Effect of Chorda Tympani Nerve Transection on Salt Taste Perception in Mice

Effects of gustatory nerve transection on salt taste have been studied extensively in rats and hamsters but have not been well explored in the mouse. We examined the effects of chorda tympani (CT) nerve transection on NaCl taste preferences and thresholds in outbred CD-1 mice using a high-throughput phenotyping method developed in our laboratory. To measure taste thresholds, mice were conditioned by oral self-administration of LiCl or NaCl and then presented with NaCl concentration series in 2-bottle preference tests. LiCl-conditioned and control NaCl-exposed mice were given bilateral transections of the CT nerve (LiCl-CTX, NaCl-CTX) or were left intact as controls (LiCl-CNT, NaCl-CNT). After recovery from surgery, mice received a concentration series of NaCl (0–300 mM) in 48-h 2-bottle tests. CT transection increased NaCl taste thresholds in LiCl-conditioned mice and eliminated avoidance of concentrated NaCl in control NaCl-exposed mice. This demonstrates that in mice, the CT nerve is important for detection and recognition of NaCl taste and is necessary for the normal avoidance of high concentrations of NaCl. The results of this experiment also show that the method of high-throughput phenotyping of salt taste thresholds is suitable for detecting changes in the taste periphery in mouse genetic studies

Polymorphisms in the Taste Receptor Gene (Tas1r3) Region are Associated with Saccharin Preference in 30 Mouse Strains.

The results of recent studies suggest that the mouse Sac (saccharin preference) locus is identical to the Tas1r3 (taste receptor) gene. The goal of this study was to identify Tas1r3 sequence variants associated with saccharin preference in a large number of inbred mouse strains. Initially, we sequenced approximately 6.7 kb of the Tas1r3 gene and its flanking regions from six inbred mouse strains with high and low saccharin preference, including the strains in which the Sac alleles were described originally (C57BL/6J, Sac(b); DBA/2J, Sac(d)). Of the 89 sequence variants detected among these six strains, eight polymorphic sites were significantly associated with preferences for 1.6 mm saccharin. Next, each of these eight variant sites were genotyped in 24 additional mouse strains. Analysis of the genotype-phenotype associations in all 30 strains showed the strongest association with saccharin preference at three sites: nucleotide (nt) -791 (3 bp insertion/deletion), nt +135 (Ser45Ser), and nt +179 (Ile60Thr). We measured Tas1r3 gene expression, transcript size, and T1R3 immunoreactivity in the taste tissue of two inbred mouse strains with different Tas1r3 haplotypes and saccharin preferences. The results of these experiments suggest that the polymorphisms associated with saccharin preference do not act by blocking gene expression, changing alternative splicing, or interfering with protein translation in taste tissue. The amino acid substitution (Ile60Thr) may influence the ability of the protein to form dimers or bind sweeteners. Here, we present data for future studies directed to experimentally confirm the function of these polymorphisms and highlight some of the difficulties of identifying specific DNA sequence variants that underlie quantitative trait loci

Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar

Although domestic cats (Felis silvestris catus) possess an otherwise functional sense of taste, they, unlike most mammals, do not prefer and may be unable to detect the sweetness of sugars. One possible explanation for this behavior is that cats lack the sensory system to taste sugars and therefore are indifferent to them. Drawing on work in mice, demonstrating that alleles of sweet-receptor genes predict low sugar intake, we examined the possibility that genes involved in the initial transduction of sweet perception might account for the indifference to sweet-tasting foods by cats. We characterized the sweet-receptor genes of domestic cats as well as those of other members of the Felidae family of obligate carnivores, tiger and cheetah. Because the mammalian sweet-taste receptor is formed by the dimerization of two proteins (T1R2 and T1R3; gene symbols Tas1r2 and Tas1r3), we identified and sequenced both genes in the cat by screening a feline genomic BAC library and by performing PCR with degenerate primers on cat genomic DNA. Gene expression was assessed by RT-PCR of taste tissue, in situ hybridization, and immunohistochemistry. The cat Tas1r3 gene shows high sequence similarity with functional Tas1r3 genes of other species. Message from Tas1r3 was detected by RT-PCR of taste tissue. In situ hybridization and immunohistochemical studies demonstrate that Tas1r3 is expressed, as expected, in taste buds. However, the cat Tas1r2 gene shows a 247-base pair microdeletion in exon 3 and stop codons in exons 4 and 6. There was no evidence of detectable mRNA from cat Tas1r2 by RT-PCR or in situ hybridization, and no evidence of protein expression by immunohistochemistry. Tas1r2 in tiger and cheetah and in six healthy adult domestic cats all show the similar deletion and stop codons. We conclude that cat Tas1r3 is an apparently functional and expressed receptor but that cat Tas1r2 is an unexpressed pseudogene. A functional sweet-taste receptor heteromer cannot form, and thus the cat lacks the receptor likely necessary for detection of sweet stimuli. This molecular change was very likely an important event in the evolution of the cat's carnivorous behavior

Behavioral genetics and taste

This review focuses on behavioral genetic studies of sweet, umami, bitter and salt taste responses in mammals. Studies involving mouse inbred strain comparisons and genetic analyses, and their impact on elucidation of taste receptors and transduction mechanisms are discussed. Finally, the effect of genetic variation in taste responsiveness on complex traits such as drug intake is considered. Recent advances in development of genomic resources make behavioral genetics a powerful approach for understanding mechanisms of taste

БАЗА ДАННЫХ АКТИВНЫХ РАЗЛОМОВ ЕВРАЗИИ

This paper describes the technique used to create and maintain the Active Faults of Eurasia Database (AFED) based on the uniform format that ensures integrating the materials accumulated by many researchers, inclu­ding the authors of the AFED. The AFED includes the data on more than 20 thousand objects: faults, fault zones and associated structural forms that show the signs of latest displacements in the Late Pleistocene and Holocene. The geographical coordinates are given for each object. The AFED scale is 1:500000; the demonstration scale is 1:1000000. For each object, the AFED shows two kinds of characteristics: justification attributes, and estimated attributes. The justification attributes inform the AFED user about an object: the object’s name; morphology; kinematics; the amplitudes of displacement for different periods of time; displacement rates estimated from the amplitudes; the age of the latest recorded signs of activity, seismicity and paleoseismicity; the relationship of the given objects with the parameters of crustal earthquakes; etc. The sources of information are listed in the AFED appendix. The estimated attributes are represented by the system of indices reflecting the fault kinematics according to the classification of the faults by types, as accepted in structural geology, and includes three ranks of the Late Quaternary movements and four degrees of reliability of identifying the structures as active ones. With reference to the indices, the objects can be compared with each other, considering any of the attributes, or with any other digitized information. The comparison can be performed by any GIS software. The AFED is an efficient tool for obtaining the information on the faults and solving general problems, such as thematic mapping, determining the parameters of modern geodynamic processes, estima­ting seismic and other geodynamic hazards, identifying the tectonic development trends in the Pliocene–Quaternary stage of the Earth's development, etc. The Active Faults of Eurasia Database is created in the format providing for inputs of new information, as well the database updating and revision.Представляется методика создания и содержание новой базы данных об активных разломах Евразии (БД), интегрировавшей в едином формате материал, накопленный к настоящему времени многими исследователями, включая авторов БД. Она вмещает более 20 тыс. географически привязанных объектов – разломов, зон разломов и связанных с ними структурных форм с признаками последних перемещений в позднем плейстоцене и голоцене. Масштаб, в котором составлена БД, – 1:500000, а базовый демонстрационный масштаб – 1:1000000. Каждый объект БД снабжен двумя видами характеристик (атрибутов) – обосновывающими и оценочными. Обосновывающие атрибуты содержат сведения об объектах – их названия, данные о морфологии и кинематике, амплитуды смещений за разные отрезки времени, рассчитанные по ним скорости движений, возраст последних зафиксированных признаков активности, проявления сейсмичности и палео­сейсмичности, соотношения объектов с параметрами коровых землетрясений и другие характеристики, а также сведения об источниках информации, список которых приложен к БД. Оценочные атрибуты – это система индексов, отражающих кинематику разломов согласно принятой в структурной геологии типизации, ранг скорости позднечетвертичных движений (три градации) и степень достоверности выделения структуры как активной (четыре градации). Индексы позволяют сопоставлять объекты по любому из атрибутов компьютерным способом между собой и с любыми другими видами оцифрованной информации с помощью любой ГИС-программы. Таким образом, БД дает возможность для получения сведений о разломах и решения более общих задач – тематического картографирования, определения параметров современных геодинамических процессов, оценки сейсмической и других геодинамических опасностей, тенденций тектонического развития на последнем, плиоцен-четвертичном, этапе развития Земли. Формат построения БД допускает ее постоянное пополнение и коррекцию с появлением новых сведений.

Использование базы данных активных разломов Евразии при решении тектонических задач

The article describes principles, methods and tasks of tectonic studies using computer processing of the Active Faults of Eurasia Database. This new database contains more than 30000 objects that are geographically linked, equipped with attributes of the kinematic type, estimated movement rates and activity confidence ranks. As an exam‐ ple, we consider processing of the data on several tectonic regions of the Alpine‐Himalayan mobile belt and construction of rose‐diagrams of faults for a comparative analysis of their Late Cenozoic kinematics. The processed data set also covered the Caucasus‐Anatolian region and the entire central part of the mobile belt, and fields of shortening/lengthening and shearing were mapped to assess the patterns of these processes in different areas and to determine the characteristics of the tectonic flow of the upper crust material. Prospects are discussed for the database processing with the use of all the available attributive information for structural‐kinematic and geodynamic analysis, including processing of the database in combination with independent remote and geophysical data.Описываются принципы, методики и задачи тектонических исследований с применением ком‐ пьютерной обработки новой базы данных активных разломов Евразии, содержащей более 30000 географиче‐ ски привязанных объектов, снабженных атрибутами кинематического типа, оценками скоростей движения и достоверности активности. В качестве примеров рассмотрена обработка отдельных тектонических областей Альпийско‐Гималайского подвижного пояса с построением роза‐диаграмм разломов для сравнительного анализа их позднекайнозойской кинематики. Также проведена обработка Кавказско‐Анатолийского региона и всей центральной части подвижного пояса с построением карт полей деформаций сокращения – удлинения и сдвига для оценки их распределения в разных областях и выяснения характеристик тектонического тече‐ ния верхнекоровых масс. Обсуждаются перспективы обработки базы данных с использованием всего ком‐ плекса содержащейся в ней атрибутивной информации для структурно‐кинематического и геодинамическо‐ го анализа, в том числе обработки базы данных совместно с независимыми дистанционными и геофизиче‐ скими материалами

Protein Hydrolysates Are Avoided by Herbivores but Not by Omnivores in Two-Choice Preference Tests

Background: The negative sensory properties of casein hydrolysates (HC) often limit their usage in products intended for human consumption, despite HC being nutritious and having many functional benefits. Recent, but taxonomically limited, evidence suggests that other animals also avoid consuming HC when alternatives exist. Methodology/Principal Findings: We evaluated ingestive responses of five herbivorous species (guinea pig, mountain beaver, gopher, vole, and rabbit) and five omnivorous species (rat, coyote, house mouse, white-footed mouse, and deer mouse; N = 16–18/species) using solid foods containing 20% HC in a series of two-choice preference tests that used a nonprotein, cellulose-based alternative. Individuals were also tested with collagen hydrolysate (gelatin; GE) to determine whether it would induce similar ingestive responses to those induced by HC. Despite HC and GE having very different nutritional and sensory qualities, both hydrolysates produced similar preference score patterns. We found that the herbivores generally avoided the hydrolysates while the omnivores consumed them at similar levels to the cellulose diet or, more rarely, preferred them (HC by the white-footed mouse; GE by the rat). Follow-up preference tests pairing HC and the nutritionally equivalent intact casein (C) were performed on the three mouse species and the guinea pigs. For the mice, mean HC preference scores were lower in the HC v C compared to the HC v Cel tests, indicating that HC’s sensory qualities negatively affected its consumption. However, responses were species-specific. For the guinea pigs, repeated exposure to HC or C (4.7-h sessions; N = 10) were found to increase subsequent HC preference scores in an HC v C preference test, which was interpreted in the light of conservative foraging strategies thought to typify herbivores. Conclusions/Significance: This is the first empirical study of dietary niche-related taxonomic differences in ingestive responses to protein hydrolysates using multiple species under comparable conditions. Our results provide a basis for future work in sensory, physiological, and behavioral mechanisms of hydrolysate avoidance and on the potential use of hydrolysates for pest management

Genetic and Molecular Basis of Individual Differences in Human Umami Taste Perception

Umami taste (corresponds to savory in English) is elicited by L-glutamate, typically as its Na salt (monosodium glutamate: MSG), and is one of five basic taste qualities that plays a key role in intake of amino acids. A particular property of umami is the synergistic potentiation of glutamate by purine nucleotide monophosphates (IMP, GMP). A heterodimer of a G protein coupled receptor, TAS1R1 and TAS1R3, is proposed to function as its receptor. However, little is known about genetic variation of TAS1R1 and TAS1R3 and its potential links with individual differences in umami sensitivity. Here we investigated the association between recognition thresholds for umami substances and genetic variations in human TAS1R1 and TAS1R3, and the functions of TAS1R1/TAS1R3 variants using a heterologous expression system. Our study demonstrated that the TAS1R1-372T creates a more sensitive umami receptor than -372A, while TAS1R3-757C creates a less sensitive one than -757R for MSG and MSG plus IMP, and showed a strong correlation between the recognition thresholds and in vitro dose - response relationships. These results in human studies support the propositions that a TAS1R1/TAS1R3 heterodimer acts as an umami receptor, and that genetic variation in this heterodimer directly affects umami taste sensitivity

The Human Sweet Tooth

Humans love the taste of sugar and the word "sweet" is used to describe not only this basic taste quality but also something that is desirable or pleasurable, e.g., la dolce vita. Although sugar or sweetened foods are generally among the most preferred choices, not everyone likes sugar, especially at high concentrations. The focus of my group's research is to understand why some people have a sweet tooth and others do not. We have used genetic and molecular techniques in humans, rats, mice, cats and primates to understand the origins of sweet taste perception. Our studies demonstrate that there are two sweet receptor genes (TAS1R2 and TAS1R3), and alleles of one of the two genes predict the avidity with which some mammals drink sweet solutions. We also find a relationship between sweet and bitter perception. Children who are genetically more sensitive to bitter compounds report that very sweet solutions are more pleasant and they prefer sweet carbonated beverages more than milk, relative to less bitter-sensitive peers. Overall, people differ in their ability to perceive the basic tastes, and particular constellations of genes and experience may drive some people, but not others, toward a caries-inducing sweet diet. Future studies will be designed to understand how a genetic preference for sweet food and drink might contribute to the development of dental caries