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Biomedical subjects

A Hodge

Publications and source records attributed to A Hodge.

At least 19 recordsLinked to original sources
PubMed2006

Neuronal network models of phase separation between limb CPGs of digging sand crabs.

Ordinary differential equations are used to model a peculiar motor behaviour in the anomuran decapod crustacean Emerita analoga. Little is known about the neural circuitry that permits E. analoga to control the phase relationships between movements of the fourth legs and pair of uropods as it digs into sand, so mathematical models might aid in identifying features of the neural structures involved. The geometric arrangement of segmental ganglia controlling the movements of each limb provides an intuitive framework for modelling. Specifically, due to the rhythmic nature of movement, the network controlling the fourth legs and uropods is viewed as three coupled identical oscillators, one dedicated to the control of each fourth leg and one for the pair of uropods, which always move in bilateral synchrony. Systems of Morris-Lecar equations describe the voltage and ion channel dynamics of neurons. Each central pattern generator for a limb is first modelled as a single neuron and then, more realistically as a multi-neuron oscillator. This process results in high-dimensional systems of equations that are difficult to analyse. In either case, reduction to phase equations by averaging yields a two-dimensional system of equations where variables describe only each oscillator's phase along its limit cycle. The behaviour observed in the reduced equations approximates that of the original system. Results suggest that the phase response function in the two dimensional system, together with minimal input from asymmetric bilateral coupling parameters, is sufficient to account for the observed behaviour.

Action Potentials↗
PubMed2005

Plastic plants and patchy soils.

Soil nutrients are distributed in a non-uniform or 'patchy' manner. It is well established that the modular nature of root systems allows them to show both morphological and/or physiological plasticity upon encountering nutrient-rich patches. These plastic responses are widely believed to be foraging mechanisms by the plant to enhance nutrient resource capture. Although morphological plasticity has traditionally been viewed as the more expensive option as it requires new root construction, more recent evidence suggests this may not necessarily be the case. Moreover, plants may be able to recapture most of the initial outlay involved in new root construction, again lowering the overall cost to the plant. Under natural conditions the roots of most plant species have an additional nutrient acquisition mechanism namely mycorrhizal symbiosis. However, the impact of these important symbiotic associations upon the host plant's response to nutrient patches has received relatively little attention. The mycorrhizal fungal symbiont should, in theory, be better able to compete directly with the rest of the microbial community for the nutrients in the patch. This could potentially be important to the host plant, as generally, root proliferation responses are more important for interspecific plant, than plant-microbial, competition.

Acclimatization↗
PubMed2005

Socio-demographic inequalities in the diets of mid-aged Australian women.

OBJECTIVES: This study reports on the distributions of food and nutrient intakes by socio-demographic factors for a large population sample of mid-aged Australian women participating in the Australian Longitudinal Study on Women's Health. DESIGN: This cross-sectional population-based study used the Cancer Council of Victoria food frequency questionnaires to derive estimates of food and nutrient intakes. SETTING: Nationwide community-based survey. SUBJECTS: A total of 10561 women aged 50-55 y, at the time of the survey in 2001. RESULTS: Analysis showed favourable patterns of food intake, with frequent consumption of many foods that are promoted as components of a healthy diet (eg, fresh fruit, leafy green and other vegetables, bread, cereals, milk and meat). Intakes of both foods and nutrients varied significantly across socio-demographic groups, with unmarried women, and women in 'labouring' occupations (eg, cleaner, factory worker, kitchenhand) having poorer nutrient intake. CONCLUSIONS: Although many mid-aged women in this sample had generally healthful diets, women in certain socio-demographic groups (particularly unmarried women and those in labouring occupations) had nutrient intakes of concern. As well as helping to address the dearth of current data on dietary intakes in the Australian population, the results highlight the need for continued targeted public health strategies aimed at improving diet of women from the various socio-economic backgrounds.

Australia↗
PubMed2003

N capture by Plantago lanceolata and Brassica napus from organic material: the influence of spatial dispersion, plant competition and an arbuscular mycorrhizal fungus.

This study investigated N capture by Plantago lanceolata L. and Brassica napus L. from complex organic material (dual-labelled with 15N/13C) added either as a thin concentrated layer (discrete patch treatment) or dispersed uniformly with the background sand:soil mix in a 10 cm band (dispersed treatment) when grown in monoculture or in interspecific competition and in the presence or absence of a mycorrhizal inoculum (Glomus mosseae). No 13C enrichments from the organic material were detected in the plant tissues, but 15N enrichments were present. Total plant uptake of N from the organic material on a microcosm basis was not affected by the spatial placement of the organic material, but Plantago monocultures captured less N than the species in interspecific competition (i.e. 23% versus 38% of the N originally added). N capture from Brassica monocultures was no different to either Plantago monocultures or both species in mixture. However, N capture from the organic material by both individual Plantago and Brassica plants was reduced when grown with Brassica plants (by 10-fold and by more than half, respectively). N capture from the organic material was directly related to the estimated root length produced in the sections containing the organic material: the individual that produced the greatest root length captured most N. Strikingly, when the organic material was added as a discrete patch the N captured by Brassica, a non-mycorrhizal species, actually increased when the G. mosseae inoculum was present compared to when G. mosseae was absent (i.e. 35% versus 19% of the N originally added).

Brassica napus↗
PubMed2001

An arbuscular mycorrhizal fungus accelerates decomposition and acquires nitrogen directly from organic material.

Arbuscular mycorrhizal fungi (order Glomales), which form mycorrhizal symbioses with two out of three of all plant species, are believed to be obligate biotrophs that are wholly dependent on the plant partner for their carbon supply. It is thought that they possess no degradative capability and that they are unable to decompose complex organic molecules, the form in which most soil nutrients occur. Earlier suggestions that they could exist saprotrophically were based on observation of hyphal proliferation on organic materials. In contrast, other mycorrhizal types have been shown to acquire nitrogen directly from organic sources. Here we show that the arbuscular mycorrhizal symbiosis can both enhance decomposition of and increase nitrogen capture from complex organic material (grass leaves) in soil. Hyphal growth of the fungal partner was increased in the presence of the organic material, independently of the host plant.

Fungi↗
PubMed2000

Microbial ecology of the arbuscular mycorrhiza.

Arbuscular mycorrhizal (AM) fungi interact with a wide variety of organisms during all stages of their life. Some of these interactions such as grazing of the external mycelium are detrimental, while others including interactions with plant growth promoting rhizobacteria (PG PR) promote mycorrhizal functioning. Following mycorrhizal colonisation the functions of the root become modified, with consequences for the rhizosphere community which is extended into the mycorrhizosphere due to the presence of the AM external mycelium. However, we still know relatively little of the ecology of AM fungi and, in particular, the mycelium network under natural conditions. This area merits attention in the future with emphasis on the fungal partner in the association rather than the plant which has been the focus in the past.

Journal Article↗
PubMed2000

Are microorganisms more effective than plants at competing for nitrogen?

Plant scientists have long debated whether plants or microorganisms are the superior competitor for nitrogen in terrestrial ecosystems. Microorganisms have traditionally been viewed as the victors but recent evidence that plants can take up organic nitrogen compounds intact and can successfully acquire N from organic patches in soil raises the question anew. We argue that the key determinants of 'success' in nitrogen competition are spatial differences in nitrogen availability and in root and microbial distributions, together with temporal differences in microbial and root turnover. Consequently, it is not possible to discuss plant-microorganism competition without taking into account this spatiotemporal context.

Fungi↗
PubMed2000

Efficacy evaluations of the use of oral tilmicosin in pneumonic calves.

The therapeutic effect of oral tilmicosin was compared with enrofloxacin, and the efficacy of three doses of the drug was examined in two fully randomized blinded field trials. Pneumonic milk-fed calves between 3 days and 2.5 months of age were allocated into two groups in trial 1 (50 animals) and into three groups in trial 2 (69 calves). In the first trial, the animals were treated with 25 mg/kg/day tilmicosin or 2.5 mg/kg/day enrofloxacin in milk for 5 days. In the second trial, the calves received either 25 mg/kg/day tilmicosin for 5 days or 3 days, or else 12.5 mg/kg tilmicosin for 5 days. All calves were clinically examined for 10 days. In the first trial, oral tilmicosin at a dose of 25 mg/kg/day for 5 days proved to be effective for the treatment of endemic pasteurellosis of milk-fed calves. The efficacy was the same as that of enrofloxacin. All three doses in the second trial were effective and were statistically equivalent to the original dose tested.

Administration, Oral↗
PubMed2000

The Anti Cancer Council of Victoria FFQ: relative validity of nutrient intakes compared with weighed food records in young to middle-aged women in a study of iron supplementation.

OBJECTIVE: To assess the validity of the Anti Cancer Council of Victoria food frequency questionnaire (ACCVFFQ) relative to seven-day weighed food records (WFRs) in 63 women of child-bearing age. METHOD: 63 women completed WFRs to assess iron intake as part of a study on iron deficiency. These women also completed the ACCVFFQ. Nutrient intakes were computed independently for the WFRs and FFQs. Intakes were compared as group means, by correlation and by quintile classification, adjusting for day-to-day variation in intakes, and for energy intake. Individual differences in results were also examined. RESULTS: The strongest associations between WFR and FFQ results were energy-adjusted, log-transformed and adjusted for day-to-day variability in intake. Correlation coefficients ranged from 0.28 for vitamin A to 0.78 for carbohydrate. Mean intakes from the WFRs and FFQs were within +/- 20% for 21 of 27 nutrients. Poor agreement between FFQs and WFRs for retinol intake was due to the inclusion of liver in two WFRs, an item which is not included in the FFQ. CONCLUSION: The ACCVFFQ performs as well as other FFQs for which validation data are available. The relatively poor measurement of retinol is consistent with other data, and with the limited number of foods in which this nutrient is abundant. IMPLICATIONS: The availability of an optically scannable valid instrument for assessing dietary intake will facilitate epidemiological studies of diet and disease, an area of current research priority.

Adolescent↗
PubMed2000

Effect of monensin on milk production of Holstein-Friesian dairy cows.

We examined the effects of monensin on feed intake and milk production in Holstein-Friesian cows receiving a total mixed rations in two experiments. In experiment 1, 60 individually fed cows consumed, during wk 7 to 26 of lactation, 1 kg/d of supplement containing either 0, 150,300, or 450 mg of monensin. In experiment 2, 98 group-fed cows also received 1 kg/d of a supplement with either 0 or 300 mg/d of monensin for two consecutive lactations. In lactations 1 and 2, treatment started at wk 8 and 3 wk prior to calving, and continued for 32 wk. In experiment 1, 150, 300, and 450 mg of monensin/d produced a small decrease in feed intake and milk yield responses of 2.8, 2.5 and 1.5 kg/d, respectively. In experiment 2, milk yield responses of 0.8 and 1.1 kg/d were recorded in lactations 1 and 2. Milk fat and milk protein content declined in experiments 1 and 2, lactations 1 and 2 by 0.46, 0.38 and 0.27%, and 0.16, 0.16 and 0.11%, respectively. Yield of milk constituents was unaffected. Efficiency of milk production was increased by 5% in experiment 1. In experiment 2, lactation 2, monensin decreased beta-hydroxybutyrate and acetoacetate but increased blood glucose concentration.

3-Hydroxybutyric Acid↗
PubMed1999

The cyclin-dependent kinase inhibitory domain of the yeast Sic1 protein is contained within the C-terminal 70 amino acids.

By inhibiting the activity of Cdc28/Clb cyclin-dependent protein kinase (CDK) complexes, Sic1 prevents the premature initiation of S phase in the yeast Saccharomyces cerevisiae. By testing a series of Sic1 truncation mutants, we have mapped the minimal domain necessary for Cdc28/Clb inhibition in vivo to the C-terminal 70 amino acids of Sic1. Site-directed mutagenesis was used to show that a sequence that matches the zRxL motif found in mammalian CDK inhibitors is essential for Sicl function. This motif is not found in the Schizosaccharomyces CDK inhibitor p25rum1, which appears to be a structural and functional homolog of Sicl. Based on the mutational data and sequence comparisons, we argue that Sic1 and p25rum1 are structurally distinct from the known mammalian CDK inhibitors, but may bind CDK complexes in a manner more closely resembling CDK substrates like the retinoblastoma and E2F proteins.

Amino Acid Sequence↗
PubMed1999

Pulmonary presentation of Dirofilaria immitis (canine heartworm) in man.

Canine heartworm or Dirofilaria immitis can occasionally infect man. We present the case of a 36-year-old Balkan woman referred to us for a thoracoscopic biopsy of a well defined pulmonary mass. The latter was thoracoscopically resected and proved to be due to Dirofilaria immitis on histopathological examination. To our knowledge this is the second reported case in Western Australia, the first being that reported by Brine et al. The prevalence of the disease in Australia was recognized in 1969 in one study in the state of Queensland, where 12% of 761 dogs at one veterinary clinic and 20% of 296 dogs at another were shown to be infected. Dirofilaria immitis resides in the right ventricle and pulmonary arteries of dogs. The microfilariae are released into the blood stream and are transmitted to secondary hosts by mosquitoes.

Adult↗
PubMed1999

Body mass index, height and cumulative menstrual cycles at the time of diagnosis are not risk factors for poor outcome in breast cancer.

Obesity, height and age at menarche have been shown to be risk factors for the development of primary breast cancer. However, their prognostic influence on breast cancer once it has presented is uncertain. The present study analysed 448 patients with primary breast cancer to determine whether or not body mass index (BMI), height and cumulative menstrual cycles at diagnosis are independent prognostic variables. The effects of all three variables on survival time and disease free interval were estimated. Of the 448 patients after a median follow up of 6 years, 190 (42%) developed recurrence and 162 (36%) had died. Body Mass Index and height could be calculated from available data in 403 patients and cumulative menstrual cycles in 388 patients. There was no evidence of an effect of BMI on survival time (P=0.99; hazard ratio=1.000; 95% Confidence Interval 0.968-1.034) or disease free interval (P=0.92; hazard ratio=1.002; 95% Confidence Interval 0.973-1.031). Similarly, height and cumulative menstrual years did not influence outcome in patients with primary breast cancer. However, nodal status and tumour size were both significant prognostic factors (P<0.001). The present study found no association between Body Mass Index, height and cumulative menstrual years and outcome in patients with primary breast cancer.

Journal Article↗