Formation of Basal Bodies in Ciliary Epithelium of Molluscs Buccinum undatum L. and Lymnaea stagnalis L.

Electron microscopic studies of the leg ciliary epithelium was carried out in two mollusks. In the epithelium of the leg of adult animals, the centrioles were mostly formed de novo with participation of deuterosomes during the formation of basal bodies. Transformation of the centriolar cylinder in a mature basal body is accompanied by the cylinder elongation and appearance of pericentriolar structures, such as rootlet system, basal legs, and basal plate. Centriolegenesis proceeds in both ciliate and nonciliate (with microvilli) cells of the epithelium. It has been proposed that the cell with microvilli represent a transitional stage in differentiation of the ciliary cells.     

Ultrastructure of oesophageal appendages ("peptonephridia") in enchytraeids (Annelida: Clitellata)

Abstract. Although the oesophageal appendages in the four enchytraeids Enchytrueus crypticus, Fredericia strinta, Buchholzia appendiculata , and Achaeta sp. are quite different from one another in shape and position, their histology and ultrastructure are basically the same. These are intestinal appendages, the lumina of which distally end blind and proximally open into the oesophagus. Almost all of the few cells in their single-layered epithelium have a microvillous, cilia-free border at the apex, facing towards the lumen, and basally comprise an extremely extensive labyrinth. The presence of the latter, composed of very thin cell processes, and of numerous mitochondria identifies the organs as energy-producing and -consuming, transport-active structures. Their possible function as a food-moistening organ or osmoregulatory organ is discussed, and they are compared with other intestinal appendages in enchytraeids and other oligochaetes.     

Relationship between the population of viable sclerotia ofSclerotium rolfsii in soil to cropping sequence in the Nigerian savanna

Populations of viable sclerotia ofSclerotium rolfsii were highest in soil in a field in which tomato was planted for three successive years before sampling and in one in which tomato followed groundnut in the 2 years prior to this study. The lowest sclerotial numbers were recorded in fields in which groundnut followed maize or in which maize or sorghum was the last crop before sampling.     

Cell Biology and Algal Taxonomy and Evolution Absolute Orientations of Basal Bodies in Green Algae Evaluated by Light Microscopy

Using high magnification Nomarski interference microscopy a series of optical sections has been obtained through flagellated cells of several green algae in an attempt to establish the absolute orientation of their basal bodies. Using this technique we have confirmed that in Spermatozopsis similis basal bodies are displaced into the 1/7 o'clock position, whereas in gametes of Enteromorpha linza, and zoospores of Trebouxia erici basal bodies are displaced into the 11/5 o'clock position. In addition we report for the first time that in zoospores of Microthamnion kuetzingianum basal bodies are also displaced into the 11/5 o'clock position. Basal body absolute orientations can thus be determined by light microscopy and do not require serial section electron microscopy. The method should be useful for class-level recognition of unknown green algae at the light microscope level.     

Relative importance of the effect of 2,4-D,glyphosate, and environmental variables on the soil microbial biomass

Two post-emergence herbicides (glyphosate and 2,4-D) were applied at field application levels to tilled field plots in a mixed cropping area in south-central Alberta. The effects of these chemicals on certain variables associated with microbial biomass and activity were monitored in these plots (as well as corresponding control plots) for 45 days. Glyphosate did not influence any of the microbial variables tested. Addition of 2,4-D significantly influenced all microbial variables investigated but these effects were transient, being detectable only within the first 1–5 days of herbicide addition. The effects of 2,4-D addition on the microbial variables tested, even when significant, were typically small and probably of little ecological consequence especially when spatial and temporal variation in these variables is taken into account.     

Hypoprolactinemic Action of Calcitonin and the Tuberoinfundibular Dopaminergic System

Abstract: The effects of calcitonin on neurochemical parameters related to the tuberoinfundibular dopaminergic system have been investigated in an attempt to elucidate how calcitonin decreases serum prolactin levels. Intracerebroventricular human or salmon calcitonin injection decreases serum prolactin, medial basal hypothalamic dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) and hypophysial DA and increases hypophysial DOPAC. Results suggest that calcitonin may decrease prolactin secretion via the tuberoinfundibular dopaminergic system.     

Response of pondcypress growth rates to sewage effluent application

Cores were collected from dominant pondcypress trees growing in a swamp that had received sewage effluent for 7 yr and a nearby control swamp to determine the combined effects of changes in nutrient supply and hydrologic regime on tree growth. The cores were used to measure two indices of tree growth: basal area increment (BAI) and relative basal area increment (RBAI, which accounts for differences in growth due to the size of teh tree) between 1970–1983 while one swamp remained untreated and the other received weekly additions of sewage effluent from 1974–1981. Throughout the whole period, the mean BAI and RBAI of pond-cypress trees in the untreated swamp remained unchanged, ranging between 5.55–6.38 cm² yr^–1 and 1.09–1.27% yr^–1, respectively. In contrast, trees in the treated swamp increased their BAI approximately two-fold from 7.40 cm² yr^–1 prior to treatment to 14.83 cm² yr^–1 after the onset of treatment and maintained this rate of growth in the 2 yr period after cessation of treatment. Relative basal area increment showed a similar response, but the proportional increase due to treatment was less (1.5-fold factor) than for BAI. The response of pondcypress trees to the sewage effluent differed depending upon whether the trees were located in the deep or shallow water zones. Trees in the deep zone of the treated swamp had lower BAIs and RBAIs than those in the shallow zone during the treatment period, whereas in pre- and post-treatment periods growth indices were equal in both zones. No significant differences in growth between deep and shallow zones were observed during all three time periods in the control swamp.     

Effects of three herbicides on soil microbial biomass and activity

Three post-emergence herbicides (2,4-D, picloram and glyphosate) were applied to samples of an Alberta agricultural soil at concentrations of 0, 2, 20, and 200 μg g⁻¹. The effects of these chemicals on certain microbial variables was monitored over 27 days. All herbicides caused enhancement of basal respiration but only for 9 days following application, and only for concentrations of 200 μg g⁻¹. Substrate-induced respiration was temporarily depressed by 200 μg g⁻¹ picloram and 2,4-D, and briefly enhanced by 200 μg g⁻¹ glyphosate. It is concluded that because changes in microbial variables only occurred at herbicide concentrations of much higher than that which occurs following field application, the side-effects of these chemicals is probably of little ecological significance.     

Taxonomy of Pyramimonas obovata and other observations on the subgenus Vestigifera of Pyramimonas (Prasinophyceae, Chlorophyta)

A vestigiferan species commonly referred to as Pyramimonas obovata N. Carter has been redescribed as P. melkonianii sp, nov. Characters of this species and a further six (P. disomata Butcher ex McFadden, Hill et Wetherbee, P. mantoniae Moestrup et Hill, P. mitra Moestrup et Hill. P. moestrupii McFadden, P. aff. nephroidea McFadden, P. orientalis Butcher ex McFadden, Hill et Wetherbee) isolated from South African waters are used to define further the subgenus Vestigifera McFadden. This includes a unique chloroplast shape and basal hyaline region with stellate or cruciform vacuoles, a transitional plate-like structure in the flagellum, and a different microtubular root system. The proximal set of basal body connectives were found to be remarkably symmetrical and like those of the subgenus Trichocystis McFadden, and a duct fibre was found associated with the Id root in all currently investigated species. The validity of the larger body (box and crown) scales as taxonomic markers at a fine level is also questioned.