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Biomedical subjects

R W Gill

Publications and source records attributed to R W Gill.

At least 19 recordsLinked to original sources
PubMed2001

Doppler sonographic measurements of arterial blood flow and their repeatability in the equine foot during weight bearing and non-weight bearing.

In six normal adult horses, pulsed-wave Doppler sonographic inspections were made of the left and right lateral palmar proper digital artery (LPPDA) of each thoracic limb. Using a two-period, crossover design with repeated measures, each LPPDA was inspected on four occasions throughout the day over a 7 hour period and, on each occasion, with the limb weight bearing and non-weight bearing. In comparison with the observations made during weight bearing, there were significant increases (P<0.001) in blood-flow velocities when the limb was non-weight bearing. There was no relationship between blood velocities and the time of day, the order in which the inspections were made, resting heart rate, age of the horse, or hoof angle. In both weight bearing and nonweight bearing, the Doppler waveform demonstrated a systolic peak followed by at least two diastolic peaks and an end diastolic plateau. Horses that moved least during sonographic inspections had the lowest co-efficients variation.

Animals↗
PubMed2001

Postprandial arterial vasodilation in the equine distal thoracic limb.

The effects of feeding on blood flow to the equine foot are poorly understood. In a temperature-controlled room, duplex Doppler ultrasonographic observations were made pre- and postprandially of the lateral proper palmar digital artery of 5 horses, randomly assigned to twice and 4 times daily feeding in an unbalanced 2 period crossover design. Arterial diameter and blood velocity were measured over 4 h and additional observations made of heart rate, blood pressure, total plasma protein, packed cell volume, plasma glucose and insulin. There was no effect of the feeding regimen on any variable. Postprandially, there were significant increases in arterial diameter, blood velocity, total plasma protein, plasma glucose and insulin; the other variables were unchanged. It appeared that the normal postprandial response was an increase in blood flow to the foot. The value of ultrasonography for noninvasive investigation of the peripheral vasculature of the conscious horse was established; and in the future it may have a role in the diagnosis of vascular diseases of the foot.

Animal Feed↗
PubMed2000

Rapid in silico cloning of genes using expressed sequence tags (ESTs).

Expressed sequence tags (ESTs) are short single-pass DNA sequences obtained from either end of cDNA clones. These ESTs are derived from a vast number of cDNA libraries obtained from different species. Human ESTs are the bulk of the data and have been widely used to identify new members of gene families, as markers on the human chromosomes, to discover polymorphism sites and to compare expression patterns in different tissues or pathologies states. Information strategies have been devised to query EST databases. Since most of the analysis is performed with a computer, the term "in silico" strategy has been coined. In this chapter we will review the current status of EST databases, the pros and cons of EST-type data and describe possible strategies to retrieve meaningful information.

Animals↗
PubMed2000

Building the Hospital Without Walls--a CSIRO home telecare initiative.

Aging populations and rising health costs have created the need to care for more patients in their own homes. Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) is developing a project, Hospital Without Walls, which aims to provide continuous monitoring of patients in certain diagnostic categories. The key technology is a miniature, wearable, low-power radio that can transmit vital sign and activity information to a home computer, from which data may be sent by telephone line and the Internet to appropriate medical professionals. The initial clinical scenario for this work is monitoring of elderly patients who have presented to hospitals following repeated falls. Accelerometers built into the radio sets will monitor activity and detect and characterise falls. Simultaneous measurement of heart rate will provide information about abnormalities of cardiovascular physiology at the time of a fall. The system has been tested in laboratory conditions and is being adapted for initial clinical trials.

Accidental Falls↗
PubMed1999

Sonographic observations of the peripheral vasculature of the equine thoracic limb.

Investigations of the equine peripheral vascular system have been constrained by the lack of a non-invasive method of examining the arteries and veins of the limbs of the conscious horse. Precise correlations were established between the gross anatomical features of the peripheral vessels and their B-mode sonographic appearance in each thoracic limb of 35 horses. A sonographic imaging protocol was established. Additional Doppler sonographic recordings defined the arterial waveforms and demonstrated that blood flow to the foot could be evaluated in the lateral proper digital artery, distal to the level of the coronary band. Valves (with 2-4 cusps) were identified in the lumina of the medial and lateral palmar common digital veins and those of the medial and lateral palmar proper digital veins. Spontaneous echo contrast, a smoke-like haze of echoic blood, was seen in the lateral and medial palmar common digital veins, the distal deep palmar venous arch and communicating branches, and the palmar proper digital veins, and occasionally seen in the distal deep palmar arterial arch and distal proper palmar digital arteries. The value of duplex sonography (B-mode and Doppler) for anatomical and physiological studies of the peripheral vasculature of the horse was clearly established. Such data could be applied to the investigation of diseases affecting the peripheral circulation.

Animals↗
PubMed1998

Automated management of gene discovery projects.

UNLABELLED: The paper reports on programs, organization and Hypertext Mark-up Language (HTML) presentation provided by the Hierarchical Automated Gene Identification System (HAGIS) designed for managing sequencing projects. AVAILABILITY: On request from the authors. CONTACT: st23646@ggr.co.uk

Computational Biology↗
PubMed1997

A new dynamic tool to perform assembly of expressed sequence tags (ESTs).

MOTIVATION: Expressed Sequence Tags (ESTs) are short single-pass DNA sequences obtained from either ends of cDNA clones. To exploit these sequences efficiently, a dynamic Web-tool has been developed which uses these data to perform fast virtual cloning of cDNAs. RESULTS: Starting with a query sequence, the user is able to identify related ESTs and extend the sequence of interest step by step, possibly to a full-length transcript. Graphical views of the clustering are used to monitor the progress of a particular 'cloning' project. Potential open reading frames are detected by positional base preference, and hyperlinks to other Worldwide Web sites allows the user to retrieve information relevant to each EST in a cluster (e.g. sequence traces, clone size, plate position). Apart from cDNA cloning, this tool also provides a mechanism for collating gene families and polymorphism sites.

Algorithms↗
PubMed1995

Computer analysis of the early diastolic notch in Doppler sonograms of the uterine arteries.

This article describes a set of processing and analysis techniques for automated identification and quantification of the early diastolic notch (EDN), a feature of Doppler sonograms from the uterine arteries which has been associated with adverse pregnancy outcomes such as preeclampsia and intrauterine growth retardation. Examples covering different sonogram types are provided to illustrate the effectiveness and reproducibility of the processing/analysis tools. Also, a receiver-operating characteristic-based evaluation of the EDN quantification and pulsatility indexes is presented, which examines the ability to predict hypertension and/or intrauterine growth retardation, using a set of uterine Doppler sonograms from 92 patients acquired at 18 weeks of gestation. In summary, the ROC results confirm the link between the EDN and abnormal pregnancy outcomes, and suggest that EDN quantification has a higher diagnostic accuracy than the pulsatility index, which characterises the flow waveform in a global manner and therefore does not take explicitly into account the localised nature of the EDN. Quantification of the EDN at 18 weeks of gestation appears to best predict the most severely abnormal pregnancy outcomes.

Arteries↗
PubMed1995

The significance of high umbilical venous blood flow measurements in a high-risk population.

We report a statistical analysis of 893 high-risk patients who underwent Doppler sonographic estimation of umbilical venous blood flow within 2 weeks of delivery. Patients with red cell isoimmunization were excluded. In a total of 84 patients, the umbilical venous flow rate was above the 95th centile for normal pregnancy. This finding was associated significantly with an increased prevalence of maternal diabetes mellitus, polyhydramnios, fetal abnormalities, premature delivery, low 5 min Apgar scores, and neonatal death. Umbilical venous flow rates per kilogram of fetal weight above the 95th centile were recorded in 93 patients. This finding was associated significantly with an increased rate of antepartum hemorrhage, premature delivery, low 5 min Apgar scores, longer stays in intensive care nursery, and neonatal death. Low umbilical venous blood flow rates have been investigated extensively and associated with impaired perinatal outcome. The work reported in this paper indicates that a percentage of fetuses will have abnormally high umbilical venous flow rates and that this is also indicative of increased risk.

Apgar Score↗
PubMed1995

Volume imaging: three-dimensional appreciation of the fetal head and face.

Quasi-three-dimensional volume imaging provides an inexpensive means of evaluating the usefulness of three-dimensional imaging. The technique works most efficiently with water-skin interfaces and therefore we investigated its application in obstetrical ultrasonography. Three-dimensional perspectives of the normal and abnormal fetal head and face were spectacular and at times provided more information than the two-dimensional images. The ability of an inexperienced observer to interpret the three-dimensional image more easily may have a role in training sonographers and counseling parents whose fetuses have structural defects. Volume imaging has certain limitations and can only be used as a complementary technique.

Artifacts↗
PubMed1994

Quantification of mitral regurgitation by integrated Doppler backscatter power.

OBJECTIVES: We attempted to determine whether continuous wave Doppler backscatter power could be used to quantify mitral regurgitation. BACKGROUND: The power of a Doppler backscatter signal is proportional to the number of scatterers insonated and, hence, to the moving volume of blood. The relative power of the continuous wave Doppler signals from mitral inflow and aortic outflow is therefore proportional to the relative volumes of blood in motion. METHODS: Computer postprocessing was used to derive the relative power of the Doppler backscatter signal from the intensity of the pixels within the spectral display of anterograde aortic and mitral flow. The power ratio was used to calculate the regurgitant fraction in 20 patients (mean age 61.4 years) with mitral regurgitation. This Doppler regurgitant fraction was compared with that derived from angiographic left ventricular volume and thermodilution cardiac output. In addition, 12 normal control subjects were studied by the Doppler method. RESULTS: Mean (+/- SD) catheterization regurgitant fraction was 0.50 +/- 0.26, and mean Doppler regurgitant fraction was 0.47 +/- 0.25 (r = 0.89). The limits of agreement between the two methods by Bland-Altman analysis were -0.21 + 0.27. In normal control subjects with an expected regurgitant fraction of close to zero, mean Doppler regurgitant fraction was 0.03 +/- 0.05. CONCLUSIONS: Doppler backscatter power from mitral and aortic inflow provides a new and accurate method for quantifying mitral regurgitation.

Adult↗
PubMed1993

Measurement of two-dimensional blood velocity vectors by the ultrasonic speckle projection technique.

A technique has been developed for measuring the two in-plane components of blood velocity using ultrasound. The principle is based on analyzing a time sequence of successive images of the speckle pattern, and forming spatial projections of the resulting three-dimensional data set. The mathematics may be understood in terms of sections through a three-dimensional Fourier transform of the original data. The technique has been tested with data from a computer-controlled scanner using a tissue-mimicking phantom, and with data from a commercial ultrasound scanner using images of flowing blood in a jugular vein. In both cases, velocity vectors with many different orientations were measured, demonstrating the feasibility of the method. A less restrictive real-time implementation is suggested.

Blood Flow Velocity↗
PubMed1992

Specific cytogenetic abnormalities and k-ras mutation in two new human colorectal-adenoma-derived cell lines.

Two new human epithelial cell lines from sporadic colorectal adenomas designated S/RR and S/BR are reported. Both cell lines have extended growth capacities in vitro, reaching passages 38 and 40 respectively and show no sign of senescence. S/RR and S/BR cell lines have retained the ability to differentiate in vitro, as shown by mucin production from goblet-like cells. S/BR was derived from a large colonic tubular villous adenoma (3 to 4 cm), whereas S/RR was derived from a small rectal adenoma (< 1 cm), and may represent a relatively early-stage adenoma. The parent S/RR cell line has given rise to a clonogenic variant, designated S/RR/Cl, which also has shown no sign of senescence and has currently reached passage 43. Both the S/BR and the S/RR cell lines had mutations in codon 12 of the K-ras gene, while retaining one normal allele. The presence of this mutation, particularly in the cell line S/RR derived from a small adenoma, is consistent with ras mutation being a relatively early event in colorectal carcinogenesis and is perhaps involved in the ability of the adenoma cells to progress and to give rise to an immortal cell line in vitro. The clonal derivatives of the S/RR cells have an isochromosome 1q and abnormalities of chromosome 13 which include an isochromosome 13q. The S/BR cells have a deletion on the short arm of chromosome 1 and trisomy 7. The common abnormality for S/RR and S/BR cells involves chromosome 1. The involvement of different chromosomes in the 2 cell lines also suggests different pathways for malignant progression of the premalignant adenoma cells.

Adenoma↗
PubMed1990

Automatic vessel tracking and measurement for Doppler studies.

In this initial report, an imaging technique is described for automatically recognising the walls of a blood vessel during Doppler measurements, and hence automatically adjusting the position of the sample volume. The method reduces the inherently two-dimensional edge detection problem to a one-dimensional one, and iterates over several imaging frames to optimise the information. The orientation and diameter of the vessel are also measured. The technique has been clinically tested off-line and is particularly applicable to Doppler volumetric flow studies.

Algorithms↗
PubMed1990

Parameters and standardization in obstetric Doppler.

Obstetric Doppler is still largely empirically based, although possible clinical applications are already under examination. This article examines some of the basic instrumentation and hemodynamic issues--which physiological parameters would we ideally like to assess, and what can we do in practice with current Doppler instrumentation? It is shown that the rate of blood flow and the flow resistance are two of the most basic hemodynamic parameters. It is possible to estimate the flow rate with (specialized) Doppler equipment, but there is no method available at present to measure the flow resistance. Analysis of the blood velocity waveform provides some information concerning flow resistance, as long as it can be assumed that other factors that might affect the waveform have not deviated significantly from the norm. Practical considerations in choosing the instrumentation and designing the examination protocol are discussed, and issues of quality control are emphasized.

Blood Circulation↗
PubMed1989

New class of pulsed Doppler US ambiguity at short ranges.

A form of range ambiguity in Doppler ultrasound has been identified. It occurs when a high pulse repetition frequency (prf) is used with a superficial range gate. "Phantom" range gates are then generated at depths beyond the desired range gate, and these may produce artifactual signals. Extremely high prf values should not normally be used, and duplex machines should be programmed to display phantom range gates wherever they fall within the displayed field of view.

Humans↗