Search PubMed⌕ Search

Biomedical subjects

K T Evans

Publications and source records attributed to K T Evans.

At least 19 recordsLinked to original sources
PubMed1994

Shear modulus-temperature meltdown profiles of gelatin and pectin gels. A cascade theory description.

In this paper, a cascade theory approach to biopolymer gelation is developed to describe variation of the shear modulus with temperature for thermoreversible gels. The broadness of this 'melting transition' is seen to depend crucially on the enthalpy of cross-linking, while the critical gel melting temperature is determined by additional factors such as the entropy of cross-linking, the polymer concentration, the molecular weight, and the number of cross-linking sites. On using the model to fit experimental data for specific gelatin and pectin systems, it was found that the behaviour of gelatin (sharp melting transition and low melting temperature) is a consequence of the large negative enthalpy and entropy of cross-linking, while, in contrast, the broad melting transition and high melting point of the pectin system are consistent with much smaller negative values for these parameters.

Animals↗
PubMed1990

Coarse mucosal folds in the duodenum: a twenty-year follow-up.

In a 20-year follow-up of 40 patients with coarse duodenal folds, details were obtained about 34 patients of whom 11 had died. Clinical details were reviewed from the remaining 23 patients, and recent barium meal examinations were reviewed from eight patients. Ten of the 23 surviving patients continued to have recurrent dyspepsia, and the radiological appearance in three of the eight recent barium meals showed that coarse mucosal folds persisted. The clinical course of those with coarse duodenal folds is similar to that of peptic ulcer, with recurrent symptoms in some patients continuing for many years, and in others complicated by development of peptic ulcer. Coarse mucosal folds in the duodenum are usually associated with a high acid secretion and treatment to reduce acid secretion is appropriate in view of the severity of symptoms and risk of ulceration.

Aged↗
PubMed1989

Assessment of volume measurement of the prostate using per-rectal ultrasonography.

A study was made of 100 cadaveric prostates (71 benign glands and 29 invaded by adenocarcinoma) using a technique that enabled per-rectal ultrasonography to be carried out and their volumes measured by computed planimetry. These volumes were compared directly with the actual volumes of the glands measured after dissection from the cadaver specimens. A high degree of correlation was obtained for the measurement of benign glands (r = 0.982) and glands containing cancers confined within the capsule (r = 0.961). Estimation of the size of cancers unconfined to the gland was poor and measurement was not possible with 3 malignant prostates that had extended beyond the prostatic capsule so that the ultrasonic boundary could not be defined.

Adenocarcinoma↗
PubMed1989

Structure and per-rectal ultrasonography of prostatic disease using cadaver specimens.

One hundred cadaver prostates were examined by per-rectal ultrasound and the findings correlated with the microradiographic and histopathological features of whole sections taken at the levels of scanning. The normal gland consists of both periurethral muscle and glands. The periurethral muscle has little structure on microradiography and is therefore hypoechoic (low amplitude echoes) on ultrasound scanning. The gland itself, both central and peripheral zones, has a lattice appearance on microradiography (reticular structure) and therefore produces mid-range amplitude echoes on ultrasound. Benign hypertrophy develops at the edge of the periurethral muscle and is microadenomatous in structure. This produces mid-range amplitude echoes which are coarser than in the normal gland. Associated calcification has a characteristic distribution around the adenomas. Cancer produces an amorphous structure resulting in loss of ultrasonic echoes (hypoechoic). In a few cancers irregular calcification is present, resulting in high echoes in the ultrasound scan (hyperechoic) which are not in the typical benign distribution. The internal structure of the prostate was therefore demonstrated in its histopathological states by the technique of microradiography and seen to relate to its representation by ultrasound.

Adolescent↗
PubMed1989

Comparative histopathology, microradiography and per-rectal ultrasonography of the prostate using cadaver specimens.

A technique for examining cadaver prostates by per-rectal ultrasonography has been developed. The ultrasonic plane was defined and corresponding sections taken for microradiographic and histopathological examination. The technique has enabled a comparison to be made of the structural changes that occur in the prostate in disease states and the corresponding ultrasonic features.

Adolescent↗
PubMed1989

The correlation of histopathological, microradiographic and ultrasonographic features in disease of the prostate gland.

The histopathological, microradiographic and ultrasonographic features of corresponding areas of 100 cadaveric prostates were examined and correlated statistically to investigate their relationship. Benign glands are seen to be related to reticular structure and mid-range echoes. Benign prostatic hyperplasia is related to microadenomatous structure and mid-range echoes, whilst cancer is related to amorphous structure and low echoes. A small number of cancers have irregular calcification present and these tumours are related to high echoes. The structure of the prostate gland is therefore related to its pathology and explains its ultrasound echogenicity.

Humans↗
PubMed1988

How accurate is the index finger? A comparison of digital and ultrasound examination of the prostatic nodule.

The per-rectal ultrasound scans and digital assessments of 193 patients with prostatic nodules were analysed retrospectively. There were 88 histologically proven cancers and per-rectal ultrasound demonstrated extracapsular spread of tumour in 36 of these patients. In the diagnosis of prostatic cancer, ultrasound had a sensitivity of 97.6% and a specificity of 93.8% whereas digital examination had a sensitivity of 96.5% and a specificity of 53.3%.

Adult↗
PubMed1988

X-ray microscopy of the prostate gland.

A technique is described for investigating the internal structure of the prostate gland (including calcification) by projection X-ray microscopy (microradiography). The results show that the technique can be used in conjunction with the corresponding histological preparations to complement the examination of the prostate gland by demonstrating tissue density and the structure and location of microcalcification less than 5 microns in diameter.

Humans↗
PubMed1988

Endothelium-derived relaxing factor (EDRF) and resistance vessels in an intact vascular bed: a microangiographic study of the rabbit isolated ear.

1. Microradiographic techniques have been used to show that endothelium-derived relaxing factor (EDRF), which is believed to be nitric oxide, influences vasomotor responses in small arteries and arterioles down to 25 micron in diameter in an isolated, intact, buffer-perfused ear preparation of the rabbit. Arteries down to 75 micron in diameter, i.e. the central ear artery (G0) and its first three generations of branch vessels (G1, G2 and G3) were studied quantitatively. 2. Relative constrictor responses to 1 micron 5-hydroxytryptamine (5-HT) and the combination of 1 microM 5-HT and 1 microM histamine diminished progressively from G0 to G3. Constrictor responses to 5-HT were doubled in all generations by 1 microM haemoglobin which abolishes EDRF activity. 3. Relative dilator responses to acetylcholine or to substance P in preconstricted arteries were, in contrast, equal in the different generations. Mean -log (IC50) values calculated from diameter measurements were 7.63 +/- 0.10 M and 9.80 +/- 0.11 M, respectively. These dilator responses were abolished by 1 microM haemoglobin, implying that they were EDRF-mediated. Spatial homogeneity of relative dilator responses was found also with glyceryl trinitrate (10 or 50 microM) whose activity is thought to depend on biotransformation to nitric oxide, in both the presence and the absence of haemoglobin. 4. This finding of spatial homogeneity of the diameter response to changes in EDRF activity (or to glyceryl trinitrate) implies that EDRF influences hydrodynamic resistance more in vessels where constrictor tone is high.

Acetylcholine↗
PubMed1987

Can the use of radiography of arms and legs in accident and emergency units be made more efficient?

The efficiency of the selection of patients with injured arms and legs for radiography was investigated. The analysis was based on data on presenting signs and symptoms collected in a multicentre study organised by the Royal College of Radiologists working party on the effective use of diagnostic radiology. The work was carried out in eight accident and emergency units in England and Wales. With the help of various computer simulation techniques a combination of signs and symptoms that might usefully improve present practice was sought. The results suggest that for injuries of arms and legs the clinical determinants of bony injury cannot be refined further to improve current selection for radiography. This study shows that existing clinical practice is probably as good as it can be.

Accidents↗
PubMed1987

The ultrasound appearances of prostatic cancer with histological correlation.

An analysis of the ultrasound appearances of the prostate with its capsule and periprostatic structures was performed in 221 patients with a histologically confirmed diagnosis of prostatic cancer. The cancers were histologically graded into well, moderate and poorly differentiated adenocarcinoma and transitional cell carcinoma. The results of this study indicate that an ill-defined hypoechoic area is the commonest appearance of prostatic cancer; this was seen in 96% of our 221 patients. The cancers were staged by ultrasound into confined (T0, T1, T2) and unconfined (T3) cancers. A breach of the capsule was seen in 55% of cases. In this unconfined group all cancers were hypoechoic in comparison with 92% in the confined group. In the confined cancer group the areas of abnormal echogenicity were present in more than one prostatic quadrant in 76%. Mostly commonly two prostatic quadrants were affected. The abnormal echogenicity was noted in the posterior quadrants of the prostate more commonly (58%) than in the anterior quadrants. The prostate gland appeared round in 67%, semicircular in 25% and crescentic in 8%. The gland was symmetrical in 68%. The prostatic capsule appeared regular in 86% of patients with a confined cancer. In 70% of cases of extensive but confined cancer there was loss of demarcation between the central and peripheral zones of the gland. The unconfined cancer group all had a breach of the capsule and all glands were heterogeneous due to hypoechoic areas. The breach affected more than one quadrant in 81% and most commonly the capsular breach involved two prostatic quadrants. An anterior breach of the capsule was noted much more frequently than a posterior breach. Forty-four per cent of cases had three or four quadrants of the gland involved. In 3% of cases of proven prostatic cancer no definite ultrasound abnormality could be detected. Calcification was seen within the gland in association with the cancer in 63% with approximately equal frequency in confined and unconfined disease. The seminal vesicles showed definite evidence of infiltration in 10%. Both seminal vesicles were seen in 61% and thought to be normal. In 8% only one was seen. Failure to demonstrate either seminal vesicle occurred in 21%. There was no correlation between the ultrasound appearances of prostatic cancer and the histological grading of the tumour.

Adenocarcinoma↗
PubMed1987

Inter-sterno-costo-clavicular ossification.

The clinical and radiological features of four patients with inter-sterno-costo-clavicular ossification are described. The process was associated with established seronegative spondyloarthropathy in three cases of whom four had long standing psoriasis, the other having ankylosing spondylitis. In the fourth case no associated arthropathy was present. A review of the literature is presented.

Adult↗
PubMed1987

Compliance with the Royal College of Radiologists' guidelines on the use of pre-operative chest radiographs.

Clinical compliance with the Royal College of Radiologists' guidelines on the use of pre-operative chest radiology was examined in a random sample of patients in four hospitals in England and Wales. Pre-operative clinical data were abstracted from medical reports and, in one hospital, from special chest radiograph request forms completed by clinicians. Seventy-five per cent of patients had clinical indications warranting a pre-operative chest radiograph. This level of compliance is compatible with that found with other guidelines and would suggest that the pre-operative chest radiograph guidelines are suitable for wider implementation in the National Health Service.

Health Planning Guidelines↗
PubMed1987

Gastric emptying and small bowel transit times in volunteers after intravenous morphine and nalbuphine.

Gastric emptying half-times and small intestinal transit times were measured in a double-blind crossover study of 17 volunteers who received an intravenous injection of nalbuphine (5 or 10 mg), morphine (5 mg) or placebo. Both times were monitored using a gamma camera after a radioactive test meal and gastric emptying half-time was calculated. Small intestinal transit time was measured by the appearance of radioactivity in the caecum and also of hydrogen in end tidal air. Gastric emptying was prolonged over placebo by nalbuphine 10 mg, which had more effect than nalbuphine 5 mg or morphine 5 mg; morphine 5 mg had less effect than nalbuphine 5 mg. Small intestinal transit time was prolonged over placebo by nalbuphine 10 mg more than by nalbuphine 5 mg or morphine 5 mg, which had approximately equal effects. In these respects, the potency ratio of nalbuphine appears roughly equivalent to morphine. Small intestinal transit times measured by end tidal hydrogen concentration and gamma camera showed close agreement.

Adult↗