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Biomedical subjects

S Evans

Publications and source records attributed to S Evans.

At least 19 recordsLinked to original sources
PubMed1992

Immunoreactivity, pharmacokinetics and bone marrow dosimetry of intrathecal radioimmunoconjugates.

Ten patients with neoplastic meningitis were treated with a variety of 131I-monoclonal antibody (MAb) conjugates, chosen to bind to their particular malignancy. Pharmacokinetic studies revealed that MAbs leave the ventricular compartment, enter the sub-arachnoid space and then pass into the blood. Once the MAbs enter the blood compartment, their clearance is determined by factors such as circulating anti-mouse Ig and circulating antigens. These lead to complex formations and the clearance of the conjugate by the reticuloendothelial system. In one individual, the anti-mouse Ig response observed systemically was not mirrored within the CSF, which has implications for planning future therapy of this type. In other patients, formation of immune complexes was due to binding to circulating antigen within the blood. The major toxicity associated with the intrathecal administration of 131I-MAbs was bone-marrow suppression. The doses to the bone marrow, resulting from the form of therapy, were calculated but showed no direct correlation with WHO grade 3/4 toxicity. Doses to the ventricular lining were also calculated, but due to the complex geometry of the compartment, calculation of potential tumour doses was not practicable.

Adult↗
PubMed1992

Ingested arsenic, keratoses, and bladder cancer.

A cohort of 478 patients treated with Fowler's solution (potassium arsenite) in Lancashire, England, during the period 1945-1969 and previously followed until January 1, 1980, was followed for an additional 11 years. A significant excess of bladder cancer mortality occurred (observed/expected ratio = 5/1.6; p = 0.05). No excess was found for other causes of death. In a subcohort of 142 patients examined for signs of arsenicism around 1970, all 11 subsequent cancer deaths occurred in those with signs of arsenicism (p = 0.0009).

Arsenic↗
PubMed1992

Inhibition of human red blood cell glutathione reductase by valproic acid.

Glutathione reductase (GR) one of the enzymes of the glutathione redox cycle, plays a salient role in maintaining appropriate cellular levels of reduced glutathione. The enzyme in human red blood cells is inhibited in vitro by the anticonvulsant drug valproic acid (VPA). The inhibition is dose-dependent, reversible, uncompetitive and does not depend on the redox state of the enzyme. VPA also inhibits red blood cell GR activity in children being treated with the drug. The level of serum VPA correlates significantly with the suppression of GR activity.

Adolescent↗
PubMed1992

Synthesis and release of acetylcholine in the rabbit kidney cortex.

Several cholinergic processes were demonstrated and partially characterized in rabbit kidney cortical minces: choline uptake, acetylcholine synthesis and calcium-dependent release. Minces took up labelled choline, acetylated it, and stored it in a pool that was not readily accessible to physostigmine-sensitive cholinesterase activity. [3H]Acetylcholine synthesis but not [3H]choline uptake was inhibited by the removal of sodium ions or incubation at 0 degrees C. The release of newly synthesized [3H]acetylcholine was increased by 300 mOsmol urea in a calcium-dependent manner, but not by potassium depolarization (300 mOsmol), vasopressin (10 microM), or bradykinin (10 microM). These results suggest that acetylcholine may be synthesized by non-neuronal rabbit kidney cortical cells and that this transmitter may be released in response to physiological levels of urea.

Acetylation↗
PubMed1992

Generalized allergic reactions during anesthesia.

Twenty-eight adults with a history of a generalized allergic reaction during anesthesia were investigated. The reactions were systemic in 23 adults, urticaria/angioedema in four, and bronchial obstruction in one adult. The study population and an additional 35 subjects with a history of use of thiopental during anesthesia but without reactions were investigated by methods including thiopental skin test, succinylcholine skin test, and IgE RAST for antibodies to thiopental, succinylcholine, or latex. Among the 28 patients with reactions, 17 had positive thiopental skin tests; 14/28 reactors and 1/35 of the control group had an IgE thiopental RAST value greater than 2 SD above the mean for control sera from ragweed-allergic subjects. The one control subject with a positive thiopental RAST also was the only control subject with a positive thiopental skin test. IgE succinylcholine RAST was negative in all 23 reactor sera tested. The IgE latex RAST was strongly positive in one reactor. In conclusion, evidence of allergy, particularly allergy to thiopental as a possible basis for the reactions, was obtained in greater than 50% of the patients who were investigated. No allergy to succinylcholine was found.

Adolescent↗
PubMed1992

Experimental results on the rewarming of a cryopreserved organ phantom in a UHF field.

We describe a UHF rewarming system which has been used to measure warming rates, and particularly the uniformity of warming on three orthogonal axes, in a rabbit kidney phantom 36 mm in diameter. The stabilizing effect is demonstrated of using an E-field directed along the temperature gradient (or normal to any surface of dielectric discontinuity). One hot spot remains unaccounted for. The average warming rates and power dissipation are related to the volumetric heat capacity of the phantom material at -30 degrees C.

Animals↗
PubMed1992

Analysis of electromagnetic heating patterns inside a cryopreserved organ.

Computer analysis of the induced electromagnetic field and heating distribution inside cryopreserved organs subjected to electromagnetic illumination at frequencies of 84 MHz, 434 MHz and 2.45 GHz were carried out using a spherical model for the organ, with special reference to heating in a single-mode resonant cavity. The interaction between the frequency of the incident field and the size and dielectric properties of the sample was investigated. It is shown that uniform heating of organs is likely to be achieved at lower frequencies, as might be expected. However, the ratio between the power penetration depth for plane waves and the size of the organ is not a sufficient basis on which to judge quantitatively the uniformity of the power absorption. Hot or cold spots can occur within the organ even when this ratio is greater than unity; the wavelength in the material is also an important factor. The results from this study indicate that the use of a resonant cavity as a heating applicator has advantages over plane-wave illumination. A sharp upper limit can be set to the frequency suitable for rapid and uniform heating of a given organ.

Animals↗
PubMed1992

Food in chronic heart failure: improvement in central haemodynamics but deleterious effects on exercise tolerance.

Food has been known to have significant central haemodynamic effects for over half a century; it causes an increase in cardiac output and a fall in systemic vascular resistance. These changes are potentially desirable in patients with chronic heart failure but how they relate to exercise tolerance is unknown. This study was designed to examine the haemodynamic effects of food with changes in exercise capability in a group of patients with chronic heart failure. Fifteen patients with chronic heart failure and 10 normal control subjects were studied. They underwent treadmill exercise testing whilst fasting and after a standardized meal. Measurements were made of symptom-limited exercise tolerance, cardiac output, limb blood flow and respiratory gases. Superior mesenteric artery blood flow was measured fasting and postprandially only. Despite an increase in cardiac output, at rest and during exercise, which was not, however, as great as that in the control subjects, the symptom-limited exercise tolerance of the patients fell by 37 s postprandially (P < 0.05). Superior mesenteric artery blood flow increased postprandially by a mean of 133 ml.min-1 (P < 0.05) in the patients and 424 ml.min-1 (P < 0.01) in the control subjects. Calf blood flow increased in both groups during exercise, but there was no change in limb blood flow when comparisons were made between the fasting and postprandial states. The normal postprandial increase in oxygen consumption did not occur in the patients although their minute ventilation was higher than the control subjects (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Design of a UHF applicator for rewarming of cryopreserved biomaterials.

The dielectric properties of cryopreserved biological tissue are discussed in relation to the problems which arise when EM fields are used for rapid rewarming. The UHF band is favored from two aspects: the avoidance of thermal runaway and the uniformity of heating inhomogeneous material. Various resonant cavity applicators are considered for efficient and uniform rewarming. The square-aspect TE 111 cylindrical applicator is favored principally because it allows variation of the E-field orientation as required during the warming profile. An appropriate kidney phantom organ is described. It is used to obtain measured values of the overall efficiency of a TE 111 applicator. The efficiency values are found to fall steadily with increasing temperature from 85% at -40 degrees C to 45% at the phase change, mainly due to the decreasing tan delta value of the phantom material.

Animals↗
PubMed1992

Factors predicting success in DC catheter ablation of accessory pathways.

In a series of 33 patients with accessory pathways, 26 had successful catheter ablation (fulguration [23 patients] or modification [3 patients]) of their accessory pathway conduction, and could be considered as a clinical success. One hundred thirteen single discharge or double discharge shocks were delivered, and each shock was studied to reveal which parameters were important to predict the success or failure of catheter ablation. Double discharge shocks resulted in successful accessory pathway modification or ablation twice as often as single discharge shocks (32% vs 16%). This effect was more pronounced in left lateral accessory pathways (48% vs 4%). Shocks in the electrophysiologically defined ventricular zone were more likely to be successful (33%) than shocks delivered in the atrial zone (14%), irrespective of accessory pathway location. The presence of a probable Kent potential was the parameter most strongly associated with success. The parameter most strongly associated with failure, with a 100% negative predictive value, was the absence of earliest activation recorded on the ablating catheter prior to shock delivery. An AV interval of < 60 msec significantly divided the successful from the unsuccessful shocks (P = 0.01). The VA interval during orthodromic reciprocating tachycardia or right ventricular stimulation did not allow for significant division into successful and unsuccessful attempts in this relatively short series. VA intervals, when longer, were predictive of failure but, when shorter, had low positive predictive value. Mean follow-up in 25 successful patients was 15 +/- 6 months. All patients did well in the follow-up period. Neither those patients with ablation nor modification of the accessory pathway had recurrent episodes of tachycardia or required pharmacological treatment for control of arrhythmias.

Adult↗
PubMed1992

Regional blood flow in chronic heart failure: the reason for the lack of correlation between patients' exercise tolerance and cardiac output?

BACKGROUND: In patients with chronic heart failure there is no relation between cardiac output and symptom limited exercise tolerance measured on a bicycle or treadmill. Furthermore, the increase in cardiac output in response to treatment may not be matched by a similar increase in exercise tolerance. More important in determining exercise capability is blood flow to skeletal muscle. This implies that the reduction in skeletal muscle blood flow is not directly proportional to the reduction in cardiac output and that there are regional differences in blood flow in patients with heart failure. METHODS: Cardiac output and regional blood flow measured in 30 patients with chronic heart failure were compared with values obtained from 10 healthy controls. Measurements were made at rest and in response to treadmill exercise and were all made non-invasively. RESULTS: Cardiac output was lower in the patients at rest and during exercise. Blood flow in the superior mesenteric and renal arteries was also lower in the patients and represented a different proportion of cardiac output than in the controls. In response to exercise the increase in blood flow to the calf and therefore to skeletal muscle, was reduced in the patients. In the patients there was no correlation between resting cardiac output and blood flow in the superior mesenteric artery, renal artery, or calf. CONCLUSIONS: Because blood flow to skeletal muscle and to the kidneys is likely to be important in determining patients' symptoms this factor may explain why central haemodynamic variables do not correlate with the exercise tolerance in patients with chronic heart failure.

Aged↗
PubMed1992

Histochemical and immunohistochemical characteristics of mast cells in nasal polyps.

In surgically excised nasal polyps, most epithelial mast cells were formalin sensitive, chloroacetate esterase (CAE) negative, and chymase negative. Thus, this represents a population of mast cells not identified by staining for CAE. On the other hand, most stromal mast cells were formalin resistant and CAE positive, and although there was some polyp-to-polyp variability in their content of neutral protease, most of these cells were positive for both tryptase and chymase. The percentage of metachromatic cells in the epithelium and the number of metachromatic cells per unit area of polyp tissue did not correlate with an index of allergy skin test reactivity or the serum IgE concentration. The percentage of mast cells surrounded by pericellular tryptase, suggesting activation/degranulation, was significantly higher in the stroma than in the epithelium. The findings demonstrate differences between the stroma and the epithelium in phenotype and state of activation of mast cells; these are postulated to be due to distinct microenvironmental factors that affect mast cells at these sites.

Acetates↗
PubMed1992

Axonal injury in closed head injury by assault: a quantitative study.

Due to the controversy in the literature regarding the time course of axonal balloon formation in human material, we wished to determine if it was possible to diagnose axonal injury before the development of axonal balloonings. The hypothesis was that the presence of axonal swellings or axonal enlargements associated with a glial reaction could be used as a diagnostic aid in human axonal injury before 12 hours. The brains of eight individuals that survived for less than 48 hours following head injury, and also had evidence of axonal injury using the criteria of Vanezis et al. (1987), were systematically studied by looking at axonal swellings, axonal balloonings, reactive astrocytes, maximum diameter of axonal enlargements and density of axonal enlargements. Controls were eight selected cases without neurological disease. The variables studied were assessed in 25 fields from ten different areas of the brain, using silver stains and immunoperoxidase for glial fibrillary acidic protein (GFAP). Logarithms of one plus the count of each variable were taken from the raw data and these were analysed using percentile distribution and the median, the t-test, Mann-Whitney U test and the Wilcoxon signed rank test. We conclude that quantitation of axonal damage allows the detection of mild degrees of axonal injury that could be overlooked on routine examination, and that the criteria of axonal enlargements, rather than axonal balloonings, are indications of axonal damage, cannot be endorsed with the evidence provided.

Axons↗
PubMed1992

Risk factors for coronary heart disease: a study in inner London.

A survey was carried out among 281 men and women aged between 30 and 64 years randomly selected from five general practices located in the inner London borough of Tower Hamlets, to determine the prevalence of risk factors for coronary heart disease. Smoking and obesity were both more pronounced in Tower Hamlets than in comparable national studies: 51% of men and 44% of women were smokers and 57% of these were smoking 20 or more cigarettes per day. A body mass index of 30 or more was present in 18% of men and 10% of women and a body mass index of 25 or more in 71% of men and 49% of women. Two or more risk factors for coronary heart disease (smoking and/or hypertension and/or raised cholesterol levels) were present in 25% of men and 22% of women. For every person known by their general practitioner to have established cardiovascular disease, there were an additional two people also at risk on the basis of multiple risk factors. In this inner city population the prevalence of cardiovascular risk, for women as well as men, has major resource and organizational implications for primary care. A strategy for change requires action based on graded multiple risks for both men and women.

Adult↗
PubMed1992

Building a healthier workforce.

The European Year of Health has put the construction industry at the top of its agenda. Sarah Evans examines the challenge presented to OH practitioners in this field and looks at the ground-breaking work of OHN, Mike King.

Facility Design and Construction↗
PubMed1991

Mercury in muscle tissue of lesser-spotted dogfish (Scyliorhinus caniculus L.) from the north-east Irish Sea.

This paper reports concentrations of mercury in muscle tissue of lesser-spotted dogfish (Scyliorhinus caniculus L.) from various locations within Liverpool Bay and the north-east Irish Sea. Concentrations of mercury in fish muscle showed distinct spatial variation, with values from the northern sectors of the Irish Sea significantly lower than those for the southern area, particularly sites in Liverpool Bay and around the mouth of the Mersey Estuary. The data support the hypothesis that there are several major populations of lesser-spotted dogfish within the study area, each of which remains quite distinct during seasonal movements. Consequently, exposure to environmental mercury is reflected in muscle concentrations of mercury. Regressions of mercury concentration against fish length showed significant relationships for the majority of sites, with the slope relating to distance from known sources of mercury contamination. Mean mercury concentrations were higher than in corresponding populations of flatfish from the same areas.

Animals↗
PubMed1991

Presence of a cholinergic projection from ventral striatum to amygdala that is not immunoreactive for NGF receptor.

By combining the retrograde axonal transport of a fluorescent dye with nerve growth factor (NGF) receptor or choline acetyltransferase (ChAT) immunocytochemistry, we show that the cholinergic neurons that project most strongly to the basolateral nucleus of the amygdala in the ferret do not possess NGF receptor immunoreactivity in their soma and are situated in the ventral striatum, an area known to receive a massive reciprocal projection from the basolateral nucleus of the amygdala.

Amygdala↗