An NTP-Binding Protein That Cross with a Ras-Specific Antibody in the Myceia of Neurospora crassa

A Ras-related NTP-binding protein was partially purified froma membrane fraction derived from the mycelia of Neurospora crassa.[-³²P]ATP and [-³²P]GTP were incubated with mem brane and solublefractions which were then irradiated with UV light to inducecrosslinking of tightly bound nucleotides. After SDS-polyacrylamidegel electrophoresis, blotting onto a nitrocellulose filter andautoradiography it was apparent that most of the proteins thatbound [-³²P]-GTP also bound [-³²P]ATP. Pretreatment of the membranefraction with Ras-specific antibody effectively blocked thebinding of [-³²P]ATP and [-³²P]GTP to several ATP-GTP-bindingproteins. The band of a protein with a molecular weight of 26kDa on the SDS-polyacrylamide gel cross-reacted strongly withthe Ras-specific antibody. The protein was extracted from thegel and further purified by repeated gel electrophoresis. Thepurified protein bound [-³²P]ATP, [-³²P]-GTP, [-³²P]CTP and[-³²P]UTP at 1.6x10^– M and was autophosphorylated in thepresence of [-³²P]ATP and [-³²P]GTP at 1.7x10 M. Pretreatmentof the protein with Ras-specific antibody partially blockedthe autophosphorylation in the presence of these nucleotides.The binding of [-³²P]ATP to the NTP-binding protein was blockedby addition of ATP at 10^–4–10^–3 M. ATP ata concentration of 10^–4 M prevented the binding of [-³²P]to a greater extent than did GTP at the same concentration.Binding of [-³²P]CTP and [-³²P]UTP to the protein was also observed. (Received October 7, 1991; Accepted July 14, 1992)     

ATP regulates anion channel-mediated organic osmolyte release from cultured rat astrocytes via multiple Ca2+-sensitive mechanisms

Ubiquitously expressed volume-regulated anion channels (VRACs) are activated in response to cell swelling but may also show limited activity in nonswollen cells. VRACs are permeable to inorganic anions and small organic osmolytes, including the amino acids aspartate, glutamate, and taurine. Several recent reports have demonstrated that neurotransmitters or hormones, such as ATP and vasopressin, induce or strongly potentiate astrocytic whole cell Cl^– currents and amino acid release, which are inhibited by VRAC blockers. In the present study, we explored the intracellular signaling mechanisms mediating the effects of ATP on D-[³H]aspartate release via the putative VRAC pathway in rat primary astrocyte cultures. Cells were exposed to moderate (5%) or substantial (30%) reductions in medium osmolarity. ATP strongly potentiated D-[³H]aspartate release in both moderately swollen and substantially swollen cells. These ATP effects were blocked (80% inhibition) by intracellular Ca²⁺ chelation with BAPTA-AM, calmodulin inhibitors, or a combination of the inhibitors of protein kinase C (PKC) and calmodulin-dependent kinase II (CaMK II). In contrast, control D-[³H]aspartate release activated by the substantial hyposmotic swelling showed little (25% inhibition) sensitivity to the same pharmacological agents. These data indicate that ATP regulates VRAC activity via two separate Ca²⁺-sensitive signaling cascades involving PKC and CaMK II and that cell swelling per se activates VRACs via a separate Ca²⁺/calmodulin-independent signaling mechanism. Ca²⁺-dependent organic osmolyte release via VRACs may contribute to the physiological functions of these channels in the brain, including astrocyte-to-neuron intercellular communication. volume-regulated anion channels; protein kinase C; calcium/calmodulin-dependent kinase II; glutamate release; neuron-glia communication     

Regulation of Na(+)-K(+)-ATPase by cAMP-dependent protein kinase anchored on membrane via its anchoring protein

Na⁺-K⁺- ATPase -subunitsin basolateral membrane vesicles (BLMVs) purified from rat parotidglands were ³²P-labeled within 5 s by incubation with[-³²P]ATP at 37°C in the presence of cAMP, but nolabeling occurred without cAMP. Phosphorylation ofNa⁺-K⁺-ATPase was associated with a decrease inits activity. This -subunit phosphorylation disappeared when BLMVswere briefly incubated with cAMP and subsequent washing before theincubation with [-³²P]ATP, indicating that catalyticsubunit of protein kinase A (PKA) associated to BLMVs via binding withits RII regulatory subunit anchored on the membrane. In theabsence of cAMP, a PKA catalytic subunit readily reassociated with themembrane-bound RII subunit. HT-31 peptide inhibited theNa⁺-K⁺-ATPase phosphorylation by membrane-boundendogenous PKA, indicating an involvement of A-kinase anchoring protein(AKAP). AKAP-150 protein in BLMVs was shown by immunoblotting and anRII overlay assay and was coimmunoprecipitated by anti-RII antibody.These results show that Na⁺-K⁺-ATPase of ratparotid gland acinar cells is regulated in vivo by membrane-anchoredPKA via AKAP rather than by free cytosolic PKA.

     

Phosphorylation of myo-inositol in ripening grains of rice and wheat. Incorporationof phosphate-32P and myo-inositol-3H into myo-inositol phosphates

To elucidate the mechanism of the phosphorylation of myo-inositolin the process of phytate formation, feeding experiments oforthophosphate-³²P and myo-inositol-³H in the ripening grainsof rice and wheat were performed. It was found that ³²P and³H were incorporated into myo-inositol mono- and hexa-phosphates.The same results were obtained when a mixture of "cold" myo-inositolpolyphosphates was administered to the grains before feedingphosphate-³²P. Based on these results it is concluded that phosphorylationof free myo-myo-inositol in the formation of phytate does nottake place in a stepwise fashion but may proceed through anunknown myo-inositol derivative. (Received August 2, 1967; )     

THE LIMPET PATELLOIDA NIGROSULCATA ON INTERTIDAL PLATFORMS IN THE PERTH AREA, WESTERN AUSTRALIA

Patelloida nigrosulcata on intertidal platforms in the Perthmetropolitan area live on the backs of shells of living abalone,Haliotis roei. Over 95% of abalone 30 mm have one or more limpets,and there is a close relationship between abalone and limpetdensity. Sexes are usually separate in P. nigrosulcata, butabout 4% of the population in hermaphroditic. The animals spawntwice annually in winter (May–June) and spring (October–November).The reproductive periodicity of P. nigrosulata is compared toother published data on acmaeids. ^*Present address: Australian Institute of Marine Science, PMBNo. 3, Townsville, Queensland 4810, Australia (Received 23 March 1987;     

Functional Reconstitution of Plasma Membrane H+-ATPase from Mung Bean (Vigna radiata L.) Hypocotyls in Liposomes Prepared with Various Molecular Species of Phospholipids

The activity of solubilized plasma membrane ATPase is affectedby the nature of exogenously added molecular species of phospholipids.To examine the role of the polar head group and of the molecularspecies of phospholipids in H⁺-pumping, the ATPase solubilizedfrom plasma membranes of mung bean (Vigna radiata L.) hypocotylswas reconstituted in liposomes prepared with a variety of phospholipids. The extent of activation of solubilized plasma membrane ATPasedue to the addition of 1-palmitoyl 2-oleoyl-phospholipids (PO-phospholipids)and asolectin decreased in the following order: POPS POPC asolectin POPG > POPE > POPA (see List of Abbreviations). H⁺-pumpinginto proteoliposomes reconstituted with asolectin and plasmamembrane ATPase was demonstrated by quinacrine fluorescencequenching in the presence of ATP-MgSO₄. H⁺-pumping was inhibitedby VO₄ and gramicidin D. When plasma membrane ATPase was reconstitutedin liposomes prepared with various PO-phospholipids, the abilityof PO-phospholipids to support H⁺-pumping into the proteoliposomesdecreased in the following order: POPG POPS > asolectin POPC. POPE and POPA failed to support any H⁺-pumping. A remarkablyhigh rate of H⁺-pumping was observed in proteoliposomes preparedwith 1-saturated 2-unsaturated fatty acids, such as POPC, butH⁺-pumping could hardly be detected in proteoliposomes preparedwith 1-, 2-unsaturated or 1-, 2-saturated fatty acids, suchas PSPC or DLPC. ATPase activity in proteoliposomes was dependenton the species of PO-phospholipids used for reconstitution anddecreased in the following order: POPS > POPG > POPC asolectin > POPA > POPE. DLPC (see List of Abbreviations)which includes a 1-, 2-unsaturated fatty acid supported onlymarkedly depressed activity. Both H⁺-pumping and the hydrolysis of ATP by the plasma membraneATPase are strongly affected by the polar head group and compositionof the fatty acyl chain of phospholipids used to prepare liposomesfor reconstitution of the ATPase. (Received May 31, 1991; Accepted September 18, 1991)     

Phosphoproteins and Protein Kinase Activities Intrinsic to Inner Membranes of Potato Tuber Mitochondria

Inside-out submitochondrial particles (IO-SMP) were isolatedand purified from potato (Solanum tuberosum L. cv.) tubers.When these IO-SMP were incubated with [ ³²P]ATP more then 20proteins became labelled as a result of phosphorylation. The³²P incorporation was stimulated by the oxidising reagent ferricyanide.Except for a 17 kDa protein which was phosphorylated only inthe absence of divalent cations, the protein phosphorylationrequired Mg²⁺. The time for half-maximum ³²P incorporation was4 mm for the 22 kDa phospho-F₁ -subunit and 2 min for the 28kDa phospho-F₀ b-subunit of the proton-ATPase. The K_m for ATPfor the detected phosphoproteins was between 65 µM and110 µM. The pH optimum for protein phosphorylation ininner membranes was between pH 6 and 8, and for the F₁ -subunitand the F₀ b-subunit the pH optima were 6.5–8 and pH 8,respectively. A 37 kDa phosphoprotein was phosphorylated ona histidine residue while the remainder of the inner membraneproteins were phosphorylated on serine or threonine residues.Two autophosphorylated putative kinases were identified: oneat 16.5 kDa required divalent cations for autophosphorylation,while another at 30 kDa did not. A 110 kDa protein was labelledonly with [-³²P] suggesting adenylylation. ³ Present address; Novartis Seeds AB, Box 302, S-261 23 Landskrona,Sweden.     

Top and root growth and nutrient absorption of Prunus avium L. at two soil pH and P levels

One-year-old Prunus avium L. were grown under greenhouse conditions in a Countesswells soil in all combinations of 2 pH and 2 P levels. The soil, obtained from a long-term liming and fertilizer experiment, provided pH values throughout the experiment of 3.75–3.99 (pH 1) and 4.81–5.41 (pH 2). The P treatments had 0.43% acetic acid extractable P of 31–44 g g^-1 (P1) and 145–173 g g^-1 (P2). The trees were harvested 92 (H1), 134 (H2), and 168 (H3) days after initiation of growth.Top (leaf+new stem) dry weight was significantly increased for pH 2 and P2 at H2 and H3. P2 also increased leaf weight (H1), the weight of the original stem-root (H2 and H3), and root length but decreased root diameter at both soil pHs (H2 and H3). Total tree uptake of N, P, K, Ca, and Mg was also increased by pH-P combinations which had significantly greater dry matter production and root length. Total Mn uptake decreased at pH2. Root nutrient inflows (uM m^-1 day^-1) were increased for Ca at pH2 and for P at P2. Mn inflow decreased at pH2 and at pH1 P2 although the increased root length associated with the latter treatmen resulted in increased total tree Mn uptake. In general, high nutrient inflows occurred in all trees at H1 and in severely stunted trees at pH1 P1; both had larger than average root diameters.     

Induction and Repression of CAM in Sedum telephium L. in Response to Photoperiod and Water Stress

Lee, H. S. J. and Griffiths, H. 1987. Induction and repressionof CAM in Sedurn relephluni L. in response to photopcnod andwater stress.—J. exp. Bot. 38: 834–841. The introduction and repression of CAM in Sedurn telephiunmL, a temperate succulent, was investigated in watered, progressivelydrouglited and rewatered plants in growth chambers. Measurementswere made of water vapour and CO₂ exchange, titratable acidity(TA) and xylem sap tension. Effects of photoperiod were alsostudied. CAM was induced by drought under long or short days,although when watered no CAM activity was expressed. C₃-CAM intermediate plants were used for the investigation ofwater supply. Those which had received water and those drought-stressedboth displayed a similar nocturnal increase in TA, with a day-nightmaximum (H+) of 69 µmol g^–1 fr. wt. The wateredplants took up CO₂ at a maximum rate of 2?2 µmol m^–2s^–1 only in the light period, while the droughted plantsshowed a maximum nocturnal CO₂ uptake rate of 0?69 µmolm^–2 s^–1. Subsequently, as CAM was repressed, thewatered S. telephiwn displayed little variation in TA, withconstant levels at 42 µmol g^–1 fr. wt. (day 10).After 10 d of drought stress, the CAM characteristics of S.telephiurn were aLso affected, with reduced net CO₂ uptake andH+. The transition between C₃ and CAM in S. telephium can be describedas a progression in terms of the proportion of respiratory CO₂which is recycled and refixed at night as malic acid, in comparisonwith net CO₂ uptake. Recycling increased from 20% (day 1) to44% (day 10) as a result of the drought stress and was highin both the CAM-C₃ stage (no net CO2 uptake at night) and alsoin the drought-stressed CAM stage (reduced net CO₂ uptake atnight). The complete C₃-CAM transition occurred in less than8 d, and the stages could be characterized by xylem sap tensionmeasurements: CAM = 0?50 MPa C₃-CAM = 0?36 MPa C₃ = 0?29 MPa. Key words: CAM, Sedum telephium L., recycling     

Anion channels transport ATP into the Golgi lumen

Anion channels provide a pathway for Cl^– influx into the lumen of the Golgi cisternae. This influx permits luminal acidification by the organelle's H⁺-ATPase. Three different experimental approaches, electrophysiological, biochemical, and proteomic, demonstrated that two Golgi anion channels, GOLAC-1 and GOLAC-2, also mediate ATP anion transport into the Golgi lumen. First, GOLAC-1 and -2 were incorporated into planar lipid bilayers, and single-channel recordings were obtained. Low ionic activities of K₂ATP added to the cis-chamber directly inhibited the Cl^– subconductance levels of both channels, with K_m values ranging from 16 to 115 µM. Substitution of either K₂ATP or MgATP for Cl^– on the cis, trans, or both sides indicated that ATP is conducted by the channels with a relative permeability sequence of Cl^– > ATP^4– > MgATP^2–. Single-channel currents were observed at physiological concentrations of Cl^– and ATP, providing evidence for their importance in vivo. Second, transport of [-³²P]ATP into sealed Golgi vesicles that maintain in situ orientation was consistent with movement through the GOLACs because it exhibited little temperature dependence and was saturated with an apparent K_m = 25 µM. Finally, after transport of [-³²P]ATP, a protease-protection assay demonstrated that proteins are phosphorylated within the Golgi lumen, and after SDS-PAGE, the proteins in the phosphorylated bands were identified by mass spectrometry. GOLAC conductances, [-³²P]ATP transport, and protein phosphorylation have identical pharmacological profiles. We conclude that the GOLACs play dual roles in the Golgi complex, providing pathways for Cl^– and ATP influx into the Golgi lumen. Golgi complex; Cl channel; mass spectrometry; phosphorylation     

Trimming and solubilization of xyloglucan after deposition in the walls of cultured rose cells

A pulse-chase technique involving the in vivo feeding of L-[1-³H]arabinoseto suspension-cultured rose (Rosa) cells at 4 d and 9 d aftersubculture (fast- and slow-growing, respectively) was used tocreate a population of [³H]xyloglucan molecules and to followtheir subsequent fate. The weight-average relative molecu larmass (M_w) of [³H]xyloglucan freshly deposited in the cell wallwas 160 000 and 240 000 in the fast- and slow-growing cells,respectively. The wall-bound [³H]xyloglucan of both culturesunderwent a decrease in M_w of 40 000 during the first 2 d afterthe pulse-labelling. At the same time, 20–30% of the initially-deposited[³H]xyloglucan disappeared from the cell wall, and a similaramount appeared in solution in the culture medium. Its failureto remain bound to the cell wall and its low M_w (39 000) indicatedthat this soluble extracellular ( was derived from partial degradationof segments of wall-bound xyloglucan that were not directlyhydrogen-bonded to microfibrils (‘loose ends’ and‘tethers’). The possible enzymic basis and biologicalroles of the degradation are discussed. Key words: Cell expansion, cell wall, hemicellulose, sloughing, xyloglucan     

Transnodal Transport of 14C in Nitella flexilis: II. TANDEM CELLS WITH APPLIED PRESSURE GRADIENTS

Using carefully standardized test conditions and tandem pairsof cells of Nitella flexilis, the influx of ¹⁴C (added as H¹⁴CO₃^–and transnodal transport were studied under various pressuregradients applied across the node up to P=± 2·5bar. When mannitol was used as the osmoticum, influx was foundto increase only when the mannitol solution was around the cellproximal to the feed. ¹⁴C was transported across the node tothe distal cell, probably as ¹⁴C-photosynthate products, evenagainst a pressure gradient of 2 bars or more, as was ³⁶Cl^–and ³²P. The % transported in general decreased with increasingP, whether assisted or opposed by added pressure. It was unchangedby the presence of mannitol at the node and was essentiallythe same whether the pressure gradient was produced by directpressure or by use of the osmoticum. Transnodal transport of¹⁴C products is almost certainly via plasmodesmata and appearsto be largely by an active mechanism. In absolute amounts itis the same whether the pressure gradient assists or opposesflow. Valving is evident at the node, increasing the resistanceto transport as the pressure gradient increases whether ¹⁴C(asHCO₃^–), ⁴²K⁺ (as KCl), ³⁶Cl^– (as NaCl) or ³²P (asNa₃PO₄) are used to detect it. The mechanism of movement ofK⁺ across the node differs from that of photosynthate products. Key words: Node, plasmodesmata, pressure gradients, active transport     

Conformational Transitions and Modifications in Ionic Exchange Properties Induced by Alkaline Ions in the Nitella flexilis Cell Wall

The decrease in the cationic exchange capacity (CEC) concomitantto the replacement in the Nitella wall of adsorbed Mn²⁺ ionswas measured in different mixtures of alkaline ions. At lowexternal concentrations, the loss of CEC is enhanced in presenceof Li⁺ ions but is weaker when Na⁺ ions are present in the exchangemixtures. The relative affinity of the wall exchange sites foralkaline ions was Na⁺>K⁺>Rb⁺Cs⁺>Li⁺. As the CEC isprogressively reduced, the wall discrimination between the differentalkaline ions tends to cancel out except for the Na⁺-K⁺ pair.The wall preference for K⁺ is then increased. A diminution ofthe effective pK of the polygalacturonic acids constitutiveof the wall is also observed, while increasing the CEC loss.The simple disruption of divalent cation crosslinks cannot fullyexplain the CEC leakage at low monovalent concentrations. Itis suggested that the alkaline ions also cleave H bonds or solvatation-likebonds between the cell wall polyuronides and then cause a concomitantunfolding of the short pectic chains which involves their solubilization. (Received May 6, 1993; Accepted November 8, 1993)     

DISTRIBUTION AND TURNOVER OF PHOSPHATE COMPOUNDS IN GROWING CHLORELLA CELLS

1. Using the Chlorella cells which had been uniformly labeled with³²P, the distribution of phosphorus in various fractions ofcell material was investigated. Uniformly ³²P-labeled Chlorellawas further grown in a P-free medium or in a standard "cold"medium, and the change of distribution of ³²P (as well as theuptake of exogenous P) in various cell fractions was followed.
2. Analysis of the ³²P-labeled algal cells showed that the highestin P-content was the fraction of RNA followed by those of polyphosphates,lipid, nucleotidic labile phosphate compounds, DNA and protein(in decreasing order). ATP and ADP were found to be only minorfractions of the total labile phosphates.
3. On incubating the³P-labeled alga in a P-free medium, the P.contentsin the fractionsof DNA, protein, lipid and ATP increased, thosein polyphosphatesand ADP decreased, and that in RNA remainedalmost unchanged.When the ³²P-labeled alga was further grownin the normal "cold"medium, DNA and protein increased withthe expenditure of endogenous³²P, but with practically no incorporationof external P. Inthe meantime the P in polyphosphates decreasedconsiderably,and the RNA fraction incorporated a large amountof externalP but only a little of endogenous³²P.
4. It was inferred that,under the experimental conditions of thepresent study, thephosphorus used in the syntheses of DNA andprotein was primarilytaken from polyphosphates, while thatused in the synthesesof RNA, phospholipid and polyphosphateswas, for the most part,taken from the extracellular P-source.

¹A part of this paper was read at the Vth International Congressof Biochemistry, Moscow, August 10–16, 1961. (Received June 4, 1961; )     

Influence of light intensity on diel variations in rates of growth, respiration and organic release of a marine diatom: comparison of diurnally constant and fluctuating light

Effects of variations in light intensity on diel patterns ofgrowth, respiration and organic release of Skeletonema costatum(Grev.) Cleve in a cyclostat were evaluated. Light intensitywas either constant during the tight period at levels from 1500to 15 µEm^–2 s^–1 or fluctuated throughout thelight period from 500 to 10 µEm^–2 s^–1 at ratesof either 1 or 12 cycles day^–1. Periodicity in cell divisionwas observed only at light intensities of 130 Em^–2 s^–1and was decreased under diurnally varying tight. Under all lightconditions carbon and pigment growth were maximal during thelight period but well coupled throughout the 24 h period. Carbonassimilation during the dark period varied from 19 to 34% oftotal daily production and was a linear function of growth rate.Respiratory activity during the light period increased relativeto total daily respiration as growth rate increased. The increasein night-time carbon assimilation with growth rate interactedwith night-time respiration through the refixation of respiredcarbon, thus, influencing the pattern of respiratory loss ofcarbon. Rates of organic release (E^c) were maximal during thelight period and did variations consistently increased withtight intensity. Fluctuating light increased E^c relative toconstant light. Net growth efficiency was maximal at 130 µEm^–2s^–1 when cell division periodicity was greatest. Underother light conditions relatively higher rates of cell divisionoccorred at night and cell division periodicity was reducedas well as net growth efficiency. Cellular chemical fractionationindicated that under high or variable light conditions fixedcarbon was stored during the tight period for subsequent synthesisof protein and pigments, and division at night. Such an uncouplingof photosynthesis and other growth parameters resulted in greatermetabolic costs to the cell. ¹Present address: Marine Biology, Lamont Doherty GeologicalObservatory, Palisades, NY 10964, USA     

[Ca2+]i-reducing action of cAMP in rat pancreatic beta -cells: involvement of thapsigargin-sensitive stores

In the presentstudy, we examined the ability of adenosine 3',5'-cyclicmonophosphate (cAMP) to reduce elevated levels of cytosolicCa²⁺ concentration([Ca²⁺]_i)in pancreatic -cells.[Ca²⁺]_iand reduced pyridine nucleotide, NAD(P)H, were measured in rat single-cells by fura 2 and autofluorescence microfluorometry. Sustained[Ca²⁺]_ielevation, induced by high KCl (25 mM) at a basal glucose concentration (2.8 mM), was substantially reduced by cAMP-increasing agents, dibutyryl cAMP (DBcAMP, 5 mM), an adenylyl cyclase activatorforskolin (10 µM), and an incretin glucagon-likepeptide-1-(7-36) amide (10⁹ M), as well as byglucose (16.7 mM). The[Ca²⁺]_i-reducingeffects of cAMP were greater at elevated glucose (8.3-16.7 mM)than at basal glucose (2.8 mM). An inhibitor of protein kinase A (PKA),H-89, counteracted[Ca²⁺]_i-reducingeffects of cAMP but not those of glucose. Okadaic acid, a phosphataseinhibitor, at 10-100 nM also reduced sustained [Ca²⁺]_ielevation in a concentration-dependent manner. Glucose, but not DBcAMP,increased NAD(P)H in -cells.[Ca²⁺]_i-reducingeffects of cAMP were inhibited by 0.3 µM thapsigargin, an inhibitorof the endoplasmic reticulum (ER)Ca²⁺ pump. In contrast,[Ca²⁺]_i-reducingeffects of cAMP were not altered by ryanodine, an ERCa²⁺-release inhibitor,Na⁺-free conditions, or diazoxide,an ATP-sensitive K⁺ channelopener. In conclusion, the cAMP-PKA pathway reduces[Ca²⁺]_ielevation by sequestering Ca²⁺ inthapsigargin-sensitive stores. This process does not involve, but ispotentiated by, activation of -cell metabolism. Together with theknown[Ca²⁺]_i-increasingaction of cAMP, our results reveal dual regulation of -cell[Ca²⁺]_iby the cAMP-signaling pathway and by a physiological incretin.

     

Aboveground biomass of tropical rain forest stands in Indonesian Borneo

Aboveground plant biomass was examined in a tall virgin tropical lowland evergreen rain forest dominated by Dipterocarpaceae in Sebulu, East Kalimantan, Indonesia, with special reference to the gap-, building- and mature phases of the forest growth cycle. From the records of dimensions of sample trees examined by the stratified clip technique and DBH inventory data of trees in a study plot, the biomass of larger trees (DBH 4.5 cm) was estimated by the allometric correlation method. The biomass of smaller plants (DBH < 4.5 cm) was estimated by harvesting the plants in small quadrat plots. Although large differences were found between aboveground-biomass-estimates in different patches of different growth stages, the aboveground biomass in a 1.0 ha plot was 509 t/ha, and the one-sided LAI was 7.3 ha/ha. These values seem to result from the tall forest architecture with huge emergent trees (over 70 m high) and a moderate packing of plant mass indicated by the basal area value of 38.8 m²/ha for trees with DBH 4.5 cm.This study was financed through a grant to H. Ogawa from the Overseas Scientific Research Funds of the Ministry of Education, Science, and Culture, Tokyo. Sponsorship from the Lembaga Ilumu Pengetahuan Indonesia (LIPI), Jakarta, the Lembaga Biologi National (LBN), Bogor, and the Herbarium Bogoriense, Bogor is gratefully acknowledged. We are also grateful to Drs Soetiyati, M. Rifai, K. Kartawinata, and the staffs of P. T. Kutai Timber Indonesia for their kind support, Dr K. Ogino for his advice and cooperation in field work, and Dr H. Kataoka for providing us with the geological map of Samarinda Province.     

Effects of salinity and two coastal waters on the growth and toxin content of the dinoflagellate Alexandrium minutum

The dinoflagellate Alexandrium minutum strain AM89BM was studiedto investigate its capacity to adapt to different salinitiesand the influence of salinity on cellular content of paralyticshellfish toxins (PST), in batch culture in enriched offshoreseawater media. The strain shows optimal growth (average rate=" BORDER="0">0.5 div day^-1) at salinities between 20 and 37p.s.u., peaking at 25 p.s.u. (0.63 ± 0.07 div day^-1).Under a high NO₃^–:PO₄^3– mole ratio (76), cell PSTcontent increased during growth phase, peaking toward the endof growth phase or in the early stationary phase. The PST contentwas low (10 fmol PST cell^-1) from 30 to 37 p.s.u., but it increasedat lower salinities, with the maximum value (50 fmol PST cell^-1)recorded at 15 p.s.u. We then compared growth rate and toxincontent of A. minutum cells grown in 3- and 0.2-µm filteredestuarine water (27 p.s.u.), and a similarly filtered seawatercollected from an oyster farming area (36 p.s.u.), with a N-and P-enriched offshore seawater (37 p.s.u.). In both estuarinewater treatments, growth was fast (=" BORDER="0">0.8 div day^-1)and the cell PST content increased only in the early growthphase, peaking in mid-growth phase at 9.56 ± 1.06 and7.63 ± 0.44 fmol PST cell^-1 in the 3- and 0.2-µmfiltered waters, respectively. In the 3-µm filtered oysterfarm water, although inorganic nutrient concentrations werevery low, A. minutum grew well (0.68 ± 0.06 div day^-1),suggesting mixotrophic nutrition; as PST production was nearlyzero, the cell toxin content decreasing to 1.11 fmol PST cell^-1,we hypothesize that toxin biosynthesis was greatly weakeneddue to the lack of amino acid precursors in prey material. Inthe offshore seawater, A. minutum grew slowly (0.18 ±0.04 div day^-1) and cells lost toxins down to 1.08 fmol PSTcell^-1, suggesting that growth was limited and PST productionstopped due to the lack of some vitamins, and/or trace metals.     

Comparison of the Effects of Root Temperature on Nitrate and Ammonium Nutrition of Oilseed Rape (Brassica napusL.) in Flowing Solution Culture: II. CATION-ANION BALANCE

Macduff, J. H., Hopper, M. J., Wild, A. and Trim, F. E. 1987.Comparison of the effects of root temperature on nitrate andammonium nutrition of oilseed rape (Brassica napusL.) in flowingsolution culture. II. Cation-anion balance.—J. exp. Bot.38: 1589-1602. The effects of root temperature and form of N nutrition (NH4or NOJ) on the mineral composition of the plant, the balanceof inorganic cation-anion uptake and on the apparent net effluxof H ⁺/OH^–ions from the roots were studied with 49-d-oldoilseed rape (Brassica napusL. cv. Bien venu) in flowing solutionculture. Plants were pre-treated for 14 d at a root temperatureof 5 °C prior to constant root temperatures of 3, 7, 11or 17°C for 14 d, with a common shoot temperature of 20/15°Cday/night. Nitrogen was supplied as NH⁺₄4 or NO^–₃ at 10mmol m³. Values of Q₁₀ (7-17°C) for mean unit absorptionrates of all the major nutrient ions (K⁺ , Mg⁺⁺ , NH⁺₄, SO₄,H₂PO₄, NO₃), except Ca⁺⁺, were > 2.0 over the first 5 d oftreatment but thereafter were < 1.5; the apparent effectof temperature on uptake rates diminished with time. Under NH⁺₄nutrition, inorganic cation uptake (Mg^{+ +} + K⁺+Ca^{+ +} +NH⁺₄)exceeded inorganic anion uptake (SO4 ^–₄+ H₂PO₄) over 14d at all temperatures, with the proportion of cation uptakeas NH4 remaining constant (0.67-0-68) irrespective of root temperature.The net efflux of H ⁺ from the roots approximately balancedNH⁺₄ uptake (1:1) over 14 d at each temperature and also balancedthe difference between the total uptake of inorganic cationsand inorganic anions. Under NO₃ nutrition, the sum of the netefflux of OH and the change in the carboxylate contents of plantsover 14 d approximately balanced the sum of NO₃ and SO ^–₄reduced in the plant. The majority of the negative charge associatedwith the reduction of NO₃ and SO ^–₄ was apparently effluxedas OH, but this fraction was lower at low root temperatures.The results are discussed in terms of mechanisms that have beenproposed to regulate the internal pH of plants. Key words: Brassica napus, oilseed rape, root temperature, cation-anion balance, H⁺/OH efflux.     

Endothelin-1 activates phospholipases and channels at similar concentrations in porcine coronary arteries

Sensitivity of endothelin-1 (ET-1)-ion channel interactions hasbeen proposed to exceed that of ET-1-phospholipase activation invascular smooth muscle. We wanted to determine whether short-circuiting ion channels with staphylococcal -toxin pores would shift the ET-1-force relation to the right as predicted from the above proposal. Medium size porcine coronary arteries (outer diameter 0.7-1.5 mm)were mounted on isometric force transducers. ET-1 concentration response curves were compared between intact rings and those subjected to -toxin treatment with Ca buffered at 0.1 µM. TheEC₅₀ for treated rings (1.5 ± 1.0 nM, n = 5 pigs) was similar tothat for intact rings (1.9 ± 0.4 nM). The Ca sensitivity of the-toxin-treated rings(EC₅₀ = 0.43 ± 0.08 µM) was similar to that reported by other laboratories for intact and-toxin-treated arteries and was shifted eightfold to the left by ahigh concentration of ET-1 (10 nM). Measurements of[³²P]phosphatidic acid([³²P]PA) levels wereused to evaluate phospholipase activity in intact arteries. The timecourses for [³²P]PAproduction and contraction were similar in response to high (100 nM)and to low (1 nM) ET-1. Significant increases in both steady-statecontraction and[³²P]PA occurred overa wide range of ET-1 concentrations tested (0.3-100 nM). Ourfindings support the concept that ET-1-phospholipase coupling isoperative over the whole concentration range that induces contractileresponses. It is suggested that both Ca entry and Ca sensitizationprocesses are activated by ET-1 at low concentrations (<EC₅₀) and that bothprocesses contribute significantly to the integrated response.