The effect of thermal effluent upon the standing crop of an epiphytic algal community

The investigation of the epiphyton associated with Scirpus validus VAHL. in Lake Wabamun commenced in May 1971 and continued until the end of August 1972. Seven stations encompassing heated, partially and non-heated areas of the lake were investigated. From July 1971 until the termination of the investigation water temperature, dissolved oxygen and water chemistry were monitored. There were no large variations in these parameters except for water temperature and dissolved oxygen levels among the stations. However, there were increases in the dissolved silica, nitratenitrogen and phosphate-phosphorus levels during the autumn and winter months at the heated stations while at a partially heated station only dissolved silica and nitrate-nitrogen increased. The epiphyton at all stations showed a spring maximum, a summer minimum, and a maximum in the late summer/early autumn. The spring dominants at all stations were Fragilaria capucina and Diatoma elongatum. During the late summer/early autumn maximum diatoms were dominant at the non-heated stations while chlorophycean species were dominant at the heated stations. The heated water caused a decrease in the number of species and a corresponding increase in the importance of a few species at the heated stations. The major impact of the heated water, however, was an extension of the period of open water and the corresponding increase in mean yearly standing crop size in the heated areas.     

Cell cycle specific induction of HL-60 cell differentiation and apoptosis by mycophenolic acid

HL-60 cells undergo terminal differentiation and apoptosis in response to different types of sub-toxic and toxic perturbations respectively. The mechanism by which cells sense different amounts of perturbation to activate pathways that lead to the engagement of a relevant biological response is not known. The response of HL-60 cells to treatment with the immunosuppressant mycophenolic acid (MPA), a specific inhibitor of dGTP/GTP-synthesis, allowed quantitation of a metabolic perturbation which triggered a cellular response. 1.5 microM MPA induced 38% terminal differentiation to CD14 positive, early monocyte-like cells and 22% cell death by apoptosis, whereas 3 microM MPA induced 70% apoptosis but no differentiation. Despite the difference in biological outcomes, 72 h exposure to both 1.5 microM and 3 microM MPA caused a similar ( approximately 75%) depletion of total GTP levels. Cells synchronized by centrifugal elutriation were treated with MPA. Elutriated cells were overall less sensitive to the effects of MPA but 3 microM MPA induced significantly less apoptosis and more differentiation in an elutriation-enriched G1-population than in a population normally distributed in the cell cycle, suggesting that the effects of MPA in S-phase may subsequently lead to cell death. However, analysis of apoptosis by using a terminal deoxynucleotidyltransferase assay and measurement of bromodeoxyuridine incorporation showed that apoptosis was engaged in G1. Analysis of the phosphorylation status of the retinoblastoma protein demonstrated that Rb was hypophosphorylated prior to apoptosis and that in apoptotic cells, separated by flow cytometry, Rb protein was absent, presumably due to proteolysis. The loss of Rb protein did not appear to permit transit to S-phase, and was not accompanied by an expression of c-Myc. Surprisingly, therefore, an antimetabolite inducing a loss of GTP brought about cell death by apoptosis in the G1 phase of the cell cycle.     

Locomotory activity of captive Cryptomys hottentotus, (Mammalia: Bathyergidae), a fossorial rodent

Locomotory activity of six mole-rats kept singly and in various sized groups was monitored for a total of 1728 hours by use of photocells, event recorder, and a 21 metre long, transparent burrow system. Movement in tunnelways was recorded for all hours of a 24 hour period. Locomotory activity for individuals and a two member group average14–24% of the total time, while a four member group averaged 57% of the total time. Approximately five rest periods per day averaged 50 minutes duration each. The effects of social isolation, burrow length, diet, and individual variation on locomotory activity of fossorial mammals are discussed.     

14-3-3 Proteins and photoneuroendocrine transduction: role in controlling the daily rhythm in melatonin

This paper describes the role 14-3-3 proteins play in vertebrate photoneuroendocrine transduction. 14-3-3 proteins form a complex with arylalkylamine N-acetyltransferase (AANAT), the enzyme which turns melatonin production on during the day and off at night. Complex formation is triggered at night by cAMP-dependent phosphorylation of the enzyme, and results in activation and protection against proteolysis. This enhances melatonin production >10-fold. Light exposure results in dephosphorylation of the enzyme and disassociation from 14-3-3, leading to destruction and a rapid drop in melatonin production and release and circulating levels.     

The spatial and temporal distribution of an epiphytic algal community in a shallow prairie-parkland lake – Alberta, Canada

In Hastings Lake (longitudes 113°15' and 53°50'N), a shallow eutrophic lake, the spatial and temporal changes in species composition. diversitv. standing crops, and primary productivity of the epiphytic algae attached to Phragmnes australis and Scirpus validus were investigated in relation to the physico-chemical environment. Of the dominant species, cyanophycean algae ( Lyngbya diguetii and Calothrix sp.) developed best in the 25 cm region below the water surface, while the chlorophycean alga, Stigeoclonium nanum and the diatoms (Cocconeis placentula, Gomphonema parvulum and Rhoicosphenia curvata) did so in the 50 cm and 75 cm regions, respectively. Certain dominant species persisted throughout, interrupted by shock periods which created spring, summer, and autumn peaks. Species diversity indices increased with depth, and generally decreased spring through winter. Standing crop maxima occurred within the top 25 cm of the host stems, and showed spring and larger autumn peaks before declining to low. yet significant winter levels. Productivity, too, was greatest in the top 25 cm region, and again peaked in the spring and autumn. Cross incubation studies elucidated vertical and seasonal relationships among productivity, photosynthetic index, and efficiency, and productivity efficiency. An interplay of sun and shade adapted populations within the community was found. The epiphytic algae displayed but a muted seasonal response to physico-chemical fluctuations: however, there was an association with overall nutrient changes as determined by meq HCO₃⁻I⁻¹.