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Biomedical subjects

A Parker

Publications and source records attributed to A Parker.

At least 73 records · Page 4Linked to original sources
PubMed1999

Modelling the contribution of individual radionuclides to the total gamma air kerma rate for the sediments of the Ribble Estuary, NW England.

The aim of this study was to test the performance of a published dose-rate model, investigate the contribution of individual radionuclides to the total gamma air kerma rate (GAKR) and derive external doses to man in the Ribble Estuary, NW England. GAKRs were measured and sediment cores were collected in order to determine radionuclide specific activities with depth. The latter values were used as input data for the external dose-rate model. The model has a slight tendency to over-predict the GAKR, but, on average, the model predictions fall within +/-26% of the measured value. Improvements, in the present case, might be made by accounting for core shortening and variations in soil density in the input data. The model predicted that, for exposed intertidal mud sites, a range of GAKRs between 0.011 and 0.022 microGy h(-1) was attributable to Springfields discharges alone. The contribution due to 234mPa and 234Th ranged between 20 and 60%. An excess GAKR (GAKR arising from anthropogenic emissions alone) of 0.139-0.150 microGy h(-1), used in conjunction with relevant habit-survey data (for a potential critical group) and conversion factors, yielded a dose to man of 0.029-0.031 mSv year(-1).

Air Pollutants, Radioactive↗
PubMed1999

The effect of diet composition and feeding state on the response to exercise in feed-restricted horses.

Eight Thoroughbred horses were used to determine the effects of long-term calorie restriction and diet composition on serum T4 and T3 concentrations and metabolic responses with exercise. Horses were randomly assigned to 2 treatment groups (n = 4): Group 1, horses were fed a calorie-restricted diet designed to have 70% of the calories from the roughage source (RHR); Group 2, horses were fed a calorie-restricted diet designed to have 70% of the calories from the concentrate source (RHC). Horses then completed 2 step-wise exercise tests; one following a 12 h fast and one 2 h after a meal of 2 kg of a grain mix. Glucose concentrations declined (P < 0.01) in fed horses on the RHR diet but did not change in fed horses on the RHC diet. Fasted horses receiving the RHR diet had a more rapid increase in glucose concentration during exercise compared to fasted horses receiving the RHC diet (P < 0.01) as well as the highest glucose concentration at fatigue (P < 0.05). Insulin concentrations were higher (P < 0.05) at fatigue in fed horses on the RHR diet. Fasted horses receiving the RHR diet had higher (P < 0.01) pre-exercise FFA concentrations and a more rapid decline (P < 0.01) in FFA during exercise. Serum T3 concentrations increased (P < 0.01) in response to exercise within all treatments. The differences in thyroid hormone, glucose and FFA responses to exercise suggest that calorie source may be important in the hormonal regulation and energy metabolism of horses consuming calorie deficient diets.

Animals↗
PubMed1999

Coinfection with influenza B virus does not affect association of Neisseria meningitidis with human nasopharyngeal mucosa in organ culture.

There is an epidemiological association between influenza virus infection and meningococcal disease. Proposed mechanisms are the destruction of the normal epithelial barrier function of the upper respiratory tract by influenza virus or the expression of human or viral surface-exposed proteins that enhance bacterial adherence and/or invasion. To test these hypotheses, human nasopharyngeal mucosa specimens from a total of 19 individual donors were successfully infected with influenza B virus and then inoculated with serogroup B Neisseria meningitidis. Subsequent bacterial association with the epithelial surface was measured in three separate series of experiments by using transmission electron microscopy (n = 6), scanning electron microscopy (n = 6), and counting of viable bacteria within homogenates of explants (n = 7). Penetration of the mucosa was estimated by measuring the count of viable bacteria recovered from explants after exposure to sodium taurocholate. Bacterial association with the surface of explants was time dependent over 24 h of superinfection. Influenza virus did not positively or negatively influence bacterial attachment to or penetration of explant mucosa compared to those of uninfected controls, even when the period of preincubation with virus was extended to 7 days. When proteins were purified from mucosal epithelium and immobilized on nitrocellulose membranes, N. meningitidis attached predominantly to bands corresponding to proteins of 210 and 130 kDa. In the presence of influenza virus infection, these proteins were gradually lost over the course of 72 h. In conclusion, influenza B virus did not increase association of serogroup B N. meningitidis with human nasopharyngeal mucosa.

Antigens, Viral↗
PubMed1999

Imaginal experiences and perceptual defence.

Three studies are reported concerning the interaction between internal imagery and perceptual defence. This interaction may be a source of the magical ideation and perceptual anomalies which are thought to be a feature of schizotypal personality. The studies were designed to test the hypothesis that scores on the Magical Ideation Scale (MIS) can be predicted effectively from scores on the Tellegen Absorption Scale (TAS) if defensiveness in handling imagery is included. The latter was measured instrumentally by a tachistoscope test known as the Defense Mechanism Test (DMT). Two studies (both N = 35) found MIS and TAS to be highly intercorrelated. The first study, using volunteers from the general student population, failed to find a global measure of defensiveness measured by the DMT to be a significant modulator of MIS scores. The second study using subjects with a greater frequency and variance in the reporting of anomalous experiences, did however confirm the hypothesis. In particular, projection scores together with TAS scores, were found to be a significant predictor of MIS scores (r = 0.79, p < .0001). A third study (N = 34), which compared the DMT profile of high scorers on the MIS with that of a comparison group, found the predicted differences on their DMT global scores and projection scores to be significant. The implications of these findings for understanding anomalous experiences are discussed.

Adult↗
PubMed1999

Cytokines and cell adhesion molecules in musculoskeletal disorders.

This paper reviews the cytokine profiles and various cell adhesion molecules expressed in the more common inflammatory joint conditions such as rheumatoid arthritis, psoriatic arthritis, the spondyloarthropathies (Reiter's syndrome, ankylosing spondylitis), as well as systemic lupus erythematosus, systemic sclerosis, Sjögren's syndrome, giant cell arteritis and polymyositis. Knowledge of the broad range of cytokines produced in these conditions and the expression of cell adhesion molecules that result from cytokine production will assist in the understanding of the pathogenesis of these conditions and may lead to new therapeutic interventions.

Journal Article↗
PubMed1999

Immunohistochemical detection of cytokines and cell adhesion molecules in the synovial membrane.

This paper describes the immunohistochemical techniques which can be used to detect cytokines and cell adhesion molecules in synovial membrane tissue, including a list of reagents and possible problems in each technique. It also describes three methods of quantitation of the resultant immunohistochemical detection, including the recent innovation computer-assisted digital video image analysis, and lists the advantages and disadvantages of each quantitation technique. This information will be a useful summary for any scientist interested in applying such techniques to the detection of cytokines and cell adhesion molecules in human tissue sections.

Alkaline Phosphatase↗
PubMed1999

5,5'-Dithiobis-(2-nitrobenzoic acid) as a probe for a non-essential cysteine residue at the medium chain acyl-coenzyme A dehydrogenase binding site of the human 'electron transferring flavoprotein' (ETF).

Human 'electron transferring flavoprotein' (ETF) was inactivated by the thiol-specific reagent 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB). The kinetic profile showed the reaction followed pseudo-first-order kinetics during the initial phase of inactivation. Monitoring the release of 5-thio-2-nitrobenzoate (TNB) showed that modification of 1 cysteine residue was responsible for the loss of activity. The inactivation of ETF by DTNB could be reversed upon incubation with thiol-containing reagents. The loss of activity was prevented by the inclusion of medium chain acyl-CoA dehydrogenase (MCAD) and octanoyl-CoA. Cyanolysis of the DTNB modified-ETF with KCN led to the release of TNB accompanied presumably by the formation of the thio-cyano enzyme and with almost full recovery of activity. Conservation studies and the lack of 100% inactivation, however, suggested that this cysteine residue is not essential for the interaction with MCAD.

Acyl-CoA Dehydrogenase↗
PubMed1999

Assessment of pulmonary lesions with 18F-fluorodeoxyglucose positron imaging using coincidence mode gamma cameras.

UNLABELLED: Accurate assessment of lung carcinoma remains a significant clinical problem, often leading to surgical procedures without curative potential. PET with 18F-fluorodeoxyglucose (FDG) has shown promise in differentiating benign from malignant lesions and in staging the extent of disease, resulting in improved treatment at a significant cost savings. This multicenter prospective study used dual-detector coincidence imaging with FDG to categorize pulmonary lesions as benign or malignant. The goal of this study was to determine the sensitivity and specificity of dual-detector coincidence imaging of FDG in patients with pulmonary lesions who were scheduled to have a diagnostic procedure for histopathologic confirmation. METHODS: A total of 96 patients with pulmonary lesions with a lesion size ranging from 1 to 7 cm with a mean of 3.44 cm based on their chest radiograph or CT scan were studied using FDG scans with a dual-detector coincidence detection system. An additional 24 patients were entered as control subjects. The studies of 120 subjects were interpreted in random order by three physicians experienced in the use of FDG in patients with lung cancer. Surgical pathology was used as the standard for identifying malignant lesions. RESULTS: There was 94% agreement between the readers in the independent interpretation of the FDG studies. In the 96 patients with pulmonary lesions, FDG studies were 97% sensitive and 80% specific in identifying proven malignant lesions. CONCLUSION: The results of this prospective study provide evidence that dual-detector coincidence imaging with FDG provides an accurate, sensitive and specific means of diagnosing malignancy in patients with pulmonary lesions.

Case-Control Studies↗
PubMed1998

Pathogenic mechanisms in the rheumatoid nodule: comparison of proinflammatory cytokine production and cell adhesion molecule expression in rheumatoid nodules and synovial membranes from the same patient.

OBJECTIVE: To investigate the production of proinflammatory cytokines and expression of cell adhesion molecules in the rheumatoid nodule. METHODS: Cytokine content (tumor necrosis factor alpha [TNFalpha], interleukin-1beta [IL-1beta], and IL-1 receptor antagonist [IL-1Ra]), at the messenger RNA (mRNA) and protein levels, and cell adhesion molecule expression were studied in 16 rheumatoid nodules and 6 synovial membranes. RESULTS: Macrophages in the rheumatoid nodules contained TNFalpha, IL-1beta, and IL-1Ra mRNA and protein, particularly in perivascular cells of the stroma and in the palisading layer. All cell adhesion molecules studied were expressed in both the rheumatoid nodules and synovial membranes, with increased expression of E-selectin in the rheumatoid nodule compared with the synovial membrane, and with the absence of vascular cell adhesion molecule 1 expression on cells of the palisading layer in the rheumatoid nodule. CONCLUSION: The presence of similar proinflammatory cytokines and cell adhesion molecules in the rheumatoid nodule and synovial membrane suggests that similar pathogenic processes result in the chronic inflammation and tissue destruction in these lesions.

Adult↗
PubMed1998

Memory after frontal/temporal disconnection in monkeys: conditional and non-conditional tasks, unilateral and bilateral frontal lesions.

Seven Cynomolgus monkeys (Macaca fascicularis) learned a series of reward-visual conditional discrimination problems, in which the arrival or non-arrival of a food pellet at the beginning of each trial acted as an instruction cue, signalling which of two visually distinct stimulus objects the animal should choose on that trial in order to obtain a further food pellet reward. Following surgical removal of the ventrolateral prefrontal cortex in one hemisphere and the inferior temporal cortex in the contralateral hemisphere, combined with forebrain commissurotomy, the four operated animals were severely impaired at relearning this task. They were not impaired, however, in non-conditional visual discrimination learning. Extending the unilateral frontal lesion to include the ventromedial prefrontal cortex had no detrimental effect, nor did complete unilateral removal of the frontal cortex. In a third experiment, the operated animals underwent a further surgery to remove either ventrolateral, ventral or complete frontal cortex similar to that in the opposite hemisphere. Compared to their previous level of performance, the animals with bilateral ventrolateral prefrontal lesions were now mildly impaired and the animals with the bilateral lesion extended to the ventromedial cortex more severely impaired on the non-conditional visual discrimination task. The bilaterally lobectomized animals were unable to relearn the task. We suggest that behaviour in visual learning tasks is controlled by cortical convergence upon subcortical structures, possibly by striatal efferents from both the visual cortex and frontal cortex, and that intrahemispheric convergence of these two efferents within the corpus striatum of one hemisphere could allow detailed control of visual choices by non-visual information, while subcortical interhemispheric transfer allows only less detailed, more general control.

Animals↗
PubMed1998

Lesions of the primate rhinal cortex cause deficits in flavour-visual associative memory.

Three Cynomolgus monkeys (Macaca fascicularis) learned a flavour-visual conditional discrimination problem, in which one of two possible food items was presented at the beginning of each trial, and acted as an instruction cue to signal which of two visually distinct stimulus objects the animal must displace on that trial in order to obtain a further food reward. The task was learned first in light then in dark conditions. Following rhinal cortex ablation the animals were unable to use the flavour properties of the food items to guide visual choices, performing at close to chance levels. Postoperative performance on a food preference test showed that their problem in associating a flavour cue with a visual object in the conditional learning task also extended to aberrant choice of foods based on their visual appearance.

Animals↗
PubMed1998

Intensive care services; a crisis of increasing expressed demand.

Critical care services appear to face increasing demand. To attempt to identify factors which may predispose to such increases in demand, the patients and their treatment were reviewed. The patients' ages, referring specialty and their risk of hospital mortality were recorded on admission. The durations of respiratory and renal support (if required) were recorded. Pulmonary artery catheter insertion and the number of vasoactive drugs infused were also noted. During the study, the capacity of the intensive care unit was initially increased by one bed (from six to seven) and later by a six-bedded high-dependency unit. This capacity increase was not matched by a proportionate decrease in occupancy. The patients' mean ages increased by 1 year per year. The number of patients referred from general surgery consistently increased. The proportion of patients receiving vasoactive drugs and pulmonary artery catheters declined as did the duration of respiratory and renal support.

Adult↗
PubMed1998

Interaction of frontal and perirhinal cortices in visual object recognition memory in monkeys.

Monkeys were trained preoperatively in visual object recognition memory. The task was delayed matching-to-sample with lists of trial-unique randomly generated visual stimuli in an automated apparatus, and the stimuli were 2D visual objects made from randomly generated coloured shapes. We then examined the effect of either: (i) disconnecting the frontal cortex in one hemisphere from the perirhinal cortex in the contralateral hemisphere by crossed unilateral ablations; (ii) disconnecting the magnocellular portion of the mediodorsal (MDmc) thalamic nucleus in one hemisphere from the perirhinal cortex in the contralateral hemisphere; or (iii) bilaterally ablating first the amygdala, then adding fornix transection, then finally perirhinal cortex ablation. We found that both frontal/perirhinal and MDmc/perirhinal disconnection had a large effect on visual object recognition memory, whereas both amygdalectomy and the addition of fornix transection had only a mild effect. We conclude that the frontal lobe needs to interact with the perirhinal cortex within the same hemisphere for visual object recognition memory, but that routes through the amygdala and hippocampus are not of primary importance.

Amygdala↗