Donation after cardiac death: where, when, and how?

The continuing shortage of donors has led to the increasing use of marginal grafts. Surgical techniques such as split, domino, and living donations have not been able to decrease waiting list mortality. Donation after cardiac death (DCD) was the only source of grafts prior to the establishment of brain death criteria in 1968. Thereafter, donation after brain death emerged as the leading source of grafts. The context in which irreversible cessation of circulatory and respiratory functions happens was the cornerstone to definite the four categories of DCD by the First International Workshop on DCD held in Maastricht in 1995. Controlled (CDCD) and uncontrolled (UDCD) categories now account for 10%-20% of the donor pool in several countries. Despite initial high rates of primary nonfunction and ischemic-type biliary lesions, refinements in protocols and surgical techniques have led to excellent 1- and 3-year graft survivals of 80% and 70%, respectively with PNF and ITBL rates below 3%. The institution of UDCD and CDCD depends on legal considerations of presumed consent and withdrawal of maneuvers, respectively. The potential for DCD programs is huge; it may be the only real, effective way to increase the grafts pool, both in adult and pediatric populations. Recent advances in perfusion machines will surely optimize this donor pool and allow new therapies for graft resuscitation.

First Report of Ascochyta rabiei Causing Ascochyta Blight of Chickpea in Argentina

In November 2011, lesions similar to those reported for Ascochyta blight (1) were observed on Cicer arietinum L. (chickpea) plants growing in three commercial fields located at Río Primero and Río Segundo (Cordoba Province) and Lobería (Buenos Aires Province), Argentina. Disease incidence (percentage of plants affected) was 100% in all fields surveyed. Plants showed leaves, petioles, stems, and pods with brown lesions. Symptoms on leaves and pods were circular to oval (2 to 14 mm) while in the stems the lesions were elongated (2 to 30 mm). Seeds appeared small and shriveled with brown discoloration. Morphology of the fungi was examined on infected tissues. Numerous black pycnidia measuring 94.6 to 217.9 μm (145.9 ± 28.8 μm), arranged in concentric rings, were observed within of all the lesions. Conidia were predominantly aseptate, straight, hyaline with blunt ends, and measured 9.3 to 12.9 (11.3 ± 1.12) × 3.3 to 5.0 μm (4.2 ± 0.51). Morphological characteristics of the pathogen were similar to those described for Ascochyta rabiei (Pass.) Labrousse (teleomorph Didymella rabiei (Kovacheski) v. Arx (= Mycosphaerella rabiei Kovacheski)) (2). Fungus from infected leaf tissues was isolated on potato dextrose agar. Pathogenicity tests were conducted on seedlings of the susceptible cultivar by spraying leaves of each of 100 seedling plants with 10 ml of a conidial suspension (2 × 10⁴ conidia/ml) of the isolated pathogen with a handheld atomizer. Plants were covered with plastic bags and placed in a growing chamber at 20 to 25°C for 3 days. The plastic bags were removed and the plants were maintained in high humidity at the same temperature. Noninoculated plants were used as controls. After 5 days, all inoculated plants showed typical symptoms. Foliar and stem lesions symptoms were similar to those originally observed in the field. Control plants remained healthy. Koch's postulates were fulfilled by isolating A. rabiei from inoculated plants. The colonies and the morphology of conidia were the same as those of the original isolates. To our knowledge, this is the first report of A. rabiei infecting chickpeas in Argentina. The outbreak of Ascochyta blight in Argentina is of concern because of its severity and the possibility that the pathogen was introduced on seed. This report underscores the need for further research on effective management programs for Ascochyta blight. References: (1) B. Bayaa and W. Chen. Compendium of Chickpea and Lentil Diseases and Pests The American Phytopathological Society, St. Paul, MN, 2011. (2) E. Punithalingam and P. Holliday. Page 337 in: CMI Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1972.

First Report of Races 11 and 12 of Cercospora sojina, the Causal Agent of Soybean Frogeye Leaf Spot, in Argentina

During the growing seasons of 2008 to 2009 and 2009 to 2010, severe outbreaks of soybean (Glycine max (L.) Merr.) frogeye leaf spot, a disease caused by Cercospora sojina Hara, occurred in several areas in Argentina (1). Two surveys were conducted in soybean fields, one in 2008 that included the provinces of Buenos Aires, Córdoba, and Santa Fe, and another that was performed in 2009 in the same provinces plus three others: Entre Ríos, Santiago del Estero, and Tucumán. In both surveys, plants presented circular lesions with reddish brown-to-gray spots and bordered by typical, narrow, reddish purple margins (3). To promote sporulation and to enable identification of the causal agent, leaves of diseased plants were collected and placed in a moist chamber for 24 h with a 12-h light cycle at 25°C. Conidia were plated on potato dextrose agar medium amended with streptomycin and were incubated at 25°C and 12 h of fluorescent light. Isolated cultures sporulated in 10 days and, on the basis of their morphology, were identified as C. sojina. A total of 147 isolates were deposited at the Culture Collection of CEREMIC (Centro de Referencia de Micología). They produced one- to nine-septate hyaline, elongate to fusiform conidia that measured 54.9 ± 16.2 × 5.7 ± 1.0 μm. Six isolates of C. sojina, each representing a province, were inoculated on a set of 12 differential soybean cultivars: Lee, Davis, Hood, Richland, Lincoln, Kent, Tracy, S 100, Palmetto, Peking, CNS, and Blackhawk (2). Fifteen plants of each differential were sprayed at V3 growth stage with a suspension of 6 × 10⁴ conidia/ml. The test was conducted twice in a complete randomized design with three replicates. Control plants were sprayed with sterile distilled water. After inoculation, plants were placed in a greenhouse bench humidity chamber at 26 to 28°C for 72 h. Disease was rated 14 days after inoculation; plants with numerous lesions were considered susceptible and each of the 15 plants was given a score of 1. Plants with small or no lesions were classified as resistant and given a score of 0. Control plants remained healthy. The pathogen was reisolated from symptomatic plants and morphological characteristics were consistent with C. sojina. Based on the response of the differentials to each isolate and on the race designations, the isolates from Buenos Aires, Córdoba, Santa Fe, and Tucumán belong to race 11, while those from Santiago del Estero and Entre Ríos province to race 12. The finding of these two races threatening soybean cultivars in Argentina may be indicative of additional races. Thus, the incorporation of multiple resistance genes may reduce the impact of the disease on soybean. To our knowledge, this is the first report of the identification of races of C. sojina in Argentina. References: (1) M. A. Carmona et al. Plant Dis. 93:966, 2009. (2) M. A. R. Mian et al. Crop Sci. 48:14, 2008. (3) D.V. Phillips. Page 20 in: Compendium of Soybean Diseases. 4th ed. APS Press, St. Paul, MN, 1999.

Entropic splitter for particle separation

We present a particle separation mechanism which induces the motion of particles of different sizes in opposite directions. The mechanism is based on the combined action of a driving force and an entropic rectification of the Brownian fluctuations caused by the asymmetric form of the channel along which particles proceed. The entropic splitting effect shown could be controlled upon variation of the geometrical parameters of the channel and could be implemented in narrow channels and microfluidic devices.

Potential thermal expansion of calcitic and dolomitic marbles from Andalusia (Spain)

Marble has historically been used as an ornamental stone because of its aesthetic appeal, ease of polishing and ex;cellent physical properties. One of the main factors affecting the durability of marbles is their thermal behaviour. Although marble is used extensively in Spain as a building and decorative material, little research has been done into its thermal behaviour. In this work, the textural and microstructural properties of seven calcitic and dolomitic marbles from Andalusia (southern Spain) were characterized to assess how these properties affect their thermal response. Rock fabric properties (grain morphology, boundaries and micro-crack populations) were studied by polarized microscopy and lattice preferred orientation using X-ray texture goniometry. Elastic properties were measured by ultrasound, thermal properties were determined by a six-rod dilatometer (thermal expansion) and the opening of micro-cracks was observed using environmental scanning electron microscopy. For each marble, thermal coefficients of calcite and dolomite crystals were calculated using thermo-X-ray diffraction, a novel application to characterize historic marbles. The results show that marble thermal expansion coefficients are related to preferred crystallographic orientation, which can help to identify the directions along which decay occurs. The results also show for the first time that the thermal expansion coefficient of the main components of marble,i.e.calcite and dolomite, is specific to each marble, and plays a key role in their different thermal behaviours. Thermal properties also depend on mineral composition, the existence of micro-cracks and hydric properties.

Electron density fluctuations accelerate the branching of positive streamer discharges in air

Branching is an essential element of streamer discharge dynamics. We review the current state of theoretical understanding and recall that branching requires a finite perturbation. We argue that, in current laboratory experiments in ambient or artificial air, these perturbations can only be inherited from the initial state, or they can be due to intrinsic electron-density fluctuations owing to the discreteness of electrons. We incorporate these electron-density fluctuations into fully three-dimensional simulations of a positive streamer in air at standard temperature and pressure. We derive a quantitative estimate for the ratio of branching length to streamer diameter that agrees within a factor of 2 with experimental measurements. As branching without this noise would occur considerably later, if at all, we conclude that the intrinsic stochastic particle noise triggers branching of positive streamers in air at atmospheric pressure.

Built-in mechanical stress in viral shells

Mechanical properties of biological molecular aggregates are essential to their function. A remarkable example are double-stranded DNA viruses such as the φ29 bacteriophage, that not only has to withstand pressures of tens of atmospheres exerted by the confined DNA, but also uses this stored elastic energy during DNA translocation into the host. Here we show that empty prolated φ29 bacteriophage proheads exhibit an intriguing anisotropic stiffness which behaves counterintuitively different from standard continuum elasticity predictions. By using atomic force microscopy, we find that the φ29 shells are approximately two-times stiffer along the short than along the long axis. This result can be attributed to the existence of a residual stress, a hypothesis that we confirm by coarse-grained simulations. This built-in stress of the virus prohead could be a strategy to provide extra mechanical strength to withstand the DNA compaction during and after packing and a variety of extracellular conditions, such as osmotic shocks or dehydration.

Expression of the vitamin K-dependent proteins GAS6 and protein S and the TAM receptor tyrosine kinases in human atherosclerotic carotid plaques

The GAS6/ProS-TAM system is composed of two vitamin K-dependent ligands (GAS6 and protein S) and their three protein tyrosine kinase receptors TYRO3, AXL and MERTK, known as the TAM receptors. The system plays a prominent role in conditions of injury, inflammation and repair. In murine models of atherosclerotic plaque formation, mutations in its components affect atherosclerosis severity. Here we used Taqman low-density arrays and immunoblotting to study mRNA and protein expression of GAS6, ProS and the TAM receptors in human carotid arteries with different degrees of atherosclerosis. The results show a clear down-regulation of the expression of AXL in atheroma plaques with respect to normal carotids that is matched by decreased abundance of AXL in protein extracts detected by immunoblotting. A similar decrease was observed in PROS1 mRNA expression in atherosclerotic carotids compared to the normal ones, but in this case protein S (ProS) was clearly increased in protein extracts of carotid arteries with increasing grade of atherosclerosis, suggesting that ProS is carried into the plaque. MERTK was also increased in atherosclerotic carotid arteries with respect to the normal ones, suggesting that the ProS-MERTK axis is functional in advanced human atherosclerotic plaques. MERTK was expressed in macrophages, frequently in association with ProS, while ProS was abundant also in the necrotic core. Our data suggest that the ProS-MERTK ligand-receptor pair was active in advanced stages of atherosclerosis, while AXL signalling is probably down-regulated.

Establishment of a pediatric liver transplantation program: experience with 100 transplantation procedures

OBJECTIVE

To analyze the primary factors that influence the development and consolidation of a pediatric liver transplantation program.

PATIENTS AND METHODS

This was a retrospective study of 100 liver transplantation procedures performed in 84 pediatric patients between May 1990 and November 2007. The male-female ratio was 40:60. Mean (SD) age was 5 years (40 patients were younger than 2 years); cold ischemia time was 7.10 (3.1) hours; surgery time was 5.2 (2.2) hours; and time on the waiting list for transplantation was 75 (range, 1-1012) days. Indications for transplantation included cholestatic disease (43%), acute hepatic failure (AHF; 34%), metabolic disorders (14%), and cirrhosis (9%). Transplanted organs included 3 split grafts, 29 partial grafts, and 8 living-donor grafts.

RESULTS

Mean graft survival was 70.4%, 59.2%, and 58.1% at 1, 3, and 5 years, respectively. Factors that influenced graft outcome were age younger than 2 years; surgery time more than 6 hours; and AHF vs cholestatic disease, metabolic disorders, and cirrhosis. There were no significant differences in long-term (51% vs 59%) and short-term (71% vs 70%) graft survival between procedures performed in 1990-1998 compared with those performed in 1999-2007; however, there was a higher percentage (P = .005) of recipients at high risk (age younger than 2 years or with AHF) in the later period. All data were consistent with those of the European Liver Transplant Registry 2007.

CONCLUSIONS

A pediatric liver transplantation program can be established by a group experienced in liver transplantation.

Teladorsagia circumcincta: survival of adults in vitro is enhanced by the presence of a mammalian cell line

Adult Teladorsagia circumcincta survival and motility in vitro was examined in a range of different cell culture media, supplements and gas mixes. Under optimum conditions, worms survived for 14 days, exhibiting high motility for 9 days and egg production for 72 h. Optimum conditions involved co-culture of worms with a HeLa cell line in a supplemented cell medium (CEM) and an atmosphere containing 10% CO(2), 5% O(2) 85% N(2), 65% humidity at 37 degrees C. The incubation medium consisted of Minimum Essential Medium with 10% fetal calf serum, 1% non-essential amino acids, 1% glutamax and 1% penicillin-neomycin-streptomycin cocktail mix. Compared with optimum conditions, incubation in CEM alone, cell conditioned CEM, RPMI alone, Medium 199 alone, reduced CO(2) or O(2), or when cells were replaced with Escherichia coli, both survival and motility were reduced. Optimum conditions for adult T. circumcincta maintenance for culture, anthelmintic testing or generation of excretory/secretory products are described.

Severe Outbreaks of Soybean Frogeye Leaf Spot Caused by Cercospora sojina in the Pampean Region, Argentina

Frogeye leaf spot of soybean (Glycine max (L.) Merr.) caused by Cercospora sojina Hara was reported to be severe from 1998 to 1999 in northwest Argentina (2). Although the disease was detected at low prevalence (5 to 25%), incidence, and severity in the Pampean Region from 2005 to 2008, no severe outbreaks have been recorded in the provinces of Córdoba, Santa Fe, and Buenos Aires. During the 2008-2009 growing season, disease spread rapidly throughout most soybean-growing areas of the Pampean Region. Disease was observed on almost all varieties of maturity group (MG) III, IV, and V. Symptoms on leaves were circular, reddish brown-to-gray spots (1 to 6 mm) and bordered by typical, narrow, reddish purple margins. Morphology of the fungi was examined on infected tissues. Conidiophores were light-to-dark brown, fasciculate, geniculate, and measured 110 to 203 μm long. Conidia were 1 to 9 septate, hyaline, elongate to fusiform, and measured 26 to 111 (47.3 ± 14.7) × 5.2 to 7.4 μm (6.1 ± 0.7). Pathogenicity tests were conducted on seedlings of a susceptible cultivar by spraying leaves of each of 80 plants at the V3 growth stage with 18 ml of a conidial suspension (3 × 10⁴ conidia/ml) with a hand-held atomizer. Plants were covered with plastic bags and placed in a greenhouse at 28 to 30°C for 48 h. The plastic bags were removed and plants were maintained in high humidity at the same temperature. The same number of noninoculated plants was used as controls. After 10 to 12 days, all inoculated plants showed typical symptoms. Koch's postulates were fulfilled by isolating C. sojina from inoculated plants. Control plants remained healthy. Foliar lesions and morphological characteristics of the pathogen were consistent with C. sojina (1). Disease assessments were made for the middle and upper canopy from 15 arbitrarily collected plants. Soybean plants were in growth stages between R3 and R5 during the survey. Incidence (percentage of plants affected) and severity (percentage of leaf area affected with lesions) were visually estimated from each of the 30 soybean-production fields located in Monte Cristo, Alta Gracia, Jesús María, W. Escalante, Monte Buey, (10 fields, Córdoba Province), Venado Tuerto, Villa Cañás, Cristophersen, María Teresa, (12 fields, Santa Fe Province), Pergamino, Rojas, and Salto (8 fields, Buenos Aires Province). Incidence was 100% in all fields from Córdoba and Santa Fe. Incidence in Buenos Aires was 0 to 100%. Highest severity levels were quantified from fields in Córdoba (severity of 30 to 60%). Lesions also developed on stems and pods. In samples from Buenos Aires, severity levels were ≤10% in the eight soybean fields. Number of lesions per leaflet was recorded from central leaflets in samples from Monte Cristo, Alta Gracia, Venado Tuerto, and María Teresa with 20 to 55 typical lesions per leaflet. Since the disease was always more important in northwest Argentina, genetic resistance is more commonly available in varieties of MG VII to VIII, so most of the varieties of MG III, IV, and V frequently planted in Pampean Region are susceptible. This fact in combination with rainfall, warm temperatures, and high relative humidity in no-till fields during this summer have encouraged the severe outbreak of frogeye leaf spot, especially in the province of Córdoba and in some regions of Santa Fe. References: (1) D. V. Phillips. Page 20 in: Compendium of Soybean Diseases. 4th ed. The American Phytopathological Society. St. Paul, MN, 1999. (2) D. L. Ploper et al. Plant Dis. 85:801, 2001.

Model for end-stage liver disease can predict very early outcome after liver transplantation

Postoperative Model for End-stage Liver Disease (MELD) values have never been assessed to predict very early (<1 week) death after liver transplantation (OLT). We retrospectively reviewed 275 consecutive OLTs performed in 252 recipients reported in a prospective database. We calculated the MELD score (pre-MELD) and consecutive postoperative MELD (post-MELD) scores computed daily during the first postoperative week and on days 15 and 30 after OLT. Post-MELD scores from nonsurviving recipients displayed on a scatterplot of immediate probability of death were adjusted to the best goodness-of-fit curve, and, finally, depicted graphically as a receiver operating characteristic (ROC) curve. Nonsurviving recipients showed higher post-MELD scores: day 1: 23.5 versus 16.6 (P = .05); day 3: 25.1 versus 12.5 (P = .000); day 5: 25.7 versus 11.8 (P = .000); and day 7: 22.1 versus 10.2 (P = .000). Overall comparisons were performed using a time-dependent general linear regression model, revealing higher post-MELD scores for nonsurviving recipients, irrespective of postoperative time (P = .002). The best goodness-of-fit curve was displayed when adjusting to a theoretical exponential regression curve calculated as follows: Probability of dying within the first week (%) = 3.36 x e(0.079 x (post-MELD)) (r = .89; P = .000). The area under the ROC curve was 0.783 (95% confidence interval, 0.630-0.935; P = .001). The model had a positive predictive value of 82.3%, a negative predictive value of 33.1%, and an accuracy of 79.2%. In conclusion, this study corroborated the suggestion that the MELD score may serve as a reliable tool to assess very early death after OLT.

Interaction of streamer discharges in air and other oxygen-nitrogen mixtures

The interaction of streamers in nitrogen-oxygen mixtures such as air is studied. First, an efficient method for fully three-dimensional streamer simulations in multiprocessor machines is introduced. With its help, we find two competing mechanisms how two adjacent streamers can interact: through electrostatic repulsion and through attraction due to nonlocal photoionization. The nonintuitive effects of pressure and of the nitrogen-oxygen ratio are discussed. As photoionization is experimentally difficult to access, we finally suggest to measure it indirectly through streamer interactions.

Atherothrombosis and plaque heterology: different location or a unique disease?

Formation of unstable plaques frequently results in atherothrombosis, the major cause for ischaemic stroke, myocardial infarction and peripheral arterial disease. Patients who have symptomatic thrombosis in one vascular bed are at increased risk of disease in other beds. However, the development of the disease in carotid, coronary and peripheral arteries may have different pathophysiology suggesting that more complex treatment protocols may have to be designed to reduce plaque development at different locations. In this review we describe the known risk factors, compare the developmental features of coronary and carotid plaque development and determine their association with end-point ischaemic events. Differences are also seen in the genetic contribution to plaque development as well as in the deregulation of gene and protein expression and cellular signal transduction activity of active cells in regions susceptible to thrombosis. Differences between carotid and coronary artery plaque development might help to explain the differences in anatomopathological appearance and risk of rupture.