Showing papers by "University of Auckland published in 1990"
TL;DR: Self-propagating high-temperature synthesis (SHS) of powder compacts is a novel processing technique currently being developed as a route for the production of engineering ceramics and other advanced materials.
Abstract: Self-propagating high-temperature synthesis (SHS) of powder compacts is a novel processing technique currently being developed as a route for the production of engineering ceramics and other advanced materials. The process, which is also referred to as combustion synthesis, provides energy- and cost-saving advantages over the more conventional processing routes for these materials. At the same time, the rapid heating and cooling rates provide a potential for the production of metastable materials with new and, perhaps, unique properties. This paper reviews the research that has been, and is being, undertaken in this exciting new processing route for high-technology materials and examines the underlying theoretical explanations which will, eventually, lead to improved control over processing parameters and product quality.
406 citations
TL;DR: The results provide support for the hypothesis that increased exposure to sunlight is protective against coronary heart disease and raised vitamin D3 levels was observed in all seasons.
Abstract: The relation between the plasma level of 25-hydroxyvitamin D3, the main metabolite of sun-induced vitamin D, and myocardial infarction (MI) was investigated in a community-based case-control study. Some 179 MI patients presenting to hospital within 12 hours of the onset of symptoms were individually matched with controls by age, sex and date of blood collection. MI patients had significantly lower mean 25-hydroxyvitamin D3 levels than controls (32.0 versus 35.5 nmol/L; p = 0.017), with the case-control differences being greatest in winter and spring. The relative risk of MI for subjects with 25-hydroxyvitamin D3 levels equal to or above the median was 0.43 (95% confidence limits = 0.27, 0.69) compared to subjects below the median. The decrease in MI risk associated with raised vitamin D3 levels was observed in all seasons. These results provide support for the hypothesis that increased exposure to sunlight is protective against coronary heart disease.
395 citations
TL;DR: The results of time-course immunocytochemical and antiserum studies suggest that some striatal neurons express c-fos protein-related antigens but not c- fos protein after haloperidol injection, and theories concerning the biochemical mechanism of action of haloperIDol are discussed.
342 citations
TL;DR: The most interesting aspect of their biological activity was the lack of cross-resistance shown to an amsacrine-resistant P388 cell line, suggesting that these compounds may not express their cytotoxicity via interaction with topoisomerase II.
Abstract: A series of substituted 2-phenylbenzimidazole-4-carboxamides has been synthesized and evaluated for in vitro and in vivo antitumor activity. These compounds represent the logical conclusion to our search for "minimal" DNA-intercalating agents with the lowest possible DNA-binding constants. Such "2-1" tricyclic chromophores, of lower aromaticity than the structurally similar 2-phenylquinolines, have the lowest DNA binding affinity yet seen in the broad series of tricyclic carboxamide intercalating agents. Despite very low in vitro cytotoxicities, several of the compounds had moderate levels of in vivo antileukemic effects. However, the most interesting aspect of their biological activity was the lack of cross-resistance shown to an amsacrine-resistant P388 cell line, suggesting that these compounds may not express their cytotoxicity via interaction with topoisomerase II.
318 citations
TL;DR: The frequency of gene transfer from Agrobacterium is extremely high within localized regions of leaf explants, but that the frequency of stable integration is several orders of magnitude lower.
Abstract: A chimaeric gene has been constructed that expresses β-D-glucuronidase (GUS) in transformed plant tissues, but not in bacterial cells. This gene has proved extremely useful for monitoring transformation during the period immediately following gene transfer from Agrobacterium tumefaciens. GUS expression was detectable 2 days after inoculation, peaked at 3–4 days and then declined; if selection was imposed expression increased again after 10–14 days. The extent of transient expression after 4 days correlated well with stable integration as measured by kanamycin resistance, hormone independence, and gall formation. Histochemical staining of inoculated leaf discs confirmed the transient peak of GUS expression 3–4 days after inoculation. The most surprising result was that the blue staining was concentrated in localized zones on the circumference of the disc; within these zones, essentially all the cells appeared to be expressing GUS. We suggest that the frequency of gene transfer from Agrobacterium is extremely high within localized regions of leaf explants, but that the frequency of stable integration is several orders of magnitude lower.
306 citations
TL;DR: It is shown that this collective behavior of water molecules amounts to a considerable biological force, which can be equivalent to a pressure of 1,000 atm (1.013 x 10(5) kPa), and suggested that cells selectively accumulate K+ ions and compatible solutes to avoid extremes of water structure in their aqueous compartments.
284 citations
TL;DR: BHR is related to, but not identical to, clinical asthma, and all grades of severity (including no BHR) were found for any given frequency of wheeze, and an existing diagnosis of asthma identified symptomatic children more accurately than did BHR.
Abstract: Bronchial hyperresponsiveness (BHR) to inhaled histamine has often been cited as the gold standard in asthma diagnosis, but recently this has been questioned. This report assesses the relationship of BHR to asthma symptoms and asthma diagnosis in a large community-based sample of children. A total of 2,053 children 7 to 10 yr of age were randomly sampled from Auckland primary schools and assessed by a questionnaire and histamine inhalation challenge. In all, 14.3% had had asthma diagnosed, 29.6% reported having had one of the four respiratory symptoms in in the previous 12 months, and 15.9% had BHR (PD20 less than or equal to 7.8 mumol histamine). After a cumulative dose of 3.9 mumol histamine, the percent change in FEV1 from postsaline FEV1 was unimodally distributed, with those in whom asthma had been diagnosed dominating the severe end of the spectrum. However, 53% of those with BHR had no asthma diagnosis, and 41% had no current asthma symptoms. On the other hand, 48% of all subjects with diagnosed asthma and 42% of children with diagnosed asthma and current symptoms did not have BHR. Although severity of BHR tended to increase with wheezing frequency, all grades of severity (including no BHR) were found for any given frequency of wheeze. An existing diagnosis of asthma identified symptomatic children more accurately than did BHR, regardless of the criteria used for BHR or for "symptomatic" and irrespective of ethnic group. In conclusion, BHR is related to, but not identical to, clinical asthma. Bronchial challenge testing is an important tool of respiratory research, but cannot reliably or precisely separate asthmatics from nonasthmatics in the general community.
279 citations
TL;DR: The pattern of cerebrovascular disease (stroke) mortality in men and women aged 40-69 years in 27 countries during 1970-1985 with the decline in coronary heart disease mortality during the same period was compared.
Abstract: We compared the pattern of cerebrovascular disease (stroke) mortality in men and women aged 40-69 years in 27 countries during 1970-1985 with the decline in coronary heart disease mortality during the same period. Stroke mortality rates declined in 21 and 25 countries for men and women, respectively. In 23 countries the decline in stroke mortality in women was greater than that in men. Countries with the highest rates of stroke mortality are also those with the least favorable secular trend. The rate of decline for stroke mortality is greater than that for coronary heart disease mortality in those countries that experienced a decline in both categories. International comparisons of risk factor levels over time are required to explain the striking differences between countries.
269 citations
TL;DR: The recent international data on trends in coronary heart disease mortality and morbidity and risk factor levels are reviewed and the possible explanations for the changes in mortality rates are assessed.
Abstract: This paper reviews the recent international data on trends in coronary heart disease mortality and morbidity and risk factor levels and assesses the possible explanations for the changes in mortality rates The implications of the trends and the associated investigations for the prevention and control of coronary heart disease and other noncommunicable diseases are discussed (EXCERPT)
254 citations
TL;DR: The results provide support for observations of selective receptor changes in Alzheimer's disease involving a broad range of receptor types which encompass both excitatory amino acid and other receptors (notably serotonin2, A1, benzodiazepine, neurotensin and opioid receptors).
201 citations
TL;DR: This paper shows how to generate k -regular graphs on n vertices uniformly at random in expected time O ( nk 3), provided k = O(n 1 3 ) .
TL;DR: Bone loss was not influenced by sex, age, duration of previous steroid treatment, or diagnosis and was not predictable from biochemical measures of calcium metabolism.
Abstract: This study addresses the impact of clinical and biochemical factors on the bone density of patients receiving glucocorticoid therapy. Vertebral mineral density was measured by quantitative computed tomography in 35 patients aged 17 to 77 years who had received therapeutic glucocorticoid drugs for 0.1 to 22 years. The mean (+/- SEM) vertebral mineral density z score in the subjects was -1.7 +/- 0.2. z score was unrelated to underlying diagnosis, sex, or age but was significantly related to the duration of previous steroid therapy (r = -.38) and to the total cumulative glucocorticoid dose (r = -.50). The rate of change of bone density in 16 of these subjects followed up over a period of 12 months was -8.9% and was significantly greater in subjects taking more than 12.5 mg of prednisone per day. Bone loss was not influenced by sex, age, duration of previous steroid treatment, or diagnosis and was not predictable from biochemical measures of calcium metabolism.
TL;DR: Criticisms of component analysis are rebutted, and the appropriateness of applying the Wagner parsimony criterion to the study of biogcography and co‐speciation is questioned.
01 Jul 1990
TL;DR: In this article, the authors presented an analysis of the space vector PWM waveform to obtain its spectrum based on a novel decomposition technique, illustrated by considering the harmonics of a regularly sampled asymmetrical sinusoidal PWM Waveform, which is in fact a partial solution to the Space vector harmonics.
Abstract: While most traditional PWM inverters use the asymmetrical regularly sampled triangulation technique to generate waveforms, a recently reported space vector PWM method is rapidly gaining favour in the industrial drives arena as an alternative technique. The paper presents an analysis of the space vector PWM waveform to obtain its spectrum. The analysis is based on a novel decomposition technique, illustrated by considering the harmonics of a regularly sampled asymmetrical sinusoidal PWM waveform, which is in fact a partial solution to the space vector harmonics. The calculated harmonics show close agreement with measured harmonics from an experimental microprocessor-controlled inverter operating with the same waveform parameters.
TL;DR: This work considers the estimation of the number of labelled simple graphs with degree sequence d 1, d 2, . . . , d n by using an n-dimensional Cauchy integral and gives as a corollary the asymptotic joint distribution function of the degrees of a random graph.
Abstract: We consider the estimation of the number of labelled simple graphs with degree sequence d 1 , d 2 , . . . , d n by using an n-dimensional Cauchy integral. For sufficiently small e and any c > 2/3, an asymptotic formula is obtained when | d i − d | n 1/2 + e for all i and d = d ( n i) satisfies min{ d , n − d − 1) ⩾ cn /log n as n → ∞. These conditions include the degree sequences of almost all graphs, so our result gives as a corollary the asymptotic joint distribution function of the degrees of a random graph. We also give evidence for a formula conjectured to be valid for all d ( n ).
TL;DR: It is concluded that Bot-Aug neurons exert widespread inhibition on all major neuron categories in the ipsilateral VRG, and should be regarded as an important element in shaping the spatiotemporal output pattern of both respiratory motoneurons and premotor neurons.
Abstract: Axonal projections and synaptic connectivity of expiratory Botzinger neurons with an augmenting firing pattern (Bot-Aug neurons) to neurons in the ipsilateral ventral respiratory group (VRG) were studied in anaesthetized cats. Antidromic mapping revealed extensive axonal arborizations of Bot-Aug neurons (24 of 45) to the rostral or caudal VRG, with some having arbors in both regions. Of 234 pairs of neurons studied with intracellular recording and spike-triggered averaging, monosynaptic inhibitory postsynaptic potentials (IPSPs) were evoked in 49/221 VRG neurons by 38/98 Bot-Aug neurons. The highest incidence of monosynaptic inhibition was found in inspiratory bulbospinal neurons (10 of 23 tested). Evidence was also found for monosynaptic inhibition, by a separate group of Bot-Aug neurons, of expiratory bulbospinal neurons (12/58), while excitatory postsynaptic potentials (EPSPs) were identified in another two of these neurons. In addition, monosynaptic IPSPs were recorded from 13 of 53 identified laryngeal motoneurons, and from 14 of 100 respiratory propriobulbar neurons. Presumptive disynaptic IPSPs were recorded from 11 of the 221 VRG neurons. We conclude that Bot-Aug neurons exert widespread inhibition on all major neuron categories in the ipsilateral VRG, and should be regarded as an important element in shaping the spatiotemporal output pattern of both respiratory motoneurons and premotor neurons.
TL;DR: In this paper, a review of the degradation processes for TBT in natural waters, sediments and biota has been conducted and it has been shown that TBT is very stable in heavily contaminated sediments.
Abstract: Degradation processes for TBT in natural waters, sediments and biota have been reviewed. Environmental degradation is principally biologically mediated and probably follows first‐order kinetics. Many studies have shown that TBT is not persistent in most natural waters. However, the tendency of TBT to accumulate in sediments and biota implies that degradation processes operating in sediments and biota will be of greater importance in determining the overall persistence of TBT in the marine environment. Recent studies indicate that TBT is very stable in heavily contaminated sediments and may continue to exert toxic effects after primary anthropogenic inputs have stopped.
TL;DR: It is concluded that LIF stimulates bone resorption by a mechanism involving prostaglandin production, but that a distinct mechanism is responsible for its stimulation of DNA and protein synthesis.
Abstract: A number of cytokines have been found to be potent regulators of bone resorption and to share the properties originally attributed to osteoclast-activating factor. One such activity, differentiation-inducing factor (DIF, D-factor) from mouse spleen cells, shares a number of biological and biochemical properties with the recently characterized and cloned leukemia inhibitory factor (LIF). We have assessed the effects of recombinant LIF on bone resorption and other parameters in neonatal mouse calvaria. Both recombinant murine and human (h) LIFs stimulated 45Ca release from prelabeled calvaria in a dose-dependent manner. The increase in bone resorption was associated with an increase in the number of osteoclasts per mm2 bone. The osteolytic effect of hLIF were blocked by 10(-7) M indomethacin. hLIF also stimulated incorporation of [3H] thymidine into calvaria, but the dose-response relationship was distinct from that for bone resorption, and this effect was not blocked by indomethacin. Similarly, hLIF increased [3H]phenylalanine incorporation into calvaria, and this was also not inhibited by indomethacin. It is concluded that LIF stimulates bone resorption by a mechanism involving prostaglandin production, but that a distinct mechanism is responsible for its stimulation of DNA and protein synthesis. The primary structure of LIF differs from that of other fully characterized, bone-active cytokines, and it, thus, represents a novel factor which may be involved in the normal regulation of bone cell function.
TL;DR: The possible effects that marine reserve protection has had on densities of some reef fish and large invertebrates were investigated near Leigh by a series of sampling programmes between 1976 and 1988 and revealed few consistent differences in fish abundances.
Abstract: The possible effects that marine reserve protection has had on densities of some reef fish and large invertebrates were investigated near Leigh (north‐eastern New Zealand) by a series of sampling programmes between 1976 and 1988. Fish counts at intervals during the 6 years after the initial establishment of the Cape Rodney to Okakari Point Marine Reserve in 1975 suggested that red moki (Cheilodactylus spectabilis) had increased in abundance whereas five others had remained at approximately constant densities. A comparison of data between 1978 and 1988 also revealed few consistent differences in fish abundances. A detailed survey in 1988 between sites inside and outside the marine reserve showed no clear patterns for sea urchins (Evechinus chloroticus) and several fish; trends for increased abundances in the marine reserve of fish such as snapper Pagrus (=Chrysophrys) auratus, blue cod (Parapercis colias), and red moki; a very striking increase in numbers of rock lobsters (Jasus edwardsii) within ...
TL;DR: This paper showed that focal brain injury in mice induced c-fos mRNA and protein in neurons throughout the damaged neocortex, including the piriform and the entorhinal cortices, as well as in non-neural brain cells (e.g., glia, pia, ependyma).
TL;DR: A gene from this organism, designated celB, has been cloned in Escherichia coli as part of a bacteriophage lambda gene library that produces a thermostable cellulase that shows both endoglucanase and exoglucAnase activities on test substrates and is able to degrade crystalline cellulose to glucose.
Abstract: "Caldocellum saccharolyticum" is an obligatory anaerobic thermophilic bacterium. A gene from this organism, designated celB, has been cloned in Escherichia coli as part of a bacteriophage lambda gene library. This gene produces a thermostable cellulase that shows both endoglucanase and exoglucanase activities on test substrates and is able to degrade crystalline cellulose to glucose. The sequence of celB has homology with both exo- and endoglucanases described by others. It appears to have a central domain without enzymatic activity which is joined to the enzymatic domains by runs of amino acids rich in proline and threonine (PT boxes). Deletion analysis shows that the exoglucanase activity is located in the amino-terminal domain of the enzyme and that endoglucanase activity is located in the carboxy-terminal domain. There are internal transcriptional and translational start sites within the gene. The intact gene has been cloned into a temperature-inducible expression vector, pJLA602, and overexpressed in E. coli. Polyacrylamide gel electrophoresis showed that celB produced a protein with a molecular weight of 118,000 to 120,000. A number of smaller proteins with activity against carboxymethyl cellulose and 4-methyl umbelliferyl-beta-D-cellobioside were also produced. These are believed to be the result of alternative translational start sites and/or proteolytic degradation products of the translated gene product.
TL;DR: The mechanism of this paradoxical induction of c-fos by MK-801 is unclear; however, the pattern of induction appears to follow the distribution of the antagonist-preferring NMDA receptor site.
TL;DR: It is demonstrated that respiratory neurons in the rostral ventrolateral medulla of the rat are intermingled with catecholamine‐containing neurons of the C1 cell group, but are not themselves catecholine‐containing.
Abstract: Intracellular recording and labelling with Lucifer yellow of respiratory neurons in the rostral ventrolateral medulla were carried out in urethane-anaesthetised rats. A combined immunofluorescence and immunoperoxidase technique enabled an assessment of the tyrosine hydroxylase immunoreactivity, as well as an examination of the morphology of inspiratory and expiratory neurons in this part of the medulla oblongata. The results demonstrate: (a) that respiratory neurons in the rostral ventrolateral medulla of the rat are intermingled with catecholamine-containing neurons of the C1 cell group, but are not themselves catecholamine-containing; (b) that many non-spinally projecting respiratory neurons have axonal arborisations within the ventrolateral medulla in the same region as the C1 cell group, other respiratory neurons, and neurons reported to have a cardiovascular function; and (c) that the dendrites of respiratory neurons in this region radiate throughout the ventrolateral medulla and frequently approach the ventral surface.
TL;DR: Alambda recombinant bacteriophage coding for xylanase and beta-xylosidase activity has been isolated from a genomic library of the extremely thermophilic anaerobe "Caldocellum saccharolyticum." Partial Sau3AI fragments of the lambda recombinant DNA were ligated into pBR322.
Abstract: A lambda recombinant bacteriophage coding for xylanase and beta-xylosidase activity has been isolated from a genomic library of the extremely thermophilic anaerobe "Caldocellum saccharolyticum." Partial Sau3AI fragments of the lambda recombinant DNA were ligated into pBR322. A recombinant plasmid with an insertion of ca. 7 kilobases of thermophilic DNA expressing both enzymatic activities was isolated. The location of the genes has been established by analyzing deletion derivatives, and the DNA sequence of 6.067 kilobases of the insert has been determined. Five open reading frames (ORFs) were found, one of which (ORF1; Mr 40,455) appears to code for a xylanase (XynA) which also acts on o-nitrophenyl-beta-D-xylopyranoside. Another, ORF5 (Mr 56,365), codes for a beta-xylosidase (XynB). The xynA gene product shows significant homology with the xylanases from the alkalophilic Bacillus sp. strain C125 and Clostridium thermocellum.
TL;DR: In this paper, the existence of cross-phase modulation instability in high birefringence fibers was identified with four-wave mixing spectra, and the effect only occurs for non-zero group velocity mismatch.
TL;DR: It is suggested that ouabain has a two-fold action, a release of toxic acidic amino acids and a prolonged depolarization of neurons leading to osmolysis or calcium necrosis.
TL;DR: There is little correlation between the degree of Fos-IR induction and the subsequent durability of LTP, and the outcome with the induction of c-fos protein(s) (Fos), as measured immunohistochemically in the dentate gyrus of separate animals 2 h post-tetanization.
TL;DR: The relative effects of fish and sea urchins on the long-term dynamics of kelp forests are unknown, and spatial and temporal patterns in herbivore abundance and behaviour, and algal demography arc urgent targets for research.
Abstract: Sea urchins are widely considered to be the major grazers in temperate subtidal systems, with herbivorous fish being browsers of minor importance. This paper reviews spatial and temporal patterns in these herbivores on rocky reels in temperate Australasia, with the aim of assessing their relative impacts on patch structure and dynamics. Herbivorous fishes are widespread and make up a significant numerical component the reel fish fauna. Sea urchins are also abundant, but not all geographic locations support actively grazing species.
Both fish and sea urchins exhibit distinct patterns of distribution among depth strata. Within depth strata, all herbivores are restricted to (sea urchins) or forage preferentially in (fish) particular habitat patches, causing a mosaic of different feeding activities. These patches are either related to specific features of the habitat (e.g. Kelp patches, topography) or behavioural interactions. Foraging by sea urchins and demersal-nesting damselfishes is intense and persistent, whereas in the kelp-feeding fish Odax cyanomelas, foraging reaches greatest intensity at predictable locations during a few months of every year.
Many fish and sea urchins consume some algae in preference to others. However, feeding preferences may determine the nature of the impact only in fishes. For sea urchins, preference may occasionally determine the order in which algae are consumed, but at high densities they consume all available macroalgae.
Impacts of both types of herbivore on the abundance of algae have been recorded. Some sea urchins (e.g. Evechinus chloroticus, Centrostephanus rodgersii) appear to severely modify biogenic habitat structure by maintaining ‘barrens’ (areas devoid of macroalgae) over long periods. In contrast to this, the effects of fishes may be more transitory (e.g. seasonal impact of Odax cyanomelas on brown algae) or occur at smaller spatial scales (e.g. nest sites maintained by male Parma victoriae) Herbivorous and other fishes appear to respond to spatial patterns in algal distributions, rallier than having it major impact upon them. The relative effects of fish and sea urchins on the long-term dynamics of kelp forests are unknown, hut temporal patterns in herbivore abundance and behaviour, and algal demography arc urgent targets for research.
TL;DR: The fact that many animals continue to exhibit coordinated sensorimotor function during changes in body temperature indicates that some form of temperature compensation has occurred within the nervous system.
Abstract: Temperature change has a major impact on the function of the nervous system and its components, including altering synaptic gain and changing synaptic and conduction delays. Although many animals are subject to changes in body temperature, the degree of temperature change actually experienced by many poikilotherms is not well documented. The fact that many animals continue to exhibit coordinated sensorimotor function during changes in body temperature indicates that some form of temperature compensation has occurred within the nervous system. Compensations may occur automatically (opposing effects of temperature offsetting each other), they may be an inherent property of closed-loop systems, or they may be effected by more sophisticated control mechanisms such as those of the vertebrate cerebellum.
TL;DR: In this article, a discussion is given of the physical approximations used in obtaining water wave dispersion relations, which relate wave length and height, period, water depth and current.