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Biomedical subjects

R A McKenzie

Publications and source records attributed to R A McKenzie.

At least 19 recordsLinked to original sources
PubMed1997

Characterisation of Australian isolates of Actinobacillus capsulatus, Actinobacillus equuli, Pasteurella caballi and Bisgaard Taxa 9 and 11.

OBJECTIVE: The objective of this work was to perform a comprehensive phenotypic characterisation of 16 isolates of bacteria previously identified as Actinobacillus equuli. DESIGN: The 16 isolates that had been obtained from Australian animals--15 from horses and one from a rabbit--were compared with reference strains of A equuli, A capsulatus, Pasteurella caballi and Bisgaard Taxa 9 and 11. RESULTS: The characterisation study demonstrated that only nine of the isolates were A equuli. The other isolates were identified as A capsulatus (the isolate from rabbit), P caballi (one isolate), Bisgaard Taxon 11 (two isolates) and Bisgaard Taxon 9 (one isolate). The final two isolates could not be assigned to any recognised species or taxa. CONCLUSION: This study has highlighted the importance of a complete characterisation of Actinobacillus-like organisms isolated from horses and rabbits. The study represents the first time that A capsulatus, P caballi and Bisgaard Taxa 9 and 11 have been recognised as being present in Australia.

Actinobacillosis↗
PubMed1996

Modified technique to recover microsporidian spores in sodium acetate-acetic acid-formalin-fixed fecal samples by light microscopy and correlation with transmission electron microscopy.

Microsporidia are an emerging cause of significant disease, particularly in the immunocompromised host. Until recently, the diagnosis of enteric infections has required invasive sampling, the use of expensive technology, and considerable technological expertise. The purpose of the present study was to examine three modifications to the processing of fecal specimens for light microscopy (LM) examination for microsporidian spores: the use of pretreatment with potassium hydroxide, modified centrifugation conditions, and a modified staining technique. A sodium acetate-acetic acid-formalin-fixed fecal sample containing numerous microsporidian spores confirmed to be positive by transmission electron microscopy (TEM) was used in all studies performed. A simulation of a heavy to lightly infected individual was used. The results of LM were correlated with those of TEM. Duplicate smears were stained with Weber's modified trichrome and Giemsa (GS) stains. The stained slides were randomized and examined blindly by LM at x 625 and x 1,250 magnifications. A portion of the dilutions after centrifugation were fixed for TEM. The Weber modified trichrome stain performance rating was higher than the Giemsa stain rating because of ease of interpretation, and material stained with Weber modified trichrome stain required less examination time at a lower magnification. The number of positive smears and the quantity of spores detected were significantly higher following pretreatment of the sample with KOH. TEM was positive only when numerous spores were present, but the quality of the photomicrographs was superior after pretreatment with KOH. Pretreatment of sodium acetate-acetic acid-formalin-fixed fecal samples with 10% KOH and then a 5-min centrifugation time and staining with Weber modified trichrome stain provide for the excellent recovery of microsporidia in the routine diagnostic parasitology laboratory.

AIDS-Related Opportunistic Infections↗
PubMed1995

The importance of a single G in the hairpin loop of the iron responsive element (IRE) in ferritin mRNA for structure: an NMR spectroscopy study.

Noncoding sequences regulate the function of mRNA and DNA. In animal mRNAs, iron responsive elements (IREs) regulate the synthesis of proteins for iron storage, uptake and red cell heme formation. Folding of the IRE was indicated previously by reactivity with chemical and enzymatic probes. 1H- and 31P-NMR spectra now confirm the IRE folding; an atypical 31P-spectrum, differential accessibility of imino protons to solvents, multiple long-range NOEs and heat stable subdomains were observed. Biphasic hyperchromic transitions occurred (52 and 73 degrees C). A G-C base pair occurs in the hairpin loop (HL) (based on dimethylsulfate, RNAse T1 previously used, and changes in NMR imino proton resonances typical of G-C base pairs after G/A substitution). Mutation of the hairpin loop also decreased temperature stability and changed the 31P-NMR spectrum; regulation and protein (IRP) binding were previously shown to change. Alteration of IRE structure shown by NMR spectroscopy, occurred at temperatures used in studies of IRE function, explaining loss of IRP binding. The effect of the HL mutation on the IRE emphasizes the importance of HL structure in other mRNAs, viral RNAs (e.g. HIV-TAR), and ribozymes.

Animals↗
PubMed1995

Identification of the glycosidase inhibitors swainsonine and calystegine B2 in Weir vine (Ipomoea sp. Q6 [aff. calobra]) and correlation with toxicity.

The polyhydroxy alkaloid glycosidase inhibitors swainsonine [1] and calystegine B2 [6] have been identified as constituents of the seeds of the Australian plant Ipomoea sp. Q6 [aff. calobra] (Weir vine) by gas chromatography-mass spectrometry and by their biological activity as inhibitors of specific glycosidases. This plant, which is known only from a small area of southern Queensland, has been reported to produce a neurological disorder when consumed by livestock. The extract of the seeds showed inhibition of alpha-mannosidase, beta-glucosidase, and alpha-galactosidase, consistent with the presence of 1 and alkaloids of the calystegine class. Histological examination of brain tissue from field cases of sheep and cattle poisoned by Weir vine showed lesions similar to those observed in animals poisoned by the swainsonine-containing poison peas (Swainsona spp.) of Australia and locoweeds (Astragalus and Oxytropis spp.) of North America. These results indicate that Weir vine poisoning is an additional manifestation of the induced lysosomal storage disease, mannosidosis, possibly exacerbated by inhibition of the enzymes beta-glucosidase and alpha-galactosidase by calystegine B2. This is the first reported example of a single plant species capable of producing structurally distinct glycosidase inhibitors, namely, alkaloids of the indolizidine and nortropane classes.

Australia↗
PubMed1995

The Queensland Poisonous Plants Committee: its history and functions.

The Queensland Poisonous Plants Committee was established in 1937 with Professor HR Seddon as chairman. It has functioned since that year, interrupted by two periods of inactivity in 1951-9 and 1962-8. Professor Seddon, first Dean of the Queensland Veterinary School, and Dr. Selwyn Everist, Queensland Government Botanist after the Second World War, provided the main impetus for committee activities in its early and middle years, respectively. The strength of the body has been its multi-disciplinary approach using contributions from veterinarians, chemists and botanists. The research work of the committee members and their associates has provided most of our current knowledge of the toxins and effects of poisonous plants in Queensland. Much of the information generated is of international significance. In equal partnership with the United States Department of Agriculture, the committee initiated a series of international symposia on plant poisoning of animals, hosting the second. This group held its 4th gathering of world authorities in the field in 1993. The committee's activities have long influenced the veterinary profession in Australia through the close involvement of its members in undergraduate and post-graduate teaching in the Queensland Veterinary School since 1951. The present committee has members from the Departments of Primary Industries, Health, and Environment and Heritage, CSIRO and the University of Queensland.

History, 20th Century↗
PubMed1994

Structure and function of IREs, the noncoding mRNA sequences regulating synthesis of ferritin, transferrin receptor and (erythroid) 5-aminolevulinate synthase.

The synthesis of least three proteins involved in iron metabolism is coordinately regulated in animals through noncoding sequences in mRNA, the IREs; the transcription of the genes encoding the proteins are also regulated. Cellular iron is the best known effector of changes in regulation of mRNA with IREs. A hairpin loop is the secondary structure of IRES which conserve the hairpin loop sequence, CAGUGU/C. However, variable stem sequences, apparently related to mRNA-specific function, create a family of IRE regulatory sequences. At least three types of proteins recognize IRE regions: (1) Nucleases which degrade mRNAs with 3' noncoding IRES; the IRE/IRE-BP stabilizes mRNAs with 3' noncoding IRES (transferrin receptor mRNA). (2) Initiation factors/ribosomes; the IRE/IRE-BP blocks ribosome binding of mRNAs with 5' noncoding IREs (ferritin, eALAS mRNAs). (3) Initiation factors to enhance translation (ferritin mRNA) when the IRE-BP does not bind; the ferritin IRE is thus both a negative and positive control element depending on which type of protein is bound. The IRE in ferritin mRNA is the most studied IRE to date. Site-directed mutagenesis shows that sites throughout the IRE alter negative control and IRE-BP binding reflecting the fact that the footprint of the IRE-BP is over the entire IRE. Base paired flanking regions (FL) which are ferritin IRE specific, enhance the effects of IRE-BP binding on negative control. Positive control is altered by modifying the single sites in stem/internal loop but not in the hairpin loop.(ABSTRACT TRUNCATED AT 250 WORDS)

5-Aminolevulinate Synthetase↗
PubMed1994

Pyrrolizidine alkaloidosis of cattle associated with Senecio lautus.

Serious incidents of pyrrolizidine alkaloidosis of cattle in 10 herds exposed to the Australian native plant, Senecio lautus (Asteraceae), were seen in central Queensland during 1988-1992. The deaths of 226 cattle were recorded. A mean of 8% of cattle died in affected groups (range 2 to 58%). Sickness and deaths usually occurred some months after access to S lautus. Typically, affected cattle lost body condition to the point of emaciation before dying and had persistent diarrhoea. Some animals developed abnormal behaviour and died after a shorter illness. Liver specimens from affected cattle in all herds contained lesions consistent with pyrrolizidine alkaloidosis. Thin layer chromatography of extracts of blood and liver samples from cattle from 5 herds detected pyrrolic metabolites. The identity of these was confirmed by mass spectroscopy on samples from one herd. Unseasonal autumn and winter rain after a dry summer appeared to favour growth of S lautus at the expense of other pasture species. A subsequent dry period promoted consumption of S lautus and was followed by a cluster of poisoning incidents.

Animals↗
PubMed1991

Ferritin mRNA probed, near the iron regulatory region, with protein and chemical (1,10-phenanthroline-Cu) nucleases. A possible role for base-paired flanking regions.

Iron stimulates ferritin synthesis in whole cells and animals, by increasing the entry of ferritin mRNA into polyribosomes. Dissection of the regulation at the molecular level has identified a 28-nucleotide, conserved, regulatory sequence (IRE = iron regulatory element) in the 5' non-coding region of ferritin mRNAs, plus trans-acting factor(s), one of which is a 90-kDa protein. The site of iron action is not entirely characterized but may involve heme; sequences in the 3' non-coding region of ferritin mRNA can modulate regulation. Ferritin mRNA is the first eukaryotic mRNA for which a conserved regulatory sequence and regulator protein have been identified. The same RNA-protein motif is used, through iron-dependent degradation of transferrin receptor mRNA, to decrease synthesis of the receptor and cellular iron uptake. The regulatory structure of the transferrin receptor mRNA is composed, in part, of five copies of the IRE in the 3' non-coding region. IRE structure, probed by cleavage with RNases T1, V1, 1,10-phenanthroline-Cu or modification with dimethyl sulfate, is a hairpin loop with conformational variations dependent on magnesium; a base-paired region flanking the IRE is also structurally sensitive to magnesium. Similar results were obtained with a synthetic 55-mer containing the IRE and with a full-length in vitro transcript with a G----A substitution in the loop.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1991

A comparison of the effects of two sitting postures on back and referred pain.

This study compared the effects of sitting with portable supports in either a kyphotic or lordotic posture on low-back and referred pain. Two hundred ten patients with low-back and/or referred pain were randomly assigned to either a kyphotic posture or lordotic posture group. The kyphotic and lordotic postures were facilitated by the use of a flat foam cushion or lumbar roll, respectively. Pain location, back pain, and leg pain intensity were assessed over a 24-48-hour period under both standardized clinical settings and general sitting environments. When sitting with a lordotic posture, back and leg pain were significantly reduced and referred pain shifted towards the low back. This study demonstrates that in general sitting environments a lumbar roll results in: 1) reductions in back and leg pain; and 2) centralization of pain. These findings do not apply to patients with stenosis or spondylolisthesis, whose symptoms may be aggravated by use of a lumbar roll.

Adult↗
PubMed1991

Dealing with plant poisoning of livestock: the challenge in Queensland.

The current and possible future situation of diagnosis, prevention and treatment of plant poisoning of livestock in Queensland is reviewed. Topics discussed are livestock producers' perceptions, field investigation, plant identification, veterinary laboratory techniques and prevention through knowledge of poisonous species and the circumstances of poisoning. Also considered are management strategies for prevention including the manipulation of rumen flora and epidemiological approaches, therapies including immunisation, plant control and sources of information on poisonous plants and poisoning.

Animals↗