SUMMARYVibrio fetus was examined in shadow-cast, negative-contrast and thinsectioned preparations. Four morphological types were noted in shadowed specimens : comma, coccoid, S-shaped and filamentous. In negative-contrast preparations organisms were differentiated into two types on the appearance of their cytoplasmic mass. A large spherical cytoplasmic inclusion was frequently evident at the flagellated pole of freshly harvested organisms. Various morphological variants, ' sports ', e.g. multiflagellate, were easily detected. A non-motile isolate was either devoid of flagella or exhibited only a short stub a t the pole.In thin-section preparations anatomical features noted were : a rugose loosely fitting membranous integument ; a complex cytoplasmic membrane of honeycomb-like structure ; a fibrillar nucleoplasm and fibrillar cytoplasmic ground substance with associated ribosomes ; lamellated or cytoplasmic granules bounded by a smooth membrane. At the flagellated pole the cytoplasmic ground substance was generally rarefied and a coneshaped flagellar basal granule was present. The flagella were enlarged a t their proximal terminus. Mesosome-like elaborations of the cytoplasmic membrane were not observed. It was concluded that Vibrio fetus closely resembles members of the genus Spirillum.
Mammalian ingestion of jervane, solanidane, and spirosolane steroidal alkaloids produces craniofacial congenital malformations in offspring upon administration during the primitive s t r d n e u r a l plate developmental phase. Structure-terata studies have shown that hamster teratogenicity induced by steroidal alkaloids is primarily related to the presence of C-5, C-6 unsaturation and secondarily to the molecular configuration at C-22 (spirosolanes and solanidanes). Teratogenic potencies of jervanes and solanidanes are appreciably higher than those of spirosolanes whereas the potency of jervanes is generally greater than that of solanidanes. The enhanced teratogenicity of functionalized steroidal alkaloids implies that their amphiphilic nature may be important in facilitating their passage of the embryonic membrane.
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