Light and electron microscope study of a new species of Urosporidium (Haplosporida), hyperparasite of trematode sporocysts in the clam Abra ovata

Abra ovata, collected at Bcauduc, France, contained sporocysts of Gymnophallus nereicola and another trematode of the family Monorchiidae. Frequently the former trematode and occasionally the latter was infected with a species of Urosporidium. Stages observed were mostly in the sporogenesis sequence. The sporoblast, an elongated body of uncertain origin, differentiates into two parts delimited by a girdle-shaped constriction between them. These are an anterior part, or sporoplasm primordium, containing a vesicular nucleus and a posterior part, or envelope primordium, containing a “parietal apparatus” (possibly a transformed nucleus). Cytoplasm of the envelope primordium (just behind the constriction) advances to enclose the sporoplasm primordium while it differentiates into endospore, exospore and an internally situated cover over the orifice. These two primordia separate late in the sporogenesis sequence. Thus, the typical haplosporidan spore may, as Cépède reported in 1911, consist of 2 cells, a generative cell enveloped by a somatic cell. Evidence that the Haplosporida have bicellular spores raises fundamental questions regarding the taxonomy of this group.     

Effect of methamphetamine on the development of acute morphine tolerance and dependence in mice

The effect of methamphetamine on morphine analgesia (tail-flick assay) was studied in non-tolerant mice and in mice made acutely tolerant to morphine following a single injection of 100 mg/kg morphine. The analgesic potency of morphine was increased in non-tolerant and tolerant mice to the same extent by 3.2 mg/kg methamphetamine (3.3 and 4.4 fold increases, respectively). In contrast, the ED50's for morphine analgesia and naloxone-precipitated jumping in mice pretreated with either 100 mg/kg morphine or both morphine and 3.2 mg/kg methamphetamine were not significantly different, indicating that methamphetamine had no effect on the development of acute morphine tolerance and dependence. Although methamphetamine had no effect on the development of acute tolerance to morphine, 4-day pretreatment with methamphetamine produced cross-tolerance to morphine analgesia. However, cross-tolerance to morphine was not accompanied by enchanced sensitivity to naloxone.