New findings in taste and smell research

04/10/05

Over 460 scientists to present cutting edge results

Sarasota, FL - Smell and taste play essential roles in our daily lives. The chemical senses serve as important warning systems, alerting us to the presence of potentially harmful situations or substances, including gas leaks, smoke, and spoiled food. Flavors and fragrances are also important in determining what foods we eat and the commercial products we use. The pleasures derived from eating are mainly based on the chemical senses. Thousands of Americans experience loss of smell or taste each year resulting from head trauma, sinus disease, normal aging and neurological disorders, such as brain injury, stroke and Alzheimer's disease. By providing a better understanding of the function of chemosensory systems, scientific and biomedical research is leading to improvements in the diagnoses and treatment of smell and taste disorders.

Among those contributing to advancements are members of The Association for Chemoreception Sciences (AChemS), which will be holding its 27th annual meeting in Sarasota, FL, April 13-18, 2005. AChemS consists of more than 800 members from 23 countries who are specialists in the chemical senses, smell, taste, and chemical irritation. In Sarasota, scientists are presenting their latest research findings on topics ranging from molecular biology to the clinical diagnosis and treatment of smell and taste disorders. The 2005 meeting is featuring presentations of new research findings, special symposia, and workshops (see Program at a Glance) sponsored by AChemS, corporations, and the National Institutes of Health. On Wednesday, April 13th, at 10:00 A.M., the meeting opens with an educational outreach program for local elementary and high school students at the GWIZ Science Center and then transitions to the annual Givaudan Lecture, which will focus on a weight control. The guest lecture by Dr. Jeffrey M. Friedman, from Rockefeller University, is titled "Leptin and the Regulation of Body Weight."

Additionally, there will be eight, special-subject symposia, the highlights of which occur Saturday evening and throughout the day on Sunday, April 17th in which the recipients of the 2004 Nobel Prize in Physiology or Medicine, Drs. Richard Axel and Linda Buck, among others, will present recent findings on chemoreceptors. Throughout the five-day meeting there will be over 460 research presentations by AChemS scientists from around the world (for details see Program Listing).

Some new findings to be presented at the meeting include:

  • Newborn Sense of Smell May Save Life -- Odorization of the incubator prevents apneas in premature infants.
  • Sperm Are Attracted by Chemicals -- Mechanisms of sperm navigation in turbulent flow.
  • Human pheromone receptors -- De-orphaning, functional characterization and cAMP signalling of five human V1R-like receptors.
  • Genetic Odorprints May Use Peptides -- Encoding immune system signals by the mammalian nose: The scent of genetic compatibility.
  • Reduced Selection for Human Odor Receptor Genes -- A genomic perspective on the evolution of olfaction in primates.

Detailed Summaries

NEWBORN SENSE OF SMELL: Leading to a decrease in cerebral blood flow velocity and in cerebral oxygenation, apnea of immaturity represents a major preoccupation for premature infants caregivers. Pharmacological treatments (methylxanthines and doxapram) currently used to treat these apneas are not fully effective and often present undesirable side effects. The present study examines whether exposure to an odor known to modulate the newborn's respiratory rate reduces the incidence of apneic spells. Fourteen premature infants born at 24-28 postconceptional weeks and presenting apneas resistant to classical treatments were exposed during the second week after birth to the odor of vanilla diffused during 24h in the incubator. The day before and the day after odorization were used as control for each subject. A significant diminution (44%) of the number of apneas longer than 20 sec (or less if associated with immediate hypoxia) was observed during odorization and this diminution was seen in all the subjects. Apneas associated with bradycardias (heart rate under 50% of baseline rate) decreased strongly (45%) during odorization and this decrease affected all the infants. No side effects were observed. Odorization of the incubator thus appears of therapeutic value for the treatment of apneas unresponsive to classical therapy and may contribute to preserve the integrity of the developing brain. Supported by the French Ministčre de la Santé. [Poster, Friday, April 15, 7:00pm - 11:00pm]

Authors: Marlier L. (1), Gaugler C. (2), Messer J. (2) 1 Centre National de la Recherche Scientifique UMR5170, Strasbourg, France; 2 Pediatrie II, Centre Hospitalier Universitaire, Strasbourg, France; contact Luc Marlier; email: marlier@cesg.cnrs.fr

SPERM: Chemical communication between sperm and egg is widely prevalent among taxa with divergent reproductive strategies. Sperm chemoattractants play a pivotal role in fertilization through mediating sperm-egg interactions and increasing gamete encounters. Surprisingly, no study has examined the influence of these signals under realistic conditions. Ubiquitous for all organisms is the presence of fluid motion at the scale of the sperm and egg. Fluid motion may have profound influence on gamete motility and sperm attractant distribution, but such effects are largely undescribed. This study investigated the mechanisms by which sperm navigate to eggs under natural flow conditions. Our discovery of tryptophan as the natural attractant of abalone (Haliotis rufescens) sperm offered the opportunity to determine the navigational mechanism used by sperm. Fluid motion stretched the tryptophan plume around eggs, vastly increasing broadcast distances. Moreover, stretching of the plume caused shallow gradients to dominate plume structure, in contrast to the sharp gradients found in diffusion. Examining the kinetics of sperm behavior revealed that sperm use klinotaxis to orient and swim towards the egg. By integrating the changing concentration over a 200ms interval, sperm can navigate to a shallow gradient within a temporally and spatially dynamic fluid environment. Moreover, the concentration gradient, not concentration itself, modulated sperm trajectories. Thus, even at microscopic scales, physics tightly constrains the chemical signaling process, dictating sperm navigation. [Oral, Saturday, April 16, 8:45pm]

Authors: Riffell J. (1), Zimmer R. (2) 1 ARL Division of Neurobiology, University of Arizona, Tucson, AZ; 2 Ecology and Evolution, University of California, Los Angeles, Los Angeles, CA; contact Jeffrey Riffell, jeffr@neurobio.arizona.edu

HUMAN PHEROMONE RECEPTORS: The human vomeronasal organ (VNO) is an anatomical entity which is generally considered to be vestigial or non-functional. However, five potentially functional genes have been identified from human genome searches, coding for receptors that are related to the family of V1 receptors of the apical part of the mouse VNO. These five human receptors have been termed hV1RL1-5, one of which has recently been demonstrated to be expressed in the human main olfactory epithelium (MOE). Since nothing was known about their function, all five human V1RL-receptors had to be addressed as true orphan receptors, so far. We found that four out of five V1RL-receptors are expressed in the human MOE. All five receptors have been rho-tagged, and expressed at the plasma membrane level of HeLa/Olf cells. We screened the human V1RL receptors against a collection of 47 odorants from different chemical classes. We de-orphaned all five human V1RL-receptors, and found that they responded to a variety of odorants in a combinatorial way, thus behaving like olfactory receptors from MOE. Testing chemically related odorants with variable sizes and functional groups, specific odorant profiles can be attributed to all human V1RL receptors. Our findings may support the notion that the human MOE has adopted pheromone perception. V1RL-receptors in the human MOE may function as odorant or pheromone receptors. [Poster, Saturday, April 16, 7:00pm-11:00pm]

Authors: Shirokova E. (1), Raguse J. (2), Meyerhof W. (1), Krautwurst D. (1) 1 Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany; 2 Clinic and Policlinic for SLIDES and Maxillofacial Surgery and Plastic Surgery, Charité - Campus Virchow Hospital, Berlin, Germany; contact: Elena Shirokova; email: chirokov@mail.dife.de

ODORPRINTS: Work over the past 25 years has shown that genes of the major histocompatibility complex (MHC), which play a well-established role in immune recognition, also influence mating preference and other social behaviors in fish, rodents, and humans. These studies led to the notion that MHC molecules are a source of unique individual odors that somehow influence the recognition of individual conspecifics. Less clear, however, are the exact cellular and molecular mechanisms by which this can occur. MHC molecules are part of an elaborate peptide presentation system. Here, we show that small peptide ligands of MHC class I molecules function also as social recognition signals in the mammalian nose, thus providing a novel molecular link between the immune system and the sense of smell. The availability of a large family of social recognition signals involving several thousand structurally defined peptide ligands provides unique opportunities to explore a variety of fundamental olfactory questions including how these molecules are encoded by neuronal populations and their receptors, what the structure-function relationships between peptide ligands and their receptors might be, and how social memories based on the recognition of these signals are formed. Supported by grants from NIH/NIDCD. [Oral, Friday, April 15, 9:00pm ]

Author: Zufall F. Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD; contact: Frank Zufall; e-mail: fzufa001@umaryland.edu

SELECTION AND ODOR GENES: Olfactory receptor (OR) genes constitute the basis of the sense of smell and are encoded by the largest mammalian gene superfamily, with more than 1,000 genes. While the OR gene repertoires of mouse, dog, chimpanzee and human are roughly the same size, the proportion of putatively functional OR genes is higher in rodents, dogs and new world monkeys than in old world monkeys and apes, and lowest in humans. By comparing the entire human and chimpanzee OR gene repertoires, we estimate that this additional accumulation of pseudogenes in humans started ~3.2 MYA. We further estimate that 133 human intact OR genes are evolving under no evolutionary constraint and may become pseudogenes over time. Our analysis identified one chimpanzee-specific OR subfamily expansion and four human-specific expansions. We also found support for the action of positive selection on a subset of human and chimpanzee OR genes. These observations suggest that while overall humans appear to have a reduced need for the sense of smell compared to chimpanzees, specific-sensory requirements have shaped the functional human OR gene repertoire. [Oral , Sunday, Apr 17, 7:00PM]

Author: Gilad Y. Yale University, New Haven, CT; contact: Yoav Gilad; email: yoav.gilad@yale.edu

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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