Biomedical subjects
Publications and source records attributed to S Butt.
Intracranial and spinal haemangiopericytomas are uncommon, durally based tumours. They macroscopically resemble meningiomas but are distinct histologically, have a more aggressive natural history and require different management. We present a pictorial review illustrating the radiological manifestations of these tumours that will aid in their preoperative identification.
Benign primary tumours of the ribs are rare and may be identified during the investigation of a clinically suspected abnormality or as an incidental finding. This review describes the spectrum of benign tumours that can involve the rib and illustrates the radiographic, computed tomography (CT) and magnetic resonance (MR) imaging appearances that may facilitate diagnosis.
We describe a case of chronic Salter-Harris I injury of the proximal tibial epiphysis. To our knowledge such an injury has not been described in the English language literature. The radiological appearance can mimic chronic infection. The possibility of chronic athletic stress-related change should be considered in such scenarios to avoid a misdiagnosis.
Lumbar spondylolisthesis is a common finding on plain radiographs. The condition has a variety of causes which can be differentiated on the basis of imaging findings. As the treatment is dependent upon the type of spondylolisthesis, it is important for the radiologist to be aware of these features. We present a pictorial review of the imaging features of lumbar spondylolisthesis and explain the differentiating points between different groups of this disorder. The relative merits of the different imaging techniques in assessing lumbar spondylolisthesis are discussed.
The adsorption/release behaviour of oligodeoxynucleotides (ODNs) on double functional core-shell polymethylmethacrylate nanospheres, with a narrow size distribution, is described. The outer shell consists of alkyl or glycolic chains containing permanently-charged quaternary ammonium groups. Ion pair formation between negatively-charged ODN phosphate groups and positively-charged groups, present on the nanosphere surface, is the main mechanism of interaction. The amount of adsorbed ODN depends on both the ODN concentration and the nanosphere surface charge density. An adsorption-induced swelling mechanism is proposed in which a modification of the charged diffuse layer around the nanospheres increases the ODN binding site accessibility with increasing ODN concentration. Adsorption on the nanosphere surface prevents serum degradation of the ODNs. ODN release is negligible in the presence of culture medium but occurs gradually in the presence of serum. No significant cytotoxicity of the free nanoparticles was found in PBMC and CEM cells after 24 h at ODN concentrations required for antisense activity.
Using solid phase synthesis techniques, we have rapidly obtained a series of eight aryl sulphonamides derived from putrescine. These conjugates with various aryl groups were evaluated for their affinity towards 5-HT6 receptors in man. This evaluation revealed the interest of two compounds which present the same activity level, in the submicromolar range, as two reference derivatives. The most potent will be considered as a new lead for further investigations.
PURPOSE: To investigate the effect of nicotinamide on normal brain and 9L tumor blood flow in the rat using magnetic resonance imaging (MRI) and arterial spin tagging. METHODS AND MATERIALS: Using MRI at 7 Tesla, measurements of blood perfusion were determined from two-dimensional maps of intracerebral 9L rat tumors and normal Fischer rat brains. The spatial and temporal influence of nicotinamide, 500 mg/kg i.p., on cerebral blood flow (CBF) was studied in normal brain and tumors between 5 and 21 days after tumor implantation. The MRI CBF measurements employed a variable tip-angle-gradient-recalled echo (VTA-GRE-CBF) readout of the magnetization of the tissue slice. The VTA-GRE-CBF required 8 minutes for a blood flow image with inplane resolution of 250 microm x 500 microm x 2 mm. RESULTS: Normal brain blood flow decreased following the administration of nicotinamide. In contrast, tumor blood flow remained unaffected in the time following nicotinamide administration. Consequently, the blood flowing in the tumor relative to that in normal brain demonstrated a significant and selective increase in response to nicotinamide administration. Relative tumor blood flow increased at 10 minutes after nicotinamide injection compared with predrug levels and remained elevated for at least 1 hour. CONCLUSION: The results suggest that nicotinamide will not enhance radiosensitivity of brain tumors. The results support the use of nicotinamide to improve delivery of anticancer therapeutics through its ability to selectively increase tumor blood flow relative to that in normal brain.
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The reverse micelle is one of many models thought to have properties more nearly resembling the biological cellular environment, than does the traditional dilute-solution biochemical reaction system. In order to evaluate the results of EMF perturbation of enzyme-catalyzed reactions, the description of the AOT reverse-micelle model, with respect to its internal pH, effect of chemical inhibitors, temperature, and electromagnetic-field perturbation has herein been extended. Acetylcholinesterase and NADPH cytochrome-P450 reductase, reacting within the AOT reverse-micelle, exhibit a temperature vs. activity profile equivalent to the same reaction in a buffered dilute-solution environment. In reverse micelles, some inhibitors of AChE (propidium, and d-tubocurarine) have much less effect upon indophenol-acetate hydrolysis than they do in a dilute solution environment. Other inhibitors act in the same manner within the structured environment of the reverse micelle as in the conventional dilute solution reaction model. These differences are explicable in terms of mechanism of action of the individual inhibitors. Perturbation by low-intensity microwave fields has a similar inhibitory effect upon dilute-solution reactions, as those in the 'low-water-activity' environment of the reverse micelle. However, the interactions between physical and chemical perturbants are differently limited by the structure of the aqueous phase of the reverse micelle. pH of the 'internal' reverse-micelle environment is a function of the availability of H-ions supplied by system components. Use of indicator dyes show that the low-molarity buffers which are compatible with reverse-micelle stability, are often insufficient to maintain a constant pH. Too, in the reverse micelle, reaction rate, for proton yielding reactions, is dramatically greater than the rate of the same reaction in dilute solution at the same acidic pH.
We have noninvasively produced low-resolution, quantitative nuclear magnetic resonance images of cerebral blood flow in 2-ml voxels in eight cats. Typical signal-to-noise of 4 to 1 was obtained in cerebral voxels in 16.5-s epochs. Mean flow during normocapnia (paCO2 = 39 +/- 4 mm Hg) and hypercapnia (paCO2 = 62 +/- 4 mm Hg) was 53 +/- 20 ml/100 g-min and 140 +/- 36 ml/100 g-min, respectively. Fast flows in normocapnia were 94 +/- 13 and 182 +/- 39 ml/100 g-min in hypercapnia. These results suggest that an atraumatic quantitative imaging assessment of cerebral perfusion may be possible in humans using these techniques.
A series of four isomeric 2'- and 6'-fluorocarbocyclic guanosine analogues have been prepared and evaluated as potential anti-herpes agents. The racemic 2' beta-fluoro isomer 2-amino-1,9-dihydro- 9-[(1 alpha, 2 alpha, 3 beta, 4 alpha)-2-fluoro-3-hydroxy-4- (hydroxymethyl)cyclopentyl]-6H-purin-6-one (11a, C-AFG) and its 2' alpha-fluoro epimer 11b plus the chiral 6' beta-fluoro isomer 2-amino-1,9-dihydro-9-[[1S-(1 alpha, 2 alpha, 3 alpha, 4 beta)]- 2-fluoro-4-hydroxy-3-(hydroxymethyl)cyclopentyl]-6H-purine-6-one (11c) and its 6' alpha-fluoro epimer 11d were prepared from their respective fluoro amino diol hydrochlorides (6a,d). For comparison, the furanosyl compound 9-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)guanine (17, AFG) was prepared by coupling 2-amino-6-chloropurine with 2-deoxy-2-fluoro-3,5-di-O-benzoyl-alpha- D-arabinofuranosyl bromide followed by base hydrolysis. The 6' alpha-fluoro derivative 11d exhibited comparable activity to that of acyclovir (ACV) against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) in vitro but was greater than 30-fold more active than ACV against HSV-1 and HSV-2 in vivo in the mouse systemic model. The 2' beta-fluoro derivative (11a, C-AFG) was extremely potent in vitro against HSV-1 and HSV-2 (ID50 0.006 and 0.05 micrograms/mL) and in vivo it was greater than 2 orders of magnitude more potent than ACV against HSV-1 and 70-fold more potent against HSV-2. The 2' alpha-fluoro 11b and 6' beta-fluoro 11c isomers were much less active.
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Two experiments are reported in which rats were trained to choose one of two goal arms in a Y-maze, for water reward. In one arm, the rats always received water (the continuously reinforced-CRF-arm). In the other arm the rats only sometimes received water (the partially reinforced-PRF-arm). During the critical test phase in both experiments, we delayed the reward in the CRF arm only by 10 s. Experiment 1 tested intact rats given saline injections, or injections of chlordiazepoxide hydrochloride (Librium, 5 mg/kg), and rats with hippocampal or cortical control lesions. When reward was immediate in both arms all rats preferred the CRF arm. Once reward was delayed, the rats with hippocampal lesions switched their preference to the PRF arm, while the rats in the other treatment groups did not. Experiment 2 tested rats with medial septal lesions, lateral septal lesions or control operations in the same way. The rats with medial septal lesions, and to a lesser extent those with lateral septal lesions, switched their preference to the PRF arm when compared to the sham-operated controls. We conclude that damage to the hippocampus or its afferent pathway from the septum increases rats' sensitivity to temporal discontiguities between the outcome of a response and its emission.
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