by Shuk-man Yuen. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Bibliography: leaves 108-121. / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- General Introduction --- p.1 / Chapter 1.2 --- Neural Regulation of Muscle Development --- p.3 / Chapter 1.3 --- "Changes in Motoneuron Number, Motoneuron Properties and Innervation during Development" / Chapter 1.3.1 --- Decrease in Motoneuron Number --- p.6 / Chapter 1.3.2 --- Reduction of Synaptic Connections --- p.7 / Chapter 1.3.3 --- Changes in Motoneuron Properties during Development --- p.9 / Chapter 1.4 --- Neural Influence on Muscle Properties in Adult Mammals / Chapter 1.4.1 --- Effect of Denervation on Muscle Properties --- p.10 / Chapter 1.4.2 --- Plasticity of Muscle Properties --- p.12 / Chapter 1.5 --- Partial Denervation --- p.15 / Chapter CHAPTER 2 --- MATERIALS AND METHODS / Chapter 2.1 --- General Plan --- p.22 / Chapter 2.2 --- Normal Unoperated Group / Chapter 2.2.1 --- Innervation of the SOL and EDL --- p.23 / Chapter 2.2.2 --- Tension Recordings --- p.24 / Chapter 2.2.3 --- Contributions of L4 and L5 to Normal Tension of the SOL and EDL --- p.26 / Chapter 2.3 --- Young Denervated and Adult Denervated Groups / Chapter 2.3.1 --- Unilateral Partial Denervation --- p.27 / Chapter 2.3.2 --- Tension Recordings --- p.28 / Chapter 2.3.3 --- Measurement of Contraction and Relaxation Speeds --- p.28 / Chapter 2.3.4 --- Recovery in Tension of Partially Denervated Muscles --- p.29 / Chapter 2.3.5 --- Motor Unit Number and Size --- p.29 / Chapter 2.3.6 --- Resting Membrane Potential --- p.31 / Chapter 2.3.7 --- Histometric Analysis and Histochemical Study --- p.32 / Chapter 2.3.8 --- Immunocytochemical Study on Different Types of Myosin --- p.34 / Chapter 2.3.9 --- Histological Study on Innervation of Muscle Fibres --- p.35 / Chapter 2.4 --- Retrograde HRP Labelling for HRP Group --- p.37 / Chapter 2.5 --- Statistic Analysis --- p.39 / Chapter CHAPTER 3 --- RESULTS / Chapter 3.1 --- Contribution of Spinal Nerves to Tension in Normal Unoperated Group --- p.44 / Chapter 3.2 --- Results from Young Denervated and Adult Denervated Groups / Chapter 3.2.1 --- Recovery in Tension --- p.45 / Chapter 3.2.2 --- Changes in Other Contractile Properties --- p.48 / Chapter 3.2.3 --- Motor Unit Number and Size --- p.49 / Chapter 3.2.4 --- Resting Membrane Potential of Adult Denervated Group --- p.51 / Chapter 3.2.5 --- Changes in Cross-sectional Area of Whole Muscle and Number of Muscle Fibres --- p.52 / Chapter 3.2.6 --- Histochemical Properties and Types of Myosin --- p.53 / Chapter 3.2.7 --- Histological Study on Innervation of Partially Denervated Muscles --- p.56 / Chapter 3.3 --- Results of HRP Group --- p.58 / Chapter CHAPTER 4 --- DISCUSSION / Chapter 4.1 --- Contribution of Spinal Nerves to Tension Development --- p.91 / Chapter 4.2 --- Recovery of Partially Denervated Muscles --- p.93 / Chapter 4.3 --- Time Courses of Functional Recovery --- p.98 / Chapter 4.4 --- Effect of Partial Denervation on Properties of Muscles --- p.100 / Chapter CHAPTER 5 --- CONCLUSION --- p.106 / REFERENCES --- p.108

The skin is the largest organ of the body and provides many functions. Among tetrapod vertebrates, amphibian skin is semi-permeable and responsible for a greater proportion of water absorption and gas exchange. Myriad factors affect the physiological performance of amphibian skin. Morphological traits linked with amphibian skin physiology or ecology have remained difficult to discern because of a lack of quantitative comparative research and the discovery of sources of intraspecific variation that are mostly ignored in study designs. This thesis aims to address the effects of these sources of variation using a trait that is known to vary between sexes, among seasons, and among body regions and thought to be linked with physiology or ecology, skin thickness. The first source of variation addressed is sexual dimorphism. Specimens of the white-lipped treefrog, Litoria infrafrenata, that display sexual dimorphism in body size and skin thickness were used to test if body size was the main determinate of sexually dimorphic skin thickness. Size corrected values did not significantly differ between males and females, although the sample size was small. Seasonal variation in skin thickness has also been documented in some species, so the American bullfrog (Lithobates catesbeianus), the Northern leopard frog (L. pipiens), and the spring peeper (Pseudacris crucifer) from multiple months of the year were sampled to determine if skin thickness increased in the autumn or winter months. Seasonal skin thickening was only detected in L. catesbeianus, and skin from autumn and winter was significantly thicker than from earlier in the year. This pattern was also detectable in museum specimens collected 80 years ago, although the signal was damped, possibly due to preservation. Using a dataset of 10 species and published data, a general pattern was uncovered whereby the dorsal skin is the thickest region and the ventral thigh region is the thinnest. However, this pattern is not always true for every individual of every species (L. pipiens and P. crucifer) and in some species the dorsal skin is thinnest (Bokermannohyla alvarengai and Litoria infrafrenata). The same dataset found that skin thickness is significantly related to body size, as was found in the chapter on Litoria infrafrenata. Summer specimens of Lithobates catesbeianus were outliers below the interspecific regression line and winter specimens fell within the range of variation of other species, hinting that seasonal skin thickening could be renamed seasonal skin thinning in this species. Finally, a link between ecology and skin thickness was tested using the 10 species from previous analyses and data from the literature. At a phylogenetially broad scale, body size explained a greater amount of the variation in environmental parameters than skin thickness. At smaller taxonomic scales, skin thickness appears more closely linked with ecology. It is concluded that amphibians generally follow an allometric trend for skin thickness and when faced with suboptimal conditions over long periods of time, evolve integumentary structures like iridiophores to compensate for any physiological disadvantage of an ‘ideal’ skin thickness. In the interim, however, skin thickness may change, thus sacrificing e.g. mechanical support.

No description available.

Striped trumpeter (Latris lineata) is a new candidate species for aquaculture in temperate Australia. Survival of larvae prior to flexion has proven a bottleneck in the production of this species for culture. In addition, almost all juveniles cultured to date exhibit malformations of the jaw that may impede larval feeding success. Body size and morphology impose constraints upon feeding success in larvae of broadcast spawning fishes. Furthermore, larvae have an absolute reliance upon sense organs for the detection and subsequent capture of prey. In this study, aspects of morphological development and feeding performance were described in larval striped trumpeter. Chemosensory and mechanosensory organs were present and presumed functional soon after hatching, while the eye was functional coincident with first-feeding on day 7 post-hatching. The structure of the photoreceptors in different regions of the retina of the larvae suggested the area specialised for the most acute image formation corresponded to a visual field in the fronto-ventral region. Analysis of videocinematography of feeding larvae in the horizontal plane confirmed a forward-directed functional visual field. The area of the visual field increased with larval ontogeny from day 13 to day 17 post-hatching, due to the wider range of reactive angles used by older larvae. Maximum reactive distances of larvae to rotifer prey (~5.1mm) were 97% of larval standard length, while the distance at which larvae initiated a strike at the prey was much lower (~0.45mm) at 8% of larval standard length. Visual angles determined from larval feeding behaviour were higher than the minimum separable angles predicted by histology, such that the functional acuity of the larvae was not as good as that predicted by retinal structure. Jaw malformation was only evident in post-flexion larvae greater than 10 mm standard length and was characterised by an open jaw in which cartilage and bone elements appeared structurally normal but were in abnormal positions. The effects of light intensity and microalgal cell density (turbidity) on larval feeding behaviour were assessed in short-term feeding trials. None of the pre-flexion larvae used to investigate optimal light conditions for feeding exhibited jaw malformations. Larvae fed equally well in clearwater (no microalgal cells present) in a light intensity range of 1-10 umol.s-1.m-2. An ontogenetic improvement in photopic visual sensitivity of larvae was indicated by improved feeding at 0.1 umol.s-1.m-2 between day 8 and day 23 post-hatching. Algae-induced turbidity had different effects on larval feeding response dependent upon the previous visual environment of the larvae. Young larvae, day 9 post-hatching, reared in clearwater showed decreased feeding capabilities with increasing turbidity, while older clearwater reared larvae fed well at all turbidities tested. Likewise, greenwater (with microalgal cells present) reared larvae had increased feeding capabilities in the highest algal cell densities tested compared with those in low algal cell density, and clearwater to which they were naive. This study demonstrated that striped trumpeter larvae are primarily visual feeders with a small visual field relative to larval body size, that jaw malformation is unlikely to impede feeding in pre-flexion larvae, and that greenwater may provide a benefit to larval feeding although the previous visual environment of larvae affected subsequent feeding responses.

In order to understand the ecology of species, it is important to know how animals use their environment. This information can be determined at a range of spatial and temporal scales, and results may vary accordingly. The habitats that animals use determine resources available to them for different purposes (e.g. feeding and resting), and risks of predation to which they are exposed. Consequently, patterns of behaviour in relation to the environment are likely to influence survival and fitness. In Tasmania, Australia, three common and widely distributed native marsupial herbivores are the red-necked or Bennett's wallaby (Macropus rufogriseus rufogriseus), the red-bellied pademelon (Thylogale billardierii) and the common brushtail possum (Trichosurus vulpecula). Information on the behaviour of these species in relation to their environment is largely unavailable. This thesis describes the abundance, spatial organisation and habitat selection patterns of these three species, within a patchy forestry landscape. The five major habitat types within this environment were: (1) a prepared site that was planted with commercial Eucalyptus nitens seedlings during the study (referred to as 'young plantation'); (2) 5-7 year old E. nitens plantation; (3) grassland; (4) native forest; and (5) harvested uncleared land. Patterns of habitat use and selection were examined at three sequential spatio-temporal scales, within a hierarchy of decisions. These were: (1) location of home-range within the landscape, (2) feeding area within the home-range, and (3) vegetation consumed within one habitat, the young plantation. A radio-telemetry study of Bennett's wallabies, pademelons and possums was used to examine Scales 1 and 2 at the individual animal level. Animal surveys were carried out to examine Scale 2 for the entire herbivore community at the population level. These data were also used to estimate herbivore densities for the overall area and individual habitats. Fenced and unfenced vegetation plots, located within the young plantation, a highly used habitat, were monitored over time to examine Scale 3. As part of this research, modifications to common line-transect sampling methods were made. These enabled methods that are usually applied to daytime surveys in open habitat, to be used in nocturnal surveys in densely vegetated habitats. Accuracy testing of the radiotelemetry system is also described, as the patchiness of the landscape required careful interpretation of results. Results showed that, at night, wallabies and pademelons used all habitats, but consistently selected for open habitats (young plantation and grassland) across spatio-temporal scales. The use of these open habitats for feeding was confirmed by the large biomass of grass and forbs consumed by herbivores in a detailed study of vegetation on the young plantation. These patterns are consistent with their feeding strategies of grazer or mixed-feeder. During the day, the two macropod species avoided open habitats and showed strong selection for closed habitats. Wallabies selected for older plantation, while pademelons selected for native forest. This difference reflects their respective predator avoidance strategy (crypsis for pademelons) or escape response (flight for wallabies). Although shelter habitat was important to the two macropod species, their lack of selection at the home-range scale was suggested to reflect the fact that resting animals require little space. Patterns of habitat use and selection were difficult to interpret for possums, because results varied between the spatio-temporal scales. Spotlighting data showed that at night, possums selected for native forest, young plantation and particularly grassland at the population level. Radio-collared animals selected only for native forest. Older E. nitens plantations were avoided by possums at every level, and appeared to represent a biological desert to this species. High overall densities of wallabies and pademelons (0.3 and 1.5 animals.ha-1, respectively), and small, round, home-ranges (61.6 ha and 22.3 ha, respectively) suggested that these species benefited from the patchiness of this environment. This is attributed to the highly heterogeneous habitats, providing complimentary resources in the absence of ecotones or transitional flora zones, existing side by side, over a small spatial scale. In contrast, extremely low possum population density (0.04 animals.ha-1) and very large home-ranges (39.1 ha) suggested that resources, presumably den sites and/or food, were limited within this forestry environment. Results on the ecological aspects of the three herbivore species, described above, are put in the context of the Tasmanian forestry industry, particularly in relation to management of herbivore browsing damage to planted seedlings. Based on this work, I suggest that future management strategies could involve: (1) reducing fragmentation of the natural environment, which supports small home-ranges and high macropod densities, by designing larger, rounder plantations; (2) considering the placement of plantations in relation to the proximity of open (feeding grounds) and closed (shelter) habitats; (3) reducing or removing windrows from newly established plantations to restrict pademelons to the plantation edge; (4) deliberately retaining groundcover or using cover crops to provision herbivores with an alternative food source, as grasses and herbaceous dicots are eaten in preference to Eucalyptus nirens seedlings; (5) recognising that wallabies and pademelons remove a large biomass of groundcover and therefore, could play a positive role in weed control, reducing the need to herbicide plantations; (6) monitoring newly planted plantations at short and regular time intervals so that damage caused by insects versus mammals can be differentiated; and (7) avoiding planting in winter when macropods may have little alternative food to eat on newly established plantations.

A review of the literature on sodium distribution in muscle has been presented including the evidence for heterogeneous distribution and the possible morphological sites of localization of this sodium. Special attention was paid to influx studies on crustacean muscle. The review reveals that while there is good evidence for a heterogeneous distribution, the morphological sites and their associated concentrations of sodium remain obscure. The experiments described in this thesis were performed on muscle fibers of the giant barnacle Balanus nubilis. Single muscle fibers of Balanus are a unique biological preparation due to their large size and ease of dissection. The major disadvantage to single fiber Balanus preparations is the extent of the extracellular space or cleft system. This cleft system contains approximately half the total fiber sodium in 6% of the fiber volume. The purpose of these experiments was to gain a picture of (22)Na+ entry into these single striated muscle fibers with special emphasis on the role of the extracellular space. A histological study revealed that the cleft system was more extensive than had been reported. From measurements made on light and electron microscope pictures it was concluded that no part of Balanus myoplasm was more than 1 - 2μ from a 0.02μ patent cleft. This study gave a picture of the morphological pathway for (22)Na+ diffusion in the extracellular space. Radioautography and radio isotope counting were two techniques used to examine (22)Na+ exchange between the extracellular space and the myoplasm. Since the extracellular space had a sodium concentration of 10 times the myoplasm, the cleft system should be adequately visualized by radioautography. However, the section thickness (15μ) and the high maximum energy of (22)Na+ (0.540MEV) limited the resolution of the radioautograms to 15 - 17.5μ. This resolution coupled with the extent of the cleft system prevented consistent radioautographic visualization of discrete clefts. Radioautographic analysis of fibers with minimal exposure (0.5 minutes) to (22)Na+ revealed a concentration gradient which could be used to define the extracellular pathway and its diffusion coefficient for Na+. The radius of the fiber cross section was found to be a reasonable approximation of the length of the pathway and the diffusion of (22)Na+ in the extracellular space along the pathway was as rapid as the self diffusion of (22)Na+ in dilute solution. A comparison of fibers that had spent 1.5 minutes in the (22)Na+ bath with similar fibers that had a 0.5 minute sucrose rinse revealed that the 0.5 minute sucrose rinse removed half of the (22)Na+ from the extracellular space. The 1.5 minute fibers and all fibers examined after periods in the (22)Na+ bath revealed a homogenous grain distribution in radioautograms. This data conflicted with the rate of (22)Na+ entry predicted by the 0.5 minute fibers. Inappropriate agitation of the 1.5 minute fibers was responsible for the lack of agreement. A further radioautographic study of (22)Na+ influx with experimental times 5, 20, 60 and 180 minutes was analyzed quantitatively. To substantiate this radioautographic study an influx experiment was done with times 5, 10, 20, 40 and 90 minutes. Each study demonstrated two compartments. An initial rapidly exchanging compartment with a half time of 6 - 10 minutes was identified as the extracellular space. The extracellular space contained approximately half the fiber sodium. Both studies detected a rnyoplasmic influx compartment which was still exchanging when the experiments were terminated. The calculated rate constant for myoplasmic exchange (5.6 x 10(-3)/minute) was in good agreement with the value of Allen and Hinke. In conclusion, a useful technique for the radioautography of soluble substances was developed. Both a morphological and a physiological picture of the pathway for (22)Na+ diffusion in the extracellular space was developed. The size and half time of loading of the extracellular space was verified. The myoplasmic influx component was identified by two methods. From these studies emerges a more comprehensive picture of the extracellular space as a pathway for diffusion in Balanus muscle. The failure to consider this compartment in microinjection or flux studies may result in ambiguous conclusions. / Land and Food Systems, Faculty of / Graduate

A study of muscle spindles in two synergistic avian muscles was undertaken to determine whether morphological or quantitative differences existed between muscle spindles residing in a slow-red (tonic) muscle and a fast-white (twitch) muscle. The avian anterior (ALD) and posterior (PLD) latissimus dorsi muscles were chosen since they are unique among vertebrates as paradigms of a slow-red and a fast-white muscle respectively. Serial frozen sections of muscle were stained with Haematoxylin and Eosin or Gomori triehrome and muscle spindles residing in the ALD were assessed and compared with those in the PLD with regard to organization, distribution and density, Contents of muscle spindles were examined for intrafusal fibre size, number and morphology. Attention was also directed to the relationship between muscle spindles and the surrounding extrafusal muscle in which they were located. Differences were found between muscle spindles residing in the two muscles. In the slow ALD, muscle spindles were relatively evenly distributed, whereas in the fast PLD, they were concentrated around the single nerve entry point into the muscle. The ALD muscle spindle index was the highest yet published for chicken muscle and was 2.3 times higher than that of its fast counterpart. A bimodal trend in intrafusal fibre diameter was noted in the ALD, and a trimodal trend was found in the PLD. The former had 42% fewer intrafusal fibres than the latter. Muscle spindles were shorter in the ALD, with an average length of 1.9mm compared with 2.3mm in the PLD. An interesting feature of the slow muscle was the monofibril muscle spindle, containing a single intrafusal fibre. With a few exceptions, ALD muscle spindles were located within the interfascicular perimysium close to a neurovascular trunk. PLD muscle spindles were rarely seen in these areas but were frequently found within a muscle fascicle, surrounded by closely apposed extrafusal fibres. Moreover, neurovascular trunks were less frequently seen in the PLD. As an adjunct to this study, three ALD-PLD pairs from the Storrs Connecticut strain of muscular dystrophic chickens were also examined to compare muscle spindles in these muscles with those of normal animals. In the PLD, which is known to exhibit early and progressive pathological change, muscle spindles appeared relatively normal until marked extrafusal fibre degeneration had occured. By this time evidence of muscle spindle involvement included capsular hypertrophy and intrafusal fibre splitting. Whereas the slow ALD has been reported to retain apparent normalcy in muscular dystrophy, subtle changes were seen in some of the muscle spindles examined. These included an increase in number of intrafusal fibres per muscle spindle compared with those in the normal. / Land and Food Systems, Faculty of / Graduate

In this study, I consider the comparative and functional anatomy of cerebrally related retial systems in the two constituent species (Monodon monoceros and Delphinapterus leucas) of the family Monodontidae (order Cetacea). The internal carotid arteries, the "classical" vessels of cerebral supply in vertebrates, are completely non-functional as cerebral supply vessels in the Monodontidae. Moreover, there are no other channels that contribute directly to intracranial supply. Rather, the brain, or more precisely, the entire central nervous system, is vascularized indirectly via an extensive arterial plexus or rete mirabile. This plexus is found in the thorax, lumbar region, neural canal and cranium. Vessels that contribute to retial formation are numerous and include those which in other mammals contribute directly to supply of the central nervous system and/or its membranes. Efferent retial vessels are few and include two pairs of subdural intracranial trunks that supply the brain, and numerous small segmental vessels that penetrate the spinal dura and vascularize the spinal cord. Subdural arterial circulation in the Monodontidae is modified after the basic mammalian pattern. Within the cranium, it is characterized by: (1) an incomplete circle of Willis (due to (a) independence of the anterior cerebral arteries and (b) the lack of anastomoses between the two pairs of trunks which take origin from the rete), (2) extensive cortical supply by the anterior choroid arteries, and (3) absence of a vertebral basilar system. Subdural arteries coursing to the spinal cord do so mainly between successive ventral spinal roots. An A. radicularis magna is not evident, nor are anterior or posterior spinal arteries. Hence, there are differences between the subdural circulatory patterns in the Monodontidae and those in other mammals, however the major site of vascular modification is epidural with formation of the rete mirabile. Though gross retial anatomy is the same in Monodon monoceros and Delphinapterus leucas, and is generally similar to that described for other odontocetes, there are two related characteristics that appear species specific: thoracic retial size and the number of intercostal spaces supplied by the supreme intercostal arteries. Both are larger in Monodon monoceros, as are hematological values (hematocrit and hemoglobin concentration) which, in this study, are used as indices of diving ability. These data are consistent with the hypothesis that cerebral related retia in the Cetacea are related to the diving habit. Microscopically, the rete generally consists of small muscular arteries embedded in fatty connective tissue interlaced with a few nerve trunks and veins. Arterial walls are characterized by a distinct internal elastic lamella, a tunica media of 12-14 layers of vascular smooth muscle, and an adventitia of alternating layers of collagen and elastin. Retial arteries are at best poorly innervated. The substructure of retial arteries resembles that of other mammalian arteries except for the presence of large deposits of glycogen (alpha particles) in vascular smooth muscle and endothelial cells. On the basis of this observation, and theoretical considerations, I generate the hypothesis that the rete may contribute to blood glucose levels during a dive. This hypothesis could not be tested directly, hence I chose an indirect approach involving biochemical and ultrastructural analyses. I conclude that free glucose release is not a major function of the rete since: (1) G-6-phosphatase activities are low, (2) LDH electrophoretic profiles suggest that most stored glycogen is used intrinsically, and (3) I could not demonstate glycogen deposits in retial vessels of other species. All proposed retial functions are evaluated, and I conclude that the system probably functions in a mechanical way (pressure reservoir) and that it does so passively. / Science, Faculty of / Zoology, Department of / Graduate

Submitted in fulfilment of the requirements for the degree of Ph.D in the F culty of Science, University of the Witwatersrand, Johannesburg. February 1957. / The roles played by fibrous proteins in nature are at present being intensively studied and some of the advances in our knowledge of these proteins are the subject of several recent symposia. (la,b) The powerful techniques of X-ray diffraction end electron— optic analysis as well as ran unprecendented improvement in the specificity and accuracy of chemical and chromatographic methods of analysis has led to ever increasing efforts to interpret biological phenomena within a framework of physicochemical principles. In many fields, particularly those of virus research and muscle contraction these efforts have already been rewarded by a large measure of success. In the present work, which forms part of a program of research into the chemistry of connective tissues of man and other vertebrates, the chemical properties and structural features of the extracellular collagenous proteins in some calcified and uncalcified connective tissues are compared. 'In vivo' calcification of connective tissue is generally thought to be the result of a physico-chemical combination between lima salt3 and the organic matrix mediated by the ionic and structural prop rties of the matrix and the activity of various cello and enzymes / IT2017

No description available.