PubMed Health⌕ Search

Biomedical subjects

R J Hyde

Publications and source records attributed to R J Hyde.

12 recordsLinked to original sources
PubMed1996

Molecular cloning and expression in COS-1 cells of pig kidney aminopeptidase P.

Aminopeptidase P (AP-P; X-Pro aminopeptidase; EC 3.4.11.9), a key enzyme in the metabolism of the vasodilator bradykinin, has been cloned from a pig kidney cortex cDNA library following the use of the PCR to identify sub-libraries enriched in AP-P clones. The complete primary sequence of the enzyme has been deduced from a full-length cDNA clone. This predicts a protein of 673 amino acids with a cleavable N-terminal signal sequence and six potential N-linked glycosylation sites. A stretch of mainly hydrophobic amino acids at the C-terminus is predicted to co-ordinate the attachment of a glycosyl-phosphatidylinositol (GPI) membrane anchor. Although AP-P is a zinc metallopeptidase, the predicted primary sequence does not contain any recognizable zinc-binding motif. Transient expression of AP-P cDNA in COS-1 cells resulted in enzymic activity characteristic of AP-P, namely apstatin- and EDTA-sensitive hydrolysis of bradykinin and Gly-Pro-Hyp. The expressed protein was recognized as a polypeptide of M(r)91,000 under reducing conditions, following immunoblotting of COS-1 membranes with a polyclonal antibody raised against purified pig kidney AP-P. The presence of a GPI anchor on expressed AP-P was established by demonstrating release of the enzyme from a membrane fraction following treatment with bacterial phosphatidylinositol-specific phospholipase C and its corresponding conversion from an amphipathic to a hydrophilic form, as assessed by phase separation in Triton X-114. Sequence comparisons confirm that AP-P is a member of the proline peptidase family of hydrolytic enzymes and is unrelated in sequence to other brush-border membrane peptidases.

Amino Acid Sequence↗
PubMed1994

MRI scanner variability studies using a semi-automated analysis system.

Due to the unique design of the Parallel Rod Test Object (PRoTO) and the associated semi-automated analysis program, it was necessary to test it extensively for precision and accuracy, and preliminarily for utility, before its distribution for wider use in MRI system quality control (QC). The test object and analysis program measured the desired quantities reproducibly and they accurately measured predicted changes from intentionally adjusted imaging system parameters, yielding sensitivity of the various test measures to deviation in the system operating parameters. From a single scan of the most recent revision of the test object, multiple quantitative quality control measures were obtained throughout the scanning volume on two MR imaging systems over periods of six and twelve months, respectively. From these and earlier trials, an initial indication was obtained of which performance measures are worth monitoring for QC. This experience suggests that signal-to-noise ratio (SNR) and distortion (including display scale) should be monitored but not necessarily the resolution. The latter was only found to alter at the same time or later than other parameters such as SNR had changed. Slice thickness was found to vary on some units and this measure was also used in normalizing the SNR by voxel volume. SNR, distortion, and resolution measurements using field-echo sequences were less stable than those using spin-echo sequences. Use of this QC program to test a wide variety of image quality measures allowed timely assessment of the long-term variability of the units tested. Long-term variability may become among the most important measures for comparison of system performance and maintenance.(ABSTRACT TRUNCATED AT 250 WORDS)

Artifacts↗
PubMed1993

Dynamic contrast: a sensory contribution to palatability.

By focusing on a sensory model for palatability, the "ice-cream effect", we speculate on some principles underlying palatability. We propose that the most highly palatable foods are likely to have higher levels of "dynamic contrast" (moment-to-moment sensory contrast from the everchanging properties of foods manipulated in the mouth). The sensory feature contributing most to dynamic contrast seems to be somatosensation. Texture, for example, over the course of masticating a crunchy food, changes markedly such that each alteration contributes differently and dynamically to sensory contrast. Our purpose herein is to propose that dynamic contrast contributes significantly to palatability of foods and beverages.

Animals↗
PubMed1993

Signal-to-noise measures for magnetic resonance imagers.

The signal-to-noise ratio (SNR) in magnetic resonance imaging represents one of the system operating variables that must be determined both for evaluating the performance of different imaging protocols on a particular machine, and for monitoring machine performance as part of a routine quality control (QC) program. Utilizing a phantom and set of automated analysis programs currently under development, this study evaluated several ways of measuring image signal and noise and demonstrated the importance of utilizing measured voxel volumes as opposed to nominal volumes in the calculation of SNR. The NEMA proposed standard for SNR is compared with several other SNR measures and is recommended as the measure to be used in routine SNR reporting. The importance of utilizing other SNR measures in addition to the NEMA proposed standard for routine QC is discussed.

Magnetic Resonance Imaging↗
PubMed1988

A simple method of producing parenchymal renograms using parametric imaging.

Standard dynamic renography procedures are used to produce time-activity curves for defined regions of interest around the kidneys. Further analysis of the acquired data using Fitted Retention and Excretion Equations (FREE) to determine single kidney glomerular filtration rate (GFR) and kidney transit time is performed at the Royal Marsden Hospital, Sutton. The disadvantage of these methods is that the renal function is assessed for the whole kidney and not on a regional basis. The aim of this study was to use parametric imaging to extend the standard analysis so that the parenchyma could be identified and analysed separately from the collecting system. The parenchyma pixel time-activity curves have shorter time-to-peak (TTP) values than the collecting system. TTP parametric images were used to set limits on the TTP values and thus define the parenchyma pixels. The time-activity curves from the parenchyma were further analysed using FREE to produce parametric images of both GFR and effective blood volume. Finally, the original dynamic data were re-analysed so that time-activity and FREE curves were generated for the parenchyma alone. A study of 15 patients (30 kidneys) showed that the extended analysis indicated parenchymal isotope clearance. By comparing the time-activity and FREE curves of the whole kidney with those from the parenchyma alone, a more useful analysis of parenchymal function was obtained. This proved to be particularly useful for patients with pelvi-ureteric junction (PUJ) obstruction.

Humans↗
PubMed1981

Age and sex effects on taste of sucrose, NaCl, citric acid and caffeine.

A procedure combining forced choice discrimination with intensity scaling served to evaluate taste perception of sucrose, NaCl, citric acid and caffeine in 24 young and 24 geriatric subjects. Each group was divided equally by sex. No overall sex differences occurred for taste discrimination, and suprathreshold taste intensity scaling for sucrose and NaCl did not differ by sex or age. However, young adults generally discriminated lower concentrations of citric acid and caffeine from water blanks than did geriatric subjects. Younger subjects judged suprathreshold concentrations of caffeine significantly more intense, as did young females compared to young males; similarly, young females judged citric acid as stronger than did older males. The present suggest that age and gender are major factors in sour and bitter perception.

Adult↗
PubMed1978

Thermistor use to monitor urine flow rates in dogs.

The small size of a new thermistor flowmeter facilitated implantation in ureters in anesthetized dogs. It consisted of a self-heating thermistor bead which was suspended centrally within an open catheter and dissipated heat as a function of fluid velocity. A continuous record of instantaneous flow rate was obtained, since the flowmeter catheter maintained a constant cross-sectional area around the thermistor bead. A continuous record of volume output was obtained simultaneously with an additional measurement technique. Spurt volumes of urine delivered in concert with ureter peristalsis were directly correlated to peak flow rates delineated by the flowmeter.

Animals↗
PubMed1977

Anatomy and cannulation of the parotid duct in the dog.

The course of the dog's parotid duct is more complex than previously reported. The newly described features are that the duct has 2 right-angle curves in its terminal part and that it perforates the fascia and mucosa of the cheek between the orbicularis oris and buccinator muscles. The duct does not perforate the buccinator muscle. Based on these findings, a rapid and reliable technique for intubation of the duct was developed.

Animals↗