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Biomedical subjects

S R Muir

Publications and source records attributed to S R Muir.

8 recordsLinked to original sources
PubMed2003

EMMA--an eye movement measurement and analysis system.

A system has been developed for stimulation, recording and analysis of a wide range of eye movements. Eye movements are stimulated with an LED bar or a video projector under the control of a PC. The eye movements are measured using a scleral reflection technique (IRIS instrument), and sampled and stored on a PC. A range of tests have been developed to measure saccadic and smooth pursuit eye movements. A variety of tools have been developed to assist in the analysis of the data. Several research studies have ably demonstrated the utility and versatility of the system.

Equipment Design↗
PubMed2001

Overexpression of petunia chalcone isomerase in tomato results in fruit containing increased levels of flavonols.

Tomatoes are an excellent source of the carotenoid lycopene, a compound that is thought to be protective against prostate cancer. They also contain small amounts of flavonoids in their peel ( approximately 5-10 mg/kg fresh weight), mainly naringenin chalcone and the flavonol rutin, a quercetin glycoside. Flavonols are very potent antioxidants, and an increasing body of epidemiological data suggests that high flavonoid intake is correlated with a decreased risk for cardiovascular disease. We have upregulated flavonol biosynthesis in the tomato in order to generate fruit with increased antioxidant capacity and a wider range of potential health benefit properties. This involved transformation of tomato with the Petunia chi-a gene encoding chalcone isomerase. Resulting transgenic tomato lines produced an increase of up to 78 fold in fruit peel flavonols, mainly due to an accumulation of rutin. No gross phenotypical differences were observed between high-flavonol transgenic and control lines. The phenotype segregated with the transgene and demonstrated a stable inheritance pattern over four subsequent generations tested thus far. Whole-fruit flavonol levels in the best of these lines are similar to those found in onions, a crop with naturally high levels of flavonol compounds. Processing of high-flavonol tomatoes demonstrated that 65% of flavonols present in the fresh fruit were retained in the processed paste, supporting their potential as raw materials for tomato-based functional food products.

Chalcone↗
PubMed1997

Inositol 1,4,5-trisphosphate-sensitive Ca2+ release across nonvacuolar membranes in cauliflower.

Previous studies have indicated that the vacuole represents the major inositol 1,4,5-trisphosphate (InsP3)-mobilizable Ca2+ pool in higher plants. This findings is in contrast to animal cells, in which the endoplasmic reticulum and plasma membrane constitute the dominant InsP3-sensitive membranes. We used membrane vesicles prepared from cauliflower (Brassica oleracae L.) inflorescences that were separated on continuous sucrose gradients to demonstrate that cauliflower possesses at least two distinct membrane populations that are sensitive to InsP3. One of these membrane populations in nonvacuolar in origin and relies upon a Ca(2+)-ATPase to accumulate Ca2+. In addition, we have shown that two polyclonal antibodies, raised against peptides corresponding to the animal type 1 InsP3 receptor, recognize immunologically related proteins in cauliflower, and that the distribution of immunoreactive proteins on a linear sucrose gradient reinforces the notion that cauliflower contains more than one membrane subtype that is sensitive to InsP3. To our knowledge, this is the first report describing an InsP3-sensitive Ca2+ store other than the vacuole in higher plant cells.

Amino Acid Sequence↗
PubMed1997

IgG subclasses specific to Staphylococcus epidermidis and Propionibacterium acnes in patients with acne vulgaris.

IgG subclasses specific to Staphylococcus epidermidis and Propionibacterium acnes were determined in sera from patients with mild, moderate or severe acne and from a control group. Titres specific to S. epidermidis were all within the same range and did not differ between groups. The titres of IgG subclasses to specific to P. acnes did vary between groups. IgG1 and IgG3 were significantly higher in severe acne patients compared with moderate acne patients, while IgG2 was significantly higher in moderate and severe patients compared with controls. Titres of IgG4 did not differ between groups. The pattern of titres observed suggests that, while the antibody response to S. epidermidis is relatively harmless, antibodies to P. acnes may be involved in the pathogenesis of acne vulgaris.

Acne Vulgaris↗
PubMed1996

Pharmacology of Ca2+ release from red beet microsomes suggests the presence of ryanodine receptor homologs in higher plants.

Cyclic ADP-ribose (cADPR) is known to release Ca2+ from plant vacuoles, implying that this NAD+ metabolite may possess a second messenger role in plants. The degree to which the plant cADPR-gated Ca2+ release mechanism resembles cADPR action in animals has been evaluated. cADPR-elicited Ca2+ release from red beet microsomes was inhibited by 1 mM procaine but insensitive to heparin. Furthermore, pre-release of Ca2+ from red beet vesicles by either 5 mM caffeine or micromolar levels of ryanodine precluded further Ca2+ mobilisation by cADPR. Thus, this study argues strongly for conservation between the plant and animal cADPR-elicited Ca2+ release mechanisms.

Adenosine Diphosphate Ribose↗
PubMed1995

Release of Ca2+ from individual plant vacuoles by both InsP3 and cyclic ADP-ribose.

Calcium mobilization from intracellular pools couples many stimuli to responses in plant cells. Cyclic adenosine 5'-diphosphoribose (cADPR), which interacts with a ryanodine receptor in certain animal cells, was shown to elicit calcium release at the vacuolar membrane of beet storage root. The vacuolar calcium release pathway showed similarities to cADPR-gated calcium release in animal cells, including inhibition by ruthenium red, ryanodine activation, and high affinity for cADPR [Michaelis constant (Km) = 24 +/- 7 nanomolar]. Analysis by patch-clamping demonstrated that the cADPR-gated pathway in beet is voltage-dependent over the physiological range, does not spontaneously desensitize, and is colocalized with an inositol 1,4,5-trisphosphate (InsP3)-gated calcium release pathway in individual vacuoles.

Adenosine Diphosphate Ribose↗