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.     

Malaria Parasite-Infected Erythrocytes Secrete PfCK1, the Plasmodium Homologue of the Pleiotropic Protein Kinase Casein Kinase 1

Casein kinase 1 (CK1) is a pleiotropic protein kinase implicated in several fundamental processes of eukaryotic cell biology. Plasmodium falciparum encodes a single CK1 isoform, PfCK1, that is expressed at all stages of the parasite’s life cycle. We have previously shown that the pfck1 gene cannot be disrupted, but that the locus can be modified if no loss-of-function is incurred, suggesting an important role for this kinase in intra-erythrocytic asexual proliferation. Here, we report on the use of parasite lines expressing GFP- or His-tagged PfCK1 from the endogenous locus to investigate (i) the dynamics of PfCK1 localisation during the asexual cycle in red blood cells, and (ii) potential interactors of PfCK1, so as to gain insight into the involvement of the enzyme in specific cellular processes. Immunofluorescence analysis reveals a dynamic localisation of PfCK1, with evidence for a pool of the enzyme being directed to the membrane of the host erythrocyte in the early stages of infection, followed by a predominantly intra-parasite localisation in trophozoites and schizonts and association with micronemes in merozoites. Furthermore, we present strong evidence that a pool of enzymatically active PfCK1 is secreted into the culture supernatant, demonstrating that PfCK1 is an ectokinase. Our interactome experiments and ensuing kinase assays using recombinant PfCK1 to phosphorylate putative interactors in vitro suggest an involvement of PfCK1 in many cellular processes such as mRNA splicing, protein trafficking, ribosomal, and host cell invasion.     

A catalogue of some ecuadorean fermented beverages,with notes on their microflora

Summary A catalogue of indigenous fermented beverages produced by different ethnic groups in Ecuador has been compiled and the microflora of selected examples examined. A diversity of fermentation substrates was encountered depending on the climatic zone. The fermentations are typicallyLactobacillus spp.—yeast fermentations except for one which includes a mould fermentation by a mixed starter ofMoniha sitophila, Rhizopus stolonifer and aFusarium sp. A discussion is made of the role of these beverages in the human ecology of certain regions.

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Resumen Se ha confeccionado un catálogo de bebidas indígenas ecuatorianas producidas por distintos grupos étnicos, examinándose la microflora de algunos ejemplos seleccionados. Las fermentaciones son generalmente del tipoLactobacillus sp.—levaduras, excepto en un caso que incluye una fermentación fúngica iniciada de forma mixta porM. sitophila, R. stolonifer y unFusarium sp. Se discute el papel de estas bebidas en la ecologia humana de ciertas regiones.

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Résumé Un catalogue des boissons fermentées indigènes produites par divers groupes ethniques de l'Equateur a été compilé et les micro-flores des exemples sélectionnés ont été éxaminés. Les substrats de fermentation varient d'une région climatique à l'autre. Les fermentations sont généralement du typeLactobacillus sp — levures, sauf dans un cas qui comporte une fermentation par des moisissures, avec un mélange initial deMoniha sitophila, Rhizopus stolonifer et une espèce deFusarium. Le rôle de ces boissons dans l'écologie humaine de certaines régions est discuté.

     

The protein kinases tightly bound to DNA are present in normal tissues and in regenerating liver, but strongly decreased in hepatomas

We have previously described in rat liver two protein kinases tightly bound to DNA, one is serine-specific, the other arginine-specific. In this work we show that both enzymes are present in various rat tissues and in liver from various species. Both kinase specific activities are strongly decreased in methyl-DBA-induced hepatomas and in HTC cells but not in regenerating liver after hepatectomy. This decrease is then not related to cell proliferation.     

Impedimetric evaluation of the efficiency of disinfectants against biofilms

An impedimetric evaluation of disinfectant efficacy has shown that biofilms of Staphylococcus aureus, Escherichia coli, Salmonella enteritidis and Listeria mono-cytogenes attached to polyvinyl chloride (PVC), Teflon, Plexiglass, wood, rubber and stainless steel are more resistant than the same bacteria in suspension. Based on the activity against the test-organisms after 1, 3 and 5 min with exposures to 0.5, 1 and 2% of each disinfectant, the resistance towards disinfection was related to the type of hard-surface to which biofilms were attached.     

Characterisation of two differently processed forms of human recombinant factor IX synthesised in CHO cells transformed with a polycistronic vector

A stable transformed cell line constitutively expressing human factor IX has been established. Wild-type Chinese hamster ovary cells (CHO cells) were transformed using a polycistronic expression vector carrying a previously isolated factor IX cDNA and a selection gene encoding the Escherichia coli xanthine-guanine phosphoribosyl transferase. One clone, CHO 622.4, contains a high number of genomically integrated plasmids and secretes 1-3 mg factor IX l-1 day-1 into the culture medium with a biological activity ranging from 25% to 40%. The recombinant molecule was purified either by conventional chromatography or by immunoaffinity chromatography using antibodies specific to a calcium-induced factor IX conformer. The purified recombinant protein migrates as a single band with the same mobility as that of natural factor IX on SDS/polyacrylamide gels. N-terminal sequencing shows tow differently processed forms of recombinant factor IX: whereas the majority of the zymogen is correctly processed, approximately 20% of the purified recombinant molecule contains an 18-amino-acid NH2-extension corresponding to the precursor form of factor IX. Analysis of the 4-carboxyglutamic acid content indicates a high but incomplete carboxylation (70%) of the recombinant molecule as compared to natural factor IX. The carbohydrate composition of both the natural and recombinant molecules has been determined. Both molecules have a N-glycan structure of similar complexity, indicating that factor IX contains all the information to direct the same glycosylation pattern in human liver cells and in an unrelated cell line such as CHO-K1.     

Lymphokine regulation of human lymphocyte proliferation: Formation of resting G0 cells by removal of interteukin 2 in cultures of proliferating T lymphocytes

The question of whether lymphocytes which have once been activated and have completed one or several cell cycle(s) can return to the G₀ phase and stay ready for a new activation (G₀-G₁ transition), rather than simply die, was investigated. To do so interleukin 2 (IL-2) was removed from cultures of continuously proliferating human T lymphocytes and the formation of resting (G₀) cells was measured. Kinetic analyses in freshly prepared peripheral blood lymphocytes (PBL) revealed that the onset of detectable RNA synthesis and the appearance of structures binding the anti-Tac antibody occurred simultaneously. This allowed the expansion of the definition of G₀ T lymphocytes as cells having a low RNA (and DNA) content, and no Tac antigen. When cultured human T cells proliferating continuously by means of IL-2 were characterized in terms of their distribution in the cell cycle, 7 days after the initial PHA stimulation, it could be demonstrated that very few cells were in the G₀ phase, supporting the concept of direct S/G₂/M-G₁ transition. However, when IL-2 was removed from the cultures, the [³H]thymidine incorporation per 10⁴ cells and correspondingly the number of cells in the S/G₂/M and G₁ phases were reduced drastically and during the following 72-hr period, the number of G₀ cells increased markedly. Restimulation of such in vitro formed G₀ cells, under conditions permitting observation of their shift from the G₀ to G₀ phase, demonstrated that most cells could respond normally. Based on these observations, it was concluded that IL-2 not only ensures T-lymphocyte survival and proliferation, but IL-2 starvation induces many continuously proliferating T lymphocytes to stop cycling and to return to the G₀ phase of the cell cycle where they remain functional.     

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.