Effect of donor nephrectomy time during circulatory-dead donor kidney retrieval on transplant graft failure.

BACKGROUND: When the blood supply ceases in a deceased organ donor, ischaemic injury starts. Kidneys are cooled to reduce cellular metabolism and minimize ischaemic injury. This cooling is slow and kidneys are lukewarm during nephrectomy. Smaller single-centre studies have shown that prolonged donor nephrectomy time decreases early kidney transplant function, but the effect on long-term outcome has never been investigated in large multicentre cohort studies. METHODS: The relationship between donor nephrectomy time and death-censored graft survival was evaluated in recipients of single adult-to-adult, first-time deceased-donor kidneys transplanted in the Eurotransplant region between 2004 and 2013. RESULTS: A total of 13 914 recipients were included. Median donor nephrectomy time was 51 (i.q.r. 39-65) min. Kidneys donated after circulatory death had longer nephrectomy times than those from brain-dead donors: median 57 (43-78) versus 50 (39-64) min respectively (P < 0·001). Donor nephrectomy time was independently associated with graft loss when kidneys were donated after circulatory death: adjusted hazard ratio (HR) 1·05 (95 per cent c.i. 1·01 to 1·09) per 10-min increase (P = 0·026). The magnitude of this effect was comparable to the effect of each hour of additional cold ischaemia: HR 1·04 (1·01 to 1·07) per h (P = 0·004). For kidneys donated after brain death, there was no effect of nephrectomy time on graft survival: adjusted HR 1·01 (0·98 to 1·04) per 10 min (P = 0·464). CONCLUSION: Prolonged donor nephrectomy time impairs graft outcome in kidneys donated after circulatory death. Keeping this short, together with efficient cooling during nephrectomy, might improve outcome.

ANTECEDENTES: La lesión por isquemia empieza en el momento que cesa la irrigación sanguínea del órgano donante. Para reducir el metabolismo celular y la lesión isquémica se reduce la temperatura de los riñones. Este enfriamiento es lento y los riñones se mantienen tibios durante la nefrectomía. Estudios unicéntricos con muestras pequeñas han demostrado que el tiempo de la nefrectomía del donante disminuye la función precoz del injerto renal, pero nunca se ha analizado su repercusión a largo plazo en grandes estudios multicéntricos. MÉTODOS: Se analizó la relación entre la duración de la nefrectomía del donante y la supervivencia del injerto en 13.914 adultos receptores de un primer riñón procedente de donante cadavérico adulto en la región de Eurotransplant entre los años 2004 y 2013. RESULTADOS: La mediana de duración de la nefrectomía del donante fue de 51 minutos (rango intercuartílico 39-65). En los riñones obtenidos en donantes a corazón parado la duración de la nefrectomía fue más prolongada que en los donantes en muerte cerebral (mediana 57 min (43-78 min) versus 50 min (39-64 min), P < 0,001). La duración de la nefrectomía en el donante se asoció de forma independiente con la pérdida del injerto (cociente de riesgos instantáneos, hazard ratio, HR, ajustado 1,05 por cada incremento de 10 minutos, i.c. del 95%: 1,01 a 1,09; P = 0,026) cuando los riñones se obtuvieron en donantes en parada cardíaca. La magnitud de este efecto fue comparable al efecto de cada hora adicional de isquemia fría (1,04, i.c. 95% 1,01-1,07, P = 0,004). En los riñones obtenidos de donantes en muerte cerebral, la duración de la nefrectomía no influyó en la supervivencia del injerto (HR ajustada 1,01 por aumento de 10 min, i.c. del 95%: 0,98 a 1,04). CONCLUSIÓN: La duración de la nefrectomía en donantes a corazón parado afecta la función de los injertos trasplantados. Reducir esta duración y disponer de un sistema de enfriamiento eficiente durante la nefrectomía podría mejorar los resultados.

No evidence for polarization sensitivity in the pigeon electroretinogram

The electroretinographical response to flashes of linearly polarized light directed at the pigeon's yellow field was compared with that to flashes of unpolarized light. This was carried out for white light and for monochromatic light of various wavelengths, including ultraviolet. In addition, responses to slow rotation of the E-vector of polarized light were measured. Neither the presence or absence of polarization, nor the orientation of the E-vector, influenced any of the electrophysiological variables that were monitored in these experiments.

The photopic sensitivity of the yellow field of the pigeon's retina to ultraviolet light.

The photopic spectral sensitivity of the yellow field of the pigeon's retina to UV light was determined electrophysiologically. The sensitivity curve could be approximated with a model in which the activity of only two cone types were incorporated. In this model, the first type of cone had a maximum sensitivity at 366 nm and was combined with an oil droplet that is completely transparent in the UV wavelength range. The second type had a sensitivity maximum at 415 nm and was associated with an oil droplet cutting off light below 390 nm.

The relation between celestial colour gradients and the position of the sun, with regard to the sun compass.

Colour gradients along the sky caused by atmospheric scattering were measured on sunny days. It is concluded that whereas the shape of the spectral intensity distribution in the short wavelength range is stable, the distribution at longer wavelengths depends on the direction of measurement. We expressed these relative intensity differences as a spectral contrast. This contrast plotted as a function of angular difference with respect to the position of the sun establishes a smooth gradient. We suggest that the pigeon's UV sensitivity is part of a colour processing system, which is well adapted to employ these gradients in order to derive the sun's position.

THE ORIENTATION OF THE E-VECTOR OF LINEARLY POLARIZED LIGHT DOES NOT AFFECT THE BEHAVIOUR OF THE PIGEON COLUMBA LIVIA

Orientation with reference to the time-compensated sun-azimuth compass has been established for the homing pigeon Columba livia. Previous qualitative studies claim that pigeons are sensitive to the orientation of a polarizer and it has been suggested that these animals are able to use sky-light polarization as an indirect reference to the sun's position when the latter is shielded from view. We report experiments which were undertaken to quantify the sensitivity of the homing pigeon to the orientation of linearly polarized light. The results of our initial experiments suggested that the animals responded to secondary cues. Further experiments were carried out to avoid such artefacts. Under circumstances where secondary cues were rigorously avoided, we were, however, not able to demonstrate any directional response that was caused by the E-vector orientation of the illumination. These results throw doubt on the suggested polarization-sensitivity of birds in general.

Artificial lighting in poultry houses: do hens perceive the modulation of fluorescent lamps as flicker?

1. Many poultry houses are illuminated by fluorescent lamps which produce discontinuous illumination with a frequency of either 100 or 120 Hz. 2. This study investigated whether domestic fowls perceive this discontinuity as flicker by training two Leghorn hens to choose between a continuous and a discontinuous light, all other variables being identical. 3. The light-stimulus was either monochromatic with 100% sinusoidal modulation or a fluorescent lamp whose modulation frequency could be electrically adjusted. 4. Each (correct) choice for the discontinuous light was followed by a 5 Hz higher frequency, whereas an incorrect choice was followed by a 10 Hz lower frequency. 5. On the basis of this principle the animals themselves established the highest perceivable frequency of the discontinuous light, called the Critical Fusion Frequency (CFF), that they could discriminate from continuous light. 6. These frequencies typically depend on the stimulus intensity increasing with increasing intensities, until a maximum value is reached. 7. Two factors limited the magnitudes of the CFF's that were recorded: the maximum stimulus intensities produced and variability in the chicken's response ("behavioural noise"). In spite of these constraints 105 Hz was established as the maximum CFF. 8. On the basis of extrapolation it is concluded that the direct light from fluorescent lamps driven by 50 Hz alternating current is seen by the chicken as flickering. 9. The results justify large-scale comparison of behaviour and production in poultry houses that are illuminated either by low-frequency or by high-frequency fluorescent lamps.