Lipophilicity and the perception of bitterness

Evidence suggesting that lipophilicity is an important parameterin inducing a bitter taste is collated. The implications ofthis association are discussed and lipophilic effects used toexplain some phenomena connected with the bitterness response.Consideration of lipophilicity offers a rationale for the observedbitterness of many sweeteners at high concentration and forthe influence of hydrogen-bonding on bitterness. ^*Present address: 1 Ham Barn Cottages, Farnham Road, Liss, Hants,England.     

Comparison of bitterness of caffeine and quinine by a time - intensity procedure

Temporal bitterness sequences elicited by four equi-bitter concentrationsof caffeine and quinine were evaluated by a time – intensityprocedure. For both compounds, the increase in bitterness intensitywas highly correlated with an increased duration of aftertaste,although the time to maximum intensity did not change. For equi-bittersolutions, the duration of aftertaste was influenced by thespecific tastant, and was longer for caffeine. Caffeine eliciteda faster maximum rate of onset and slower maximum rate of decayof bitterness. Only one significant difference between subjectswho were sensitive to l-phenyl-2-thiourca (PTC) and those whowere non-tasters was found. Tasters rated the maximum intensityof quinine solutions higher than non-tasters.     

The correlation of sweetness and bitterness of enantiomeric aminoacids

A correlation discovered between the sweetness of $\text{D}$ and the bitterness of $\text{L}$-aminoacids suggests the possible existence of corresponding taste receptors with enantiomeric active sites. They offer possible explanations for the reported taste characteristics of various other substances ($\text{L}$-aspartic acid amides, quinine, perillartine, etc.).     

Effect of compound sequence on bitterness enhancement

The nature and occurrence of carry-over effects, i.e. the response to a stimulus is influenced by previous samples, were examined for selected bitter compounds. A time-intensity procedure was used to rate the bitterness of six compounds (caffeine, denatonium benzoate, limonin, naringin, quinine and sucrose octa-acetate). For each subject concentrations of these compounds were determined that were approximately equal in intensity to 1.18 x 10(-5) M limonin. To test carry-over effects of each compound the 36 paired sequences (pairs) were evaluated. Within a session three pairs were tested, between which two-stage rinses were used to remove any effects of the previous pairs. Within a pair only water rinses were used between stimuli. For all compounds carry-over or sensitization effects were observed in which values for maximum intensity, rate of onset and total area under the time-intensity curve were higher for a compound when tested in the second position than in the first. In addition, the degree of sensitization and susceptibility to sensitization were compound-specific. Caffeine increased the bitterness by the largest amount for all other compounds, while it was least affected. Regardless of the compound in the first position, the bitterness of quinine and denatonium were most enhanced.     

Effect of chlorhexidine on a chlorhexidine-sensitive and a chlorhexidine-resistant strain of Providencia stuartii

The sensitivity and resistance of three strains of Providencia stuartii to various antibacterial agents, and especially to chlorhexidine, are described. Providencia stuartii Pv 2 was the most sensitive, and Pv 67 the most resistant, to chlorhexidine and to polymyxin B. These two strains took up approximately equal amounts of chlorhexidine from solution, but the biguanide had a considerably greater effect on the electrophoretic mobility of cells of strain Pv 2. Greater inner membrane damage (determined by the leakage of K⁺ and of pentoses) occurred with Pv 2. Chlorhexidine at 20 μg/ml achieved a 2-log reduction and 50 μg/ml a > 7-log reduction in viable numbers in strain Pv 2 over a 120 min contact period at 20C. In contrast, these concentrations induced < 0.5 log reduction in strain Pv 67.     

Reduction of surgical site infections after implementation of a bundle of care

Background

Surgical Site Infections (SSI) are relatively frequent complications after colorectal surgery and are associated with substantial morbidity and mortality.

Objective

Implementing a bundle of care and measuring the effects on the SSI rate.

Design

Prospective quasi experimental cohort study.

Methods

A prospective surveillance for SSI after colorectal surgery was performed in the Amphia Hospital, Breda, from January 1, 2008 until January 1, 2012. As part of a National patient safety initiative, a bundle of care consisting of 4 elements covering the surgical process was introduced in 2009. The elements of the bundle were perioperative antibiotic prophylaxis, hair removal before surgery, perioperative normothermia and discipline in the operating room. Bundle compliance was measured every 3 months in a random sample of surgical procedures.

Results

Bundle compliance improved significantly from an average of 10% in 2009 to 60% in 2011. 1537 colorectal procedures were performed during the study period and 300 SSI (19.5%) occurred. SSI were associated with a prolonged length of stay (mean additional length of stay 18 days) and a significantly higher 6 months mortality (Adjusted OR: 2.71, 95% confidence interval 1.76–4.18). Logistic regression showed a significant decrease of the SSI rate that paralleled the introduction of the bundle. The adjusted Odds ratio of the SSI rate was 36% lower in 2011 compared to 2008.

Conclusion

The implementation of the bundle was associated with improved compliance over time and a 36% reduction of the SSI rate after adjustment for confounders. This makes the bundle an important tool to improve patient safety.     

The use of chlorhexidine

Summary An investigation was carried out on the therapeutic value of chlorhexidine (I.C.I.). We are of the opinion that this substance, which has very few toxic side-effects, may prove to be of great importance as a general disinfectant in surgical practice, of prophylactic value in paediatrics, in urogical practice, in the treatment of burns, and generally to prevent cross infection. Further, it was established that chlorhexidine possesses fungistatic and fungicidal action. A preliminary investigation with chlorhexidine showed a favourable therapeutic response in skin diseases due to fungi andCandida albicans. In vitro tests suggest that chlorhexidine may be of value in the mouth to combat β-haemolytic streptococci, without influencing the oral flora.     

Individual differences in perceived bitterness predict liking of sweeteners

Although recent molecular studies suggest that only one receptorand one signaling pathway are involved in the perception ofsweetness, this seems to contradict everyday experience thatpeople not only have different likes and dislikes of certainsweeteners but also perceive the sweeteners differently. Onepossible explanation is that variation in liking of sweetenersis due, in part, to variation across individuals in sensitivityto nonsweet tastes, such as bitterness, which are transducedby a variety of receptors. Fifty individuals were asked to rateintensities of several taste attributes of 10 sweeteners andto give hedonic assessments of each sweetener. Additionally,their sensitivity to 6-n-propyl-3-thiouracil (PROP) was determined.Results indicated that when matched for sweetness, the perceptionof bitterness and the sweetener compound were the 2 largestfactors contributing to overall liking of a sweetener. Sensitivityto PROP did not contribute significantly to the model.     

The role of fluoride and chlorhexidine in preserving hardness and mineralization of enamel and cementum after gamma irradiation

The purpose of this study was to evaluate the effect of 0.05% sodium fluoride and 0.12% chlorhexidine mouthwashes on the micro-hardness of tooth enamel and cementum that was exposed to therapeutic doses of gamma radiation. Sixty extracted human teeth were divided into two groups, one was irradiated, the other was not irradiated. The two groups were further subdivided into three subgroups, which were each treated either with 0.05% sodium fluoride or with 0.12% chlorhexidine; the third subgroup served as a control. After demineralization–remineralization cycling, teeth from the irradiated groups showed a significantly lower micro-hardness when compared to those from the non-irradiated groups. Both in the irradiated and non-irradiated groups, teeth from the control subgroups showed a significantly lower micro-hardness, as compared to teeth treated with sodium fluoride and chlorhexidine. For non-irradiated enamel samples, those treated with chlorhexidine showed a significantly less micro-hardness compared to those treated with sodium fluoride. In contrast, irradiated enamel showed no significant difference in micro-hardness, whatever treatment (chlorhexidine or sodium fluoride) was applied. For cementum, treatment with chlorhexidine resulted in a significantly lower micro-hardness compared to sodium fluoride, both for the irradiated and non-irradiated groups. It is concluded that gamma irradiation with therapeutic doses typically used for head and neck carcinoma treatment has a direct effect in reducing micro-hardness of tooth enamel and cementum. Mouthwash protocols including, for example, application of 0.05% sodium fluoride or 0.12% chlorhexidine three times per day for 6 weeks, can protect enamel and cementum against the reduction in hardness and demineralization caused by gamma irradiation. Sodium fluoride offers more protection compared to chlorhexidine.     

Surface roughness of denture base and reline materials after disinfection by immersion in chlorhexidine or microwave irradiation

doi: 10.1111/j.1741‐2358.2011.00484.x
Surface roughness of denture base and reline materials after disinfection by immersion in chlorhexidine or microwave irradiation Background: This study evaluated the effect of disinfection by immersion and microwave irradiation on the roughness of one denture base resin (Lucitone‐L) and five relining materials, three hard (Tokuyama Rebase II‐TR, New Truliner‐NT, Ufigel Hard‐UH) and two resilient (Trusoft‐T, Sofreliner‐S). Methods: Fifty specimens were made and divided into groups: CL2 specimens were brushed with 4% chlorhexidine (1 min), immersed in the same solution (10 min) and immersed in water (3 min); MW2 specimens were immersed in water and microwave irradiated (650W; 6 min); CL2 and MW2 specimens were disinfected twice; CL7 and MW7 specimens were submitted to seven cycles using chlorhexidine or microwave irradiation, respectively; W specimens were not disinfected and remained in water (37°C; 7 days). Results: Results were statistically analysed (p = 0.05) and revealed that, at baseline, the highest mean value was observed for T (p < 0.001). Material NT showed increase in roughness after the first (p = 0.003), second (p = 0.001), seventh (p = 0.000) cycles of microwave disinfection and after 7 days of immersion in water (p = 0.033). Conclusions: Resilient liner S presented significant increase in roughness after the second cycle of disinfection with chlorhexidine (p = 0.003). Material T exhibited significantly decreased roughness in group W (p = 0.010), while microwaving produced severe alterations on its surface.     

Individual differences in perception of bitterness from capsaicin, piperine and zingerone

It was recently shown that in some subjects capsaicin can evoke bitterness as well as burning and stinging, particularly in the circumvallate (CV) region of the tongue. Because perception of bitterness from capsaicin is characterized by large individual differences, the main goal of the present study was to learn whether people who taste capsaicin as bitter also report bitterness from structurally similar sensory irritants that are known to stimulate capsaicin-sensitive neurons. The irritancy and taste of capsaicin and two of its most commonly studied congeners, piperine and zingerone, were measured in individuals who had been screened for visibility of, and reliable access to, the CV papillae. Approximately half of these individuals reported tasting bitterness from all three irritants when the stimuli were swabbed directly onto the CV papillae. Concentrations that produced similar levels of burning sensation across subjects also produced similar (though lower) levels of bitter taste. These results are consistent with the hypothesis that capsaicin and its congeners stimulate bitterness via a common sensory receptor that is distributed differentially among individuals. Additionally, bitter tasters rated gustatory qualities (but not burning and stinging) slightly but significantly higher than did bitter non-tasters, which suggests that perception of capsaicin bitterness is associated with a higher overall taste responsiveness (but not chemesthetic responsiveness) in the CV region.     

Delay expression of limonoid UDP-glucosyltransferase makes delayed bitterness in citrus

Genes encoding limonoid UDP-glucosyltransferase from albedo of six Citrus species with different levels of delayed bitterness are isolated and cloned in vector pTZ57R/T. Our results indicate that gene sequence of sweet lime (with intense juice delayed bitterness) have complete identity with Satsuma mandarin (without distinctive juice delayed bitterness). Also gene sequence of Marsh seedless grapefruit, local orange and Thompson navel orange (with mild juice delayed bitterness) have very similarity with Satsuma mandarin. On the other hand, this gene started to express 60, 120, and 210 days after full blooming in albedo of Satsuma mandarin, sweet oranges and sour orange, and both grapefruit and sweet lime, respectively. Expression pattern of limonoid glucosyltransferase gene in leaves was quite different with albedo. Thus, we supposed the delayed bitterness in this species was related to delay in expression of limonoid glucosyltransferase gene in albedo and lower limonoid glucoside accumulation in fruits.     

The molecular basis of individual differences in phenylthiocarbamide and propylthiouracil bitterness perception

Individual differences in perception are ubiquitous within the chemical senses: taste, smell, and chemical somesthesis . A hypothesis of this fact states that polymorphisms in human sensory receptor genes could alter perception by coding for functionally distinct receptor types . We have previously reported evidence that sequence variants in a presumptive bitter receptor gene (hTAS2R38) correlate with differences in bitterness recognition of phenylthiocarbamide (PTC) . Here, we map individual psychogenomic pathways for bitter taste by testing people with a variety of psychophysical tasks and linking their individual perceptions of the compounds PTC and propylthiouracil (PROP) to the in vitro responses of their TAS2R38 receptor variants. Functional expression studies demonstrate that five different haplotypes from the hTAS2R38 gene code for operatively distinct receptors. The responses of the three haplotypes we also tested in vivo correlate strongly with individuals' psychophysical bitter sensitivities to a family of compounds. These data provide a direct molecular link between heritable variability in bitter taste perception to functional variations of a single G protein coupled receptor that responds to compounds such as PTC and PROP that contain the N-C=S moiety. The molecular mechanisms of perceived bitterness variability have therapeutic implications, such as helping patients to consume beneficial bitter-tasting compounds-for example, pharmaceuticals and selected phytochemicals.     

大枣对杜仲风味修饰与功效增强作用的研究

通过大枣与杜仲配伍的研究,发现大枣对杜仲有风味修饰和增强杜仲功效的作用,两者配伍后,不仅具有杜仲补肝肾的功能,还具有大枣补脾胃的作用,达到了既补肝肾、又调脾胃的特异效果。     

Determination of saltiness from the laws of thermodynamics--estimating the gas constant from psychophysical experiments

One can relate the saltiness of a solution of a given substance to the concentration of the solution by means of one of the well-known psychophysical laws. One can also compare the saltiness of solutions of different solutes which have the same concentration, since different substances are intrinsically more salty or less salty. We develop here an equation that relates saltiness both to the concentration of the substance (psychophysical) and to a distinguishing physical property of the salt (intrinsic). For a fixed standard molar entropy of the salt being tasted, the equation simplifies to Fechner's law. When one allows for the intrinsic 'noise' in the chemoreceptor, the equation generalizes to include Stevens's law, with corresponding decrease in the threshold for taste. This threshold reduction exemplifies the principle of stochastic resonance. The theory is validated with reference to experimental data.     

Utilization of chlorhexidine gluconate to evaluate a nonhuman primate skin-degerming model

We have developed a nonhuman skin-degerming model to predict the in vivo effectiveness of topical antimicrobial formulations. The model incorporates a balanced, randomized, complete block design and uses the hands of anesthetized cynomolgus monkeys as treatment sites to measure product effectiveness. Two different 4% chlorhexidine gluconate formulations were evaluated in the primate model and then retested in a human skin-degerming model of identical design. Statistical analysis of the data revealed no significant differences between the two models with regard to the response exhibited by each to the test formulations.