Activity of the natural algicide, cyanobacterin, on eukaryotic microorganisms

Abstract The natural product cyanobacterin has been shown to be toxic to most cyanobacteria at a concentration of approx. 5 μM. We demonstrate here that cyanobacterin will also inhibit the growth of most eukaryotic algae at a similar concentration. Some algae, such as Euglena gracilis , are resistant because they are able to maintain themselves by heterotrophic nutrition. Others, such as Chlamydomonas reinhardtii , can apparently induce a detoxification mechanism to maintain photosynthesis in the presence of low concentrations of the inhibitor. Non-photosynthetic microorganisms are not affected by cyanobacterin.     

Nutrient and chlorophyll a temporal patterns in eutrophic mountain ponds with contrasting macrophyte coverage

Hydrobiologia - In shallow lakes, macrophytes have important effects on food webs, community structure and nutrient dynamics. For this reason they play a significant role in the restoration of...     

Effect of pH on growth and ethanol production byZymomonas

Summary In a mineral salts medium containing yeast extract, NH₄Cl and glucose (50g/L), the pH range producing the fastest growth ofZ. mobilis was 5.5–6.5 with an apparent optimum at 6.5. At constant growth rate of 0.15hr^–1, the specific rates of glucose utilization (q_s) and ethanol production (q_p) were relatively unaffected by pH over the range 7.0–5.5 but increased sharply as the pH was further decreased below 5.5 to 4.0. Under these conditions the ethanol yield was unaffected by pH over the range 4.0–6.5 but decreased markedly at pH of 7.     

Tyrosine mutations within the alpha platelet-derived growth factor receptor kinase insert domain abrogate receptor-associated phosphatidylinositol-3 kinase activity without affecting mitogenic or chemotactic signal transduction.

A phosphatidylinositol-3 (PI-3) kinase activity of unknown biological function associates with tyrosine kinase-containing proteins, including a number of growth factor receptors after ligand stimulation. In the beta platelet-derived growth factor (beta PDGF) receptor, phosphorylation of a specific tyrosine residue within the kinase insert domain was required for its interaction with this enzyme. We show that substitutions of phenylalanine for tyrosine residue 731 or 742 within the kinase insert domain of the alpha PDGF receptor do not impair PDGF-induced tyrosine phosphorylation of the receptor or of an in vivo substrate, phospholipase C-gamma. Moreover, phosphatidylinositol turnover in response to ligand stimulation is unaffected. However, both lesions markedly impair receptor association with PI-3 kinase. Antiphosphotyrosine antibody-recoverable PI-3 kinase was also dramatically reduced in PDGF-stimulated cells expressing either mutant receptor. Since neither mutation abolished PDGF-induced mitogenesis or chemotaxis, we conclude that alpha PDGF receptor-associated PI-3 kinase activity is not required for either of these major PDGF signalling functions.     

Genetic determinants of glutamine synthetase inDrosophila melanogaster: A gene for glutamine synthetase I resides in the 21B3-6 region

Recombinational and deletion mapping of electrophoretic variants of the glutamine synthetase I isozyme (GSI) in Drosophila melanogaster locates the gene in the 21B region on the second chromosome. We have conducted a genetic analysis of the region extending cytologically from 21A to 21B4-6. Recessive lethal mutations were generated by ethyl methanesulfonate (EMS) and ethyl nitrosourea (ENU) mutagenesis and by hybrid dysgenesis (HD). These lethals fall into seven functional groups, which were partially ordered by complementation with cytologically defined deficiencies of this region generated by hybrid dysgenesis. Two of the EMS- and two of the ENU-induced lethals fulfill biochemical criteria expected for null alleles of the GSI gene.     

The effects of gonadotropins on metabolism of isolated rat granulosa cells

FSH $\text{in vitro}$, but not LH, increased the O₂ uptake of isolated granulosa cells from 23 day old rats previously treated with DES or with DES and FSH. Dose response studies showed that the cells were most sensitive to FSH when the cellular binding of FSH was highest. LH increased the O₂ uptake of granulosa cells of untreated 30 day old rats. DES treatment inhibited the LH induced rise in O₂ uptake when the rats were implanted with DES capsules unless FSH was injected to induce LH receptors. Addition of dbcAMP $\text{in vitro}$ increased O₂ uptake of granulosa cells from 30 day old rats at concentrations 10X lower than those required to stimulate O₂ uptake in cells from 23 day old rats treated with DES alone.FSH $\text{in vitro}$ increased lactate formation in the absence of added substrates but did not do so when glucose was added to the media. In contrast, LH greatly increased lactate formation with added glucose. Dose response studies showed that less than 0.6 ug/ml LH S21 was effective in increasing lactate above control levels. These data suggest that FSH affects aerobic pathways while LH affects anaerobic pathways in the process of the differentiation of granulosa cells toward luteal cells.It is well known that FSH and LH interact with their target cells in the ovary by binding to specific receptors and that FSH stimulates LH-receptor production (1). Receptor binding by either hormone activates adenylate cyclase (2) raising cyclic adenosine monosphosphate (cAMP) levels (3) and increasing protein kinase activity (4). Such changes probably trigger changes in the major metabolic pathways that support follicular development because cells of corpora lutea have glycogen (5) which is not present in follicular granulosa cells (6–9). Several studies suggest that FSH and LH may regulate metabolic processes in the ovary. LH increases lactate in whole prepuberal ovaries (10,11,12) and also increases the uptake of glucose (13). FSH increases oxygen uptake in chick ovaries (14), rat ovaries (15) and prairie dog ovaries (16). However, only one study has been done using isolated ovarian cells. Hamberger (17) has reported that FSH increased the oxygen uptake of thecal cells of immature rats while LH increased the oxygen uptake of granulosa cells. Since granulosa cells from immature rats are reported to have FSH receptors while theca cells have LH receptors the effects of these hormones appear unclear.The present studies were undertaken to more accurately characterize the actions of FSH, LH, and dibutyryl cAMP (dbcAMP) on the oxygen uptake of isolated granulosa cells and remaining tissues of immature ovaries and to determine the effects of FSH and LH on the production of lactate by granulosa cells.     

Production of indole alkaloids by gel-entrapped cells of Catharanthus roseus in a continuous flow reactor

Summary Calcium alginate gel-entrapped cells ofCatharanthus roseus were used to study the production of indole alkaloids in a flow through process. The bioreactor was functional for more than two months and product recovery was analyzed under various operating conditions.     

The genetic control of alkaline phosphatase activity in the duodenum of the mouse

The inheritance of duodenal alkaline phosphatase activity has been studied in two inbred strains of Swiss mice. These two strains consistently maintained a three- to fourfold difference in duodenal phosphatase activity for six generations before the start of the genetic studies. Males of both the high-activity strain (HAS) and the low-activity strain (LAS) were mated to females of the other strain to produce an F₁ generation, members of which were sib-mated to produce an F₂ generation. The frequency distributions of the parental, F₁, and F₂ generations reveal that the activity of the enzyme is under polygenic control. Distribution of activities in the F₂'s derived from HAS grandmothers differs from that of the F₂'s from LAS grandmothers, indicating that a maternally inherited factor, probably contained in the milk of one strain, influences the activity. Heritability estimates based on half-sib correlation coefficients show that additive genetic variance makes up about 50–70% of the total variance of duodenal phosphatase activity in LAS, and approximately 30–45% in HAS. The latter strain is the more variable, both within generations and within litters; its activity is also more strongly enhanced by injection of substrate into the stomach, and is more severely reduced by starvation. Chromatographic analysis of butanol extracts of phosphatase from 11-day-old mice of the two strains reveals that both contain the same two isozymes. HAS does, however, appear to have 6–8 times as much as LAS of an isozymic form of phosphatase having a relatively high phenylphosphate/-glycerophosphate ratio, and only about twice as much of a low PhP/bGP ratio form.Supported by Research Grant GM 03937 from the National Institutes of Health, U.S. Public Health Service.