in Poland and to explain the factors that drive GPs' need to implement a telehealth system in primary care using the modified Technology Acceptance Model (TAM). In Poland, 361 GPs from a representative sample of 361 clinics drawn from 21,500 outpatient institutions in Poland participated in the empirical study. Structural equation modelling (SEM) was used to evaluate the causal relationships that were formulated in the proposed model. Research has shown that Polish GPs reported a positive perception and high acceptance of the telehealth system during the COVID-19 pandemic. Overall, the results show that the social factors (image, decision autonomy, perception of patient interaction) significantly positively influence the technological factors (perceived ease of use and perceived usefulness) that influence the need to implement a telehealth system. The proposed socio-technological model can serve as a theoretical basis for future research and offer empirical predictions for practitioners and researchers in health departments, governments, and primary care settings.

Organizational E-Readiness for the Digital Transformation of Primary Healthcare Providers during the COVID-19 Pandemic in Poland

The COVID-19 pandemic has forced many countries to implement a variety of restrictive measures to prevent it from spreading more widely, including the introduction of medical teleconsultations and the use of various tools in the field of inpatient telemedicine care. Digital technologies provide a wide range of treatment options for patients, and at the same time pose a number of organizational challenges for medical entities. Therefore, the question arises of whether organizations are ready to use modern telemedicine tools during the COVID-19 pandemic. The aim of this article is to examine two factors that impact the level of organizational e-readiness for digital transformation in Polish primary healthcare providers (PHC). The first factor comprises operational capabilities, which are the sum of valuable, scarce, unique, and irreplaceable resources and the ability to use them. The second factor comprises technological capabilities, which determine the adoption and usage of innovative technologies. Contrary to the commonly analyzed impacts of technology on operational capabilities, we state the reverse hypothesis. The verification confirms the significant influence of operational capabilities on technological capabilities. The research is conducted using a questionnaire covering organizational e-readiness for digital transformation prepared by the authors. Out of the 32 items examined, four are related to the operational capabilities and four to the technological capabilities. The result of our evaluation shows that: (i) a basic set of four variables can effectively measure the dimensions of OC, namely the degree of agility, level of process integration, quality of resources, and quality of cooperation; (ii) a basic set of three variables can effectively measure the dimensions of TC, namely adoption and usage of technologies, customer interaction, and process automation; (iii) the empirical results show that OC is on a higher level than TC in Polish PHCs; (iv) the assessment of the relationship between OC and TC reveals a significant influence of operational capabilities on technological capabilities with a structural coefficient of 0.697. We recommend increasing the level of technological capability in PHC providers in order to improve the contact between patients and general practitioners (GPs) via telemedicine in lockdown conditions.

Fluorine-18 fluorodeoxyglucose positron emission tomography-computed tomography for staging of canine insulinoma: 3 cases (2019-2020)

OBJECTIVES

Canine insulinomas are uncommon malignant functional pancreatic neuroendocrine tumours with a high metastatic rate. Diagnostic imaging aids with staging and surgical planning of these tumours; however, identification is unpredictable across modalities. High-grade human pancreatic neuroendocrine tumours display increased avidity on ¹⁸ F-fluorodeoxyglucose positron emission tomography-CT.

MATERIALS AND METHODS

Dogs with clinicopathologic findings consistent with pancreatic insulinoma were prospectively enrolled. Patients underwent ¹⁸ F-fluorodeoxyglucose positron emission tomography-CT and CT angiography, followed by exploratory laparotomy.

RESULTS

Three patients met the inclusion criteria and had histologically confirmed insulinomas. Both metastatic lesions in patient 1 were mildly avid (SUV_max 2.79 and 3.01). In patient 2, the primary pancreatic insulinoma was minimally avid (SUV_max 2.16). The primary pancreatic lesion in patient 3 had similar avidity to normal pancreatic parenchyma (SUV_max 1.54) and was undetected on ¹⁸ F-fluorodeoxyglucose positron emission tomography-CT. Insulinomas demonstrated variable attenuation and contrast enhancement patterns on CT angiography and certain lesions were more conspicuous than on ¹⁸ F-fluorodeoxyglucose positron emission tomography-CT. Two metastatic lesions not visible on either imaging modality were discovered in patient 2 at surgery.

CLINICAL SIGNIFICANCE

Canine insulinomas were inconsistently avid on ¹⁸ F-fluorodeoxyglucose positron emission tomography-CT. This finding is likely attributable to the confounding clinicopathological features and multifaceted transformation of these tumours, in addition to the influence of variable tumour size, composition and vascularity. Unpredictable tumoural avidity limits the value of ¹⁸ F-fluorodeoxyglucose positron emission tomography-CT for staging canine insulinomas.

Gev-Scale Accelerators Driven by Plasma-Modulated Pulses from Kilohertz Lasers

We describe a new approach for driving GeV-scale plasma accelerators with long laser pulses. We show that the temporal phase of a long, high-energy driving laser pulse can be modulated periodically by copropagating it with a low-amplitude plasma wave driven by a short, low-energy seed pulse. Compression of the modulated driver by a dispersive optic generates a train of short pulses suitable for resonantly driving a plasma accelerator. Modulation of the driver occurs via well-controlled linear processes, as confirmed by good agreement between particle-in-cell (PIC) simulations and an analytic model. PIC simulations demonstrate that a 1.7 J, 1 ps driver, and a 140 mJ, 40 fs seed pulse can accelerate electrons to energies of 0.65 GeV in a plasma channel with an axial density of 2.5×10^{17}  cm^{-3}. This work opens a route to high repetition-rate, GeV-scale plasma accelerators driven by thin-disk lasers, which can provide joule-scale, picosecond-duration laser pulses at multikilohertz repetition rates and high wall-plug efficiencies.

The impact of medical teleconsultations on general practitioner-patient communication during COVID- 19: A case study from Poland

According to the outbreak of the Covid-19 pandemic, medical teleconsultations using various technologies have become an important tool to mediate communication between general practitioners (GP) and the patients in primary health care in many countries. The quality of the GP-patient communication is an essential factor, which improves the results of treatment and patient satisfaction. The objective of this paper is to study patients' satisfaction from teleconsultation in primary care and the impact of teleconsultations on GP-patient communication through the Covid-19 pandemic in Poland. We analyse whether the teleconsultations performed without physical examinations have a positive impact on GP-patient communication. The quality of teleconsultation and GP-patient communication have been measured using a questionnaire regarding the quality of medical care in a remote care conditions. Among 36 items, nine questions have been related to the dimension of GP-patient communication and ten to system experience. Our results suggest that the quality of teleconsultations is not inferior to the quality of consultation during a face-to-face visit. The patients indicated a high level of satisfaction regarding communication with their GP during teleconsultation. We have also identified that the technical quality and the sense of comfort during teleconsultation positively impact the communication quality.

Meter-scale conditioned hydrodynamic optical-field-ionized plasma channels

We demonstrate through experiments and numerical simulations that low-density, low-loss, meter-scale plasma channels can be generated by employing a conditioning laser pulse to ionize the neutral gas collar surrounding a hydrodynamic optical-field-ionized (HOFI) plasma channel. We use particle-in-cell simulations to show that the leading edge of the conditioning pulse ionizes the neutral gas collar to generate a deep, low-loss plasma channel which guides the bulk of the conditioning pulse itself as well as any subsequently injected pulses. In proof-of-principle experiments, we generate conditioned HOFI (CHOFI) waveguides with axial electron densities of n_{e0}≈1×10^{17}cm^{-3} and a matched spot size of 26μm. The power attenuation length of these CHOFI channels was calculated to be L_{att}=(21±3)m, more than two orders of magnitude longer than achieved by HOFI channels. Hydrodynamic and particle-in-cell simulations demonstrate that meter-scale CHOFI waveguides with attenuation lengths exceeding 1 m could be generated with a total laser pulse energy of only 1.2 J per meter of channel. The properties of CHOFI channels are ideally suited to many applications in high-intensity light-matter interactions, including multi-GeV plasma accelerator stages operating at high pulse repetition rates.

Hydrodynamic optical-field-ionized plasma channels

We present experiments and numerical simulations which demonstrate that fully ionized, low-density plasma channels could be formed by hydrodynamic expansion of plasma columns produced by optical field ionization. Simulations of the hydrodynamic expansion of plasma columns formed in hydrogen by an axicon lens show the generation of 200 mm long plasma channels with axial densities of order n_{e}(0)=1×10^{17}cm^{-3} and lowest-order modes of spot size W_{M}≈40μm. These simulations show that the laser energy required to generate the channels is modest: of order 1 mJ per centimeter of channel. The simulations are confirmed by experiments with a spherical lens which show the formation of short plasma channels with 1.5×10^{17}cm^{-3}≲n_{e}(0)≲1×10^{18}cm^{-3} and 61μm≳W_{M}≳33μm. Low-density plasma channels of this type would appear to be well suited as multi-GeV laser-plasma accelerator stages capable of long-term operation at high pulse repetition rates.

Released from ZrO2/SiO2 coating resveratrol inhibits senescence and oxidative stress of human adipose-derived stem cells (ASC)

The rapid aging of the population results in increased number of metabolic and degenerative disorders, especially in the elderly.Thus, a novel approach in the fields of orthopedic and reconstructive surgery for bone regeneration is strongly desirable. A new perspective in the therapy of bone fractures is tissue engineering which combines living cells with biomaterials to develop modern substitutes that can restore tissue functions. Metallic biomaterials, including stainless steel and pure titanium, have been extensively used for the fabrication of surgical implants over decades. Chemical modification of material surface for example incorporation of chemotactic factors may significantly improve the therapeutic effect. In this paper we describe titanium substrate modifications with ZrO2/SiO2coating functionalized with resveratrol using a sol – gel, dip-coating technique. Moreover, we established the effects of fabricated scaffolds on adipose stem cells isolated from elderly patients. Using fluorescence imaging, polymerase chain reaction (PCR)and cytotoxicity tests, we established that 0.5 Res_ZrO2/SiO2significantly reduced apoptosis and accumulation of oxidative stress factors in adipose derived stem cells (ASC). Thus exploitation of fabricated biomaterials in regenerative medicine as a strategy for rejuvenate ASC from elderly patientsin vivo, seems fully justified.

Excitation and Control of Plasma Wakefields by Multiple Laser Pulses

We demonstrate experimentally the resonant excitation of plasma waves by trains of laser pulses. We also take an important first step to achieving an energy recovery plasma accelerator by showing that a plasma wave can be damped by an out-of-resonance trailing laser pulse. The measured laser wakefields are found to be in excellent agreement with analytical and numerical models of wakefield excitation in the linear regime. Our results indicate a promising direction for achieving highly controlled, GeV-scale laser-plasma accelerators operating at multikilohertz repetition rates.

Assessing the safety of del Nido cardioplegia solution in adult congenital cases

PURPOSE

del Nido cardioplegia solution (CPS) has been successfully used for myocardial protection in the pediatric population. We propose this solution can be used safely in adult congenital patients. The proposed benefit of this solution is the avoidance of the need for repetitive interruption of the operation to administer multiple doses of standard cardioplegia.

METHODS

As part of a quality improvement initiative, 47 consecutive adult patients (mean age 40.9 years, range 18-71) undergoing congenital heart surgery were given del Nido CPS. Cardiac function was assessed pre- and post-operatively by echocardiography (ECHO). Inotrope use, troponin levels and restoration of cardiac rhythm were also evaluated.

RESULTS

The average duration of the longest ischemic time was 52.5 minutes ± 15.57 minutes. In patients receiving a single dose (40%, n=19) of CPS, the average ischemic time was 49.8 minutes ± 18.8 minutes. No patients demonstrated any ventricular electrical activity while the aorta was cross-clamped. Post-operative ECHO showed that 94% (n=44) had no change in ejection fraction from the pre-operative ECHO. Patients requiring inotropic support at the time of leaving the operating room (OR) was 43% (n=20). The percentage of patients requiring inotropic support twenty-four hours post-operatively was 17% (n=8). Spontaneous restoration of cardiac rhythm (without the need for defibrillation) after cross-clamp removal occurred in 91% (n=43) of patients. The average troponin T level post-op was 1.86 ± 2.9 µg/L.

CONCLUSIONS

del Nido CPS can be used for myocardial protection during adult congenital cardiac surgery without any apparent adverse effects. In addition, we were able to change our re-dosing protocol to 45 minutes with del Nido CPS compared to 20 minutes with our adult 4:1 blood CPS.

Carboxyhemoglobinemia in a pediatric cardiopulmonary bypass patient derived from a contaminated unit of allogenic blood

A 4.3 kg, three-month-old patient, diagnosed with a perimembranous ventricular septal defect, presented for cardiac surgery. Upon initiation of cardiopulmonary bypass (CPB), the patient developed carboxyhemoglobinemia (11.1%). Potential sources for the unexpected acquired carboxyhemoglobinemia were sought quickly. Testing of residual blood from the unit of packed red blood cells (PRBCs) used to prime the CPB circuit revealed a carboxyhemoglobin (COHb) of 15.1 %. A decrease in cerebral oximetry (rSO2) on CPB was initially felt to be a result of the elevated COHb levels. When ventilation of the oxygenator with 100% oxygen (O2) failed to decrease COHb levels, a partial exchange transfusion was performed with reduction in COHb to 7.1%. The operation was completed successfully and the patient’s COHb levels returned to normal within 75 minutes.

Post case analysis of events and data collected during the case revealed a broader differential for explaining the compromised patient’s O2 delivery than the transient acquired carboxyhemoglobinemia. A partial obstruction of the superior vena cava could have triggered the drop in rSO2 on CPB.

Follow-up of the donor blood confirmed the donor had previously undiagnosed carboxyhemoglobinemia as a result of chronic carbon monoxide exposure from a faulty vehicle exhaust system.

Inclusive K(S);(0)K(S);(0) resonance production in ep collisions at HERA

Inclusive K_{S};{0}K_{S};{0} production in ep collisions at the DESY ep collider HERA was studied with the ZEUS detector using an integrated luminosity of 0.5 fb;{-1}. Enhancements in the mass spectrum were observed and are attributed to the production of f_{2}(1270)/a_{2};{0}(1320), f_{2};{'}(1525) and f_{0}(1710). Masses and widths were obtained using a fit which takes into account theoretical predictions based on SU(3) symmetry arguments, and are consistent with the Particle Data Group values. The f_{0}(1710) state, which has a mass consistent with a glueball candidate, was observed with a statistical significance of 5 standard deviations. However, if this state is the same as that seen in gammagamma-->K_{S};{0}K_{S};{0}, it is unlikely to be a pure glueball state.

A clinical evaluation of the Dideco Kids D100 neonatal oxygenatora

In August 2006, Duke University Perfusion Services had the opportunity to be the first institution in the United States to clinically evaluate the Dideco D100 Neonatal Oxygenator. The device was used on six pediatric patients to facilitate correction or palliation of their cardiac defects, which included two arterial switch operations, two truncus arteriosus repairs, one stage 1 Norwood and one repair of total anomalous pulmonary venous return. The average patient weight was 3.1 kg. The average cardiopulmonary bypass(CPB) time was 135 minutes and the average cross-clamp time was 61 minutes. Arterial and venous blood gasses were drawn and used to calculate oxygen transfer. The average oxygen transfer was 14.8 ± 10.3 ml/O2/min. The Dideco D100 Oxygenator is the first oxygenation device designed specifically for neonates. The Dideco D100 is a microporous hollow-fiber device. It has a static priming volume of 31 ml and a maximum rated flow of 700 ml/min. The integral hard-shell venous reservoir has a minimum operating level of 10 ml and a reservoir capacity of 500 ml. For this evaluation, the Dideco Kids D100 Neonatal Oxygenator performed adequately on patients weighing up to 5 kg. This device provides an excellent first step towards offering very small children appropriate circuitry without having to sacrifice safety or performance.

Autoregulation of the human liver X receptor alpha promoter

Previous work has implicated the nuclear receptors liver X receptor alpha (LXR alpha) and LXR beta in the regulation of macrophage gene expression in response to oxidized lipids. Macrophage lipid loading leads to ligand activation of LXRs and to induction of a pathway for cholesterol efflux involving the LXR target genes ABCA1 and apoE. We demonstrate here that autoregulation of the LXR alpha gene is an important component of this lipid-inducible efflux pathway in human macrophages. Oxidized low-density lipoprotein, oxysterols, and synthetic LXR ligands induce expression of LXR alpha mRNA in human monocyte-derived macrophages and human macrophage cell lines but not in murine peritoneal macrophages or cell lines. This is in contrast to peroxisome proliferator-activated receptor gamma (PPAR gamma)-specific ligands, which stimulate LXR alpha expression in both human and murine macrophages. We further demonstrate that LXR and PPAR gamma ligands cooperate to induce LXR alpha expression in human but not murine macrophages. Analysis of the human LXR alpha promoter led to the identification of multiple LXR response elements. Interestingly, the previously identified PPAR response element (PPRE) in the murine LXR alpha gene is not conserved in humans; however, a different PPRE is present in the human LXR 5'-flanking region. These results have implications for cholesterol metabolism in human macrophages and its potential to be regulated by synthetic LXR and/or PPAR gamma ligands. The ability of LXR alpha to regulate its own promoter is likely to be an integral part of the macrophage physiologic response to lipid loading.

Structural analysis of new local features in SECIS RNA hairpins

Decoding of the UGA selenocysteine codon for selenoprotein translation requires the SECIS element, a stem-loop motif in the 3'-UTR of the mRNA carrying short or large apical loops. In previous structural studies, we derived a secondary structure model for SECIS RNAs with short apical loops. Work from others proposed that intra-apical loop base pairing can occur in those SECIS that possess large apical loops, yielding form 2 SECIS versus the form 1 with short loops. In this work, SECIS elements arising from eight different selenoprotein mRNAs were assayed by enzymatic and/or chemical probing showing that seven can adopt form 2. Further, database searches led to the discovery in drosophila and zebrafish of SECIS elements in the selenophosphate synthetase 2, type 1 deiodinase and SelW mRNAs. Alignment of SECIS sequences not only highlighted the predominance of form 2 but also made it possible to classify the SECIS elements according to the type of selenoprotein mRNA they belong to. Interestingly, the alignment revealed that an unpaired adenine, previously thought to be invariant, is replaced by a guanine in four SECIS elements. Tested in vivo, neither the A to G nor the A to U changes at this position greatly affected the activity while the most detrimental effect was provided by a C. The putative contribution of the various SECIS motifs to function and ligand binding is discussed.

[Infrared thermographic imaging of normal vulva and uterine cervix: a preliminary report]

OBJECTIVES

To evaluate in the standardized conditions the thermal emission by normal uterine cervix and vulva.

MATERIALS AND METHODS

Infrared telethermography (ITT) was used to examine vulva and uterine cervix in 32 women aged 24-54 years without colposcopic and cytologic abnormalities.

RESULTS

The measured temperatures differed between different topographic points of vulva and uterine vaginal portio. The inter-individual variability of temperatures determined at the same vulvar structures was relatively low.

CONCLUSION

The obtained results constitute a basis for further studies on thermovisual definition of therapeutic targets in cases of vulvar and cervical lesions.

[Expression of fetal antigens of gonocytes in the investigation of pathogenesis of germinal cell neoplasia]

Expression of fetal antigens of germinal cells reacting with antibodies M2A and TRA-1-60 has been studied in fetal germinal cells-gonocytes (G) persisted in gonads of prepubertal boys because of male pseudohermaphroditism (MP) and in germinal carcinoma cells in situ (CIS) of adult men. The presence of G and CIS cells was detected immunohistochemically by identification of placental like alkaline phosphatase (PLAP). CIS cells showed expression of M2A in all adult men and additionally TRA-1-60 in one case. These antigens were present in G cells only in 2 out of 6 G bearing testes of boys with MP (30%). G cells were not found in testes of 3 other older boys with MP. So, in 1/3 cases of children with MP G cells show similar features like CIS cells during the prepubertal period indicating that they are able to enter malignant transformation in early prepubertal testis. Although total frequency of occurrence of G cells in MP boys was 2/3 (60%), their malignant transformation may be lower.

An essential non-Watson-Crick base pair motif in 3'UTR to mediate selenoprotein translation

The SECIS element is an RNA hairpin in the 3'UTR of selenoprotein mRNAs required for decoding UGA selenocysteine codons. Our experimentally derived 2D structure model for the SECIS RNA revealed the conservation of four consecutive non-Watson-Crick base pairs, with a central G.A/A.G tandem. The present study was dedicated to gaining insight into the role of this quartet of base pairs. The effects of mutations introduced into the SECIS quartet of the glutathione peroxidase (GPx) cDNA, an enzyme with selenocysteine in its active center, were reported in vivo by the GPx activity. The detrimental consequence of an all-Watson-Crick mutant quartet disclosed the paramount importance of the non-Watson-Crick base pairs for GPx activity. Next, structure probing established that base pair changes in the central G.A/A.G tandem, predicted by the model to be structurally unfavorable, effectively led to local opening of the helix at the quartet. A concomitant abolition of GPx activity was observed, arising from translational impairment of full-length GPx. In contrast, an isosteric base pair replacement in the tandem did not affect base pairing in the quartet, leading to an almost wt GPx activity. Collectively, the data provided conclusive evidence for the functional relevance of these non-Watson-Crick base pairs in vivo, thus identifying a noncanonical RNA motif crucial to SECIS function in mediating selenoprotein translation. Within the quartet, the prominent requirement for the central G.A/A.G tandem is highlighted, our previous structural model and the mutagenesis data presented here strongly arguing in favor of a sheared arrangement for the G.A base pairs. The SECIS RNA is therefore another member to be added to the growing list of RNAs containing building blocks of non-Watson-Crick base pairs, required for structure and/or function.

Solution structure of SECIS, the mRNA element required for eukaryotic selenocysteine insertion--interaction studies with the SECIS-binding protein SBP

Selenocysteine, a selenium-containing analog of cysteine, is found in the prokaryotic and eukaryotic kingdoms in active sites of enzymes involved in oxidation-reduction reactions. This aminoacid is cotranslationally incorporated at UGA codons which usually act as translation stop codons. In eukaryotes, decoding of selenocysteine necessitates the participation of the selenocysteine insertion sequence (SECIS), an element lying in the 3'-untranslated region of selenoprotein mRNAs. A detailed experimental study of the secondary structures of the SECIS elements of rat and human type 1 iodothyronine deiodinases and rat glutathione peroxidase was performed. Enzymatic and chemical structure probing led us to propose a secondary structure model, supported by sequence comparison of 23 SECIS mRNAs. The secondary structure model revealed the existence of a novel type of RNA motif composed of four consecutive non-Watson-Crick base-pairs. Using gel shift experiments, we identified in several mammalian cell type extracts the protein SBP, for SECIS-binding protein, that specifically recognizes the iodothyronine deiodinases and glutathione peroxidase SECIS elements. The structural model that we derived for the SECIS RNAs discloses RNA features possibly implicated in the binding of SBP and/or SECIS function.

IS911-mediated transpositional recombination in vitro

A cell-free system is described that accomplishes an unusual type of transposition/recombination involving the bacterial insertion sequence IS911. Using a plasmid substrate carrying a derivative of IS911, we show that bacterial cell extracts enriched for the IS911 transposase, OrfAB, carry out a single-strand cleavage and transfer reaction. This results in the formation of a figure-eight molecule in which a single strand of the element is circularized, faithfully reproducing an event previously detected in vivo. Moreover, when presented with a figure-eight substrate, OrfAB is capable of "reversing" strand transfer. This activity is equivalent to the "disintegration" reaction carried out by retroviral integrases. We demonstrate that the domain of OrfAB responsible for this catalytic activity is located in the carboxy-terminal region of the protein, since a peptide composed of this region retains disintegration activity. The OrfAB-mediated excision-circularization process previously observed in vivo was proposed to proceed via a figure-eight intermediate by circularization of the second transposon strand. The absence of transposon circles in cell-free reaction suggests either that the figure-eight form is not an intermediate or that additional host factors are required that are eliminated from the cell extract. Two types of model, replicative and non-replicative, are discussed to explain how the figure-eight molecule could be processed into the transposon circle.

A novel RNA structural motif in the selenocysteine insertion element of eukaryotic selenoprotein mRNAs

In eukaryotes, co-translational insertion of selenocysteine into selenoproteins necessitates the participation of the selenocysteine insertion sequence (SECIS), an element lying in the 3'-untranslated region of selenoprotein mRNAs. We report a detailed experimental study of the secondary structures of the SECIS elements of three selenoprotein mRNAs, the rat and human type I iodothyronine deiodinase (5'DI) and rat glutathione peroxidase (GPx). Based on RNase and chemical probing, a new secondary structure model is established. It is characterized by a stem-loop structure, comprising two helices (I and II) separated by an internal loop, with an apical loop surmounting helix II. Sequence comparisons of 20 SECIS elements, arising from 2 5'DI, 13 GPx, 2 selenoprotein P, and 1 selenoprotein W mRNAs, confirm the secondary structure model. The most striking finding of the experimental study concerns a set of conserved sequences in helix II that interact to form a novel RNA structural motif consisting of a quartet composed of non-Watson-Crick base pairs 5'UGAY3': 5'UGAU3'. The potential for forming the quartet is preserved in 15 SECIS elements, but three consecutive non-Watson-Crick base pairs can nevertheless form in the other five SECIS, the central G.A tandem being invariant in all cases. A 3D model, derived by computer modeling with the use of the solution data, suggests that the base pairing interactions in the G.A tandem are of the type found in GNRA loops. The 3D model displays the quartet lying in an accessible position at the foot of helix II, which is bent at the internal loop, suggesting that the non-Watson-Crick base pair arrangement provides an unusual pattern of chemical groups for putative ligand interaction.

A protein binds the selenocysteine insertion element in the 3'-UTR of mammalian selenoprotein mRNAs

Several gene products are involved in co-translational insertion of selenocysteine by the tRNA(Sec). In addition, a stem-loop structure in the mRNAs coding for selenoproteins is essential to mediate the selection of the proper selenocysteine UGA codon. Interestingly, in eukaryotic selenoprotein mRNAs, this stem-loop structure, the selenocysteine insertion sequence (SECIS) element, resides in the 3'-untranslated region, far downstream of the UGA codon. In view of unravelling the underlying complex mechanism, we have attempted to detect RNA-binding proteins with specificity for the SECIS element. Using mobility shift assays, we could show that a protein, present in different types of mammalian cell extracts, possesses the capacity of binding the SECIS element of the selenoprotein glutathione peroxidase (GPx) mRNA. We have termed this protein SBP, for Secis Binding Protein. Competition experiments attested that the binding is highly specific and UV cross-linking indicated that the protein has an apparent molecular weight in the range of 60-65 kDa. Finally, some data suggest that the SECIS elements in the mRNAs of GPx and another selenoprotein, type I iodothyronine 5' deiodinase, recognize the same SBP protein. This constitutes the first report of the existence of a 3' UTR binding protein possibly involved in the eukaryotic selenocysteine insertion mechanism.

RNAs mediating cotranslational insertion of selenocysteine in eukaryotic selenoproteins

Selenocysteine, a selenium-containing analog of cysteine, is found in the prokaryotic and eukaryotic kingdoms in active sites of enzymes involved in oxidation-reduction reactions. Its biosynthesis and cotranslational insertion into selenoproteins is performed by an outstanding mechanism, implying the participation of several gene products. The tRNA(Sec) is one of these. In eukaryotes, its transcription mode by RNA polymerase III differs from that of classical tRNA genes, both at the level of the promoter elements and transcription factors involved. In addition, enhanced transcription is afforded by a newly characterized zinc finger activator. Not only transcription of the gene, but also the tRNA(Sec) itself is atypical since its 2D and 3D structures exhibit features which set it apart from classical tRNAs. Decoding of eukaryotic selenocysteine UGA codons requires a stem-loop structure in the 3'UTR of mRNAs, the selenocysteine insertion sequence (SECIS) element. Structure probing and sequence comparisons led us to propose a 2D structure model for the SECIS element, containing a novel RNA motif composed of four consecutive non-Watson-Crick base-pairs. A 3D model, rationalizing the accessibility data, was elaborated by computer modeling. It yields indicative or suggestive evidence for the role that could play some conserved residues and/or structural features in SECIS function. These might act as signals for interaction with SBP, the SECIS binding protein that we have characterized.

Characterization of heat-shock response of the marine bacterium Vibrio harveyi

We have investigated heat-shock response in a marine bacterium Vibrio harveyi. We have found that 39 degrees C was the highest temperature at which V. harveyi was able to grow steadily. A shift from 30 degrees C to 39 degrees C caused increased synthesis of at least 10 proteins, as judged by SDS-PAGE, with molecular masses of 90, 70, 58, 41, 31, 27, 22, 15, 14.5 and 14kDa. The 70, 58, 41 and 14.5 kDa proteins were immunologically homologous to DnaK, GroEL, DnaJ and GroES heat-shock proteins of Escherichia coli, respectively. V. harveyi GroES protein had a lower molecular mass (14.5 kDa) than E. coli GroES, migrating in SDS-PAGE as 15kDa protein. We showed that a protein of approximately 43 kDa, immunologically reactive with antiserum against E. coli sigma 32 subunit (sigma 32) of RNA polymerase, was induced by heat-shock and co-purified with V. harveyi RNA polymerase. These results suggest that the 43 kDa protein is a heat-shock sigma protein of V. harveyi. Preparation containing the V. harveyi sigma 32 homologue, supplemented with core RNA polymerase of E. coli, was able to transcribe heat-shock promoters of E. coli in vitro.

[Eosin and water tests and results of conventional semen analysis]

Semen analysis was performed in 95 men and the results of routine examination were correlated with two sperm viability tests: eosin (TE) and water test (TW). Results of TE and TW were expressed as a percent of spermatozoa revealing a functional integrity of the cell membrane. Linear regression analysis was used. Patients were divided into 3 groups: normozoospermia (n = 46), oligozoospermia (n = 27) and profound oligozoospermia (2-4 x 10(6) sperm/ml). No correlations were demonstrated between viability tests and the sperm number. TE and TW significantly positively correlated with each other in all groups. At normo- and oligozoospermia TE and TW positively correlated with the percent of motile spermatozoa. TW did not show such a correlation in men with profound oligozoospermia. It seems that TE and TW can be used alternatively. TW may be of great importance in men with very low sperm count.