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Articles by Jesus SANCHEZ
Total Records ( 2 ) for Jesus SANCHEZ
  Angel Manteca , Ruben Alvarez , Nuria Salazar , Paula Yague and Jesus Sanchez
  Despite the fact that most industrial processes for secondary metabolite production are performed with submerged cultures, a reliable developmental model for Streptomyces under these culture conditions is lacking. With the exception of a few species which sporulate under these conditions, it is assumed that no morphological differentiation processes take place. In this work, we describe new developmental features of Streptomyces coelicolor A3(2) grown in liquid cultures and integrate them into a developmental model analogous to the one previously described for surface cultures. Spores germinate as a compartmentalized mycelium (first mycelium). These young compartmentalized hyphae start to form pellets which grow in a radial pattern. Death processes take place in the center of the pellets, followed by growth arrest. A new multinucleated mycelium with sporadic septa (second mycelium) develops inside the pellets and along the periphery, giving rise to a second growth phase. Undecylprodigiosin and actinorhodin antibiotics are produced by this second mycelium but not by the first one. Cell density dictates how the culture will behave in terms of differentiation processes and antibiotic production. When diluted inocula are used, the growth arrest phase, emergence of a second mycelium, and antibiotic production are delayed. Moreover, pellets are less abundant and have larger diameters than in dense cultures. This work is the first to report on the relationship between differentiation processes and secondary metabolite production in submerged Streptomyces cultures.
  Jose L. ESPINOZA , Jesus SANCHEZ , Jose A. GRACIA , Jesus R. SANCHEZ , Ricardo ORTEGA and Alejandro PALACIOS
  In order to evaluate heat tolerance, physiological constants of 32 cows were measured (Chinampo: n = 12; Holstein: n = 10; Jersey: n = 10). From June to December 2006, rectal temperature and respiratory rate were recorded every Monday at 0600 and 1700 h. Holstein rectal temperature was affected by heat most, followed by Jersey, and Chinampo (the most heat-resistant). Respiratory rate of the 3 breeds was affected by climatic factors, but the Holstein and Jersey cows registered values higher than those of Chinampo cows. With a temperature-humidity index (THI) above 72 the physiological variables of all 3 breeds increased. The most heat accumulation during the day was registered in the dairy breeds. The difference in respiratory rate between morning and evening measurements was greater in Holstein and Jersey cows than in Chinampo cows. We conclude that Chinampo cows were the most tolerant to heat stress.
 
 
 
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