Photoperiod in three xanthium populations from the tropic of cancer in Mexico

Diverse photoperiodic responses were shown by three populations of Xanthium strumarium L. originating between 22 degrees and 25 degrees N on the western coast near Culiacán, Sinaloa; in the Chihuahuan Desert near Matehuala, San Luis Poto?; and on the Gulf Coast near Ciudad Mante, Tamaulipas, respectively. A combination of differences in critical night length and in ripeness-to-flower response (maturity) appears to be the basis for reproductive adaptation of these populations to different climatic regimes that prevail at the same latitude (and photoperiodic regime).     

Inherited myopathy in a young Great Dane

A 3-year-old, male Great Dane was evaluated for an 18-month history of progressive weakness. Histologic evaluation of muscle biopsies revealed distinct cytoarchitectural changes that were indistinguishable from the central "core-like" structures previously described as central core myopathy in this breed. Clinical features of this inherited myopathy are described.