Sugar-activated ion transport in canine lingual epithelium. Implications for sugar taste transduction

There is good evidence indicating that ion-transport pathways in the apical regions of lingual epithelial cells, including taste bud cells, may play a role in salt taste reception. In this article, we present evidence that, in the case of the dog, there also exists a sugar-activated ion-transport pathway that is linked to sugar taste transduction. Evidence was drawn from two parallel lines of experiments: (a) ion-transport studies on the isolated canine lingual epithelium, and (b) recordings from the canine chorda tympani. The results in vitro showed that both mono- and disaccharides in the mucosal bath stimulate a dose-dependent increase in the short-circuit current over the concentration range coincident with mammalian sugar taste responses. Transepithelial current evoked by glucose, fructose, or sucrose in either 30 mM NaCl or in Krebs-Henseleit buffer (K-H) was partially blocked by amiloride. Among current carriers activated by saccharides, the current response was greater with Na than with K. Ion flux measurements in K-H during stimulation with 3-O-methylglucose showed that the sugar-evoked current was due to an increase in the Na influx. Ouabain or amiloride reduced the sugar-evoked Na influx without effect on sugar transport as measured with tritiated 3-O-methylglucose. Amiloride inhibited the canine chorda tympani response to 0.5 M NaCl by 70-80% and the response to 0.5 M KCl by approximately 40%. This agreed with the percent inhibition by amiloride of the short-circuit current supported in vitro by NaCl and KCl. Amiloride also partially inhibited the chorda tympani responses to sucrose and to fructose. The results indicate that in the dog: (a) the ion transporter subserving Na taste also subserves part of the response to K, and (b) a sugar-activated, Na-preferring ion-transport system is one mechanism mediating sugar taste transduction. Results in the literature indicate a similar sweet taste mechanism for humans.     

A two-dimensional thin-layer chromatographic procedure for the estimation of plasmalogens

1. The use of two-dimensional thin-layer chromatography is described that allows the rapid and simultaneous determination of phospholipid classes and their constituent plasmalogens. 2. The method is based on the specific hydrolysis of plasmalogens to (2-acyl) lysophospholipid in the presence of a mercuric chloride spray reagent. 3. The proportion of mercuric chloride-labile phospholipid present in each phospholipid class, calculated on the basis of phosphorus recoveries from the charred chromatogram, was compared with the proportion of long-chain aldehyde and of total lipid phosphorus found in small-scale preparations of each class of phospholipid. 4. The method permits the determination of individual plasmalogens on preparations containing as little as 0.2mug.atom of total lipid phosphorus.     

A comparative study on three analytical methods for the determination of the neurotoxin BMAA in cyanobacteria

The cyanobacterial neurotoxin β-N-methylamino-L-alanine (BMAA) has been considered a serious health threat because of its putative role in multiple neurodegenerative diseases. First reports on BMAA concentrations in cyanobacteria were alarming: nearly all cyanobacteria were assumed to contain high BMAA concentrations, implying ubiquitous exposure. Recent studies however question this presence of high BMAA concentrations in cyanobacteria. To assess the real risk of BMAA to human health, this discrepancy must be resolved. We therefore tested whether the differences found could be caused by the analytical methods used in different studies. Eight cyanobacterial samples and two control samples were analyzed by three commonly used methods: HPLC-FLD analysis and LC-MS/MS analysis of both derivatized and underivatized samples. In line with published results, HPLC-FLD detected relatively high BMAA concentrations in some cyanobacterial samples, while both LC-MS/MS methods only detected BMAA in the positive control (cycad seed sarcotesta). Because we could eliminate the use of different samples and treatments as causal factors, we demonstrate that the observed differences were caused by the analytical methods. We conclude that HPLC-FLD overestimated BMAA concentrations in some cyanobacterial samples due to its low selectivity and propose that BMAA might be present in (some) cyanobacteria, but in the low μg/g or ng/g range instead of the high μg/g range as sometimes reported before. We therefore recommend to use only selective and sensitive analytical methods like LC-MS/MS for BMAA analysis. Although possibly present in low concentrations in cyanobacteria, BMAA can still form a health risk. Recent evidence on BMAA accumulation in aquatic food chains suggests human exposure through consumption of fish and shellfish which expectedly exceeds exposure through cyanobacteria.     

刺吸电位技术实验中固定昆虫的三种方法比较研究

刺吸电位技术(Electrical penetration graph,EPG)是用来记录刺吸式口器昆虫的口针在其寄主植物组织中刺探所引起的电信号变化特征的技术,其核心在于建立昆虫取食行为与EPG波形的对应关系。近年来,EPG技术在昆虫取食行为及其传毒行为,以及植物抗虫机制等研究中得到越来越广泛的应用。其中,昆虫固定是影响EPG电极连接成功与否的关键技术,进而影响EPG实验结果。本文以灰飞虱Laodelphax striatellus(Fallén)为例,就EPG实验中电极连接时常用的3种昆虫固定技术(麻醉法、冷冻法和负压法)进行了详细描述与比较。研究结果表明,固定灰飞虱最优的方法为负压法,其次为麻醉法和冷冻法。     

A comparative study of three methods for intracellular loading of the calcium indicator aequorin in ferret papillary muscles

We compared the results of loading the bioluminescent Ca++ indicator aequorin by standard microinjection techniques to those obtained with two new chemical approaches to loading that utilize low concentrations of Ca++ chelator; i.e., 1) Immersion and 2) Macroinjection. After loading with the immersion and macroinjection methods, twitch tension returned to pre-load values indicating lack of damage to the muscles. The aequorin signals obtained with all three methods were similar and converted to similar quantitative values for [Ca++]i. Our data suggest that chemical loading (in particular macroinjection) may be preferable to microinjection, particularly in muscles with increased connective tissue content.     

A new spectrofluorimetric method for renal renin activity: a comparative study with other methods

A new spectrofluorimetric method for protein estimation has been developed and applied to study the renin-angiotensin system. The fluorometric reagent, 1-4-diamino-2-3-dichloro-anthraquinone, is introduced in this field and used for the first time. Renal semipurified rat renin is incubated with a synthetic substrate (N-acetyl-tetra-decapeptide) at 0 degrees C and 37 degrees C, at optimal pH, during 3 hours. The incubated mixture is studied by bioassay (BA), radioimmunoassay (RIA) and spectrofluorimetric analysis (SFA), and values obtained with these methods are compared. Blank samples for spectrofluorimetric analysis were prepared by substituting the incubated mixture with the unincubated components of the reaction. Its fluorescence values were subtracted from those of the incubated mixture. Precision and sensitivity for RIA and SFA were similar in both cases, but different in the case of BA. Renal renin activity (RRA) values for RIA (7.15 x 10-(3) nM/ml angio. I/3 h) and SFA (7.08 x 10-(3) nM/ml angio. I/h) were statistically equal (t = 1.05; p less than 0.05), while RRA values for BA (6.23 x 10-(2) nM/ml angio. I/3 h), were higher and significantly different from the statistical point of view. The graphical representation of RRA values for RIA versus SFA values gives an objective expression where RRA(RIA) = 0.78 RRA(SFA) + 0.02.     

A comparative study in methods of cryoprotection for human semen

A comparative study using either glycerol or an egg yolk-citrate-glycerol mix for cryoprotection under the conditions described showed the latter to give a significantly better post-thaw motility. The greatest drop was noted within the first hour, suggesting that freezability of a sample could be judged accurately by rethawing at that time.Controlled studies using scanning electron microscopy clearly showed a greater head disruption after freezing with glycerol and looped tails after centrifugation, which could account for some of the findings of the first part of the study.These findings are reviewed and it is recommended that seminal samples are not centrifuged and that a complex medium be employed for seminal freezing and storing.     

A comparative study of clustering methods for molecular data

The research aim is to use three clustering technologies for establishing molecular data model of large size sets by comparison between low energy samples (LES) and local molecular samples (LMS). Hierarchical cluster of multi-level tree distance relation, competitive learning network of similar inputs falling into the same cluster and topological SOM are used to analyze 6,242 LES and 5,000 LMS. Our experiments show that in SOM, there are 24 to 25 Davies-Boulding clustering index and color map cluster units in the LES more than 10 to 12 in the LMS, which is consistent with the results of hierarchical cluster and competitive learning network in the rough. The hierarchical cluster reflects the biggest inter-cluster distance about 30 for the LES is far larger than that of LMS about 10. The intra-cluster distance of LES about 15 is also far bigger than that of LMS about 3. In SOM, there are more cluster borders of high values (black) reflecting large distance and more clusters in the D-matrix and U-matrix of LES than that of LMS, due to the biggest standard deviation range from -8 to 10 of samples feature of the LES is bigger than that of LMS from -2.5 to 2.5.     

Optimisation of total urinary aldosterone estimation: comparison with other laboratory methods for assessment of mineralocorticoid status

We have demonstrated that conventional methods for measuring total urinary aldosterone (TUA) may markedly and inconsistently underestimate aldosterone output, since under the conditions usually employed (pH 1.0), the hydrolysis of aldosterone conjugates in urine is incomplete. The use of more acidic hydrolysis conditions (pH 0.2) overcomes this problem. However free aldosterone may be damaged at this pH. Therefore to accurately measure TUA output, it is necessary to isolate the undamaged aldosterone chromatographically and to correct for procedural losses based on the recovery of aldosterone tracer added to the urine prior to hydrolysis. We compared a number of laboratory estimates of aldosterone status (including urinary free aldosterone) with the 24-h urinary sodium output in normal subjects, since this provides a good bioassay of aldosterone. Sodium output correlated best with "optimised" 24 h TUA, i.e. hydrolysed at pH 0.2, (r = -0.589, P less than 0.001), and with plasma aldosterone (r = -0.504, P less than 0.005). Both aldosterone in random urine specimens and plasma renin activity correlated poorly with 24-h sodium output. Therefore, while the measurement of optimised TUA excretion provides the best index of aldosterone activity, assay of aldosterone in random specimens of plasma, which is more convenient for patient and laboratory, may be adequate for many clinical purposes.     

Changes of the lingual epithelium in Ambystoma mexicanum

Changes in the lingual epithelium during ontogenesis and after induced metamorphosis in Ambystoma mexicanum are described as observed by light microscopy and scanning electron microscopy. The epithelium of the tongue is always multilayered in the larva as well as in the adult. It consists of a stratum germinativum with little differentiated basal cells and a stratum superficiale (superficial layer) with specialized superficial cells and goblet cells. Usually, there are more than two layers because of a stratum intermedium consisting of replacement cells. The apical cell membrane of the superficial cells is perforated by fine pores. Its most typical feature are microridges. Maturing superficial cells possess microvilli. Goblet cells occur in early larvae primarily in the centre of the tongue. They spread throughout the dorsal face of the tongue as their numbers increase during ontogenesis. The small apices of the goblet cells are intercalated in the wedges between the superficial cells. Leydig cells are not found on the larval tongue but on that of adults. Due to metamorphosis, the epithelium of the tongue changes. It is furrowed in its anterior part. The furrows house the openings of the lingual glands. The surface is further modulated by ridges which are densely coated by microvilli and which bear the taste buds. The villi of the tongue which lack extrusion pores show cilia and microvilli but lack microridges. The Leydig cells disappear during metamorphosis. In addition to the two types of goblet cells found in different regions of the glandular tubules, goblet cells occur in the caudal part. They secrete directly into the cavity of the mouth. The posterior part is characterised by a dense coat of cilia.     

A comparative study of laboratory methods for the preparation of arabic acid

Different methods of precipitation of arabic acid from natural gum arabic are compared in terms of yield and molecular weight derived from gel chromatography experiments. All of the precipitation methods used gave products which were closely similar in terms of $\text{M}$_n, but precipitation with HCl/acetone and HAc/ethanol gave low yields (25 and 3%, respectively).     

A comparative study of three leaf wetness sensors

The laboratory and field performance of two electrical resistance (ER) sensors of leaf surface wetness were compared with that of a beta-ray gauge (BRG). The BRG provided the most accurate measurements of wetness duration, which were in agreement with visual observations. A Campbell and a cotton cloth ER sensor consistently underestimated the duration of leaf surface wetness compared to the value obtained with the BRG in a dew chamber. However, the response of the Campbell sensor improved considerably with increase in the severity of dewfall. A superior performance of one of the two ER sensors could not be decisively established on the basis of the field experiments of 1989 and 1990 on soybean and tobacco crops, respectively. For studies where accurate measurements of surface wetness are critical, it is suggested that a beta-ray gauge should be used.     

Screening of plant extracts for antioxidant activity: a comparative study on three testing methods

Three methods widely employed in the evaluation of antioxidant activity, namely 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, static headspace gas chromatography (HS-GC) and beta-carotene bleaching test (BCBT), have been compared with regard to their application in the screening of plant extracts. The strengths and limitations of each method have been illustrated by testing a number of extracts, of differing polarity, from plants of the genus Sideritis, and two known antioxidants (butylated hydroxytoluene and rosmarinic acid). The sample polarity was important for the exhibited activity in the BCBT and HS-GC methods but not for the DPPH method. The complex composition of the extracts and partition phenomena affected their activity in each assay. The value of the BCBT method appears to be limited to less polar samples. Although slow, the HS-GC method is preferable for assessing the antioxidant inhibitory properties on the formation of unwanted secondary volatile products. Being rapid, simple and independent of sample polarity, the DPPH method is very convenient for the quick screening of many samples for radical scavenging activity.     

Hair removal methods: A comparative study for dermoscopy images

Removal and restoration of hair and hair-like regions within skin lesion images is needed so features within lesions can be more effectively analyzed for benign lesions, cancerous lesions, and for cancer discrimination. This paper refers to “melanoma texture” as a rationale for supporting the need for the proposed hair detection and repair techniques, which incompletely represents why hair removal is an important operation for skin lesion analysis. A comparative study of the state-of-the-art hair-repaired methods with a novel algorithm is also proposed by morphological and fast marching schemes. The hair-repaired techniques are evaluated in terms of computational, performance and tumor-disturb patterns (TDP) aspects. The comparisons have been done among (i) linear interpolation, inpainting by (ii) non-linear partial differential equation (PDE) and (iii) exemplar-based repairing techniques. The performance analysis of hair detection quality, was based on the evaluation of the hair detection error (HDE), quantified by statistical metrics and manually used to determine the hair lines from a dermatologist as the ground truth. The results are presented on a set of 100 dermoscopic images. For the two characteristics measured in the experiments the best method is the fast marching hair removal algorithm (HDE: 2.98%, TDP: 4.21%). This proposed algorithm repaired the texture of the melanoma, which becomes consistent with human vision. The comparisons results obtained, indicate that hair-repairing algorithm based on the fast marching method achieve an accurate result.     

A comparative study of covalently-bound fatty acids in keratinized tissues.

1. Covalently-bound fatty acids were characterized in keratinous tissues obtained from a wide range of animals. 2. 18-Methyleicosanoic acid was a major component in all the mammalian fur samples examined except monotreme fur. In monotreme fur 26-carbon fatty acids predominated. 3. Fatty acids from feather keratin and reptile skin had different profiles to the alpha-keratins of mammalian fur. 4. The major forms of covalently-bound fatty acids are very similar in species that diverged up to 125 million years ago.