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.     

Salt-dependent binding of Escherichia coli initiation factor 3 to nucleic acids determined by sedimentation partition chromatography

The binding of 14CH3- initiation factor 3 (IF3) to polynucleotides is strongly dependent upon the concentration of added salt. The observed association constant, Kobs, increases by ca. a factor of 10(2) when the NaCl concentration is lowered from 200 to 100 mM for the binding of 14CH3-IF3 to all nucleic acids examined. This salt-dependent binding suggests that at physiological salt concentrations the formation of an IF3-polynucleotide complex is primarily driven by the release of cations from the nucleic acid, although anion effects are involved also. For single-stranded nucleic acids, nonelectrostatic interactions may contribute a factor of 10(2) to the value of Kobs, although accurate assessment of these interactions is complicated by anion effects. The binding of 14CH3-IF3 to the double helix, poly(A).poly(U), appears to be exclusively electrostatic. 14CH3-IF3 forms a maximum of 8 +/- 2 ion pairs with most single-stranded polynucleotides. The value of Kobs increases from ca. 10(3) to 10(5) M-1 when the NaCl concentration is lowered from 200 to 100 mM for the binding of 14CH3-IF3 to poly(A), poly(C), poly(U), and poly(A).poly(U). At physiological salt concentrations, IF3 shows no preference for any of these bases or for single or double-stranded structures. However, 14CH3-IF3 binds ca. 60 times greater to poly(A,G), at al NaCl concentrations examined, than to the other nucleic acids, indicating that IF3 has some preference for guanine-containing polynucleotides. The presence of 10 mM Mg2+ tends to reduce the value of Kobs at any given NaCl concentration, but to a smaller degree than predicted by simply a competition between Mg2+ and IF3 for the nucleic acid lattice.     

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.     

Improving vegetatively propagated crops

Book reviews

Improving vegetatively propagated cropsA.J. Abbott and R.K. Atkin (Eds.), London: Academic Press, 1987. xvii + 416 pages. £37.00. 0-12-041410-4     

Association of enkephalin catabolism inhibitors and CCKB antagonists: A potential use in the management of pain and opioid addiction

The overlapping distribution of opioid and cholecystokinin (CCK) peptides and their receptors (μ and δ opioid receptors; CCK-A and CCK-B receptors) in the central nervous system have led to a large number of studies aimed at clarifying the functional relationships between these two neuropeptides. Most of the pharmacological studies devoted to the role of CCK and enkephalins have been focused on the control of pain. Recently the existence of regulatory mechanisms between both systems have been proposed, and the physiological antagonism between CCK and endogenous opioid systems has been definitely demonstrated by coadministration of CCK-B selective antagonists with RB 101, a systemically active inhibitor, which fully protects enkephalins from their degradation. Several studies have also been done to investigate the functional relationships between both systems in development of opioid side-effects and in behavioral responses. This article will review the experimental pharmacology of association of enkephalin-degrading enzyme inhibitors and CCK-B antagonists to demonstrate the interest of these molecules in the management of both pain and opioid addiction. Special issue dedicated to Dr. Eric J. Simon.     

Solubilization and reconstitution of the mitochondrial peptide-sensitive channel

In addition to the voltage-dependent anion channel (VDAC), mitochondrial outer membranes contain a cationic channel of large conductance, which is blocked by a mitochondrial addressing peptide (peptide-sensitive channel, PSC). Bovine adrenal cortex mitochondria were solubilized in 1.5% octyl -glucoside, and membrane vesicles were reconstituted by slow dilution with a low ionic strength buffer. The reconstituted vesicles contained a functional channel possessing the electrical characteristics of the cationic channel, including its sensitivity to the mitochondrial addressing peptide. Important features of the described protocol are the nature of the detergent, its concentration, and the addition of glycerol during the whole procedure. No solubilization could be observed in the presence of cholate.     

Development of predictive models of laboratory animal growth using artificial neural networks

Traditional regression analysis of body weight growth curvesencounters problems .when the data are extremely variable. Whiletransformations are often employed to meet the criteria of theanalysis, some transformations are inadequate for normalizingthe data. Regression analysis also requires presuppositionsregarding the model to be fit and the techniques to be usedin the analysis. An alternative approach using artificial neuralnetworks is presented which may be suitable for developing predictivemodels of growth. Neural networks are simulators of the processesthat occur in the biological brain during the learning process.They are trained on the data, developing the necessary algorithmswithin their internal architecture, and produce a predictivemodel based on the learned facts. A dataset of Sprague–Dawleyrat (Rattus norvegicus) weights is analyzed by both traditionalregression analysis and neural network training. Predictionsof body weight are made from both models. While both methodsproduce models that adequately predict the body weights, theneural network model is superior in that it combines accuracyand precision, being less influenced by longitudinal variabilityin the data. Thus, the neural network provides another toolfor researchers to analyze growth curve data.