Biomedical subjects

K A Beattie

Publications and source records attributed to K A Beattie.

At least 19 recordsLinked to original sources

PubMed2005

Abnormalities identified in the knees of asymptomatic volunteers using peripheral magnetic resonance imaging.

OBJECTIVE: To estimate the prevalence of bone and soft tissue abnormalities in asymptomatic knees using peripheral magnetic resonance imaging (pMRI) and to examine the relationship between these abnormalities and Kellgren-Lawrence (K-L) graded X-rays. METHOD: Volunteers (20-68 years) with no history of knee pain, injury or bone or joint disease were recruited. Individuals underwent a single MRI scan and radiograph of their non-dominant knee. pMR images were acquired in sagittal plane using a 3-D gradient-echo protocol. Two radiologists graded the presence and severity of cartilage degeneration, osteophytosis, meniscal and ligamentous abnormalities, bone marrow edema and subchondral cysts. X-rays were acquired using a fixed-flexion technique and graded using the K-L scale. RESULTS: Forty-four individuals, mean age (SD) 41.1 (14.2) years, participated. K-L grading of X-rays revealed 29 individuals were grade 0, 12 were grade 1 and 3 were grade 2. Five individuals showed evidence of cartilage lesions, the femoral trochlea, medial femur and patella being those regions most commonly affected. Twelve individuals (27.3%) showed evidence of osteophytosis, nine of whom did not show evidence on X-ray. Forty-three individuals showed evidence of at least one meniscal abnormality while 27 individuals (61.4%) had abnormalities in at least three of the four regions of the knee. CONCLUSION: Our results suggest that osteophytes may be more prevalent in this population than radiographic data suggests due to the limitations of two-dimensional imaging. Meniscal degeneration or tears, a risk factor for knee osteoarthritis, are highly prevalent in asymptomatic individuals with the medial anterior and posterior horns being the most commonly affected regions.

Adult↗

PubMed2005

The relationships between bone mineral density in the spine, hip, distal femur and proximal tibia and medial minimum joint space width in the knees of healthy females.

OBJECTIVE: To investigate the relationships between bone mineral density (BMD) in the hip, spine, distal femur and proximal tibia and minimum joint space width (mJSW) in the knees of healthy women. METHODS: Women 22-68 years old without a history of knee pain, bone or joint disease or injury underwent a single, fixed-flexion knee X-ray. Radiographs were graded according to the Kellgren-Lawrence scale and analyzed for mJSW using a computer algorithm. Dual X-ray absorptiometry scans of the spine, hip, distal femur and proximal tibia were also acquired for each participant. Femur and tibia scans were acquired and analyzed using a modified version of the lumbar spine software. RESULTS: Forty-five females, mean [standard deviation (SD)] age and body mass index (BMI) of 40.1 (13.9) years and 24.6 (4.5)kg/m(2), respectively, participated. The mean (SD) mJSW was 4.64 (0.68)mm. Linear regression analyses controlling for age and BMI revealed that BMD in the femoral trochanter and the central two regions of the tibia (T2 and T3) was significantly related to mJSW in the knee. A backwards regression analysis performed to determine which region of interest is most significantly related to mJSW revealed that femoral trochanter BMD (beta-value=0.416) is the most significant. CONCLUSIONS: In contrast to the suggestion that BMD is negatively correlated with mJSW in the knees of osteoarthritic individuals, these results suggest that increasing BMD in the femoral trochanter and tibia is significantly associated with increasing mJSW in healthy females. Further investigation of this relationship is warranted.

Absorptiometry, Photon↗

PubMed2002

Effects of organic solvents on the high performance liquid chromatographic analysis of the cyanobacterial toxin cylindrospermopsin and its recovery from environmental eutrophic waters by solid phase extraction.

The effect of organic solvents on the high performance liquid chromatography (HPLC) analysis of cylindrospermopsin using photodiode array detection was examined since organic solvents are commonly used to extract this toxin from cyanobacteria and in the mobile phase compositions used in HPLC. Increasing concentrations of methanol resulted in an increase in the UV absorbance of purified cylindrospermopsin according to spectrometry, but to a marked decrease during HPLC analysis when the concentration of this solvent was greater than 50% methanol, or when acetonitrile concentrations exceeded 30% (v/v). Precipitation of cylindrospermopsin at these high concentrations of organic solvents was not observed. Solid phase extraction methods were developed to recover the toxin from spent extracellular growth medium after laboratory culture of Cylindrospermopsis raciborskii strain CR3 as an aid to toxin purification and from spiked environmental water samples. Using C18 and polygraphite carbon cartridges in series, 100% recoveries of cylindrospermopsin were achieved for lake waters spiked at 1 micro g l(-1).

Alkaloids↗

PubMed2002

Toxicity of cylindrospermopsin to the brine shrimp Artemia salina: comparisons with protein synthesis inhibitors and microcystins.

The Artemia salina bioassay was successfully applied to the analysis of the hepatotoxic cyanobacterial alkaloid and protein synthesis inhibitor, cylindrospermopsin. A dose-dependent response in mortality was observed for purified cylindrospermopsin and LC(50) values decreased with time from 8.1 to 0.71 microg/ml(-1), between 24 and 72 h, respectively. Cylindrospermopsin was slightly less potent than micro cystin-LR, with similar LC(50) values on a gravimetric basis, but was more toxic to A.salina than the protein synthesis inhibitors, cycloheximide, chloramphenicol and tetracycline. Cylindrospermopsin-containing strains of the cyanobacterium Cylindrospermopsis raciborskii were found to be toxic to A.salina and the LC(50) concentration for these strains over time was greater than the LC(50) for purified cylindrospermopsin, with the exception of C. raciborskii strain CR1.

Alkaloids↗

PubMed2001

Losses of the cyanobacterial toxin microcystin-LR from aqueous solution by adsorption during laboratory manipulations.

The effect of plastic and methanol on the loss of microcystin-LR from solution was analysed by HPLC with photodiode array detection (HPLC-PDA). With plastic disposable pipette tips, the loss from an aqueous microcystin-LR (MC-LR) solution was 4.2% per tip operation. Using the same pipette tip, four operations were required to completely saturate a single tip with toxin. MC-LR attached to plastic pipette tips could subsequently be eluted by methanol and detected by HPLC-PDA. At methanol concentrations below 25% (v/v), recovered concentrations of MC-LR decreased significantly. Differences in MC-LR concentration were also noted by performing 50% dilution with Milli-Q water or methanol. The results are discussed in relation to the hydrophobicity of MC-LR, analytical procedures and the avoidance of toxin losses from solution during laboratory manipulations.

Adsorption↗

PubMed2001

Effects of adsorption to plastics and solvent conditions in the analysis of the cyanobacterial toxin microcystin-LR by high performance liquid chromatography.

Effects of adsorption to plastics and solvent conditions in the high performance liquid chromatographic analysis of the cyanobacterial toxin microcystin-LR were investigated. Aqueous microcystin-LR readily adsorbed to the disposable polypropylene pipette tips commonly used in laboratory manipulations. This was not affected by the pH or salinity of the solution. Furthermore, dilutions of microcystin-LR in varying concentrations of methanol and acetonitrile influenced the quantification of the microcystin-LR concentration by high performance liquid chromatography.

Adsorption↗

PubMed2001

Uptake, effects, and metabolism of cyanobacterial toxins in the emergent reed plant Phragmites australis (cav.) trin. ex steud.

The commonly occurring cyanobacterial toxin microcystin-LR (MC-LR) was rapidly taken up by the emergent reed plant Phragmites australis with clear distribution in the different cormus parts of the plant. Highest uptake was detected in the stem, followed by the rhizome. Enzyme extracts of the rhizome system, the stem, and the leaf revealed the presence of soluble glutathione S-transferases (sGST) measured with the model substrate 1-chloro-2,4-dinitrobenzene. A significant elevation of sGST activity in the rhizome and stem parts of P. australis was detected after a 24-h exposure to 0.5 microg/L MC-LR. Rhizome, stem, and leaf tissues were also able to conjugate several microcystin toxins. However, no conjugation, either chemical nor enzymatic, was detected using the related cyanobacterial toxin nodularin as substrate. Highest glutathione S-transferase activity for the toxin substrates was detected in the pkat/mg range in the stem of P. australis. For MC-LR, a complete metabolism from the formation of a glutathione conjugate to the degradation of a cysteine conjugate in all cormus parts of the plant is reported. The stepwise degradation of the MC-LR-glutathione conjugate to a gamma-glutamylcysteine and a cysteine conjugate was demonstrated by comparison with chemically formed reference compounds and by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This is the first evidence for the uptake and metabolism of cyanobacterial toxins by an emergent aquatic macrophyte.

Bacterial Toxins↗

PubMed2000

Immuno-crossreactivity and toxicity assessment of conjugation products of the cyanobacterial toxin, microcystin-LR.

Immunoassays are increasingly used to investigate the production, properties and fates of the cyanobacterial hepatotoxic microcystins in vitro and in vivo. Responses of an ELISA immunoassay to microcystins have been determined using the authentic toxin antigen, microcystin-LR, and conjugation products between the toxin and glutathione, cysteine-glycine and cysteine. The antibodies against microcystin-LR crossreacted with the toxin conjugation products with similar affinities (96-112%) to that of microcystin-LR, when assayed at a concentration of 1 microg l(-1). Toxicity assessment of the conjugates, in comparison to microcystin-LR, indicated a reduction according to mouse bioassay. In vitro protein phosphatase inhibition assay indicated that the conjugates possessed approximately 3-9-fold lower toxicity than microcystin-LR.

Animals↗

PubMed2000

The cyanobacterium Nodularia PCC 7804, of freshwater origin, produces [L-Har2]nodularin.

The cyanobacterium Nodularia PCC 7804, an axenic, non gas-vacuolate strain from a freshwater source, produces several metabolites with cyanobacterial hepatotoxin characteristics. The most abundant is a cyclic pentapeptide, [L-Homoarginine2]nodularin. [L-Har2]nodularin is of similar toxicity, in terms of bioassay in vivo, and the inhibition of protein phosphatase-1 in vitro to nodularin, which was present in lesser amounts in the cultures.

Amino Acids↗

PubMed2000

[D-Leu1]Microcystin-LR, from the cyanobacterium Microcystis RST 9501 and from a Microcystis bloom in the Patos Lagoon estuary, Brazil.

[D-Leu1]Microcystin-LR was identified as the most abundant microcystin from a laboratory strain of the cyanobacterium Microcystis sp. isolated from a hepatotoxic Microcystis bloom from brackish waters in the Patos Lagoon estuary, southern Brazil. Toxicity of [D-Leu1]microcystin-LR, according to bioassay and protein phosphatase inhibition assay, was similar to that of the commonly-occurring microcystin-LR, which was not detectable in the Patos Lagoon laboratory isolate. This is the first report of a microcystin containing [D-Leu1] in the cyclic heptapeptide structure of these potent cyanobacterial toxins.

Brazil↗

PubMed2000

Direct analysis of microcystins by microbore liquid chromatography electrospray ionization ion-trap tandem mass spectrometry.

Microcystins are a group of structurally similar cyclic heptapeptide hepatotoxins and tumor promoters, produced by cyanobacteria. A microbore liquid chromatography electrospray ionization ion-trap mass spectrometry (LC-ESI-ITMS) method has been developed which is capable of separating and detecting trace amounts of microcystin variants in environmental samples. Extracted water sample was loaded onto a LC trapping column and, using a column switching technique, the compounds of interest were back-flushed onto a 1-mm LC column. Structural elucidation was achieved using ion-trap with tandem mass spectrometry in the data dependent scan mode. Collision-induced dissociation to MS3 allowed tentative identification of these cyclic peptides. Full-scan LC-ESI-MS mass spectrum was obtained when 250 pg of the authentic compound was injected onto the HPLC column, which represents the detection limit for microcystin-LR. This study demonstrated that LC-ESI-ITMS is a reliable and sensitive technique for analysing trace levels of microcystins.

Bacterial Toxins↗

PubMed2000

Effects of physicochemical variables and cyanobacterial extracts on the immunoassay of microcystin-LR by two ELISA kits.

Two types of commercially available ELISA kits for the immunoassay of cyanobacterial microcystins were evaluated for potential interference effects due to methanol, salinity, pH, plasticware and cyanobacterial extract. Of the treatments examined, methanol had the greatest effect, giving false positive microcystin concentrations with increasing methanol concentrations up to 30% (v/v) compared with the negative calibrators of each kit. False positive microcystin results were also produced with increasing salinity up to full strength seawater. Decreases in microcystin-LR equivalents were observed when assaying purified microcystin-LR at pH values between 6.25 and 10. Aqueous microcystin-LR solutions in plastic microcentrifuge tubes after pipetting with disposable plastic tips had lower toxin concentrations than expected when analysed by ELISA. Indicated microcystin concentrations in cyanobacterial extracts varied between kit types and the choice of blanks used. Although ELISAs can be useful tools for the screening of water and cyanobacterial blooms for microcystins and nodularins, users should be aware that commercial kits can be susceptible to interference by commonly encountered environmental and laboratory conditions and materials.

Cyanobacteria↗

PubMed1999

Retention of Microcystis aeruginosa and microcystin by salad lettuce (Lactuca sativa) after spray irrigation with water containing cyanobacteria.

Colonies and single cells of Microcystis aeruginosa and the hepatotoxin microcystin were retained by salad lettuce after growth with spray irrigation water containing the microcystin-producing cyanobacteria. These findings are discussed in terms of crop spray irrigation with water containing cyanobacteria and potential human exposure to cyanobacterial toxins via plant foods grown in such circumstances.

Carcinogens↗

PubMed1998

Identification of an enzymatically formed glutathione conjugate of the cyanobacterial hepatotoxin microcystin-LR: the first step of detoxication.

Cyanobacterial toxins have adverse effects on mammals, birds and fish and are being increasingly recognised as a potent stress factor and health hazard factor in aquatic ecosystems. Microcystins, cyclic heptapeptides and a main group of the cyanotoxins are mainly retained within the producer cells during cyanobacterial bloom development. However, these toxins are released into the surrounding medium by senescence and lysis of the blooms. Any toxin present could then come into contact with a wide range of aquatic organisms including phytoplankton grazers, invertebrates, fish and aquatic plants. Recent studies showed the conversion of microcystin in animal liver to a more polar compound in correlation with a depletion of the glutathione pool of the cell. The present study shows the existence of a microcystin-LR glutathione conjugate formed enzymatically via soluble glutathione S-transferase in various aquatic organisms ranging from plants (Ceratophyllum demersum), invertebrates (Dreissena polymorpha, Daphnia magna) up to fish eggs and fish (Danio rerio). The main derived conjugate was characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry yielding a mass of m/z 1302, which is equivalent to the mass assumed for a glutathione microcystin-LR conjugate. This conjugate appears to be the first step in the detoxication of a cyanobacterial toxin in aquatic organisms.

Animals↗

PubMed1998

Two (Z)-dehydrobutyrine-containing microcystins from a hepatotoxic bloom of Oscillatoria agardhii from Soulseat Loch, Scotland.

Two (Z)-dehydrobutyrine(Dhb)-containing microcystins, [d-Asp3, (Z)-Dhb7]microcystin-HtyR (1) and [d-Asp3, (Z)-Dhb7]microcystin-LR (2), were isolated from a hepatotoxic bloom of the cyanobacterium Oscillatoria agardhii from a freshwater lake in Scotland. The geometrical structure of the Dhb units in the microcystins was determined as Z on the basis of NOE and ROESY experiments.

Carbohydrate Sequence↗

PubMed1997

Colorimetric protein phosphatase inhibition assay of laboratory strains and natural blooms of cyanobacteria: comparisons with high-performance liquid chromatographic analysis for microcystins.

Microcystins are cyclic heptapeptide hepatotoxins commonly produced by bloom-forming genera of cyanobacteria. These toxins are potent and specific inhibitors of protein phosphatases 1 and 2A. We have optimised a rapid, simple and sensitive colorimetric protein phosphatase 1 inhibition assay, utilising the activity of protein phosphatase 1 as expressed in a recombinant strain of Escherichia coli, towards the chromogenic substrate, p-nitrophenyl phosphate. A standard curve for the inhibition of protein phosphatase 1 by microcystin-LR was constructed with an IC50 of about 38 ng ml-1 and a limit of detection of 10-20 ng ml-1. Twenty-three laboratory-grown strains and 25 natural bloom samples of cyanobacteria were analysed by high-performance liquid chromatography for microcystins and by the protein phosphatase 1 inhibition assay. Agreement for the microcystin contents of the samples detected by high-performance liquid chromatography and the protein phosphatase 1 inhibition assay showed good correlation (R2 > 0.93, P < 0.0001). The suitability of the colorimetric protein phosphatase 1 inhibition assay as a screen for cyanobacterial microcystins is discussed.

Chromatography, High Pressure Liquid↗

PubMed1995

Isolation and characterization of microcystins from laboratory cultures and environmental samples of Microcystis aeruginosa and from an associated animal toxicosis.

Six microcystins were identified in a laboratory culture of the cyanobacterium (blue-green alga) Microcystis aeruginosa PCC 7813 using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) and mass spectrometry (LC-MS). The toxins were purified and further characterized by amino acid analysis and tandem mass spectrometry (MS-MS). The presence of the previously reported microcystin-LR and microcystin-LY was confirmed. Two further microcystins were characterized as microcystin-LW and microcystin-LF. Another two toxins were partially characterized and are believed to be an analog of microcystin-LR (molecular weight 1008) and microcystin-LM (molecular weight 969). Natural bloom material of M. aeruginosa collected from 2 reservoirs was found to have similar microcystin profiles using HPLC-DAD and LC-MS, indicating the widespread occurrence of these microcystin variants. In addition, the presence of 5 of the microcystins was confirmed in the rumen contents of a lamb by LC-MS and LC-MS-MS, providing the first report of microcystins identified in an animal suspected of being poisoned by cyanobacterial hepatotoxins.

Amino Acid Sequence↗

PubMed1995

Pores formed in lipid bilayers and in native membranes by nodularin, a cyanobacterial toxin.

Nodularin (NODLN), a cyclic pentapeptide hepatotoxin from the cyanobacterium Nodularia spumigena, induces pores in bilayers of diphytanoyl lecithin (DPhL) and in locust muscle membrane. NODLN increases the surface pressure of a DPhL monolayer; except when the surface pressure of the monolayer is high when the toxin causes a reduction of this parameter. NODLN pores exhibit many open conductance states; the higher state probabilities increasing when the transmembrane pressure is increased. The results from these studies are discussed in terms of two models for a NODLN pore, a torroidal model and a barrel-stave model. The edge energy of the NODLN pore of 1.4 x 10(-12) J/m is determined.

Animals↗