Showing papers by "University of Queensland published in 1988"

Patterns of cell death.

Abstract: Cell death takes two distinct forms, necrosis and apoptosis. Necrosis is a degenerative phenomenon that follows irreversible injury. Apoptosis, in contrast, appears to be an active process requiring protein synthesis for its execution; it is implicated in physiological regulation of tissue size, and, where it occurs pathologically, a homeostatic role for the death is often evident. Morphologically, apoptosis involves condensation of the nuclear chromatin and cytoplasm, fragmentation of the nucleus, and budding of the whole cell to produce membrane-bounded bodies in which organelles are initially intact. These bodies are disposed of by adjacent cells without inflammation. Biochemically, there is distinctive internucleosome cleavage of DNA in apoptosis, which is quite different from the random DNA degradation observed in necrosis.

Kurtosis: A Critical Review

Abstract: We critically review the development of the concept of kurtosis. We conclude that it is best to define kurtosis vaguely as the location- and scale-free movement of probability mass from the shoulders of a distribution into its center and tails and to recognize that it can be formalized in many ways. These formalizations are best expressed in terms of location- and scale-free partial orderings on distributions and the measures that preserve them. The role of scale-matching techniques and placement of shoulders in the formalizations that have appeared in the literature are emphasized.

Immediate and chronic changes in responses of somatosensory cortex in adult flying-fox after digit amputation

Abstract: The somatosensory cortex of adult mammals has been shown to have a capacity to reorganize when inputs are removed by cutting afferent nerves or amputating a part of the body. The area of cortex that would normally respond to stimulation of the missing input can become responsive to inputs from other parts of the body surface. Although a few animals have been studied with repeat recording, no attempt has been made to follow the time-course of changes at cortical loci and the immediate effects of a small amputation have not been reported. We have followed the changes in response in the primary somatosensory cortex in the flying-fox following amputation of the single exposed digit on the forelimb. Immediately after amputation, neurons in the area of cortex receiving inputs from the missing digit were not silent but responded to stimulation of adjoining regions of the digit, hand, arm and wing. In the week following amputation, the enlarged receptive fields shrank until they covered only the skin around the amputation wound. The immediate response is interpreted as a removal of inhibition and the subsequent shrinking of the field may be due to re-establishment of the inhibitory balance in the affected cortex and its inputs.

The accuracy of manual diagnosis for cervical zygapophysial joint pain syndromes.

Abstract: The ability of a manipulative therapist to diagnose symptomatic cervical zygapophysial joint syndromes accurately was evaluated in a series of 20 patients. In 11 patients the presence, or absence, of a symptomatic joint was established by means of radiologically-controlled diagnostic nerve blocks. These patients were assessed by the manipulative therapist, without knowledge of the medical diagnosis. Another nine patients were first seen by the manipulative therapist whose diagnosis was then evaluated by means of diagnostic blocks. The manipulative therapist identified correctly all 15 patients with proven symptomatic zygapophysial joints, and specified correctly the segmental level of the symptomatic joint. None of the five patients with asymptomatic joints was misdiagnosed as having symptomatic zygapophysial joints. Thus, manual diagnosis by a trained manipulative therapist can be as accurate as can radiologically-controlled diagnostic blocks in the diagnosis of cervical zygapophysial syndromes. However, before generalized claims about the reliability of manual diagnosis can be made, further studies of this nature are required to validate intertherapist reliability and the ability of manual techniques to diagnose other spinal pain syndromes.

Peak density and distribution of ganglion cells in the retinae of microchiropteran bats: implications for visual acuity.

Abstract: Wehave estimated the total number, distribution and peak density of retinal ganglion cells (RGCs) in retinal wholemounts of several species of microchiropteran (echolocating) bats. The estimates are b

Note on the use of the Wigner distribution for time-frequency signal analysis

Abstract: It is shown that a correct use of the Wigner distribution (WD) for time-frequency signal analysis requires use of the analytic signal. This version, often referred to as the Wigner-Ville distribution (WVD), is straightforward to compute, does not exhibit any aliasing problem, and introduces no frequency artifacts. The problems introduced by the use of the Wigner distribution with a real signal are clarified. >

The innervation of the cervical intervertebral discs

Abstract: Microdissection and histologic studies were undertaken to determine the innervation of the cervical intervertebral discs. The cervical sinuvertebral nerves were found to have an upward course in the vertebral canal, supplying the disc at their level of entry and the disc above. Branches of the vertebral nerve supplied the lateral aspects of the cervical discs. Histologic studies of discs obtained at operation showed the presence of nerve fibers as deeply as the outer third of the anulus fibrosus. These anatomic findings provide the hitherto missing substrate for primary disc pain and the pain of provocation discography.

The British Discovery of Buddhism

Abstract: Preface Introduction 1. The discovery of Buddhism 2. Buddhism and the 'oriental mind' 3. The Buddha - from myth to history 4. The Victorians and Buddhist doctrine 5. Victorian precepts and Buddhist practice 6. 'The heathen in his blindness'? Conclusion Notes Bibliography Index.

English Grammar: An Outline

Abstract: 1. Preliminaries 2. The parts of speech: a preliminary outline 3. Verbs 4. The structure of kernel clauses 5. Tense, aspect and modality 6. Nouns and noun phrases 7. Adjectives, determinatives and numerals 8. Adverbs and prepositions 9. Clause type 10. Negation 11. The subordination of clauses 12. Thematic systems of the clause 13. Coordination.

Retinal topography in reef teleosts. I. Some species with well-developed areae but poorly-developed streaks

Abstract: The retinal ganglion cell layer of five species of teleosts has been studied from Nissl-stained whole-mounts and the distribution of neuronal elements determined quantitatively. Isodensity contour maps of neurons in the ganglion cell layer revealed areas of high density (areae centrales) predominantly in the temporal retina, but other areae were also found in the nasal and dorso-nasal retina. Neuronal densities within the ganglion cell layer at the areae centrales ranged from 0.4 x 10(4) to 4.7 x 10(4) cells/mm2. Species that were found to lack a horizontal streak of high ganglion cell density appear to be those whose behaviour suggests they possess an interrupted view of the sand-water horizon and are 'enclosed' species. Concentric density contours around an area centralis seem to be associated with enclosed environments. The relationship between retinal topography and niche is also discussed.

Retinal topography in reef teleosts. II. Some species with prominent horizontal streaks and high-density areae.

Abstract: The retinal ganglion cell layer of five species of reef teleosts was studied from Nissl-stained whole-mounts and the distribution of neural elements determined quantitatively. Iso-density contour maps

Attention Deficit Disorder-Hyperactivity and Academic Failure: Which Comes First and What Should Be Treated?

Abstract: Evidence on the relationship between attention deficit disorder-hyperactivity (ADDH) and learning difficulties is reviewed in the light of: (1) the degree of overlap between the two disorders, (2) possible causal directions between the two, and (3) the appropriate focus of treatment. The evidence suggests a substantial overlap in prevalence between the two types of disorder and that there is no qualitatively distinct pattern of cognitive deficits associated with each disorder. Furthermore, what longitudinal data there are suggest that learning difficulties lead to ADDH rather than the reverse. Finally, the appropriate focus of treatment would seem to be the learning difficulties of the child with ADDH. The authors recommend more longitudinal research on the relationship between ADDH and learning difficulties, particularly in terms of the potential behavioral effects of treating learning difficulties.

The effects of information load and information diversity on decision quality in a structured decision task

Abstract: The major objective of this research was to study the effects of information load and diversity on decision quality in a structured decision task. The concept of information load was subdivided into the concepts of (1) quantity of repeated dimensions and (2) quantity of different dimensions. The latter concept was called information diversity. Two other independent variables studied were task learning and decision experience. Decision quality was operationalized to decision accuracy and time. It was hypothesized that the relationship between the quantity of repeated dimensions and accuracy would be an inverted U curve, and that repeated dimensions and time would produce a U curve. The initial rise in the accuracy curve and fall in the time curve did not occur in the results but the remainder of the curves were largely supported. There were exceptions, however, that require further investigation. It was further hypothesized that higher diversity would result in lower accuracy and higher time, and that higher learning and experience would both result in higher accuracy and lower time. These hypotheses were also largely supported by the results. Again there were exceptions that require clarification. The results also showed a number of interesting interactions between variables. The practical implications of these findings for accounting and information systems were outlined.

Insulin stimulates protein synthesis in compacted mouse embryos

Abstract: Preliminary work suggested that insulin affects preimplantation mouse embryos. We investigated the effects of insulin on incorporation of [3H]-leucine by embryos cultured for long (greater than 24 h) or short (4 h) terms with insulin. Insulin stimulated incorporation by compacted 8-cell embryos, blastocysts and expanded blastocysts. The stimulation in blastocysts had an EC50 of 0.5 pM in the presence of 1 g/L BSA and was blocked by anti-human insulin anti-serum. Inclusion of insulin in the medium elevated the levels of incorporation towards those of embryos developing in vivo. The stimulation was not observed in uncompacted 8-cell embryos. The ontogeny of stimulation at compaction coincides with a switch in energy dependence from lactate and pyruvate to glucose and an increase in protein synthetic activity.

Fitting Mixture-Models to Grouped and Truncated Data Via the Em Algorithm

Abstract: The fitting of finite mixture models via the EM algorithm is considered for data which are available only in grouped form and which may also be truncated. A practical example is presented where a mixture of two doubly truncated log-normal distributions is adopted to model the distribution of the volume of red blood cells in cows during recovery from anemia.

Children's knowledge of contagion and contamination as causes of illness.

Abstract: Children's knowledge of contagion and contamination as causes of illness was examined in 3 experiments. In Experiment 1, preschoolers and children in grades 1 and 3 were shown videotaped segments of puppets with colds and toothaches who explained their ailments in terms of contagion and immanent justice. The children were instructed to evaluate and correct the puppets' explanations and, in addition, to indicate the possible effects on health of drinking milk that had come into contact with objects such as a cockroach, used comb, and spoon. Even preschoolers displayed some knowledge of contagion and contamination. However, compared to the third graders, younger children were less likely to reject proximity to a sick person and naughty behavior as causes of toothaches. They were also more likely to indicate that to drink milk that had come into contact with a spoon was unhealthy. In Experiment 2, preschoolers rejected the proposition that an ailment caused by accident (i.e., a scraped knee) is contagious and, in Experiment 3, they generally accepted that contamination through contact with a dirty spoon can be prevented by washing. Altogether, preschoolers have a more substantial knowledge of contagion and contamination than has been estimated previously. The results are discussed in terms of children's ability to understand causal relations.

The performance of unseasoned new equity issues-cum-stock exchange listings in Australia☆

Abstract: The market behaviour of unseasoned new issues of common stock at the time of initial listing and during the period following initial listing on the Sydney Stock Exchange is investigated. The results indicate large and widespread initial returns to the new issue-cum-listing process. The average aftermarket performance was negative but was not statistically significant. We suggest that the joint process of initial issue-cum-listing in Australia, the listing requirements of the Australian Associated Stock Exchanges and the vesting of allocation rights to the issue in the broker, together with barriers to entry to stockbroking in Australia, provided the market structure which facilitated underpricing of the new issues.

Metalinguistic ability and early reading achievement.

Abstract: This study explored the conceptual status of metalinguistic ability by determining whether or not metalinguistic ability can account for variation in early reading achievement independently of more general language abilities. First-grade children were given a test battery assessing phonemic awareness, syntactic awareness, receptive vocabulary, syntactic proficiency, word decoding ability, and reading comprehension ability. Strong zero-order correlations were observed among all experimental measures. However, multiple regression analyses revealed that metalinguistic ability did not contribute to the prediction of early reading achievement when general language ability effects were statistically controlled.

Valproate-Associated Hepatotoxicity and its Biochemical Mechanisms

Abstract: Intake of the anticonvulsant drug valproic acid, or its sodium salt, has been associated with occasional instances of severe and sometimes fatal hepatotoxicity. Probably at least 80 cases have occurred worldwide. The syndrome affects perhaps 1 in 10,000 persons taking the drug, and usually develops in the early weeks or months of therapy. Most instances have involved children, usually those receiving more than 1 anticonvulsant. Multiple cases have occurred in 2 families. The typical presentation is of worsening epilepsy, increasing depression of consciousness, and progressive clinical and biochemical evidence of liver failure. The liver has sometimes shown hepatocyte necrosis, and on other occasions widespread microvesicular steatosis, while cholestatic changes have also occurred. The appearances are interpreted as consistent with a drug toxicity reaction. During the hepatotoxicity increased amounts of unsaturated metabolites of valproate, notably 4-en-valproate, have been found in blood and urine. In 4 cases there has been evidence of impaired β-oxidation of valproate with, in 1 case, accumulation of isomers of valproate glucuronide caused by intramolecular rearrangement of the conjugate. There are molecular structural similarities between 4-en-valproate and 2 known hepatotoxins (4-en-pentanoate and methylenecyclopropylacetic acid, the latter being responsible for hypoglycin poisoning). There are also clinical and histopathological similarities between valproate hepatotoxicity and both hypoglycin poisoning and certain spontaneous disorders of isoleucine metabolism (one pathway ofvalproate metabolism is analogous to oxidative degradation of isoleucine). Unsaturated metabolites of valproate, in particular 4-en-valproate, may contribute to the hepatotoxicity of the drug. However, since the hepatotoxicity appears to involve an element of idiosyncrasy, the primary defect in some cases may be an inherited or acquired deficiency in the drug’s β-oxidation. This defect may divert valproate metabolism towards ω-oxidation, with increased formation of the toxin 4-en-valproate, but may also allow increased formation of a toxic metabolite derived from isoleucine, since β-oxidation of isoleucine derivatives will also be impaired.

The generalized integration method for predicting impulse volt-time characteristics for non-standard wave shapes-a theoretical basis

Abstract: A theoretical basis for the integration method of predicting the strength of insulation subjected to impulses of nonstandard wave shapes is presented. Two theoretical approaches are developed for a general physical model of impulse breakdown applicable to gaseous, liquid, and solid insulation, and from an energy-balance model applied to an incipient breakdown channel in a general dielectric. It is therefore not surprising to find that the integration method is reasonably successful as a tool for predicting nonstandard wave-shape insulation strengths, using as input the data derived from tests with standard-wave-shape impulses. Numerical results are presented that provide an understanding of the shape of volt-time curves. An energy balance model has also been used to derive the resistance of the channel after breakdown has occurred. >

The ontogeny of growth hormone receptors in the rabbit tibia.

Abstract: To address the question of the mode of action of GH in stimulating longitudinal bone growth, we have used a panel of anti-GH receptor monoclonal antibodies to demonstrate GH receptors in the rabbit tibia and have studied the ontogeny of these receptors. In the neonate, receptors were localized in the hypertrophic zone between the cartilage canals, a region that develops into a secondary ossification center. In support of this finding, receptors were also localized on monolayer cultures of human infant costal chondrocytes. In 20- and 50-day-old rabbits, receptors were localized on reserve and proliferative chondrocytes in the growth plate. In 50- and 130-day-old rabbits receptors were localized on proliferative chondrocytes in the condylar cartilage. In older (180-day-old) rabbits with closed growth plates, GH receptors could not be detected, even in condylar cartilage. These results support the case for revision of the somatomedin hypothesis to accommodate a direct interaction between GH and receptors on epiphyseal chondrocytes.

Age-Related Changes in Contrast Sensitivity in Central and Peripheral Retina

Abstract: Eight young (average age 20.4 years) and eight elderly (average age 64.4 years) observers took part in three experiments designed to study age-related changes in peripheral retinal function. A further eight young (average age 22.3 years) and eight elderly (average age 63.8 years) observers took part in a replication of experiment 3. All observers had normal or better-than-normal visual acuity and no evidence of ocular pathology. All testing was monocular and the eye with better visual acuity was used. In the first experiment contrast sensitivity was measured in central retina and 10 deg temporally, at spatial frequencies of 0.2, 0.8, 2.0, and 5.0 cycles deg-1. Young observers had better contrast sensitivities than older observers, but only at higher spatial frequencies (2.0 and 5.0 cycles deg-1). For both groups, contrast sensitivity was poorer with peripheral presentation of stimuli than with central presentation, but not for the lowest spatial frequency used (0.2 cycle deg-1). In the second experiment observers had to detect the presence of a sharp edge (square-wave luminance profile), while in the third and fourth experiments the target was a "fuzzy' edge (sine-wave profile). Edges were again presented centrally or 10 deg temporally. As expected from the data of experiment 1, young observers were better able to detect the sharp edge than were the older observers in both central and peripheral viewing conditions. For both age groups, edge detection was better during central viewing than during peripheral viewing. However, contrary to expectations based on the results of experiment 1, detection of the fuzzy edge was better for central than for peripheral viewing for both age groups in experiments 3 and 4. The apparent (and expected) equality of performance found in experiment 3 for young and elderly observers in detecting the fuzzy edge was shown to be due to the range of contrast values used. When appropriate contrast values were used in experiment 4, young observers detected fuzzy edges presented in central retina better than did elderly observers. The results of experiment 1 show sparing of the ability to process low spatial frequencies across (i) age and (ii) retinal location, and are discussed in terms of the notion of (i) models of age-related loss of visual function and (ii) cortical magnification. The results of experiments 2, 3, and 4 provide some support for the proposition that the contrast sensitivity of observers may be used to predict their performance on other visual tasks.(ABSTRACT TRUNCATED AT 400 WORDS)

Melanosis coli. A consequence of anthraquinone-induced apoptosis of colonic epithelial cells.

Abstract: A condition closely resembling human melanosis coli was induced in the guinea pig large intestine by daily oral administration of the anthraquinone danthron. Each treatment caused a transient, dose-related wave of apoptosis of the colonic surface epithelial cells. Most of the resulting apoptotic bodies were phagocytosed by intraepithelial macrophages and carried by them through fenestrae in the epithelial basement membrane to the lamina propria. Here, the apoptotic bodies were transformed into typical lipofuscin pigment in macrophage heterolysosomes. Continued danthron administration caused progressive accumulation of pigmented macrophages in the bowel wall, whereas ongoing migration of pigmented macrophages to regional lymph nodes resulted, after danthron was ceased, in sequential loss of the pigmented cells from the superficial and deep lamina propria. Examination of colonic biopsies from patients with melanosis coli shows increased numbers of apoptotic bodies in the surface epithelium and lamina propria, suggesting implication of the same cellular processes in the formation of the pigment in man.

Critical free-surface flow over a semi-circular obstruction

Abstract: Numerical solutions are presented for the problem of two-dimensional “critical” flow of an ideal fluid over a semi-circular obstacle attached to the bottom of a running stream. The upstream Froude number and downstream flow speed are known in advance, and are therefore computed as part of the solution. The dependence of flow behaviour on obstacle size is discussed.

A koala (Phascolarctos cinereus Goldfuss) population crash during drought and heatwave conditions in south-western Queensland

Abstract: In the summer of 1979–80, there was a sharp decline in the koala population along Mungalalla Creek in south‐western Queensland. The decline was associated with a heatwave and drought. Live animals and carcasses were counted soon after the decline and at three subsequent periods. It was estimated that more than 63% of the population died. The drought and heatwave caused extensive leaf‐fall and/or browning of the foliage in food trees along stretches of dry creek. The proximate cause of death was thought to be a combination of malnutrition and dehydration. There was evidence, including the differential survival of koalas along the creek, of marked heterogeneity in the quality of the habitat. At sites where the trees were not affected (mainly on large permanent water‐holes) koalas had good body condition and mortality was low, whereas on stretches of dry creek (marginal habitat), koalas were in poor health (poor condition, anaemia, high tick loads) and mortality was very high. Survival of the population was not threatened because many animals survived at the permanent water‐holes. There is evidence that mortality was highest among young animals which may be excluded from optimal sites by older dominant animals. In the years after the crash, continuing drought appeared to prevent recovery of the population. It is thought that such population crashes are rare events as they are apparently caused partly by unusual climatic conditions.