The ear is the organ used for hearing and maintaining equilibrium. In the inner ear, the vestibular system is responsible for the sense of balance. The main organs of the vestibular system are the semicircular canals, the saccule, and the utricle. Within each of the vestibular organs, sensory receptors in the form of hair cells detect motion and send a message to the brain for interpretation. Hair cells found in different parts of the inner ear are structurally different and are mechanically specialized to perform different functions. In this study, the linear and torsional stiffnesses were measured for hair cells located in the red ear slider turtle utricle. The system used to measure the stiffnesses was composed of a glass whisker (attached to a pipette) used to produce a force on the tip of the bundle, an extrinsic Fabry-Perot interferometer (EFPI) to measure the displacement of the pipette, and a photoelectronic motion transducer (PMT) to measure the displacement of the bundle. Using the measured values of whisker stiffness, whisker displacement, and bundle displacement, the stiffness of the bundle was calculated using statics. For each bundle tested, the location of the bundle was determined by measuring its position from a landmark in the utricle, the line of polarity reversal, characterized by a 180o change in direction of the hair bundles. Stiffness results showed that the linear stiffness of a bundle increased in the area surrounding the line of polarity reversal, otherwise referred to as the striolar region (average linear stiffness of 2.27 E-04 N/m). The average linear stiffness value of bundles found lateral to the striolar region was 6.30 E-05 N/m and in the region medial to the striolar region was 1.16 E-04 N/m. A wide range of linear stiffnesses were found in hair cells medial to the striolar region. There was no correlation found between the torsional stiffness of a bundle and its position and the height of a bundle and its linear or torsional stiffness. As the force applied to a hair bundle was increased, the measured linear stiffness of the bundle also increased. / Master of Science

The vestibular system is one of our main organs responsible for the sense of balance. This system is located within the inner ear and contains cells with ciliary bundles. These hair cells are transducers that convert a mechanical movement, detected by the bundle of cilia extending from their top surface, into an electrochemical signal to be sent to the brain. The bundles vary structurally within the organs of the inner ear, and this structural difference may play a role in the mechanical properties of each bundle. Analyzing the mechanical properties of the cells will provide information necessary for understanding the transduction process. In an effort to evaluate one of these properties, cell bundle stiffness, a system was designed to mechanically stimulate the bundles within their physiological range and then measure the resulting displacement. The mechanical stimulation was the result of a force applied to the tip of a bundle with the end of a glass whisker. The distance the base of the whisker moves is measured by an extrinsic Fabry-Perot interferometer (EFPI). The magnitude of this movement is compared with the amount the bundle is deflected, detected by a photoelectronic motion transducer (PMT). Knowing these displacements and the stiffness of the glass whisker, simple kinematics is used to determine the bundle stiffness. System tests were conducted on imitation bundles (whiskers of known stiffness) and the experimental stiffness differed from the known value by less than 4.5% for every test. These results lead us to conclude the system was in good working order and could be used to conduct tests on cell bundles. For tissue tests, this work focused on the hair cells located within the utricle, which senses linear accelerations of the head. Within the utricle, we examined two types of hair cells: non-striolar (medial type II) and striolar. Tests on twelve medial type II cells found bundles ranging in stiffness from 0.26 to 2.62 x 10⁻⁵ N/m. Results with striolar bundles provided a range from 2.83 to 27.10 x 10⁻⁵ N/m. The results of the preliminary tissue tests lead us to conclude that the average stiffness of the striolar and non-striolar bundles seems to vary by an order of magnitude. This is consistent with the relative relationship produced through a computer model. However, the model predicted larger stiffness values for both types of cells. / Master of Science

No / The pro-opiomelanocortin (POMC)-derived peptides, -melanocyte-stimulating hormone, and adrenocorticotropic hormone, are important mediators of human skin pigmentation via action at the melanocortin-1 receptor. Recent data suggests that such a regulatory role also exists for the endogenous opiate, -endorphin (-END). A role for this -END in the regulation of follicular pigmentation, however, has not been determined. This study was designed to examine the involvement of the -END/-opiate receptor system in human follicular melanocyte biology. We employed RT-PCR, and immunohisto/cytochemistry and immunoelectron microscopy using -END and -opiate receptor specific antibodies and a functional role for -END was assessed by direct stimulation with the peptide. This study has demonstrated that human hair follicle melanocytes (HFM) express mRNA for the -opiate receptor and POMC. Furthermore, -END and its high affinity -opiate receptor are expressed at the protein level in glycoprotein100-positive follicular melanocytes and as a function of their anatomic location and differentiation status during the hair growth cycle. Functional studies revealed that -END is a modifier of HFM phenotype via its ability to upregulate melanogenesis, dendricity, and proliferation. These findings suggest a new regulatory role for -END in human HFM biology, providing a new research direction into the fundamental regulation of human hair pigmentation.

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No / The 15th century Inuit mummies excavated at Qilakitsoq in Greenland in 1978 were exceptionally well preserved and represent the largest find of naturally mummified specimens from the Arctic. The estimated ages of the individuals, their distribution between two adjacent graves, the results of tissue typing, and incomplete STR results led researchers to conclude that the eight mummies formed two distinct family groups: A grandmother (I/5), two daughters (I/3, I/4), and their two children (I/1, I/2) in one grave, and two sisters (II/6, II/8) and a daughter (II/7) of one of them in the other. Using mtDNA from hair and nail, we have reanalyzed the mummies. The results allowed the unambiguous assignment of each of the mummies to one of three mtDNA haplogroups: A2b (I/5); A2a (I/2, I/3, II/6, II/8); A2a-311 (I/1, I/4, II/7), excluded some of the previous relations, and pointed to new ones. I/5 is not the grandmother/mother of the individuals in Grave I, and she is not maternally related to any of the seven other mummies; I/3 and I/4 are not sisters and II/7 is neither the daughter of II/6 nor of II/8. However, I/1 may be the child of either I/4 or II/7 and these two may be sisters. I/2 may be the son of I/3, who may be the daughter of either II/6 or II/8, and these two may be sisters. The observation of haplogroups A2a and A2b amongst the 550-year-old Inuit puts a lower limit on the age of the two lineages in Greenland.

No / We have investigated the susceptibility of degraded human hair shaft samples to contamination by exogenous sources of DNA, including blood, saliva, skin cells, and purified DNA. The results indicate that on the whole hair shafts are either largely resistant to penetration by contaminant DNA, or extremely easy to successfully decontaminate. This pertains to samples that are both morphologically and biochemically degraded. We suggest that this resistance to the incorporation of contaminant DNA relates to the hydrophobic and impermeable nature of the keratin structures forming the hair shaft. Therefore, hair samples represent an important and underestimated source of DNA in both forensic and ancient DNA studies.

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