This thesis investigates hair cell (He) homeostasis and the compression wave cochlear amplifier. In the first part of the thesis, an accurate physiological treatment of a generic HC is conducted using a nonlinear distributed parameter physical model. This model includes the major ionic species (sodium, potassium and chlorine), defining the active cellular homeostatic properties. This model is used for transient response analysis. Resting state and transient responses of the HC model are in excellent agreement with the experimental literature. HCs in this model are most simply classified as instantaneous nonlinear transduction devices (i. e. their homeostatic mechanisms are not significantly frequency selective). A compression wave cochlear amplifier (CW-CA) is defined and modelled for the first time in the second part of the thesis. It is a physiological model that addresses three main elements present in the peripheral hearing circuit: cochlear mechanics, HC nonlinearity, and neurology. The actual physiological feedback mechanism of the CW-CA is realistic. A passive travelling wave (or other mechanical) vibration is the input to the system. Whilst the travelling wave wiggles the Organ of Corti, the compression wave pulsates it. The CW-CA is an alternative to the physiologically ill-defined locally active travelling wave cochlear feedback amplifier proposed by others. The new CW-CA model results in a cycle-by-cycle amplifier with nonlinear response. It is capable of assuming an infinite number of different operating states. The stable and first few amplitude-limited unstable states are significant in describing the operation of the peripheral hearing system. The CW-CA model can explain a large number of hearing phenomena. Several of these are investigated by means of a system analysis for both the stable and unstable cases. The system is studied and the tone, two-tone suppression and distortion product responses are found to align well with published results. Explanations for various mechanical, HC and neurological phenomena are discussed and presented. For example, previously poorly understood phenomena such as otoacoustic emissions and neural spontaneous rates are accounted for.

Offprints of the author's articles inserted / Bibliography: leaves [122]-145 / vii, 147 leaves, [22] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1985

Dissertation (Ph.D.)--University of Toledo, 2007. / Typescript. "Submitted as partial fulfillment of the requirements for the Doctor of Philosophy degree in Psychology." Bibliography: 76-83.

The present investigation deals with the study of non-glandular epidermal hairs from the leaves of two hundred representative dicotyledons of forty-eight families in the Central North Texas area. Special attention has been given to the Compositae and Leguminosae in an effort to find a possible correlation between epidermal hair morphology and the taxonomic position of the plants concerned.

No description available.

Dying produces human remains and is a unique period of human lives that remains poorly understood. The aims of this research were to validate the use of hair cortisol concentration (HCC) analysis in the study of stress at the end of life and to explore the effects of biocultural factors on stress experience in the last months of life. This study examined the dead from the 1st century CE Egypt, 19th-20th century Missouri, and 21st century Florida. A framework of embodiment and the good death was employed to interpret lived experience from HCC and examine the relationships between HCC, death, cause of death, duration of disease, and medical care and treatment. HCC in the dead is higher than in the living, varies considerably between individuals, and can fluctuate across the last months of life. High HCC at the end of life cannot be easily accounted for by medications, serious disease, or decomposition; are within possible biological ranges; and are dynamic. However, leaching of cortisol from the archaeological samples is likely. Duration of disease or presence of multiple medical conditions does not influence HCC. While modern medical advancements do not improve stress levels in the dead, a reduction in stress is observed following hospital entry in the past. HCC is a valid measure of stress at the end of life. The last months of life are periods of significant stress but dying is an inherently personal and dynamic experience that varies between individuals and over many months leading up to death due to the interaction of multiple biocultural factors. These findings contribute to the understanding of a unique period of individual lives, suggest that studies of HCC in bioarchaeology must focus on the dying period and be wary of leaching, and highlight the potential of HCC in palliative care research. / Dissertation / Doctor of Philosophy (PhD) / Today, death is often regarded with uncertainty and even fear, yet little is known about the experience of dying, especially in the past. Dying is difficult to study in modern people because of communication challenges and the number of complex factors at play while studies of the past are limited because human remains do not reveal how individuals felt. A better understanding of the dying experience can help bioarchaeologists clarify the relationship between dying, death, and skeletal remains and could help improve the care of dying people today. This research evaluated a new method of stress assessment to study experiences in the last months of life in archaeological, historic, and modern samples. Hair cortisol concentration (HCC) analysis measures stress hormones in human hair to reconstruct stress experience at the time the hair was growing. High levels of HCC in dead individuals from 1st century AD Egypt, 19th-20th century Missouri, and 21st century Florida indicate that dying is stressful across time and place. HCC values from the Egyptian sample were higher than most living people but were lower than other archaeological samples which may be a result of cortisol leaching out of the hair shaft after death. Although higher than living people, HCC levels still differed between individuals and across individual hair shafts, indicating that stress experience can be different between individuals and change over an individual’s final months. These differences are not a result of biological factors such as duration of disease or the presence of certain preexisting conditions suggesting that stress at the end of life is complex. Despite advancements in medicine, the modern sample displayed similar HCC levels to those from earlier historic periods and for a number of individuals from the historic sample, hospital entry led to a temporary reduction in HCC levels. Together, these findings suggest that, while modern medical advancements have not improved stress levels at the end of life, some aspects of care could reduce stress. The results of this study indicate that dying is a stressful, complex, and dynamic phenomenon that modern medical treatment alone may not be able to improve. Furthermore, studies of HCC in archaeology must focus on the effects of dying and be wary of leaching. Ultimately, HCC analysis could contribute to a greater knowledge of the dying experience, the understanding of past peoples, and improvement of the experience of dying.

No / We have assessed the histological preservation of naturally degraded human hair shafts, and then assayed each for levels of amplifiable mitochondrial DNA and damage-associated DNA miscoding lesions. The results indicate that as sample histology is altered (i.e. as hairs degrade) levels of amplifiable mitochondrial DNA decrease, but no correlation is seen between histology and absolute levels of mitochondrial DNA miscoding lesions. Nevertheless, amplifiable mitochondrial DNA could be recovered across the complete range of the histological preservation spectrum. However, when template copy number is taken into consideration, a correlation of miscoding lesions with histology is again apparent. These relationships indicate that a potential route for the generation of misleading mitochondrial sequence data exists in samples of poor histology. Therefore, we argue that in the absence of molecular cloning, the histological screening of hair may be necessary in order to confirm the reliability of mitochondrial DNA sequences amplified from hair, and thus represents a useful tool in forensic mitochondrial DNA analyses.

No / As a highly visual and social species we communicate significantly via our physical appearance. Thus, it is unsurprising that the phenotypic aspects (including color) of our skin and hair feature prominently in such communication. Perhaps, one of the more potent reminders of aging is the change in pigmentation from birth to puberty and through to young adulthood, middle age, and beyond. Indeed, the hair bulb melanocyte may be viewed as an exquisitely sensitive aging sensor. In this context, we can appreciate that the loss of pigmentation from the hair tends to be earlier and much more striking than the age-associated pigmentation changes that we see in the epidermis. This phenotypic difference between the hair follicle and the epidermis-melanocyte subpopulations is of considerable interest, not least as both subpopulations originate from the same embyrologic neural crest and that the melanoctye stem cells in the adult hair follicle can occupy vacant niches in the epidermis. A major source of the differential aging of melanocytes in the hair bulb vs. the epidermis is likely due to the former¿s stringent coupling to the hair growth cycle when compared with the latter¿s continuous and UV-sensitive melanogenesis. Also likely to be involved is the maintenance of permissive microenvironments in these different skin compartments including their differing redox environments and variable connectivity with neuroendocrine axis. Over the last few years, we and others have striven to develop advanced cell culture methodologies for isolated hair follicle melanocytes and for intact anagen hair follicle organ culture, which may provide research tools to elucidate the regulatory mechanisms of hair follicle pigmentation. Others have assessed the robustness of the hair follicle-melanocyte stem compartment with age and other functional stressors. In the long term, it may be feasible to develop strategies to modulate some of these aging-associated changes in the hair follicle that impinge particularly of the melanocyte populations.

No / Chemotherapy has severe side effects in normal rapidly proliferating organs, such as hair follicles, and causes massive apoptosis in hair matrix keratinocytes followed by hair loss. To define the molecular signature of hair follicle response to chemotherapy, human scalp hair follicles cultured ex vivo were treated with doxorubicin (DXR), and global microarray analysis was performed 3 hours after treatment. Microarray data revealed changes in expression of 504 genes in DXR-treated hair follicles versus controls. Among these genes, upregulations of several tumor necrosis factor family of apoptotic receptors (FAS, TRAIL (tumor necrosis factor–related apoptosisinducing ligand) receptors 1/2), as well as of a large number of keratin-associated protein genes, were seen after DXR treatment. Hair follicle apoptosis induced by DXR was significantly inhibited by either TRAIL-neutralizing antibody or caspase-8 inhibitor, thus suggesting a previously unreported role for TRAIL receptor signaling in mediating DXR-induced hair loss. These data demonstrate that the early phase of the hair follicle response to DXR includes upregulation of apoptosis-associated markers, as well as substantial reorganization of the terminal differentiation programs in hair follicle keratinocytes. These data provide an important platform for further studies toward the design of effective approaches for the management of chemotherapy-induced hair loss.

Yes / Hair fibres are extraordinary materials, not least because they are exquisitely formed by each of the 5 million or so hair follicles on our bodies and have functions that cross from physiology to psychology, but also because they have well known resistance to degradation as seen in hair surviving from archaeological and historical samples [1]. Hair fibres on the head grow at around 1cm each month, together totalling approximately 12km of growth per person per year. Each fibre is incredibly strong for its small diameter; with one fibre typically holding 100g and together a well-formed ponytail [allegedly] has the collective strength to support the weight of a small elephant! Hair – and from here I mean scalp hair – is under constant scrutiny by each of us; whether it be style, split ends, the first few grey hairs or the collection of hairs in the shower that should be firmly attached - leading to the fear that is hair loss.