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Biomedical subjects

M C Fyfe

Publications and source records attributed to M C Fyfe.

8 recordsLinked to original sources
PubMed2000

Toward interlocked molecules beyond catenanes and rotaxanes.

A linear bis secondary dialkylammonium ion-containing scaffold-based upon an anthracenyl core-has been synthesized. It has been demonstrated that it is possible to dock either one or two dibenzo[24]crown-8 (DB24C8) macrocycles onto this scaffold to afford either a [2]- or [3]pseudorotaxane, respectively. In solution, the association constants for the formation of each of these species has been quantified by employing (1)H NMR spectroscopy, and both species survive in the "gas phase" as evidenced by FAB mass spectrometry. Additionally, the X-ray crystal superstructure of the [3]pseudorotaxane has been determined.

Journal Article↗
PubMed2000

Ammonium ion binding with pyridine-containing crown ethers.

Dipyrido[24]crown-8 (DP24C8) has been synthesized and shown to form [2]pseudorotaxanes spontaneously with dibenzylammonium ions. These complexes, which have been demonstrated by (1)H NMR spectroscopy to form faster in solution than when the macrocyclic polyether is dibenzo[24]crown-8 (DB24C8), are also stronger than their DB24C8 counterparts. One of the [2]pseudorotaxanes has been used to construct a [2]rotaxane (see above) comprising a dumbbell-shaped component based on a dibenzylammonium ion which is encircled by a DP24C8 macrocycle and terminated by (triphenylphosphonium)methyl stoppers.

Journal Article↗
PubMed1989

Mediators of the plasma extravasation response to silver nitrate in the rat skin, subplantar region and ankle joint.

Plasma extravasation responses to silver nitrate (AgNO3), histamine, 5-hydroxytryptamine (5-HT), bradykinin and prostaglandin E1 (PGE1) in the abdominal skin, hindpaw ankle joint and subplantar region of rats have been investigated using the Evans blue dye leakage technique. All substances tested produced plasma extravasation and combination of low doses (5 x 10(-10) mol) of either histamine or bradykinin with PGE1 (5 x 10(-10) mol) exhibited potentiation of responses of all regions. Responses to AgNO3 (1 x 10(-6) mol) were significantly reduced by the H1 receptor antagonist, mepyramine, only in the abdominal skin, but the H2 receptor antagonist metiamide reduced the responses at subplantar and ankle joint regions. Indomethacin significantly reduced the AgNO3 responses at the ankle joint only, but aprotinin reduced it at the other two regions. In rats pretreated with a combination of all antagonists the residual plasma extravasation response to AgNO3 was very small, indicating that the response could be almost totally accounted for by the combined actions of mast cell amines, kinins and prostanoids. The finding that prostanoids played a major role in the plasma extravasation response of the rat ankle joint to AgNO3 indicated that this model would be useful for the screening of non-steroidal anti-inflammatory drugs.

Alprostadil↗
PubMed1984

Mast cell degranulation and increased vascular permeability induced by 'therapeutic' ultrasound in the rat ankle joint.

Ultrasound at frequencies between 0.75 and 3.0 MHz is widely used in the treatment of musculoskeletal injuries in human and veterinary patients. The mechanisms by which ultrasound affects clinical recovery are, however, incompletely understood. At present no clear rationale has been evolved to guide the selection and use of all the factors comprising the dosage of ultrasound in treatment designed to encourage tissue healing. In the present study applications of ultrasound considered to be therapeutic caused a small but significant increase in vascular permeability in the hindpaw ankles of rats in vivo which was abolished by pre-treatment of the rats with a combination of a histamine H1-receptor antagonist and a serotonin antagonist. Histological sections from rat ankles showed that ultrasound also caused a significant increase in the number of degranulated mast cells above control values. Since mast cells contain histamine, low concentrations of which have been associated with healing, the finding that ultrasound produces mast cell degranulation and evidence of histamine release provides a new direction for investigation of the mechanism of its therapeutic action, and for determination of appropriate regimens of treatment.

Animals↗
PubMed1982

The importance of measurement of effective transducers radiating area in the testing and calibration of "therapeutic" ultrasonic instruments.

The data presented show early results from a longitudinal survey of "therapeutic" ultrasonic instrument performance in clinical physiotherapy. Previous studies undertaken in North America and the United Kingdom have shown that these units tend not to be scientifically tested and recalibrated, and have been found to have measured outputs at variance with the metered values if tests have been undertaken. This study measured effective transducer radiating area and, concurrently, the total power output at the metered intensity used for the area estimations. Actual output, in terms of total power and space averaged intensity was then compared with expected values derived both from manufacturers' data and from measured transducer radiating area. Only four of eighteen transducers (22%) were within the specified tolerance when actual transducer area was taken into account. Range was 179-31% of expected values. False assumptions of acceptable and unacceptable output can arise from failure to measure actual transducer radiating area.

Calibration↗
PubMedDate not supplied

The effect of single or repeated applications of "therapeutic" ultrasound on plasma extravasation during silver nitrate induced inflammation of the rat hindpaw ankle joint in vivo.

The effect of "therapeutic" ultrasound upon plasma extravasation during the inflammatory process induced in the rat hindpaw ankle by intra-articular injection of silver nitrate was investigated in two series of experiments. Both series utilised three ultrasonic frequencies, 0.75, 1.5, and 3.0 MHz, and two pulse ratios, mark:space 1:4 and 1:1. Series 1 examined the effect of two durations of ultrasound, 1 or 2 min, administered once only, and series 2 examined the effect of single or repeated insonations of 1 min duration. It was found that ultrasound treatment increased plasma extravasation compared to controls during the first 24 hr, but later reduced it significantly compared to controls. This secondary effect of reduction in plasma extravasation was delayed in animals given three insonations, this number of insonations being found to prolong the plasma extravasation phase.

Animals↗