Liposomes as model for taste cells: receptor sites for bitter substances including N-C=S substances and mechanism of membrane potential changes

Various bitter substances were found to depolarize liposomes. The results obtained are as follows: (1) Changes in the membrane potential of azolectin liposomes in response to various bitter substances were monitored by measuring changes in the fluorescence intensity of 3,3'-dipropylthiocarbocyanine iodide [diS-C3(5)]. All the bitter substances examined increased the fluorescence intensity of the liposome-dye suspension, which indicates that the substances depolarize the liposomes. There existed a good correlation between the minimum concentrations of the bitter substances to depolarize the liposomes and the taste thresholds in humans. (2) The effects of changed lipid composition of liposomes on the responses to various bitter substances vary greatly among bitter substances, suggesting that the receptor sites for bitter substances are multiple. The responses to N-C=S substances and sucrose octaacetate especially greatly depended on the lipid composition; these compounds depolarized only liposomes having certain lipid composition, while no or hyperpolarizing responses to these compounds were observed in other liposomes examined. This suggested that the difference in "taster" and "nontaster" for these substances can be explained in terms of difference in the lipid composition of taste receptor membranes. (3) It was confirmed that the membrane potential of the planar lipid bilayer is changed in response to bitter substances. The membrane potential changes in the planar lipid bilayer as well as in liposomes in response to the bitter substances occurred under the condition that there is no ion gradient across the membranes. These results suggested that the membrane potential changes in response to bitter substances stem from the phase boundary potential changes induced by adsorption of the substances on the hydrophobic region of the membranes.     

Optimal strategy of plant antiherbivore defense: Implications for apparency and resource-availability theories

Plants produce chemicals as methods against animal herbivory. Such chemical defenses are classified into two major categories: (i) quantitative defenses with massive production of indigestible substances; and (ii) qualitative defenses with production of poisonous substances. A mathematical model was developed that identified factors that favored the evolution of quantitative defenses. Selecting an annual plant for simplicity, the allocation of photosynthetic production between growth substances and defense substances was considered. If the plant invests more in defense substances, it can protect itself more efficiently from herbivory but with a reduced growth rate. If it invests more in growth substances, the contrary holds. Using Pontoryagin's maximum principle, the following results were obtained: (i) the plant should conduct quantitative defenses when the growth rate (G), reflecting resource-availability, is low and the growth period (T) is long as well; (ii) if the plant invests in quantitative defenses, the optimal proportion of defense substances (χ^*) should be higher asG is smaller, but it is independent ofT; and (iii) the value of χ^* is not monotone for the effectiveness of defense substance (A), but has a maximum at an intermediate value ofA. Predictions of the model partly supported both Feeny's apparency theory, claiming that apparent plants or their parts for herbivores should quantitatively defend themselves, and Coley's resource-availability theory, claiming that plants with rich resources should invest in growth rather than defense.     

Evidence for gibberellin-like substances in phloem exudate of higher plants

Summary Samples of sieve-tube sap were obtained as honeydew from aphids feeding on three species of higher plants. The honeydew was extracted, chromatographed and tested in several bioassays for the presence of gibberellin-like substances. The bioassay results indicated that gibberellin-like substances were translocated in the phloem of dandelion (Taraxacum officinale), broad bean (Vicia faba) and willow (Salix viminalis). Results obtained with willow showed that the concentration of gibberellin-like substances in the sieve-tube sap is daylength dependent, high levels being present in plants maintained under long days and low levels in short day plants.     

Using Nanotechnology for the Substitution of Hazardous Chemical Substances

It is often assumed that nanotechnology (NT) holds the potential to provide a substantial contribution to the solution of various ecological problems, including high consumption of energy and materials and the generation of waste. However, problems surrounding the use and release of hazardous substances remain largely unexplored. For this reason, the Scientific Technical Option Assessment (STOA) Panel of the European Parliament initiated a study on “The Role of Nanotechnology in Chemical Substitution.” The subject and aim of the study was an investigation into preexisting and potential applications of NT that could lead to a reduction in hazardous substances by providing substitutes for them. In terms of method, it was based on electronic searches of the literature, expert interviews, and an expert workshop. This article discusses the results of the project. It focuses on the methodological challenges and the principal problems resulting from a combination of the broad and ill‐defined concept of NT and the specific concept of hazardous substances. The hazardous substances addressed had to be reduced to a manageable number, and the term substitution was understood according to the characteristics of NT and the way in which the latter could reduce the use of hazardous substances. Although several applications of NT were identified that could lead to a considerable reduction in the use of hazardous substances, ambiguities in both the concept of NT and the concept of substitution in relation to NT prevent a comprehensive assessment of the potential of NT in respect to substitution.     

A simple procedure for the isolation of high quality RNA from ripening banana fruit

Isolation of high quality RNA from ripening banana fruit tissue is difficult due to high levels of polysaccharides and other substances that interfere when using conventional procedures for RNA isolation. These substances not only decrease the yield but the quality of RNA is almost unusable. We describe here a simple RNA procedure that effectively removes these contaminating substances without affecting the yield. Following this procedure, we routinely obtained 80–150 μg of total RNA per g fresh tissue. The RNA is of good quality and suitable for northern analysis, RT-PCR and cDNA library construction. NBRI publication No. 488(NS).     

A comprehensive experimental study of industrial,domestic and environmental interferences with the forensic luminol test for blood

This paper presents the ?rst comprehensive and quantitative study of substances that interfere with the forensic luminol test for blood. Two hundred and ?fty substances have been selected on the basis of modern lifestyles and of contiguity with crime scenes. The intensity of the chemiluminescence produced by each substance has been measured relative to that of haemoglobin and the peak wavelength shift has also been determined. The following is a short list of nine substances that produce chemiluminescence intensities comparable with that of haemoglobin: turnips, parsnips, horseradishes, commercial bleach (NaClO), copper metal, some furniture polishes, some enamel paints, and some interior fabrics in motor vehicles. Care needs to be taken when the luminol test for blood is used in the presence of these substances. Copyright © 2003 John Wiley & Sons, Ltd.     

Biodegradation behavior of natural organic matter (NOM) in a biological aerated filter (BAF) as a pretreatment for ultrafiltration (UF) of river water

In this study, biodegradation of natural organic matter (NOM) in a biological aerated filter (BAF) as pretreatment of UF treating river water was investigated. Photometric measurement, three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy and liquid chromatography with online organic carbon detector (LC-OCD) were used to investigate the fate of NOM fractions in the BAF + UF process. Results showed that the BAF process could effectively remove particles and parts of dissolved organic matter, which led to a lower NOM loading in the UF system, but different NOM fractions showed different biodegradation potentials. Further biodegradation batch experiments confirmed this observation and identified that polysaccharides and proteins (quantified using photometric methods) contained a large proportion of readily biodegradable matter while humic substances were mainly composed of inert organic substances. According to EEM measurements, it is evident that protein-like substances were more readily eliminated by microorganisms than humic-like substances. LC-OCD data also supported the phenomena that the polysaccharides and large-size proteins were more degradable than humic substances.     

Patterns in air pollution as model for the physical basis for olfactory navigation in pigeon homing

Spatial distribution and temporal variability of air pollution were used as a model to describe the stability and predictability of the distribution of airborne substances, postulated by some to be used by homing pigeons to navigate. If the man-made substances reflect the distributional characteristics of natural airborne substances, navigation based on airborne substances is unlikely to be possible.     

Endotoxins and their significance for murine trypanosomiasis

The study of endotoxins is complicated by their heterogenous nature, their multiple effects and the complex methodologies required for their identification. In this brief review, Vic Pentreath summarizes how the substances have been implicated in the pathogenesis of several diseases caused by parasitic protozoa, and how the parasites (eg. Plasmodium falciparum and Trypanosoma cruzi) may themselves contain endotoxin-like materials. Recent studies have shown that, during T. b. brucei infection in mice, serum endotoxin levels become markedly elevated and that endotoxin-like substances are also present in the purified parasite extracts.     

Suggestions for a mathematical model of a pathological neuron with spontaneous repetitive discharges

A formal mathematical model is proposed for a spontaneously repetitively firing neuron. It is based on the assumption that an excitatory and inhibitory substance, possibly different from those involved in synaptic transmissions, is formed in the soma of everynormal neuron. Furthermore, the decay of the substances is ascribed to their combination with some other substances, present in healthy individuals. A generalized two factor system of differential equations is used. It is shown that when the normally present substances are absent, possibly due to genetic defects so that the decay constants become zero, the equations lead to undamped sinusoidal solutions of the difference between excitatory and inhibitory factors, thus producing a trulyspontaneous repetitive discharge, in the absence of external currents or other stimulation. It is suggested that convulsants may act by destroying the substances present in healthy individuals. It is further suggested that by administering to epileptics those substances, which are present in normal healthy persons, perhaps by using brain extracts fromhealthy higher animals which sometimes suffer from epilepsy, an actual cure rather than symptomatic treatment by anticonvulsants may be obtained.     

Mechanism of fluorescent cocoon sex identification for silkworms Bombyx mori

By using silkworms, Bombyx mori, fluorescent cocoon sex identification (FCSI) as an experimental material, direct fluorescence spectrometry of the cocoon surface indicates that the fluorescent color of silkworm cocoons is made up of two peaks of yellow and blue-purple fluorescence emission. The fluorescent difference between male and female cocoons is attributed to the differential absorption of yellow fluorescent substances by the midgut tissue of 5th instar female silkworms. Thin layer chromatography (TLC) and fluorescent spectra indicate that blue-purple fluorescent substances are composed of at least five blue-purple fluorescent pigments, and yellow fluorescent substances are made up of at least three. UV spectra and AlCl₃ color reaction show that the three fluorescent yellow pigments are flavonoids or their glycosides. Silkworm FCSI is due to selective absorption or accumulation of the yellow fluorescent pigments by the posterior midgut cells of female 5th instar larvae. The cells of the FCSI silkworm midgut, especially the cylinder intestinal cells of the posterior midgut have a component which is a yellow fluorescent pigment-specific binding protein that may be vigorously expressed in the 5th instar larvae.     

Histo-Blood Group Antigen-Like Substances of Human Enteric Bacteria as Specific Adsorbents for Human Noroviruses

Histo-blood group antigens (HBGAs) have been suggested to be receptors or coreceptors for human noroviruses (HuNoVs) expressed on the intestinal epithelium. We isolated an enteric bacterium strain (SENG-6), closely related to Enterobacter cloacae, bearing HBGA-like substances from a fecal sample of a healthy individual by using a biopanning technique with anti-HBGA antibodies. The binding capacities of four genotypes of norovirus-like particles (NoVLPs) to Enterobacter sp. SENG-6 cells were confirmed by enzyme-linked immunosorbent assay (ELISA). Transmission electron microscopy demonstrated that NoVLPs bound mainly to extracellular polymeric substances (EPS) of Enterobacter sp. SENG-6, where the HBGA-like substances were localized. EPS that contained HBGA-like substances extracted from Enterobacter sp. SENG-6 was shown by enzyme-linked immunosorbent assay (ELISA) to be capable of binding to NoVLPs of a GI.1 wild-type strain (8fIIa) and a GII.6 strain that can recognize A antigen but not to an NoVLP GI.1 mutant strain (W375A) that loses the ability to bind to A antigen. Enzymatic cleavage of terminal N-acetyl-galactosamine residues in the bacterial EPS weakened bacterial EPS binding to the GI.1 wild-type strain (8fIIa). These results indicate that A-like substances in the bacterial EPS play a key role in binding to NoVLPs. Since the specific binding of HuNoVs to HBGA-positive enteric bacteria is likely to affect the transmission and infection processes of HuNoVs in their hosts and in the environment, further studies of human enteric bacteria and their binding capacity to HuNoVs will provide a new scientific platform for understanding interactions between two types of microbes that were previously regarded as biologically unrelated.     

MTT比色法测定促肝细胞生长物质对肝细胞生长的刺激活性

本实验建立了用简便的ＭＴＴ比色法对促肝细胞生长物质的促肝细胞增殖作用的测定方法,确定了实验的最适条件。与传统的３Ｈ ＴｄＲ掺入法进行比较的结果显示,ＭＴＴ比色法与３Ｈ ＴｄＲ掺入法测定结果基本相符,灵敏度相近,但消除了同位素的污染,是一个测定促肝细胞生长物质刺激肝细胞增殖活性的简便方法。     

Neurotranmission systems as targets for toxicants: a review

Neurotransmitters are chemicals that transmit impulses from one nerve to another or from nerves to effector organs. Numerous neurotransmitters have been described in mammals, amongst them acetylcholine, amino acids, amines, peptides and gases. Toxicants may interact with various parts of neurotransmission systems, including synthetic and degradative enzymes, presynaptic vesicles and the specialized receptors that characterize neurotransmission systems. Important toxicants acting on the cholinergic system include the anticholinesterases (organophosphates and carbamates) and substances that act on receptors such as nicotine and the neonicotinoid insecticides, including imidacloprid. An important substance acting on the glutamatergic system is domoic acid, responsible for amnesic shellfish poisoning. 4-Aminobutyric acid (GABA) and glycine are inhibitory neurotransmitters and their antagonists, fipronil (an insecticide) and strychnine respectively, are excitatory. Abnormalities of dopamine neurotransmission occur in Parkinson’s disease, and a number of substances that interfere with this system produce Parkinsonian symptoms and clinical signs, including notably 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, which is the precursor of 1-methyl-4-phenylpyridinium. Fewer substances are known that interfere with adrenergic, histaminergic or seroninergic neurotransmission, but there are some examples. Among peptide neurotransmission systems, agonists of opioids are the only well-known toxic compounds.     

Dynamical behavior of lipid bilayer membranes for taste substances under random membrane-potential fluctuations

The dynamical behavior of the lipid bilayer membranes was experimentally studied under superposition of random or periodic membrane-potential fluctuations. The analysis of the mutual information has revealed that, in less than 10 Hz of random fluctuations, each of the time series of the mutual information of the transmembrane current for the five chemical substances (taste substances) has its inherent pattern, but not in a periodic fluctuation. On the other hand, the analysis of the power spectrum of the frequency could not distinguish those five basic taste substances in both random and periodic fluctuations. We provide the new detection idea of chemical substances by random fluctuations.     

The importance of SH-containing substances for red blood cells in acute myeloic leukemia

Electron spin resonance (ESR) spectra of lyophilized erythrocytes obtained from patients with acute myeloid leukemia (AML) show, in comparison to controls, a characteristic change especially in the low-field region of the spectrum concomitant with a reduction of the spin concentration. This effect can be simulated by addition of SH-containing substances (e.g. reduced glutathione or cysteine) to healthy erythrocytes. S-S containing compounds exhibit no effect. Since SH-containing substances can hardly permeate plasma membranes, the membrane surface seems to be defective in the case of "AML" erythrocytes. Furthermore, it can be concluded that the concentration of SH-containing substances, such as cysteine, is increased in the plasma of AML-patients, which could be confirmed by HPLC-measurements. In the case of a successful treatment of the patients with alexan, daunoblastin, and thioguanine the spin concentration increased again and the resulting ESR spectrum is very similar to the control spectrum. It should be pointed out, that the ascorbic acid concentration is very low in both plasma and erythrocytes of AML patients.     

In-house validation of the EpiOcular(TM) eye irritation test and its combination with the bovine corneal opacity and permeability test for the assessment of ocular irritation

In 2009, the Bovine Corneal Opacity and Permeability (BCOP) test was accepted by the regulatory bodies for the identification of corrosive and severe ocular irritants (Global Harmonised System [GHS] Category 1). However, no in vitro test is currently accepted for the differentiation of ocular irritants (GHS Category 2) and non-irritants (GHS No Category). Human reconstructed tissue models have been suggested for incorporation into a tiered testing strategy to ultimately replace the Draize rabbit eye irritation test (OECD TG 405). The purpose of this study was to evaluate whether the EpiOcular(TM) reconstructed cornea-like tissue model and the COLIPA pre-validated EpiOcular Eye Irritation Test (EpiOcular-EIT) could be used as suitable components of this testing strategy. The in-house validation of the EpiOcular-EIT was performed by using 60 test substances, including a broad variety of chemicals and formulations for which in vivo data (from the Draize rabbit eye irritation test) were available. The test substances fell into the following categories: 18 severe irritants/corrosives (Category 1), 21 irritants (Category 2), and 21 non-irritants (No Category). Test substances that decreased tissue viability to ≤ 60% (compared to the negative control tissue) were considered to be eye irritants (Category 1/2). Test substances resulting in tissue viability of > 60% were considered to be non-irritants (No Category). For the assessed dataset and the classification cut-off of 60% viability, the EpiOcular-EIT provided 98% and 84% sensitivity, 64% and 90% specificity, and 85% and 86% overall accuracy for the literature reference and BASF proprietary substances, respectively. Applying a 50% tissue viability cut-off to distinguish between irritants and non-irritants resulted in 93% and 82% sensitivity, 68% and 100% specificity, and 84% and 88% accuracy for the literature reference and BASF proprietary substances, respectively. Further, in the EpiOcular-EIT (60% cut-off), 100% of severely irritating substances under-predicted by the BCOP assay were classified as Category 1/2. The results obtained in this study, based on 60 test substances, indicate that the EpiOcular-EIT and the BCOP assay can be combined in a testing strategy to identify strong/severe eye irritants (Category 1), moderate and mild eye irritants (Category 2), and non-irritants (No Category) in routine testing. In particular, when the bottom-up strategy with the 60% viability cut-off was employed, none of the severely irritating substances (Category 1) were under-predicted to be non-irritant. Sensitivity for Category 1/2 substances was 100% for literature reference substances and 89% for BASF SE proprietary substances.     

Electrochemical enzyme immunoassay for detection of toxic substances.

Sensors that provide reliable, rapid measurement of toxic substances are needed to solve significant human health and safety problems. We developed a new biosensor design that combines the advantages of immunoassay with electrochemical response. We established that this enzyme-linked immunosensor measures toxic substances in biological samples. The biosensor consists of two major elements: (1) an electrical conducting layer having immobilized enzyme, polyclonal or monoclonal antibodies, and other necessary reagents, and (2) the electronic components used in the signal readout. The result is an amperometric immunoassay based on coupling the immunochemical reaction to the enzyme electrode response by using a soluble, electrochemically active mediator. The specific question addressed was: Does the system's immunochemical detection reliably respond at sufficiently low analyte concentrations? We present our results in these areas: (1) enzyme immobilization on colloidal gold; (2) colloidal gold-enzyme deposition on the electrode surface; (3) mediator-antigen conjugate synthesis; (4) antibody incorporation at the electrode surface; (5) bioelectrode characterization and optimization; and (6) immunosensor demonstration to detect antigen. Sensors that employ immunochemical detection will have broad applicability to detect/diagnose toxic substances in biological samples such as blood and urine and in environmental samples such as wastewater and drinking water.     

Improved Hemagglutination Inhibition Assay for Mammary Tumor Virus Antigen

It is our experience that the use of sheep red blood cells pretreated with formaldehyde and pyruvaldehyde before sensitizing with viral antigen yields results that are comparable to that obtained by using the tannic acid method. The double aldehyde method provides the added advantage of being useful for assaying the viral antigen content in substances which contain high levels of interfering substances which would preclude the use of other assay methods.