In vivo activity of nifurzide and nifuroxazide in intestinal bacteria in man and gnotobiotic mice

Although Gram-negative enteropathogenic bacteria are the target strains of nifurzide and nifuroxazide treatments, neither drug affected faecal counts of in vitro -susceptible Enterobacteriaceae in healthy volunteers. This absence of activity was shown to be due to the poor solubility of the drugs tested. Therefore, effect of high doses of nifurzide was investigated in gnotobiotic mice. Activity against in vitro susceptible enteropathogens was then observed. Normal bacterial cells were replaced in the faeces by elongated, nonseptate and unflagellated mutants. Moreover, the resistance to colonization by enterotoxigenic Escherichia coli and Shigella flexeri of an anaerobic flora of human origin was sharply decreased.     

Aspects of Cell Wall Structure and the Development of the Velamen in Ansellia gigantea Reichb. f.

A transmission and scanning electron microscope study was madeof cell wall development in the root velamen of Ansellia gigantea.The pattern of fibrillar deposition in the primary walls wasestablished by means of shadowed surface preparations. The helicalwall thickenings were shown to originate by the localised appositionof bundles of orientated 20–30 nm cellulose fibrils. Thisproceeds from near the tips of the radially elongated cells.Although microtubules were associated with later stages of helixdeposition, there was no evidence for cytoplasmic pre-patteming.The large wall perforations, circumscribed by secondary walldepositions, develop at the sites of pit fields. The implicationsof the present observations are discussed, particularly as theyappear to relate to general principle of wall development intracheary elements.     

Position and development of oocytes in velvet worms shed light on the evolution of the ovary in Onychophora and Arthropoda

Onychophora or velvet worms are of considerable importance in current reconstructions of animal phylogeny. Despite their otherwise conservative morphology, the detailed anatomy of the onychophoran ovary displays significant variation. However, the evolutionary significance of this variation is not well understood. We recognize three major ovarian types in the Onychophora: (1) the exogenous ovary; (2) the pseudoendogenous ovary; and (3) the endogenous ovary. The germ cells in all three ovarian types are intraepithelial in that they occur between the basal lamina and the epithelial cells that line the cavity of the gonad. This is the condition found in the endogenous ovary. Even in the exogenous ovary, with stalked oocytes projecting into the haemocoel, the maturating oocytes are still covered by a basal lamina. Stalked oocytes that are similar to those found in the exogenous ovary, but retain their intra‐ovarian position, characterize the pseudoendogenous ovary. This and additional observations support the assumption that the pseudoendogenous ovary is derived from an exogenous type and the similarities with the endogenous ovary are superficial. Embryological data and an outgroup comparison with arthropods suggest that the exogenous ovary is the ancestral condition in velvet worms and a synapomorphy of Onychophora and Arthropoda. The embryonic origin, growth, and position of oocytes outside the ovarian lumen in Onychophora and various groups of Arthropoda do not support the Articulata hypothesis, which proposes a sister‐group relationship of Panarthropoda and Annelida.     

Characterization of seven polymorphic microsatellites for the study of two Ranunculaceae: Ranunculus nodiflorus L., a rare endangered species and Ranunculus flammula L., a common closely related species

Ranunculus nodiflorus and Ranunculus flammula are two closely related Ranunculaceae. In France, the first one is rare and endangered, whereas the second is common. To compare their population genetic structure, seven polymorphic microsatellite markers were characterized. We found no polymorphism in R. nodiflorus, whereas R. flammula was polymorphic at each locus. The total number of alleles per locus varied from three to eight. Observed heterozygosities ranged from 0 to 0.261. This set of microsatellites offers an efficient tool to study population genetic structure and to compare the results between closely related endangered and common species.     

Collagen in the pterobranch coenecium and the problem of graptolite affinities

Amino-acid analysis of the extracellular skeleton (coenecium) of two pterobranchs (Hemichordata) Rhabdopleura normani and Cephalodiscus (C.) hodgsoni shows that both contain considerable quantities of collagenous material with relatively high hydroxyproline and low hydroxylysine levels. The appearance of the fibrous material in the skeleton of pterobranchs, although collagenous, differs from standard EM characteristics of collagen. The identification of the collagenous nature of the pterobranch skeleton with the presumed presence of collagen-like material in the periderm of fossil graptolites, taken in conjunction with other data, supports the hypothesis that both groups may be closely related phylogenetically.     

Phyllomorph Senescence in Streptocarpus molweniensis

Examination of the phyllomorph of Streptocarpus molweniensisestablishes that notwithstanding its cotyledonary origin andcontinued growth from a basal meristem, it has a fairly typicalleaf anatomy. The most unusual feature is the seasonal senescenceand loss of the distal 60 per cent of the lamina. This is accompaniedby direct development from the mesophyll of a senescence boundaryof phellem. There is no predetermined abscission zone. Thistype of senescence is a means of perennation, whereby the meristemis safeguarded against a depletion of nutrient and water reserves.The phyllomorph presents a system very suited to the study ofthe initiation and control of senescence and abscission. Itis proposed that cytokinin distribution has a primary role inthis respect.