DIFFERENTIATION OF RAT LENS EPITHELIAL CELLS IN TISSUE CULTURE (III) FUNCTIONS IN VITRO OF A TRANSFORMED RAT LENS EPITHELIAL CELL LINE

Epithelial cells isolated from one-day-old rat lens were neoplastically transformed using Rous Sarcoma Virus (Schmidt-Ruppin-D strain) and have been in continuous culture for over 30 months. This cell line displays some of the characteristics of lens epithelial cells, but can be shown to represent a permanent cell line in that it has been transferred more than 50 times and is continuing to grow, while primary lens cell cultures have never survived beyond 8 weeks. The infecting viral genome can be rescued from the cell line upon fusion with uninfected chick embryo cells. It is anticipated that this newly established cell line, designated RLE-R, will be useful in studies on cellular differentiation.     

A Study of Stelar Ultrastructure in the Heterosporous Water Fern Marsilea quadrifolia L

Sieve tube elements occur in the rhizomes and petioles of Marsileaquadrifolia. These are either thick walled with compound sieveplates in oblique end walls or thin walled with simple sieveplates in transverse end walls. Vessels are restricted to themetaxylem in the roots where the phloem contains sieve cellsonly. The sieve pores are invariably callose lined and as inother pteridophytes, excepting the Lycopsida, refractive spherulesare ubiquitous in the sieve elements of Marsilea. The luminaof the protoxylem tracheary elements in the rhizomes and petiolesare occluded by tyloses but probably remain functional in theroots. Pericycle cells backing on to the root protoxylem armspossess wall ingrowths. Transfer cells are however absent fromthe vascular tissue of the rhizomes and leaves. It is suggestedthat their presence in the root pericycle is related to theretrieval of ions from the xylem sap which may be particularlycritical in water plants. The incidence of transfer cells incryptogams appears to be far more sporadic than in angiosperms.The root endodermis of Marsilea possesses a casparian stripand abundant vacuolar tannin deposits. Plasmalemmasomes arenumerous adjacent to the pericycle transfer cells. vascular ultrastructure, Marsilea quadrifolia L, transfer cells, sieve tube elements, tyloses     

Evidence for the use of non-detrital dissolved organic matter by microheterotrophs on plant detritus in a woodland stream

SUMMARY 1. Recent studies provide evidence for the use of exudates from living plants by epilithic microheterotrophs in streams. This study investigated the possible use of such non-detrital sources of dissolved organic matter (DOM) by streatn microheterotrophs colonizing leaf litter. Biomass of bacteria and of fungi accumulating in situ on autumn-shed leaves in flow-through troughs from which light was excluded was compared to that accumulating on leaves in troughs open to natural illumination.
2. In experiments repeated at different times of year and in different stream sections, greater biomass of microheterotrophs consistently accumulated on the leaf detritus in troughs open to natural illumination. Differences in water temperature or in grazing of leaf surfaces by macroinvertebrates could not account for these consistent differences. Further, greater microheterotroph biomass accumulated on light- and dark-incubated leaves in a stream section relatively open to sunlight, compared to corresponding leaves in a section heavily shaded by canopy and understorey vegetation.
3. These and other results suggest that, to some yet undetermined extent, detritus-associated microheterotrophs use non-detrital DOM. This conclusion is consistent with a priori predictions based on consideration of microbial energetics involved in the use of detrital versus non-detrital DOM.
4. Studies of trophic pathways in streams and other aquatic habitats have failed to assess some potentially important sources of non-detrital DOM. The ability of available techniques to assess the relative roles of detrital and non-detrital sources of DOM is evaluated, and alternative approaches to this problem are suggested.     

The West African species of Bathygobius (Teleostei: Gobiidae) and their affinities

The circumtropical gobiid fish genus Bathygobius Bleeker, 1878 is discussed and defined in terms of external features, including the head lateral-line system, and osteology. Three West African species are recognized and redescribed: the amphiatlantic B. soporalor (Valenciennes, 1837) and two endemics, B. burtoni (O'Shaughnessy, 1875) and B. casamancus (Rochebrune, 1880). West African B. soporator differs significantly from western Atlantic material only in average values for predorsal scales and some body proportions, so that separation of eastern and western Atlantic populations as morphological species is not warranted. The affinities of the West African Bathygobius species are examined by means of phenetic (presence-only group-average clustering) and cladistic (Camin-Sokal, Dollo and Wagner) numerical processing of a binary database comprising 46 character states in 15 Operational Taxonomic Units (OTUs) formed by species of Bathygobius. Results do not indicate close common ancestry between the West African endemic species and B. soporator , which has probably colonized West Africa from the New World. The implications of various cladistic schemes for the relationships of certain other American species are also noted.