Odorant-induced kinetics of Ca<Superscript>2+</Superscript>, NADH,and oxidized flavoproteins in frog olfactory mucosa

A study was made of the odorant-induced changes in the fluorescence of the Ca²⁺-chlortetracycline-membrane complex, NADH, and oxidized flavoproteins in the frog olfactory epithelium. Cineole and vanillin induce faster changes than camphor and pentanol. The different kinetics of NADH and membrane calcium evoked by these odorants are attributed to the heterogeneity of the molecular mechanisms involved in olfactory signal transduction. By contrast, ammonia and β-mercaptoethanol permeate the olfactory cells and without second messengers inhibit the mitochondrial respiratory chain and suppress the motility of olfactory cilia.     

Simple empirical intensity and buffering capacity measurements to predict potassium uptake by white clover

Summary This experiment examined the feasibility of predicting K uptake in white clover by the use of simple and relatively rapid tests that would dispense with the need of knowing the quantity of plant available potassium. Potassium uptake was found to correlate highly (R=>0.9) in linear bivariate regressions using K concentration in the soil solution displaced by centrifuging and an empirical estimate of potassium retention. There was no advantage in determining activity ratios because in at least some of the soils used the ratio law did not apply. Exchangeable potassium alone correlated rather poorly with uptake except at very low soil potassium status. This was not because nonexchangeable potassium was an important source of this nutrient to white clover but because of the large differences in the retention of K amongst the soils used.     

Assessment of plant secondary metabolites in oil palm seedlings after being treated with calcium,copper ions and salicylic acid

The effect of calcium, copper ions and salicylic acid (SA) amendment on the incidence of basal stem rot and activity of secondary metabolites in oil palm seedlings were investigated in glasshouse study. Disease incidence (DI) in positive control (T8) was 75% at nine months after inoculation (9 MAI). However, weekly pre-immunisation with Ca^2+?+^?Cu^2+?+^?SA prior to inoculation significantly suppressed DI and delayed disease onset as noted in T7. In the present study, the lowest %DI was observed in T7 (15%) followed by T1, T5, T6, T3, T4 and T2. The Ca²⁺, Cu²⁺ and SA amendments were resulted in earlier and higher accumulation of plant secondary metabolites as noted in leaves, stems and root tissues in response to invasion by Ganoderma boninense. High total phenolic content concentration was detected in T7 (leaf: 233.38 ± 0.12 mg/g; stem: 132.78 ± 0.04 mg/g and root: 86.98 ± 0.28 mg/g). Similar trend was obtained in peroxidase activity, total lignin content and hydrogen peroxide scavenging activity. These results suggested that it could be due to the accumulation of phenolics, peroxidase activities, lignin content and hydrogen peroxide scavenging activities in oil palm seedling tissues which might have collectively contributed to induce resistance against G. boninense.     

Computational and biochemical analysis of type IV pilus dynamics and stability

1. Download : Download high-res image (282KB)
2. Download : Download full-size image

     

Computation,wiring, and plasticity in synaptic clusters

Synaptic clusters on dendrites are extraordinarily compact computational building blocks. They contribute to key local computations through biophysical and biochemical signaling that utilizes convergence in space and time as an organizing principle. However, these computations can only arise in very special contexts. Dendritic cluster computations, their highly organized input connectivity, and the mechanisms for their formation are closely linked, yet these have not been analyzed as parts of a single process. Here, we examine these linkages. The sheer density of axonal and dendritic arborizations means that there are far more potential connections (close enough for a spine to reach an axon) than actual ones. We see how dendritic clusters draw upon electrical, chemical, and mechano–chemical signaling to implement the rules for formation of connections and subsequent computations. Crucially, the same mechanisms that underlie their functions also underlie their formation.     

Lipoxygenase- mediated cleavage of fatty acids in plant mitochondria

Incubation of cauliflower bud mitochondria in the presence of 5 mM CaCl2 results in a rapid hydrolysis of the main membrane phospholipsds. Under the action of phospholipase D, phosphatidic acid is produced and forms, within the membranes, a very labile complex with Ca2+ and HPO42-ions present in the incubation medium. With time, one observes a first step characterized by the formation of phosphatidic acid, followed by a second step linked to the breakdown of this phospholipid. The enzyme responsible for the disappearance of phosphalidic acid has been identified as lipoxygenase. In the presence of molecular oxygen, this enzyme acts on the polyun-saturated fatty acids of phosphatidic add (mainly C18:2 and C18:3) yielding small water-soluble molecules, one of them being identified as malondialdehyde (1, 3-propanedial). Experiments involving inhibitory conditions of the breakdown of phosphatidic acid indicate that lipoxygenase acts directly on membrane-bound phosphatidic acid without previous, involvement of a lipolytic acyl hydrolase activity. In addition, the lipoxygenase activity is fully sensitive to hydroxamate derivatives. It is proposed that the lipoxygenase activity may account for a part of the mitochondrial alternative electron pathway that is insensitive to cyanide.     

Enhanced Calcium Absorption in the Small Intestine by a Phytate-removed Deamidated Soybean Globulin Preparation

Soybean globulins were deamidated after removing phytate using ion-exchange resins, and then hydrolyzed by digestive enzymes. The phytate-removed deamidated soybean globulins (PrDS) retained high calcium-binding ability even after the hydrolysis by digestive enzymes. PrDS and its hydrolysates enhanced calcium absorption from the small intestine when injected into the small intestine together with a calcium solution.     

Cannabinoid receptor agonists inhibit depolarization-induced calcium influx in cerebellar granule neurons.

Neuronal cannabinoid receptors (CB(1)) are coupled to inhibition of voltage-sensitive Ca(2+) channels (VSCCs) in several cell types. The purpose of these studies was to characterize the interaction between endogenous CB(1) receptors and VSCCs in cerebellar granule neurons (CGN). Ca(2+) transients were evoked by KCl-induced depolarization and imaged using fura-2. The CB(1) receptor agonists CP55940, Win 55212-2 and N-arachidonylethanolamine (anandamide) produced concentration-related decreases in peak amplitude of the Ca(2+) response and total Ca(2+) influx. Pre-treatment of CGN with pertussis toxin abolished agonist-mediated inhibition. The inhibitory effect of Win 55212-2 on Ca(2+) influx was additive with inhibition produced by omega-agatoxin IVA and nifedipine but not with omega-conotoxin GVIA, indicating that N-type VSCCs are the primary effector. Paradoxically, the CB(1) receptor antagonist, SR141716, also inhibited KCl-induced Ca(2+) influx into CGN in a concentration-related manner. SR141716 inhibition was pertussis toxin-insensitive and was not additive with the inhibition produced by Win 55212-2. Confocal imaging of CGN in primary culture demonstrate a high density of CB(1) receptor expression on CGN plasma membranes, including the neuritic processes. These data demonstrate that the CB(1) receptor is highly expressed by CGN and agonists serve as potent and efficacious inhibitory modulators of Ca(2+) influx through N-type VSCC.     

The action of excessive,inorganic silicon (Si) on the mineral metabolism of calcium (Ca) and magnesium (Mg)

The influence of silicon treatment on the levels of calcium and magnesium in blood serum and tissues was studied in rats. The concentrations of both elements were estimated in samples of sera and tissues of rats receiving per os a soluble, inorganic silicon compound—sodium metasilicate nonahydrate (Na₂SiO₃·9H₂O (REACHIM, USSR)), dissolved in the animals' drinking water. A decrease of magnesium concentration in serum was observed with accompanying elevation of registered calcemia. Moreover, a reduction of tissue calcium levels was found with a simultaneous increase of magnesium tissue pool. The results provide evidence for silicon involvement in mineral metabolism. It could result in a modification of pathological processes concerning bone tissue.