3. Electronic Theses and Dissertations (ETDs)

Now showing 1 - 4 of 4

Anatomy of the Tree Pangolin (Manis tricuspis) Brain
(2019) Aminu, Imam
Pangolins are the most highly trafficked mammals globally, and as such are under great threat of extinction. Unfortunately, our knowledge of their biology, and thus our ability to counter such threats through targeted breeding and re-introduction program is restricted. Historically, only a handful of scientific papers have examined aspects of the anatomy of the central nervous system, with the current thesis addressing this gap in our knowledge by providing comprehensive architectural and chemical neuroanatomical analyses of portions of the central nervous system of the tree pangolin (Manis tricuspis) including qualitative and quantitative analyses of: the olfactory system; the unusual locus coeruleus complex; the hippocampal formation; the diencephalon; and the brainstem and cerebellum. The observations made in the current series of studies highlights that the majority of the anatomy and neurochemistry of the tree pangolin central nervous system is what could be considered typical for a generalized mammal. Despite this, many observations of either specializations or reductions of specific parts of the nervous system were observed. Features that are of specific interest in terms of understanding pangolin behaviour include a very short spinal cord, enhanced olfactory and auditory systems, unusual aspects related to both the cholinergic and noradrenergic systems, and a rostral decussation of the pyramidal tract connecting with an enlarged hypoglossal nucleus, which is associated with a specialized serotonergic innervation (raphe obscurus nucleus) and an unusual architecture of the salivatory nuclei of the medulla oblongata. In summary, the observations made appear to relate to neural control of behaviours associated with predator avoidance (spinal cord, olfactory and auditory systems), the location of food (olfactory and auditory systems), sleep (cholinergic and noradrenergic systems), and the ingestion of food (pyramidal tract, hypoglossal nucleus, raphe obscurus, salivatory nuclei). These observations indicate that interesting avenues for developing a greater understanding of pangolin behaviour should focus in these areas as indicated by the current neuroanatomical analysis. While additional anatomical studies need to be undertaken, for example on the amygdaloid complex and cerebral cortex, the current series of studies has identified several important aspects of pangolin biology that should help guide future research into these most unusual mammals.
An examination of some physiological and instrumental parameters affecting the contraction of circulated mammalian muscle.
(1963) Geffen, Laurence Basil
The rapid progress of the last decade has made possible the synthesis of the molar and molecular approaches to the mechanism of muscle contraction. It is now possible to offer a molecular explanation for many of the gross mechanical properties of muscle. As a result there is a necessity to re-examine the validity of the classical terminology used to describe these properties, and to define them more accurately. Since Pick (1882), various "types” of contraction have been ascribed to muscle, according to the changes in length and tension of the activated muscle. These are dependent upon the load opposing the muscle. If the load is less than the force developed in the muscle, shortening occurs at a constant tension just exceeding the load. This process is termed isotonic contraction. If, on the other hand, the load is equal to the tension developed in the muscle,there is no overall change in length, although tension in the system rises. This constitutes an isometric contraction. Recently, studies of the ultra-structure and mechanical properties of muscle have revealed inherent difficulties in the classical terminology.
A neuroanatomical evaluation of cholinergic,catecholaminergic, serotonergic and orexinergic neural systems in mammals pertaining to the phylogenetic affinities of the Chiroptera
(2015) Calvey, Tanya
One of the few remaining mysteries in mammalian phylogeny is the issue of Chiropteran phylogeny. In order to further investigate the diphyletic hypothesis that states that Megachiroptera evolved from primate-like gliders and that Microchiroptera evolved from insectivores, the cholinergic, catecholaminergic, serotonergic and orexinergic systems were analyzed in, not only five insectivores (Crocidura cyanea, Crocidura olivieri, Sylvisorex ollula, Paraechinus aethiopicus and Atelerix frontalis) and three prosimian primates (Galagoides demidoff, Perodicticus potto and Lemur catta), but in species from other orders of interest including the Afrotheria (Potamogale velox, Amblysomus hottentotus and Petrodromus tetradactylus), Lagomorpha (Lepus capensis) and Scandentia (Tupaia belangeri). Brains of the mammals were coronally sectioned and immunohistochemically stained with antibodies against cholineacetyltransferase, tyrosine hydroxylase, serotonin and orexin-A. The presence or absence of 93 nuclei within these neuromodulatory systems was entered into modern cladistics software for analysis of the 13 studied species, as well as an additional 40 previously studied mammals. The majority of nuclei revealed in the current study were similar among the species investigated and to mammals generally, but certain differences in the nuclear complement highlighted potential phylogenetic interrelationships. The Afrotherian, A. hottentotus, presented unusual cholinergic interneurons in the cerebral cortex, hippocampus, olfactory bulb and amygdala, and exhibited an unusual foreshortening of the brain, such that a major mesencephalic flexure in the brainstem was evident. The Afrotherian, P. tetradactylus, lacked the catecholaminergic A15d nucleus as in a previously studied member of Macroscelididae. The three Insectivoran shrews lacked the cholinergic parabigeminal and Edinger-Westphal nuclei, had a mediodorsal arch of the cholinergic laterodorsal tegmental nucleus, lacked the catecholaminergic A4 and A15d nuclei and presented an incipient ventral division of the substantia nigra which is identical to previously studied Microchiroptera. All three prosimians presented a central compact division of catecholaminergic locus coeruleus (A6c) surrounded by a shell of less densely packed (A6d) tyrosine hydroxylase immunopositive neurons. This combination of compact and diffuse divisions of the locus coeruleus complex is only found in primates and Megachiropterans of all the mammalian species studied to date. T. belangeri of the Scandentia contained ChAT+ neurons within the nucleus of the trapezoid body as well as the superior olivary nuclear complex, which has not been described in any mammal studied to date. L. capensis of the Lagomorpha presented vi the rodent specific rostral dorsal midline medullary nucleus (C3), while T. belangeri was lacking both the ventral and dorsal divisions of the anterior hypothalamic group (A15v and A15d), and both species were lacking the primate/Megachiropteran specific compact portion of the locus coeruleus. Our neuroanatomical analysis suggests a phylogenetic relationship between the Soricidae (shrews) and the Microchiropterans, supports the phylogenetic grouping of primates with Megachiropterans, confirms previous molecular evidence of the relationship between lagomorphs and rodents within the super-order Glires, and suggests that primates are phylogenetically closer to Megachiroptera than to any members of the Euarchontoglires. The cladistic analysis confirmed the neuroanatomical analysis with the most parsimonious tree placing Megachiroptera into the Euarchontoglires as a sister group to primates and the Microchiroptera next to Soricidae within the Laurasiatheria.
Some new machaerodonts from Makapansgat limeworks
(2015-02-13) Collings, G E

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