Biomedical subjects
Publications and source records attributed to R Allen.
A strain of St. Louis encephalitis virus has been isolated from Mexican free-tailed bats (Tadarida b. mexicana) collected at the time of an outbreak of encephalitis in Texas in 1964.
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BACKGROUND: The overexpression of transforming growth factor-beta (TGF-beta) in hepatocellular carcinoma (HCC) appears to induce immunosuppression toward the tumor cells. METHODS: A rat HCC cell line, Morris hepatoma rat cell line (MRH)-7777 (MRH), was transfected with antisense TGF-beta2 in pCEP-4 vector and used as immunotherapy against the development of wild-type tumors. An enzyme-linked immunosorbent assay (ELISA) confirmed that TGF-beta2 production was markedly lower for antisense modified cells as compared to wild-type tumor cells. Tumors were initiated by injecting MRH cells into the flanks of Buffalo rats. This was followed by biweekly vaccinations with irradiated MRH cells (unmodified, pCEP-4 alone, or antisense TGF-beta2 modified). RESULTS: In the group that received irradiated MRH unmodified cells, 55% of rats died from tumor burden, and 36% developed tumor regression. In the group that received irradiated MRH cells modified with pCEP-4 vector alone, 50% died from tumors and 33% had spontaneous regression. In animals treated with pCEP-4/TGF-beta antisense modified cells, none developed tumors. Cell-mediated cytotoxicity assays demonstrated a twofold increase in lytic activity in the effector cells of the animals treated with antisense modified cells. CONCLUSIONS: These results demonstrate the successful treatment of HCC tumors in rats by a HCC vaccine genetically altered with antisense TGF-beta2. Decreased production of TGF-beta in HCC vaccine enhances immunogenicity against wild-type HCC tumor cells.
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The utility of the auditory evoked potential (AEP) is under investigation as a feedback signal for the automatic closed-loop control of general anaesthesia using neural networks and fuzzy logic. The AEP is a signal derived from the electroencephalogram (EEG) in response to auditory stimulation, which may be useful as an index of the 'depth' of anaesthesia. A simple back-propagation neural network can learn the AEP and provides a satisfactory input to a fuzzy logic infusion controller for the administration of anaesthetic drugs, but the problem remains that of reliable signal acquisition.
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Intracranial hypertension is a dangerous condition and is common in patients suffering from a severe head injury or from a variety of pathological problems. Measurement of intracranial pressure (ICP) is considered by many to be a valuable aid in the management of such patients. Despite the invasive nature of the more widely-used measurement techniques, and hence their associated risks, results from many centres have convincingly shown that ICP measurement enables management of intracranial hypertension to be rationally approached, and a direct measure of the progress and outcome of treatment to be obtained. This paper begins with a description of normal cerebrospinal fluid (c.s.f.) pressure. This is followed by an account of the pressure-volume relationship of the intracranial system, and the control mechanisms that regulate the ICP during limited increases in mass volume within the cranium. The consequences of these for patient management are discussed. Reasons why ICP is monitored, and the benefits arising, are described. The paper then concentrates upon the methods of measuring ICP and discusses their relative merits and limitations. A selection of typical pressure sensors is described. Finally, methods that have been devised to monitor ICP and to anticipate intracranial hypertension are reviewed, and the direction of work in this area is assessed.
The kinematic behaviour of the vertebral segments under the influence of spinal injury and other mechanical problems is difficult to quantify in patients. This paper describes the use of a calibration model and human subjects to investigate the accuracy of a method for determining lumbar intervertebral rotations using images digitized from an image intensifier. The main influences were found to be observer error in marking co-ordinates, scaling of the image presented by the computer's monitor, distortion caused by out-of-plane images and loss of image quality as a result of scattered radiation from the soft tissues. The technique may be valuable in the light of its efficiency and low X-ray exposure to patients.
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The metabolism and excretion of 14C-labeled 3,4,4'-trichlorodiphenylurea has been studied in the rat after oral and iv administration. More than 80% of the administered radioactivity was excreted in the feces and urine over 5 days. Five isolated metabolites were characterized by mass spectrometry and by comparative thin-layer chromatography with synthesized compounds. Metabolites found include 2'-hydroxy-, 3'-hydroxy-, 6-hydroxy-, 2',6-dihydroxy- and 3',6-dihydroxy-3,4,4'-trichlorodiphenylurea.
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