Human olfactory neurons respond to odor stimuli with an increase in cytoplasmic Ca2+.

The sense of smell allows terrestrial animals to collect information about the chemical nature of their environment through the detection of airborne molecules. In humans smell is believed to play an important role in protecting the organism from environmental hazards such as fire, gas leaks and spoiled food, in determining the flavor of foods, and perhaps in infant-parent bonding. In addition, the study of human olfaction is relevant to a number of medical problems that result in olfactory dysfunction, which can affect nutritional state, and to the study of the etiology of neurodegenerative diseases which manifest themselves in the olfactory epithelium. Although much is known about behavioral aspects of human olfaction, little is understood about the underlying cellular mechanisms in humans. Here we report that viable human olfactory neurons (HON) can be isolated from olfactory tissue biopsies, and we find that HON respond to odorants with an increase in intracellular calcium concentration ([Cai]).     

Individual differences in sensitivity to bitter-tasting substances

Perception of several bitter-tasting compounds was tested in52 subjects. Stable individual differences in the perceivedintensity of the bitterness of suprathreshold concentrationsof quinine sulfate (QSO₄) and urea were found. Whereas 18 subjectsjudged selected concentrations of these compounds to be equallybitter, 17 found QSO₄ to be more bitter than urea, and 17 foundurea to be more bitter than QSO₄. These reliable individualdifferences were significantly related to threshold sensitivityto QSO₄; that is, individuals who perceived QSO₄ to be moreintense than urea at suprathreshold concentrations also hadlower QSO₄ thresholds than did those who perceived urea to bemore intense than QSO₄. There appeared to be no relationshipbetween the relative perceived intensities of these compoundsand rating of the bitterness of PROP (6-n-propylthiouracil).However, QSO₄-sensitive individuals tended to find the bitternessof suprathreshold caffeine and sucrose octaacetate to be greaterthan that of suprathreshold magnesium sulfate, whereas the reversewas true for urea-sensitive individuals. This pattern parallelsthe pattern of cross-adaptation among these compounds reportedby other investigators. These results are consistent with theexistence of multiple bitter transduction sequences and suggestthat individual differences in response to various bitter compoundsmay reflect differences in teh relative availability of specifictransduction sequences.     

The Yeast Oxysterol Binding Protein Kes1 Maintains Sphingolipid Levels

The oxysterol binding protein family are amphitropic proteins that bind oxysterols, sterols, and possibly phosphoinositides, in a conserved binding pocket. The Saccharomyces cerevisiae oxysterol binding protein family member Kes1 (also known as Osh4) also binds phosphoinositides on a distinct surface of the protein from the conserved binding pocket. In this study, we determine that the oxysterol binding protein family member Kes1 is required to maintain the ratio of complex sphingolipids and levels of ceramide, sphingosine-phosphate and sphingosine. This inability to maintain normal sphingolipid homeostasis resulted in misdistribution of Pma1, a protein that requires normal sphingolipid synthesis to occur to partition into membrane rafts at the Golgi for its trafficking to the plasma membrane.     

Sphingosine Kinase 1 Is Regulated by Peroxisome Proliferator-activated Receptor α in Response to Free Fatty Acids and Is Essential for Skeletal Muscle Interleukin-6 Production and Signaling in Diet-induced Obesity

We previously demonstrated that sphingosine kinase 1 (Sphk1) expression and activity are up-regulated by exogenous palmitate (PAL) in a skeletal muscle model system and in diet-induced obesity in mice; however, potential functions and in vivo relevance of this have not been addressed. Here, we aimed to determine the mechanism by which PAL regulates SphK1 in muscle, and to determine potential roles for its product, sphingosine-1-phosphate (S1P), in muscle biology in the context of obesity. Cloning and analysis of the mouse Sphk1 promoter revealed a peroxisome proliferator-activated receptor (PPAR) α cis-element that mediated activation of a reporter under control of the Sphk1 promoter; direct interaction of PPARα was demonstrated by chromatin immunoprecipitation. PAL treatment induced the proinflammatory cytokine interleukin (IL)-6 in a manner dependent on SphK1, and this was attenuated by inhibition of the sphingosine-1-phosphate receptor 3 (S1PR3)_. Diet-induced obesity in mice demonstrated that IL-6 expression in muscle, but not adipose tissue, increased in obesity, but this was attenuated in Sphk1^−/− mice. Moreover, plasma IL-6 levels were significantly decreased in obese Sphk1^−/− mice relative to obese wild type mice, and muscle, but not adipose tissue IL-6 signaling was activated. These data indicate that PPARα regulates Sphk1 expression in the context of fatty acid oversupply and links PAL to muscle IL-6 production. Moreover, this function of SphK1 in diet-induced obesity suggests a potential role for SphK1 in obesity-associated pathological outcomes.     

A new class of potent non-imidazole H(3) antagonists: 2-aminoethylbenzofurans

2-aminoethylbenzofurans constitute a new class of H(3) antagonists that are more rotationally constrained than most previously reported H(3) antagonists. They retain high potency at human and rat receptors, with efficient CNS penetration observed in 35. The SAR of the basic amine moiety was compared in three different series of analogues. The greatest potency was found in analogues bearing a 2-methylpyrrolidine, a 2,5-dimethylpyrrolidine, or a 2,6-dimethylpiperidine.     

Acute activation of de novo sphingolipid biosynthesis upon heat shock causes an accumulation of ceramide and subsequent dephosphorylation of SR proteins

Recent studies are beginning to implicate sphingolipids in the heat stress response. In the yeast Saccharomyces cerevisiae, heat stress has been shown to activate de novo biosynthesis of sphingolipids, whereas in mammalian cells the sphingolipid ceramide has been implicated in the heat shock responses. In the current study, we found an increase in the ceramide mass of Molt-4 cells in response to heat shock, corroborating findings in HL-60 cells. Increased ceramide was determined to be from de novo biosynthesis by two major lines of evidence. First, the accumulation of ceramide was dependent upon the activities of both ceramide synthase and serine palmitoyltransferase. Second, pulse labeling studies demonstrated increased production of ceramide through the de novo biosynthetic pathway. Significantly, the de novo sphingolipid biosynthetic pathway was acutely induced upon heat shock, which resulted in a 2-fold increased flux in newly made ceramides within 1-2 min of exposure to 42.5 degrees C. Functionally, heat shock induced the dephosphorylation of the SR proteins, and this effect was demonstrated to be dependent upon the accumulation of de novo-produced ceramides. Thus, these studies disclose an evolutionary conserved activation of the de novo pathway in response to heat shock. Moreover, SR dephosphorylation is emerging as a specific downstream target of accumulation of newly made ceramides in mammalian cells.     

4-[6-(2-Aminoethyl)naphthalen-2-yl]benzonitriles are potent histamine H3 receptor antagonists with high CNS penetration

4-[6-(2-Tertiaryaminoethyl)naphthalen-2-yl]benzonitriles are conformationally constrained histamine H3 receptor antagonists with high potency and selectivity. The analogs were designed around a naphthalene core, with the goal of enhancing lipophilicity and CNS penetration, as compared to a previously reported benzofuran series. The SAR of the tertiary amine moiety is similar to that reported for the benzofuran series, with analogs bearing a 2-methylpyrrolidine substituent possessing the greatest rat and human H3 receptor binding affinities.     

Histamine H3 receptor antagonists: preclinical promise for treating obesity and cognitive disorders

The histamine H3 receptor is an attractive G protein-coupled receptor drug target that regulates neurotransmission in the central nervous system and plays a role in cognitive and homeostatic functions. Drug discovery efforts by numerous pharmaceutical companies have focused on the preclinical development of H3 receptor antagonists for the potential treatment of attention-deficit hyperactivity disorder, dementias, schizophrenia, as well as obesity and sleep disorders. This receptor exhibits molecular, pharmacological, and functional heterogeneity that informs the preclinical development of effective antagonists. Herein, we describe the biological and chemical implications for developing H3 receptor antagonists and their therapeutic potential as disclosed through animal models of cognition, sleep, and obesity.     

Behavior of a cross-linked attachment site: testing the role of branch migration in site-specific recombination.

Integrative recombination of bacteriophage lambda requires perfect homology between partners over a short segment of DNA, the overlap region, that separates the positions of top and bottom strand exchange. We constructed a specific cross-link between complementary strands in the overlap region of one partner, using a method designed to introduce minimal distortion of DNA. The modified attachment site could initiate recombination, forming a Holliday junction, but could not resolve this junction so as to complete the recombination. This demonstrates that the ability of complementary base-pairs to dissociate is important for overlap region function and strongly supports the view that branch migration across this region is the way homology is sensed during integrative recombination.