Pharyngeal cavity and the gills are the target organ for the repellent action of pardaxin in shark

Summary Pardaxin, an active principle of the repellent secretion of the Red Sea flatfish,Pardachirus marmoratus, elicited severe struggling, mouth paralysis, and transient increase in urea leakage from the gills only when administered to the medium bathing the shark's pharyngeal cavity and gills. An apparatus was constructed which prevents a mixing of the outflow from shark's gills with water bathing its surface skin. It is concluded that in sharks the gills and/or the pharyngeal cavity are the target organ for the repellent action of pardaxin.     

Furospongolide,a new C21 furanoterpene from a marine organism

Summary The structure of a new linear C₂₁ furanoterpene, furospongolide (1), obtained from the marine spongeDysidea herbacea, was determined by spectral means.We thank Professor J. Vacelet for the identification and Dr Loya and Mr Benayahu for the collection of the sponge.     

Pharyngeal cavity and the gills are the target organ for the repellent action of pardaxin in shark

Pardaxin, an active principle of the repellent secretion of the Red Sea flatfish, Pardachirus marmoratus, elicited severe struggling, mouth paralysis, and transient increase in urea leakage from the gills only when administered to the medium bathing the shark's pharyngeal cavity and gills. An apparatus was constructed which prevents a mixing of the outflow from shark's gills with water bathing its surface skin. It is concluded that in sharks the gills and/or the pharyngeal cavity are the target organ for the repellent action of pardaxin.     

Ca2+-dependence and metabolic status of an obligate thermophile,Thermoactinomyces vulgaris,under shake culture conditions

Summary Ca²⁺ stimulates germination ofT. vulgaris spores. There is a higher mycelial yield as well as higher protein, DNA, RNA and free Pi content in cultures grown in the presence of Ca²⁺ as compared to those grown in the absence of this divalent cation.Grateful thanks are due to Professor R. P. Roy for providing the necessary facilities. V. P. S. acknowledges with thanks the receipt of a Post Doctoral Research Fellowship of the Council of Scientific and Industrial Research, New Delhi.     

Cannflavin A and B,prenylated flavones fromCannabis sativa L.

Summary Two novel prenylat flavones, termed Cannflavin A and B, were isolated from the cannabinoid free ethanolic extract ofCannabis sativa L. Both compounds inhibited prostaglandin E₂ production by human rheumatoid synovial cells in culture.This communication is dedicated to the memory of the late Professor J. W. Fairbairn and the late Dr. J. T. Pickens. We are grateful to the Medical Research Council for a project grant and to Ms J. Elliot of King's College London for NMR spectra.     

Biological effects of singlet delta oxygen on respiratory tract epithelium

Summary Exposure of hamster tracheal organ cultures to gas phase singlet delta oxygen,¹O₂, at atmospheric pressure produced significant alterations in the mucociliary epithelium resulting in changes in ciliary activity and cellular morphology.Acknowledgments. The authors acknowledge helpful conversations with Professor R.W. Murray of the University of Missouri (St. Louis). We would like to thank the National Institute of Environmental Health Sciences for supporting this work through Public Health Grant 1-RO1-ESO1-O1A1-PHTB.     

Reduction of aflatoxin B1 with zinc borohydride: An efficient preparation of aflatoxicol

Summary A simple and mild reduction of aflatoxin B₁, involving treatment of aflatoxin B₁ with ethereal zinc borohydride to give 57–65% yield of diastereomeric aflatoxicols, is described.This work was supported by the College of Agricultural and Life Sciences, the University of Wisconsin, Madison, and by Public Health Service Research, grant No. CA 15064, from the National Cancer Institute, and by funds from contributions of food industries to the Food Research Institute. We are grateful to Professor Dennis Hsieh for a gift of natural aflatoxicol, to Mr William Harder for technical assistance throughout this investigation, and to Mr Gary Girdaukas for taking mass spectra.     

Isolation and properties of cell walls fromAgrobacterium tumefaciens B 6 1

Summary Purified cell walls were prepared fromAgrobacterium tumefaciens B ₆ by extraction of intact cells with hot sodium dodecyl sulfate and digestion with proteases. Such preparations contained peptidoglycan that accounted for about 40% of their dry weight. Electron micrographs of the purified walls showed that they conserved their characteristic shape despite the drastic extraction procedure.This work was supported in part by a contribution from a friend of the Weizmann Institute of Science in Buenos Aires, Argentine.I wish to thank Professor Nathan Sharon for his constant interest and critical discussion during this work.     

Na+/NH 4 + co-transport in isolated perfused gills of the Chinese crabEriocheir sinensis acclimated to fresh water

Summary In isolated perfused posterior gills ofE. sinensis acclimated to fresh water, NH ₄ ⁺ may be used as a counter-ion for Na⁺ active transport. This Na⁺/NH ₄ ⁺ coupled transport can, however, only account for a small part of the Na⁺ total active influx.Chargé de Recherches du FNRS-Acknowledgments. This work has been aided by a grant crédit aux chercheurs from the FNRS and by a grant No. 2.4511.76 from the FRFC.     

The effect of pH and methylation on the interaction of deoxycholate with rat liver alcohol dehydrogenase

Summary The activation of rat liver alcohol dehydrogenase by deoxycholate depends on the anionic form of the steroid. Methylation of the enzyme protein leads to an increase of both turnover number and K_m for ethanol and to a change in the effect of deoxycholate, which behaves as an inhibitor. It is suggested that the steroid and methylation effects depend on the same basic mechanism, in which one or more Lys groups are involved.Acknowledgment. We thank Professor A. Guerritore for his help and advice. This work was supported by a grant from the Italian Consiglio Nazionale delle Ricerche.     

In vitro translation of human placental pregnancy-specific beta1-glycoprotein (SP1)

Summary Synthesis of SP₁-glycoprotein by the human placenta was directly demonstrated, by in vitro translation of RNA extracted from full term and from early placentas in a cell-free wheat germ system followed by specific immunoprecipitation of the radioactively labeled nascent peptides. De novo synthesized SP₁-glycoprotein in both RNA preparations accounted for 1–1.3% of total protein synthesis.Acknowledgment. The authors thank Drs A. Nirapatpongporn, V. Sirivasin and Professor H.F. Lodish for kindly providing placental tissues and wheat germ respectively. This work was supported by The Rockefeller Foundation (RF-8031).W.H. was supported by a Graduate Studies Fellowship, Mahidol University.     

Synergism of terramycin to inhibit the reproductivity ofAphis fabae Scop

Zusammenfassung Nachweis, dass Piperonylbutoxid (0,2%) in Kombination mit Terramycin (0,2%) und dem Emulgator NP₁₀ (0,1%) die Larvalentwicklung verlangsamt und sowohl das Gewicht wie die Reproduktionsfähigkeit der resultierenden Adulten vonAphis fabae reduziert. Durch Zugabe des allein unwirksamen Piperonylbutoxyds werden diese Effekte gesteigert.

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I express my sincere thanks to Professor Dr.H. Schmutterer, Giessen University, West Germany, for advice and encouragement, and to the German Academic Exchange Service for the financial assistance.     

Rejection of worm load through singly and repeatedly sensitized peritoneal exudate cells during experimental ancylostomiasis

Summary Sensitized peritoneal exudate cells from Swiss albino mice donors infected with a single dose of 1000A. caninum larvae could expel a challenge dose of 500 larvae from recipients at a faster rate when compared to cells from repeatedly infected (250+250+500) donors. However, at 36 h after challenge, the larval expulsion was almost the same in both the groups. Because of the bowel sensitization by the cells, some larvae (not expelled) in the 1st group, readily migrated into muscles where they met allergic immobilization and death due to infiltration of inflammatory cells and their exudates at these sites.Acknowledgment. We thank Professor H. Swarup for providing facilities and to the Council of Scientific and Industrial research, New Delhi for financial assistance.     

Toxicity of Dithane M-45 onDrosophila melanogaster

Summary The toxicity of different concentrations of Dithane M-45 onDrosophila melanogaster was determined. The chemical was administered by larval feeding. It has been estimated that the LC₅₀ is 17.5 mg/100 ml food medium. The studies have suggested that Dithane M-45 has a pronounced effect on the rate of development and viability.Acknowledgments. The authors are grateful to Dr M.R. Rajasekarasetty, F.N.A., Professor and Head of the Department of Postgraduate Studies and Research in Zoology, Manasa Gangotri, University of Mysore, Mysore, for his constant encouragement and valuable suggestions. One of us (V.V.) is thankful to the UGC for the financial assistance.     

Extracellular Mg2+ regulates intracellular Mg2+ and its subcellular compartmentation in fission yeast, Schizosaccharomyces pombe

Effects of extracellular magnesium ions ([Mg²⁺]_o ) on intracellular free Mg²⁺ ([Mg²⁺]_i ) and its subcellular distribution in single fission yeast cells, Schizosaccharomyces pombe, were studied with digital-imaging microscopy and an Mg²⁺ fluorescent probe (mag-fura-2). Using 0.44 mM [Mg²⁺]_o , [Mg²⁺]_i in yeast cells was 0.91±0.08 mM. Elevation of [Mg²⁺]_o to 1.97 mM induced rapid (within 5 min) increments in [Mg²⁺]_i (2.18±0.11 mM). Lowering [Mg²⁺]_o to 0.06 mM, however, exerted no significant effects on [Mg²⁺]_i (0.93±0.14 mM), at least for periods of up to 30 min. Irrespective of the [Mg²⁺]_o used, the subcellular distribution of [Mg²⁺]_i remained hetero geneous, i.e. where the sub-plasma membrane region >cytoplasm >nucleus. [Mg²⁺] in all three subcellular compartments increased significantly, two- to threefold, concomitant with [Mg²⁺]_i when placed in 1.97 mM [Mg²⁺]_o . We conclude that [Mg²⁺]_i in fission yeast is maintained at a physiologic level when [Mg²⁺]_o is low, but intracellular free Mg²⁺ rapidly rises when [Mg²⁺]_o is elevated. Like most eukaryotic cells, yeast may have a Mg²⁺ transport system(s) which functions to maintain gradients of Mg²⁺ from the outside to inside the cell and among its subcellular compartments. Received 18 April 1996; received after revision 4 July 1996; accepted 26 July 1996     

Synthesis and contractile activity of the C-terminal heptapeptide of substance P with N5-dimethyl glutamine in the 6-position. Active site studies

Summary The synthesis and testing of [N⁵-dimethyl-Gln⁶]-SP_5–11 showed 37±12% contractile activity relative to SP, and intrinsic efficacy 98±4%. This finding indicates that the carboxamide groups of the dual Gln⁵-Gln⁶ moiety are not equally related with the contractile response of the C-terminal heptapeptide of SP.The authors wish to express their deep appreciation to Professor H. Niedrich and Dr J. Bergmann of the Institute of Drug Research, Academy of Sciences of DDR, Berlin, for their valuable help in providing the biological data.     

IP<Subscript>3</Subscript> receptor signaling and endothelial barrier function

The endothelium, a monolayer of endothelial cells lining vessel walls, maintains tissue-fluid homeostasis by restricting the passage of the plasma proteins and blood cells into the interstitium. The ion Ca²⁺, a ubiquitous secondary messenger, initiates signal transduction events in endothelial cells that is critical to control of vascular tone and endothelial permeability. The ion Ca²⁺ is stored inside the intracellular organelles and released into the cytosol in response to environmental cues. The inositol 1,4,5-trisphosphate (IP₃) messenger facilitates Ca²⁺ release through IP₃ receptors which are Ca²⁺-selective intracellular channels located within the membrane of the endoplasmic reticulum. Binding of IP₃ to the IP₃Rs initiates assembly of IP₃R clusters, a key event responsible for amplification of Ca²⁺ signals in endothelial cells. This review discusses emerging concepts related to architecture and dynamics of IP₃R clusters, and their specific role in propagation of Ca²⁺ signals in endothelial cells.     

Complex modulation of Cav3.1 T-type calcium channel by nickel

Nickel is considered to be a selective blocker of low-voltage-activated T-type calcium channel. Recently, the Ni²⁺-binding site with critical histidine-191 (H191) within the extracellular IS3–IS4 domain of the most Ni²⁺-sensitive Ca_v3.2 T-channel isoform has been identified. All calcium channels are postulated to also have intrapore-binding site limiting maximal current carried by permeating divalent cations (PDC) and determining the blockade by non-permeating ones. However, the contribution of the two sites to the overall Ni²⁺ effect and its dependence on PDC remain uncertain. Here we compared Ni²⁺ action on the wild-type “Ni²⁺-insensitive” Ca_v3.1_w/t channel and Ca_v3.1_Q172H mutant having glutamine (Q) equivalent to H191 of Ca_v3.2 replaced by histidine. Each channel was expressed in Xenopus oocytes, and Ni²⁺ blockade of Ca²⁺, Sr²⁺, or Ba²⁺ currents was assessed by electrophysiology. Inhibition of Ca_v3.1_w/t by Ni²⁺ conformed to two sites binding. Ni²⁺ binding with high-affinity site (IC₅₀ = 0.03–3 μM depending on PDC) produced maximal inhibition of 20–30 % and was voltage-dependent, consistent with its location within the channel’s pore. Most of the inhibition (70–80 %) was produced by Ni²⁺ binding with low-affinity site (IC₅₀ = 240–700 μM). Q172H-mutation mainly affected low-affinity binding (IC₅₀ = 120–160 μM). The IC₅₀ of Ni²⁺ binding with both sites in the Ca_v3.1_w/t and Ca_v3.1_Q172H was differentially modulated by PDC, suggesting a varying degree of competition of Ca²⁺, Sr²⁺, or Ba²⁺ with Ni²⁺. We conclude that differential Ni²⁺-sensitivity of T-channel subtypes is determined only by H-containing external binding sites, which, in the absence of Ni²⁺, may be occupied by PDC, influencing in turn the channel’s permeation.     

The effects of manganese and barium on the cardiac pacemaker current,i f,in rabbit sino-atrial node myocytes

Summary The isolation of ionic fluxes contributing to electric currents through cell membranes often requires block of other undesired components which can be achieved, among others, by divalent cations. Mn²⁺ and Ba²⁺ are often used, for example, to block Ca and K currents. Here we have investigated the effects of these two cations on the properties of the hyperpolarization-activated pacemaker current i_f, in rabbit sino-atrial node myocytes, as obtained by voltage clamp analysis. We find that 2 mM Mn²⁺ shifts the i_f activation curve by 3.2±0.3 mV towards more positive values. However, when 1 mM Ba²⁺ is also added, the positive shift is more than halved (1.3±0.2 mV). We find, too, that in the absence of blocking cations the ACh-induced i_f inhibition is slightly higher than in their presence. These results indicate that the alteration of i_f kinetic properties by Ba²⁺ plus Mn²⁺-containing solutions is minimal.     

Calcium signaling in plants

Changes in the cytosolic concentration of calcium ions ([Ca²⁺]_i) play a key second messenger role in signal transduction. These changes are visualized by making use of either Ca²⁺-sensitive fluorescent dyes or the Ca²⁺-sensitive photoprotein, aequorin. Here we describe the advances made over the last 10 years or so, which have conclusively demonstrated a second messenger role for [Ca²⁺]_i in a few model plant systems. Characteristic changes in [Ca²⁺]_i have been seen to precede the responses of plant cells and whole plants to physiological stimuli. This has had a major impact on our understanding of cell signaling in plants. The next challenge will be to establish how the Ca²⁺ signals are encrypted and decoded in order to provide specificity, and we discuss the current understanding of how this may be achieved.