A Novel Psychophysical Procedure for Bitter Taste Assessment in Rats

A persistent problem with attempts to examine bitter taste mechanismshas been the lack of adequate behavioral methodology providingdata which parallels that obtained from physiological investigations.We developed a brief contact procedure to assess the abilityof rats to detect the presence of a weak bitter compound dissolvedin a strong sucrose solution. Male Fischer 344 rats were trainedto drink immediately to multiple 10-s presentations of acetaminophen(2, 8, 32, 128 mM), chlorpheniramine maleate (1, 3, 9, 27 mM)L-tryptophan (13.5, 27, 54, 108 mM), pseudoephedrine hydrochloride(1, 4, 16, 64 mM) and quinine hydrochloride (0.008, 0.04, 0.2,1.0 mM) dissolved in 0.8 M sucrose. The number of licks to sucroseand water were also measured. A microcomputer controlled stimuluspresentations and measured the animal's licks of each solutionduring each 10-s presentation. The responses to the bitter +sucrose mixture were significantly decreased at most concentrationswith increasing levels of the bitter component. This was truefor all five bitter-tasting compounds, but over different concentrationranges relatively unique to each compound. The present studyis the first to characterize the sensory effects of acetaminophen,pseudoephedrine, and chlorpheniramine maleate, all purportedto taste bitter to humans. These results demonstrate rats' acuteability to discriminate by taste not only the presence but theconcentration of a dilute bitter compound dissolved in a strongsucrose solution. Chem. Senses 20: 305–312, 1995.     

Top-Down Control of Sweet and Bitter Taste in the Mammalian Brain

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Exercise Increases Markers of Spermatogenesis in Rats Selectively Bred for Low Running Capacity

The oxidative stress effect of exercise training on testis function is under debate. In the present study we used a unique rat model system developed by artificial selection for low and high intrinsic running capacity (LCR and HCR, respectively) to evaluate the effects of exercise training on apoptosis and spermatogenesis in testis. Twenty-four 13-month-old male rats were assigned to four groups: control LCR (LCR-C), trained LCR (LCR-T), control HCR (HCR-C), and trained HCR (HCR-T). Ten key proteins connecting aerobic exercise capacity and general testes function were assessed, including those that are vital for mitochondrial biogenesis. The VO2 max of LCR-C group was about 30% lower than that of HCR-C rats, and the SIRT1 levels were also significantly lower than HCR-C. Twelve weeks of training significantly increased maximal oxygen consumption in LCR by nearly 40% whereas HCR remained unchanged. LCR-T had significantly higher levels of peroxisome proliferator-activated receptor-gamma coactivator-1 (PGC-1α), decreased levels of reactive oxygen species and increased acetylated p53 compared to LCR-C, while training produced no significant changes for these measures in HCR rats. BAX and Blc-2 were not different among all four groups. The levels of outer dense fibers -1 (Odf-1), a marker of spermatogenesis, increased in LCR-T rats, but decreased in HCR-TR rats. Moreover, exercise training increased the levels of lactate dehydrogenase C (LDHC) only in LCR rats. These data suggest that rats with low inborn exercise capacity can increase whole body oxygen consumption and running exercise capacity with endurance training and, in turn, increase spermatogenesis function via reduction in ROS and heightened activity of p53 in testes.     

Social Defeat in Recovery-Oriented Supported Housing: Moral Experience, Stigma, and Ideological Resistance

Drawing from ethnographic observations and interview data gathered during 6?months working as a home caregiver at the Pinewood Apartments, a recovery-oriented supported housing community in Texas, I demonstrate how stigma and social defeat were moral and social processes that pervaded life for all involved, including service providers. Yet, because of the extreme power differentials that characterized tenant-staff relationships, the assault of stigma and social defeat was much more frequent, existentially intense, and morally and materially consequential for certain tenants, whose attempts at ideological resistance were delegitimized by service providers, including myself, who were backed by the authority of dominant psychiatric and moralistic discourses concerning the inherent irrationality and irresponsibility of people with severe mental illness. Nevertheless, due to the indeterminate and at times inharmonious nature of moral experience, it is not my intention to portray tenants as wholly defeated. Rather, individual tenants often exhibited defeat and resistance simultaneously.     

Success and Failure of Parliamentary Motions: A Social Dilemma Approach

Parliamentary motions are a vital and frequently used element of political control in democratic regimes. Despite their high incidence and potential impact on the political fate of a government and its policies, we know relatively little about the conditions under which parliamentary motions are likely to be accepted or rejected. Current collective decision-making models use a voting power framework in which power and influence of the involved parties are the main predictors. We propose an alternative, social dilemma approach, according to which a motion’s likelihood to be accepted depends on the severity of the social dilemma underlying the decision issue. Actor- and dilemma-centered hypotheses are developed and tested with data from a stratified random sample of 822 motions that have been voted upon in the Dutch Parliament between September 2009 and February 2011. The social dilemma structure of each motion is extracted through content coding, applying a cognitive mapping technique developed by Anthony, Heckathorn and Maser. Logistic regression analyses are in line with both, actor-centered and social-dilemma centered approaches, though the latter show stronger effect sizes. Motions have a lower chance to be accepted if voting potential is low, the proposer is not from the voting party, and if the problem underlying the motion reflects a prisoner’s dilemma or a pure competition game as compared to a coordination game. The number of proposing parties or a battle of the sexes structure does not significantly affect the outcome.     

Neural Interaction between Cortical Taste Neurons in Rats: a Cross-correlation Analysis

In the rat cortical taste area (CTA), we recorded 31 pairs oftaste neurons and seven pairs of taste and non-taste neurons,with single or double electrodes. By using a cross-correlogram(CCG) in a stationary state, we examined the functional interactionbetween neurons of the pairs while activating them by tastestimulation. Though only 14.3% of the taste and non-taste neuronpairs were correlated, 54.8% of the taste neuron pairs showedcorrelated activities, 41.9% of them showing common inputs,including one with an additional excitatory connection. Theremainder (12.9%) showed excitatory connections with a timelag of 1–3 ms. When pairs were recorded using single ordouble electrodes with an intertip distance of <50µmin a dorsoventral direction, a larger fraction had correlatedactivities than when the intertip distance was >50 µm.Whereas pairs of neurons showed correlated activities in areaDI whatever the vertical intertip distance was, most of thepairs having correlated activities in area GI were found within50 µm of the vertical intertip distance. The taste profilesof common inputs to the pair were estimated on the basis ofpeak at time 0 in CCGs for various taste stimuli. The efficacycontribution of the source to target neurons tended to be largerwhen both had the same best stimulus. This tendency held truefor pairs showing excitatory connections. Interlayer excitatoryconnections were also evident. It is concluded that a functionalcolumn with a diameter of 50 µm may present in the CTAin rats, and that information flow is larger between pairs ofneurons with the same best stimulus. Chem. Senses 22: 517–528,1997.     

Quantitative Autoradiography on [(35)S]TBPS Binding Sites of Gamma- Aminobutyric Acid(A) Receptors in Discrete Brain Regions of High- Alcohol-Drinking and Low-Alcohol- Drinking Rats Selectively Bred forHigh- and Low-Alcohol Preference

It has been documented that ethanol can potentiate brain -aminobutyric acid (GABA)ergic function, and there is a close link between the GABA_A receptor complex and effects of ethanol, including reinforcement of alcohol which is a fundamental element of alcohol preference. However, it is unknown in what discrete brain regions GABA_A receptors might be associated with alcohol preference. In the present study, [³⁵S]t-butylbicyclophosphorothionate ([³⁵S]TBPS) was used to localize GABA_A receptors in high-alcohol-drinking (HAD) rats and low-alcohol-drinking (LAD) rats which were selectively bred for high and low alcohol preference, respectively. Initial qualitative observations indicated that [³⁵S]TBPS binding sites were abundant in many brain areas including the cerebral cortex, hypothalamus and amygdala of HAD and LAD rats. Furthermore, the quantitative autoradiographic analysis revealed fewer [³⁵S]TBPS binding sites of GABA_A receptors in the amygdaloid complex, central medial thalamic nucleus, lateral hypothalamic nucleus and anterior hypothalamic nucleus of HAD rats than LAD rats. Collectively, this study has indicated that HAD rats selectively bred for high alcohol preference possess lower [³⁵S]TBPS binding in the brain. Since lower TBPS binding has been proposed to reflect enhanced GABAergic function, as evidenced in rats with seizure or under alcohol withdrawal, the results from the present study suggest that HAD rats might have an enhanced GABAergic function. It is thus likely that enhanced GABAergic function in the brain might be related to high alcohol preference which is characteristic in HAD rats. In addition, the present result showing no difference of [³⁵S]TBPS binding in the nucleus accumbens is also in agreement with a notion that [³⁵S]TBPS binding may represent only a small spectrum of the GABA_A receptor complex which is constituted of a sophisticated subunit combination whose functional compositions are still unknown. In conclusion, the present study supports the working hypothesis that GABA_A receptors are involved in alcohol preference in HAD rats.     

Interspecific Social Interactions and Breeding Success of the Frog Rana latastei: A Field Study

Interspecific reproductive interference can affect fitness‐related breeding performance, thus influencing fitness and distribution of populations. Laboratory studies demonstrated the social interference of Rana dalmatina males on R. latastei breeding females: the presence of heterospecific males reduced the percentage of viable embryos in R. latastei eggs. Here, we tested if the negative effects of R. dalmatina males on R. latastei reproductive success occur in field conditions. We compared the percentage of viable embryos of eggs laid in field conditions from populations where R. latastei breeds alone with the percentage of viable embryos of populations where R. latastei cohabits with R. dalmatina. We did not find any significant difference in percentage of viable embryos between R. latastei populations syntopic and allotopic with R. dalmatina, nor a relationship between the relative abundance of heterospecifics and reproductive success. In natural conditions, the presence of heterospecific males does not seem to interfere with the reproductive success of R. latastei. The experimental procedure may influence the interaction among individuals. Therefore, we suggest to validate on natural populations the results of experiments dealing with complex interactions.     

Fluoride Toxicity and Status of Serum Thyroid Hormones, Brain Histopathology, and Learning Memory in Rats: A Multigenerational Assessment

High-fluoride (100 and 200?ppm) water was administered to rats orally to study the fluoride-induced changes on the thyroid hormone status, the histopathology of discrete brain regions, the acetylcholine esterase activity, and the learning and memory abilities in multigeneration rats. Significant decrease in the serum-free thyroxine (FT4) and free triiodothyronine (FT3) levels and decrease in acetylcholine esterase activity in fluoride-treated group were observed. Presence of eosinophilic Purkinje cells, degenerating neurons, decreased granular cells, and vacuolations were noted in discrete brain regions of the fluoride-treated group. In the T-maze experiments, the fluoride-treated group showed poor acquisition and retention and higher latency when compared with the control. The alterations were more profound in the third generation when compared with the first- and second-generation fluoride-treated group. Changes in the thyroid hormone levels in the present study might have imbalanced the oxidant/antioxidant system, which further led to a reduction in learning memory ability. Hence, presence of generational or cumulative effects of fluoride on the development of the offspring when it is ingested continuously through multiple generations is evident from the present study.     

Reduced Anti-Pseudomonas aeruginosa Activity of a Cephalosporin,Cefodizime, in Rats Whose Neutrophils Were Selectively Depleted by a Monoclonal Antibody

In order to clarify the mechanisms of the in vivo antibacterial activity of a cephalosporin, cefodizime (CDZM), the effect of this antibiotic on Pseudomonas aeruginosa E7 infection was examined in rats whose neutrophils had been selectively depleted by monoclonal antibody RP-3. CDZM was less effective in RP-3-treated rats than in untreated rats. However, treatment of rats with recombinant human granulocyte-colony stimulating factor (rhG-CSF) augmented the in vivo activity of this antibiotic. Furthermore, the in vivo antibacterial activity of two other cephalosporins, cefpimizole (CPIZ) and cefoperazone (CPZ), was bilaterally affected by a rise or fall in the neutrophil number, although to a lesser degree than was the case with CDZM. Taken together, neutrophils play an important role in the in vivo antibacterial activity of certain cephalosporins.     

Formamide Sensitivity: A Novel Conditional Phenotype in Yeast

Yeast mutants unable to grow in the presence of 3% formamide have been isolated in parallel with mutants sensitive to either 37° or 6% ethanol. The number of formamide-sensitive mutations that affect different genes that can be identified from yeast cells is at least as large as the number of thermosensitive or ethanol-sensitive mutations. These mutations are of two types: those that are sensitive to formamide, temperature and/or ethanol simultaneously; and those that are specific for formamide sensitivity and show no temperature or ethanol sensitivity phenotype. Those genes susceptible to giving rise to formamide-sensitive alleles include the structural gene for DNA ligase, CDC9, and the structural gene for arginine permease, CAN1. The results indicate that formamide sensitivity can be used as a novel conditional phenotype for mutations on both essential and nonessential genes. This work also confirms that ethanol-sensitivity can be used as a conditional phenotype to identify mutations in at least as many genes as those susceptible to temperature or formamide sensitive mutations.     

The Sweet Potato in Oceania: A Reappraisal

The Sweet Potato in Oceania:. Reappraisal . Chris Ballard, Paula Brown, Michael Bourke, and Tracy Harwood, eds. Pittsburgh: University of Pittsburgh Press, 2005. 227 pp.     

Diving-for-Food: A New Model to Assess Social Roles in a Group of Laboratory Rats

In an experimental situation called “diving for food”, groups of laboratory rats are tested in an aquarium where they have to dive and swim under water to reach the single source of food located at the other end. A behavioural differentiation appears: some rats — the carriers — dive to get food and others — non-carriers — stay in the cage and feed by stealing. We examine whether carrier and non-carrier profiles can be considered as social roles, defined as supraindividual features dependent on the social context. Carrier/non-carrier differentiation resulted in all groups tested. Individually tested, almost all rats can get food by diving and swimming. Differentiation also occurred in groups that had been previously trained alone in the device, and in groups whose members had all been carriers or non-carriers exclusively in a preliminary stage. As the access-to-food behaviour of a rat having to cope with the diving-for-food situation is settled by its social environment, we consider that the present experimental model is promising for the study of interactions between the individual and the social structure.     

Expression of the Bitter Taste Receptor,T2R38, in Enteroendocrine Cells of the Colonic Mucosa of Overweight/Obese vs. Lean Subjects

Bitter taste receptors (T2Rs) are expressed in the mammalian gastrointestinal mucosa. In the mouse colon, T2R138 is localized to enteroendocrine cells and is upregulated by long-term high fat diet that induces obesity. The aims of this study were to test whether T2R38 expression is altered in overweight/obese (OW/OB) compared to normal weight (NW) subjects and characterize the cell types expressing T2R38, the human counterpart of mouse T2R138, in human colon. Colonic mucosal biopsies were obtained during colonoscopy from 35 healthy subjects (20 OW/OB and 15 NW) and processed for quantitative RT-PCR and immunohistochemistry using antibodies to T2R38, chromogranin A (CgA), glucagon like peptide-1 (GLP-1), cholecystokinin (CCK), or peptide YY (PYY). T2R38 mRNA levels in the colonic mucosa of OW/OB were increased (> 2 fold) compared to NW subjects but did not reach statistical significance (P = 0.06). However, the number of T2R38 immunoreactive (IR) cells was significantly increased in OW/OB vs. NW subjects (P = 0.01) and was significantly correlated with BMI values (r = 0.7557; P = 0.001). In both OW/OB and NW individuals, all T2R38-IR cells contained CgA-IR supporting they are enteroendocrine. In both groups, T2R38-IR colocalized with CCK-, GLP1- or PYY-IR. The overall CgA-IR cell population was comparable in OW/OB and NW individuals. This study shows that T2R38 is expressed in distinct populations of enteroendocrine cells in the human colonic mucosa and supports T2R38 upregulation in OW/OB subjects. T2R38 might mediate host functional responses to increased energy balance and intraluminal changes occurring in obesity, which could involve peptide release from enteroendocrine cells.     

Lithium-Induced Hypothyroidism: Oxidative Stress and Osmotic Fragility Status in Rats

The present study was conducted to explore the possible effects of different doses of lithium carbonate on thyroid functions, erythrocyte oxidant–antioxidant status, and osmotic fragility. Twenty-four Wistar-type male rats were equally divided into three groups: groups I and II received 0.1 and0.2 % lithium carbonate in their drinking water, respectively, for 30 days. The rats in group III served as controls, drinking tap water without added lithium. At the end of the experimental period, the erythrocyte osmotic fragility and the levels of triiodothyronine (T₃), thyroxine (T₄), thyroid-stimulating hormone (TSH), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) were measured in blood samples. Compared to controls, there was a statistically significant increase of TSH but decreases of the T₃ and T₄ levels in group II. Both experimental groups showed a statistically significant increase of the maximum osmotic fragility limit. The minimum osmotic fragility values of the animals in group II were statistically higher than those of controls. The standard hemolytic increment curve of both experimental groups was shifted to the right when compared to the curve obtained from the controls. Also, relative to controls, the activities of MDA and SOD were significantly higher and the GSH level lower in group II, but not so in group I. The results of the present study show that treatment with lithium carbonate may result in thyroid function abnormalities, increased oxidative damage, and possible compromise of the erythrocyte membrane integrity resulting from increased osmotic fragility.