Kidney transplantation substantially improves endothelial progenitor cell dysfunction in patients with end-stage renal disease

Endothelial progenitor cells (EPC) are involved in endothelial repair and maintenance. Dysfunction of EPC may contribute to accelerated arteriosclerosis in chronic kidney disease. Kidney transplantation (KTx) improves both survival and endothelial function of dialysis patients. In a prospective study, we tested to which extent KTx changes EPC biology. We studied number and function (migratory activity, adhesion to extracellular matrix proteins and to mature endothelial cells [EC]) of EPC in 20 patients during dialysis and 3, 6, 9 and 12 months after KTx. Twenty-two healthy volunteers served as matched controls. Circulating precursor populations were measured by flow cytometric analysis. Cytokines relevant for EPC mobilization were monitored. Compared to the dialysis state, KTx increased the migration of EPC to approximately 2-fold. Adhesion to fibronectin and to collagen type IV was significantly increased after KTx. An improved adhesion rate of EPC to mature EC was observed. The number of EPC decreased. The amount of precursor populations showed no difference compared to the pretransplant state. Our study shows an improved function of EPC after KTx. This finding indicates an improved potential for endothelial repair which in turn may contribute to enhanced endothelial function and reduced cardiovascular morbidity after KTx.

Low-level activity measurement of 131Xem, 133Xem, 135Xe and 133Xe in atmospheric air samples using high-resolution dual X–γ spectrometry

High-resolution dual X and gamma spectrometry has been optimized to improve the sensitivity in analyzing radioxenon from environmental samples, especially for the metastable isotopes (131Xem and 133Xem). The full-energy peak (FEP) efficiency curve in the 20-700 keV range has been established with a global uncertainty better than +/-3% using a Monte Carlo simulation. The minimum detectable activity concentrations (MDC) achievable at the laboratory for 131Xem, 133Xem, 133Xe and 135Xe are presented and the influence of 133Xe activity on the metastable radioxenon MDCs is evaluated.

Efficacy and safety of the vasopressin antagonist conivaptan in patients with euvolemic hyponatremia evaluated in a phase III clinical trial

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Background: Hyponatremia, often caused by the inappropriate secretion of arginine vasopressin (AVP), is a common electrolyte disorder in patients with small-cell lung cancer (15%), head and neck cancer (3%), and non-small-cell lung cancer (0.7%). Conivaptan (CNV), a novel V1A and V2 AVP antagonist, produces aquaresis–the electrolyte-sparing excretion of water. CNV was recently approved for the treatment of euvolemic hyponatremia in hospitalized patients. The efficacy of CNV 40 mg/d was compared with that of placebo (PBO) on days 2 and 4 of a 4-day study in patients with euvolemic hyponatremia. Methods: This randomized, double-blind, multicenter, PBO-controlled trial enrolled 84 patients with euvolemic or hypervolemic hyponatremia (serum [Na+] 115 to <130 mEq/L). Patients were assigned to a PBO or a CNV 20-mg IV loading dose, followed by a continuous infusion of PBO or CNV 40 or 80 mg/d for 4 days. The primary efficacy measure was the change in serum [Na+] from baseline during treatment, as measured by the area under the serum [Na+]-time curve (AUC). Secondary efficacy measures included the change from baseline in serum [Na+]; time from first dose to achieve a confirmed ≥4 mEq/L increase in serum [Na+]; and the number of patients achieving a confirmed ≥6 mEq/L increase in serum [Na+] or normal serum [Na+] (≥135 mEq/L). Of the 84 patients enrolled, 56 (66.7%) had euvolemic hyponatremia; presented here are the results from 21 given PBO and 18 given CNV 40 mg/d. Results: The baseline serum [Na+] was similar in both treatment groups (PBO: 124.3 mEq/L, CNV 40 mg/d: 123.6 mEq/L). CNV 40 mg/d improved serum [Na+] and all secondary efficacy measures significantly more than PBO (Table). CNV was well tolerated; the most common adverse events associated with CNV at the end of the 4-day treatment were infusion-site reactions, postural hypotension, and thirst. Conclusion: CNV 40 mg/d increased serum [Na+] significantly more than PBO on days 2 and 4 in patients with euvolemic hyponatremia.

[Table: see text]

[Table: see text]

HIV infection does not influence clinical outcomes in hospitalized patients with bacterial community-acquired pneumonia: results from the CAPO international cohort study

In a case-control study, outcomes for 58 human immunodeficiency virus (HIV)-positive patients with community-acquired pneumonia (CAP) were compared with outcomes for 174 HIV-negative patients with CAP. No differences were found in the time to clinical stability, the length of hospitalization, and mortality. Clinical outcomes for hospitalized patients with CAP may not be influenced by HIV infection.

Vitronectin stabilizes thrombi and vessel occlusion but plays a dual role in platelet aggregation

The role of vitronectin (Vn) in thrombosis is currently controversial; both inhibitory and supportive roles have been reported. To monitor directly the function of Vn in thrombotic events at the site of vascular injury, we studied Vn-deficient (Vn-/-) and wild-type (WT) control mice with two real-time intravital microscopy thrombosis models. In the mesenteric arteriole model, vessel injury was induced by ferric chloride. We observed unstable thrombi and a significantly greater number of emboli in Vn-/- mice. Vessel occlusion was also delayed and frequent vessel re-opening occurred. In the cremaster muscle arteriole model, vessel injury was induced by a nitrogen dye laser. We observed significantly fewer platelets, lower fibrin content, and unstable fibrin within the thrombi of Vn-/- mice. To define further the role of Vn in thrombus growth, we studied platelet aggregation in vitro. Consistent with our in vivo data, the second wave of thrombin-induced aggregation of gel-filtered platelets was abolished at a low concentration of thrombin in Vn-/- platelets. Interestingly, adenosine diphosphate (ADP)-induced platelet aggregation was significantly increased in Vn-/- platelet-rich plasma (PRP) and this effect was attenuated by adding purified plasma Vn. We also observed increased platelet aggregation induced by shear stress in Vn-/- whole blood. These data demonstrate that Vn is a thrombus stabilizer. However, in contrast to released platelet granule Vn which enhances platelet aggregation, plasma Vn inhibits platelet aggregation.

Induction of antiviral immunity by double-stranded RNA in a marine invertebrate

Vertebrates mount a strong innate immune response against viruses, largely by activating the interferon system. Double-stranded RNA (dsRNA), a common intermediate formed during the life cycle of many viruses, is a potent trigger of this response. In contrast, no general inducible antiviral defense mechanism has been reported in any invertebrate. Here we show that dsRNA induces antiviral protection in the marine crustacean Litopenaeus vannamei. When treated with dsRNA, shrimp showed increased resistance to infection by two unrelated viruses, white spot syndrome virus and Taura syndrome virus. Induction of this antiviral state is independent of the sequence of the dsRNA used and therefore distinct from the sequence-specific dsRNA-mediated genetic interference phenomenon. This demonstrates for the first time that an invertebrate immune system, like its vertebrate counterparts, can recognize dsRNA as a virus-associated molecular pattern, resulting in the activation of an innate antiviral response.

Role of endothelial progenitor cells in cardiovascular pathology

Replacement of injured endothelial cells by bone marrow derived endothelial progenitor cells (EPC's) is a new pathway of vascular repair after ischemia. Endothelial progenitor cells contribute less than 0.01% to the peripheral venous compartment of mononuclear cells. The detection of EPC's requires a demonstration of CD 34 and VEGFR-2 (vascular endothelial growth factor receptor-2) antigenic cell membrane determinants and proof of endothelial characteristics after outgrowth and differentiation in cell culture. The most important stimuli to the mobilization and proliferation of EPC's are VEGF, GM-CSF (granulocyte-macrophage colony stimulating factor), erythropoietin, HMG-CoA-reductase inhibitors and tissue ischemia. In vivo in patients EPC's appear to contribute to endothelialization of vascular grafts, the formation of collaterals of ischemic limbs and the healing of myocardial infarcts. The role of EPC's in uremia is currently under investigation.

Microsecond pulsed optical parametric oscillator pumped by a Q-switched fiber laser

We report on what is to our knowledge the first optical parametric oscillator (OPO) pumped by microsecond pulses from a wavelength-tunable solid-state laser. The singly resonant OPO (SRO) is based on a periodically poled LiNbO3 crystal and pumped with 2.1-micros-long pulses from an actively Q-switched Yb fiber laser. At an average fiber laser power of 3.6 W, the SRO generates 1.9-micros-long pulses with a repetition rate of 25 kHz and an average power of 560 mW at 3360 nm. The SRO was tuned from 1518 to 1634 nm (signal) and from 3145 to 3689 nm (idler) via the crystal temperature and poling period. By all-electronic tuning of the fiber laser wavelength over 19 nm, tuning of the mid-infrared idler wavelength over 195 nm was achieved.

Rapidly tunable continuous-wave optical parametric oscillator pumped by a fiber laser

We report on rapid, all-electronically controlled wavelength tuning of a continuous-wave (cw) optical parametric oscillator (OPO) pumped by an ytterbium fiber laser. The OPO is singly resonant for the signal wave and consists of a 40-mm-long periodically poled lithium niobate crystal in a four-mirror ring cavity. By tuning of the fiber-laser wavelength over 33 nm through an intracavity acousto-optic tunable filter, the OPO idler wavelength is tuned from 3160 to 3500 nm in 330 micros, corresponding to an idler frequency-tuning speed of 28 THz/ms. At a fiber-laser power of 6.6 W at 1074 nm, the singly resonant OPO generates 1.13-W cw idler radiation at 3200 nm.

Thrombus formation: direct real-time observation and digital analysis of thrombus assembly in a living mouse by confocal and widefield intravital microscopy

We have developed novel instrumentation using confocal and widefield microscopy to image and analyze thrombus formation in real time in the microcirculation of a living mouse. This system provides high-speed, near-simultaneous acquisition of images of multiple fluorescent probes and a brightfield channel, and supports laser-induced injury through the microscope optics. Although this imaging facility requires interface of multiple hardware components, the primary challenge in vascular imaging is careful experimental design and interpretation. This system has been used to localize tissue factor during thrombus formation, to observe defects in thrombus assembly in genetically altered mice, to study the kinetics of platelet activation and P-selectin expression following vascular injury, to analyze leukocyte rolling on arterial thrombi, to generate three-dimensional models of thrombi, and to analyze the effect of antithrombotic agents in vivo.

Wide wavelength tuning of an optical parametric oscillator through electro-optic shaping of the gain spectrum

We present a novel technique for tuning an optical parametric oscillator (OPO) through electro-optically induced shape variations of the parametric gain spectrum in quasi-phase-matched lithium niobate (LN). The diode-pumped, triply resonant continuous-wave OPO is based on a 58-mm-long LN crystal that consists of three equally long sections, the outer sections being periodically poled with a 50% duty cycle. The center section is single-domain material and serves as a tunable phase shifter through the electro-optic effect. By application of a voltage of up to 1230 V, the OPO signal and idler wavelengths are tuned over 102 nm from 1560 to 1660 nm, in good agreement with theory.

[Pollution of the groundwater in the city of Niamey, Niger]

We conducted a study on chemical and bacteriological groundwater pollution in Niamey, a Sahelian city of some 700,000 inhabitants. A total of 22 wells and 24 bore-holes were selected on a geological and socio-economic basis. The superficial aquifers, located on each bank of the River Niger and connected to the wells, presented high levels of oxidizable nitrogen and bacteriological pollution (coliform and faecal Streptococcus) which make the water unfit for human consumption. The deep aquifer, which supplies pumps, was also polluted but to a lesser degree. Faecal pollution increased after the rainy season. The lack of sanitation in Niamey and the seepage of polluted matters from the superficial layers could explain this pollution. Eventually, the use of the groundwater could increase and constitute a major health risk for the majority of the inhabitants of Niamey.

Peutz-Jeghers colonic tumour in a newborn

The authors refer a case report of the Peutz-Jeghers tumour localised in transverse colon found during a systematic clinical examination of the 4-day-old newborn, without any signs of intestinal occlusion. The end-to-end colic resection was made. Post-operative course was without any complications. The observation is rarely due to the tumour's atypical localisation as well as its presence in the newborn.

Fiber-laser-pumped continuous-wave singly resonant optical parametric oscillator

We report on what is to our knowledge the first continuous-wave (cw) optical parametric oscillator (OPO) that is pumped by a tunable fiber laser. The OPO is singly resonant for the signal wave and consists of a 40-mm-long periodically poled LiNbO(3) crystal in a four-mirror ring cavity. At a pump power of 8.3 W provided by the wavelength-tunable Yb-doped fiber laser, the singly resonant OPO generates 1.9 W of 3200-nm cw idler radiation. The singly resonant OPO was tuned from 1515 to 1633 nm (signal) and from 3057 to 3574 nm (idler) by means of the crystal temperature and poling period. We obtained a wide idler tuning range, from 2980 to 3700 mn, by tuning the wavelength of the fiber laser from 1032 to 1095 nm.

Observations on mortality during the 1918 influenza pandemic

The original purpose of our study was to examine the unusual W-shaped mortality curve associated with the 1918 influenza pandemic and possibly explain the peak in mortality among individuals aged 20-40 years. We plotted age-specific excess mortality instead of total mortality for the 1918 pandemic using a 5-year baseline. For comparison, we also graphed excess mortality curves for the 1957 and 1968 pandemics using 5-year baselines. The 1957 and 1968 curves exhibited the usual U-shaped curve, with high excess mortality among infants and the elderly population relative to young adults. The 1918 curve, however, presented unexpected results. A peak in excess mortality among infants and young adults was seen, but the expected W shape did not result. We instead found negative excess mortality among elderly individuals, suggesting that this group was exposed, at an earlier date, to an influenza strain similar to the so-called Spanish influenza (H1N1) strain.

Characterization of antibody responses to annual influenza vaccination over four years in a healthy elderly population

The effects of yearly influenza immunization on the level of antibody responses were assessed in 92 healthy elderly subjects immunized over four contiguous years (1993-1996) with a trivalent influenza vaccine that included A/Texas annually. Anti-A/Texas antibodies increased significantly and similarly post-vaccination each year, but returned to comparable baseline levels annually. Percentages of subjects with anti-A/Texas titers > or =40 post-vaccination were comparable over four years. Importantly, post-vaccination titers > or =40 to A/Texas in 1993-1994 predicted anti-A/Texas titers > or =40 in subsequent years. Thirty percent of individuals produced four-fold rises to any vaccine component the first year it was included in the vaccine, however, this percentage decreased to about 10% after subsequent vaccination with the same component. This study clearly supports the concept that annual immunization with the same influenza vaccine component over multiple years does not significantly decrease antibody titers in a healthy elderly population.

The role of V2 vasopressin antagonists in hyponatremia

Hyponatremia is a frequent electrolyte disorder. It is often found in congestive cardiac failure, liver cirrhosis, plasma volume contraction and in SiADH. In these disorders hyponatremia is caused by nonosmotic vasopressin and sustained fluid intake. This provides a rationale for V2 vasopressin receptor antagonists in the treatment of hyponatremia. There is now convincing evidence from different animal models of congestive cardiac failure that peptide and non-peptide V2 vasopressin antagonists effectively increase renal water diuresis and plasma sodium concentration. In addition, several of the experimental studies also showed an improvement of hemodynamic changes of cardiac failure in response to V2 antagonists. Data in patients indicated that oral non-peptide V2-antagonists correct hyponatremia and may improve hemodynamic derangements in cardiac failure. In addition, experimental and clinical studies of V2 antagonists have been undertaken in liver cirrhosis and SiADH. In those studies hyponatremia was improved or corrected, too. Taken together, V2 vasopressin antagonists promise to become therapeutic agents in hyponatremic disorders.

Comparison of dosimetric standards of Canada and France for photons at 60Co and higher energies

We report the results of a comparison of the dosimetric standards of Canada and France for photon beams at 60Co and a few higher energies. The present primary standard of absorbed dose to water for NRC, Canada is based on measurements made with a sealed water calorimeter. The corresponding standard of the LNHB, France is based on measurements made with a graphite calorimeter at 60Co energy and transferred to absorbed dose to water for 60Co and higher-energy photon beams using both ion chambers and Fricke dosemeters as transfer instruments. To make this comparison, we used three graphite-walled NE2571 Farmer chambers. The absorbed dose to water determined by the LNHB was greater than that determined by NRC by 0.20% at 60Co energy. This difference is not significant given the uncertainties on the standards. In order to do the comparison for higher-energy photons, we interpolated the NRC data set at the beam qualities used at the LNHB. When %dd(10)x is used as the method of specifying beam quality, the determination of absorbed dose to water by the LNHB is about 0.2% greater than that determined by NRC and consistent with the results at 60Co. However, when using TPR20,10 as the beam quality specifier, the LNHB determination is greater than the NRC's determination by 0.8% and 1.2% at 12 and 20 MV respectively. This discrepancy, which systematically increases with increasing energy, eventually exceeds the uncertainties in the ratio of the standards, estimated to be 0.7%. This underscores the importance of selecting the method of specifying beam quality, either %dd(10)x or TPR20,10, at least for the 'soft' beams used by NRC in this comparison. In the case of the air kerma standards, which were also compared at 60Co energy, the LNHB determination was greater than NRC's by 0.14%, which is not significant given the uncertainties on the standards.