Daños por granizo en vid : su secuela en futuras cosechas

Se trata de confirmar la hipótesis de que en vid, el daño por granizo produce secuelas en futuras producciones y determinar su magnitud con relación al daño tasado. Las pérdidas por granizo se pueden desagregar en: • Disminución del volumen cosechado el año del siniestro. • Secuelas en la futura capacidad productiva. • Pérdida del valor comercial del remanente cosechado. Analizados 268 casos debidamente documentados se concluye que: • Sólo para daños entre 90 y 100 % se puede probar estadísticamente que la producción de la primera y segunda temporadas, posteriores al evento, disminuyen por daños de granizo, conforme al modelo lineal: y = -0.16 + 0.23 x, donde y es la relación de cada producción con la producción media sin granizo y x, el tiempo en años, arrojando un R2 de 75.24. • Para daños inferiores a 90 % las secuelas quedan enmascaradas por la variación natural de la producción. • Para daños menores al 90 % se aconseja no considerar las secuelas fruto de la relación: % de daño-producción, ya que no se ha podido aislar su variabilidad.

The nature of shield abnormalities in the turtle shell / [by] Rainer Zangerl -- and Ralph G. Johnson --.

v.10:no.29(1957)

Visual stimuli induce waves of electrical activity in turtle cortex

The computations involved in the processing of a visual scene invariably involve the interactions among neurons throughout all of visual cortex. One hypothesis is that the timing of neuronal activity, as well as the amplitude of activity, provides a means to encode features of objects. The experimental data from studies on cat [Gray, C. M., Konig, P., Engel, A. K. & Singer, W. (1989) Nature (London) 338, 334–337] support a view in which only synchronous (no phase lags) activity carries information about the visual scene. In contrast, theoretical studies suggest, on the one hand, the utility of multiple phases within a population of neurons as a means to encode independent visual features and, on the other hand, the likely existence of timing differences solely on the basis of network dynamics. Here we use widefield imaging in conjunction with voltage-sensitive dyes to record electrical activity from the virtually intact, unanesthetized turtle brain. Our data consist of single-trial measurements. We analyze our data in the frequency domain to isolate coherent events that lie in different frequency bands. Low frequency oscillations (<5 Hz) are seen in both ongoing activity and activity induced by visual stimuli. These oscillations propagate parallel to the afferent input. Higher frequency activity, with spectral peaks near 10 and 20 Hz, is seen solely in response to stimulation. This activity consists of plane waves and spiral-like waves, as well as more complex patterns. The plane waves have an average phase gradient of ≈π/2 radians/mm and propagate orthogonally to the low frequency waves. Our results show that large-scale differences in neuronal timing are present and persistent during visual processing.

A heme-protein-based oxygen-sensing mechanism controls the expression and suppression of multiple proteins in anoxia-tolerant turtle hepatocytes.

The O2 sensitivity of protein expression was assessed in hepatocytes from the western painted turtle. Anoxic cells consistently expressed proteins of 83.0, 70.4, 42.5, 35.3, and 16.1 kDa and suppressed proteins of 63.7, 48.2, 36.9, 29.5, and 17.7 kDa. Except for the 70.4-kDa protein, this pattern was absent during aerobic incubation with 2 mM NaCN, suggesting a specific requirement for O2. Aerobic incubation with Co2+ or Ni2+ increased expression of the 42.5-, 35.3-, and 16.1-kDa protein bands which was diminished with the heme synthesis inhibitor 4,6-dioxoheptanoic acid. Proteins suppressed in anoxia were also suppressed during aerobic incubation with Co2+ or Ni2+ but this was not relieved by 4,6-dioxoheptanoic acid. The anoxia- and Co2+/Ni2+-induced expression of the 42.5-, 35.3-, and 16.1-kDa protein bands was antagonized by 10% CO; however, with the exception of the 17.7-kDa protein, this was not found for any of the O2- or Co2+/Ni2+-suppressed proteins. Anoxia-induced proteins were compared with proteins expressed during heat shock. Heat shock proteins appeared at 90.2, 74.8, 63.4, 25, and 15.5 kDa and were of distinct molecular masses compared with the anoxia-induced proteins. These results suggest that O2-sensing mechanisms are active in the control of protein expression and suppression during anoxia and that, in the case of the 42.5-, 35.3-, 17.7-, and 16.1-kDa proteins, a conformational change in a ferro-heme protein is involved in transducing the O2 signal.

Does Müller cell differentiation occur prior to the emergence of synapses in embryonic turtle retina?

Müller cells are the main glial cells in the retina, and are related to plexiform layer activity. Recent studies have demonstrated that Müller cells are involved in the synaptic conservation, plasticity, development and metabolism of glutamate. During turtle retinal development, layers, cells and synapses appear at different times. The aim of this research is to study the emergence of Müller cells during embryonic development and their relationship with the synaptogenesis. The authors used retinas from Trachemys scripta elegans embryos at stages S14, 18, 20, 23, and 26. Some retinas were processed with immunocytochemistry in order to detect the presence of glutamine synthetase in Müller cells, which was used as a marker of these cells. Other retinas from the same stages were processed for ultrastructural studies. Samples were observed in confocal and transmission electron microscopes, respectively. The present results show that glutamine synthetase expression in Müller cells occurs at S18, before the emergence of the retinal layers and the early synapses.

A new specimen of Desmatochelys lowi Williston; a primitive cheloniid sea turtle from the Cretaceous of South Dakota / Rainer Zangerl -- and Robert E. Sloan --.

v.14:no.2(1960)

Sea turtles and the turtle industry of the West Indies, Florida and the Gulf of Mexico...

Mode of access: Internet.

The 5 sea turtle species of the Atlantic and Gulf Coast of the United States.

Mode of access: Internet.

Turtles lined up on log in turtle pool beside Ruthven Museums Building, June 1930

Published October 1930 Michigan Alumnus, page 14.