Biomedical subjects
R Potter
Publications and source records attributed to R Potter.
Discovery and analysis of a series of C2-symmetric HIV-1 proteinase inhibitors derived from penicillin.
In order to identify a suitable peptide substrate for human immunodeficiency virus-1 (HIV-1) proteinase, a range of peptides from various cleavage sites within the gag-pol polyprotein were assayed by HPLC for specific cleavage. The peptide with the optimal combination of favorable kinetics and good solubility was based on the N-terminus cleavage site of HIV-1 proteinase (KQGTVSFNF*PQIT). The HPLC assay, using the above peptide, was developed into a rapid isocratic method in order to analyze inhibition kinetics. An assay suitable for high-throughput screening was developed using a radioactively labeled peptide with the same sequence, coupled to a solid phase. Using this assay, a C2-symmetric HIV-1 proteinase inhibitor derived from penicillin was discovered during random screening of a compound library. A chemical synthesis program developed this structure into a series of potent inhibitors. The lead structures were highly selective for HIV-1 proteinase with good antiviral activity in vitro against HIV and no cytotoxicity. The HPLC assay was used to demonstrate that these compounds are competitive tight-binding inhibitors of HIV-1 proteinase.
The promoter of the barley aleurone-specific gene encoding a putative 7 kDa lipid transfer protein confers aleurone cell-specific expression in transgenic rice.
This paper describes the aleurone-specific gene Ltp2 from barley, which encodes a putative 7 kDa non-specific lipid transfer protein. As shown by Northern and in situ hybridization analyses, the Ltp2 transcript is present in barley aleurone cells shortly after the initiation of aleurone cell differentiation. The expression of Ltp2 increases until grain mid-maturity, but the mRNA is absent from mature grains. The Ltp2 transcript is undetectable in the embryo and vegetative tissues, confirming the aleurone specificity of the Ltp2 gene. The ability of the isolated 801 bp Ltp2 promoter to direct aleurone-specific expression in immature barley grains is demonstrated by particle bombardment experiments. In these experiments, the activity of the Ltp2 promoter is 5% of the activity of the strong constitutive Actin1 promoter from rice, as quantified by GUS activity measurements. In stably transformed rice plants containing the Ltp2 promoter-Gus construct, the specificity of the Ltp2 promoter is confirmed in vivo by the presence of GUS activity exclusively in the aleurone layer. This study demonstrates the conserved nature of the regulatory signals involved in aleurone-specific gene transcription in cereal grains.
Quality assurance in obstetric ultrasound.
Ultrasound examination is a routine element of antenatal care, and an accurate and reliable ultrasound service is essential for confident patient management. Qualitative findings, e.g. fetal normality and placental site, may be confirmed at delivery, but this form of audit is not suitable for fetal measurements owing to the variation in gestation at delivery and the complexity of neonatal assessment. Our aim was to develop a simple audit method applied a short time after the ultrasound scan. The method was based on assessment of measured images against measurement criteria which are clearly defined in the literature, results for each criterion being recorded in a spreadsheet. Two main forms of report were generated, the first showing overall achievement of satisfactory measurements for each sonographer, the second providing graphical information to show which criteria required greater attention by individual sonographers. Over several phases of audit problems of quality recognition and technical skill were isolated, graphical reports were used to guide tuition and the levels of performance were improved. The method itself and the results satisfy managers at all levels that standards are in place and are being maintained.
Histologic effects of smokeless tobacco and alcohol on the pouch mucosa and organs of the Syrian hamster.
This study's intent was to measure the histologic effects of smokeless tobacco and alcohol on the buccal pouch mucosa and internal organs of male Syrian hamsters. Eighty hamsters were divided into four groups: tobacco only, alcohol only, tobacco and alcohol, and negative control. 200 mg of smokeless tobacco were placed in each pouch of the tobacco groups five times a week. In the alcohol groups, 2 ml of 15% ethyl alcohol were placed in each pouch five times a week. The negative control group had mechanical stimulation of the right pouch to simulate the placement of the tobacco. After 26 wk the animals were sacrificed with pouches and abdominal organs removed. Alterations were observed in the abdominal organs, but not of statistical significance. However, significant acanthosis of the pouch epithelium was noted in the tobacco and tobacco and alcohol groups. This study reaffirms the lack of carcinogenic potential of smokeless tobacco upon the hamster pouch mucosa and internal organs.
The role of 99Tcm-HMPAO white cell imaging in suspected orthopaedic infection.
Accurate diagnosis is essential for the effective management of suspected bone infection. Current imaging techniques have had limited success and further work is required. Although white cell labelling techniques have been available for many years the radiopharmaceuticals employed have disadvantages, particularly in their availability and suitability for imaging. These problems have been overcome by the use of 99Tcm-HMPAO as an in vitro leukocyte labelling agent. The aims of this study were to assess retrospectively its role and accuracy in imaging orthopaedic infection and to compare the results with three-phase bone imaging. 30 patients with suspected bone infection underwent three-phase methylene diphosphonate (MDP) bone imaging and labelled leukocyte imaging on separate occasions. 16 bone scans were positive for infection, of which 14 were subsequently confirmed, and there were no false negatives. There were no false positive white cell studies and only one infection was not identified. 99Tcm-HMPAO white cell imaging has been shown to be an accurate technique for the diagnosis of bone infection but should be performed only following a positive finding on three-phase bone scanning, since the latter is highly sensitive but significantly less expensive, making it a more appropriate screening procedure.
Video signal analyser with applications for head movement monitoring of severely handicapped people.
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Thymic involvement in Hodgkin disease: CT and sonographic findings.
To evaluate the morphologic characteristics and frequency of thymic enlargement in Hodgkin disease, the initial and follow-up computed tomographic (CT) scans of 43 patients with newly diagnosed Hodgkin lymphoma were retrospectively analyzed. Sonograms of the thymic region in 21 patients were also available and were compared with the CT scans. Initial CT scans showed thymic enlargement in 17 of the 43 patients, no evidence of thymic enlargement in 15 patients, and equivocal findings in 11 patients. Analysis of follow-up CT scans indicated that seven of the 11 patients with initially equivocal findings had had thymic enlargement. In all seven patients, the anterior mediastinal tumor shrank with therapy and adopted a typical tongue-shaped thymic configuration. In nine of the 24 patients with thymic enlargement, the thymus remained enlarged after therapy and full clinical remission. The comparison of sonograms and CT scans showed that sonography could not help differentiate the normal-size thymus from surrounding fatty tissue. All thymic glands that were considered diseased because of enlargement at CT were sonographically visible due to an abnormal, hypoechoic structure. The results of the study show that thymic enlargement presumed to be due to involvement by Hodgkin disease seems to occur more frequently than previously reported.
Acquired hearing impairment and psychiatric disorder amongst Australian Vietnam veterans.
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A week in the life of Mary: the impact of microtechnology on a severely handicapped person.
Microtechnology has an important role to play in maximizing the independence of severely handicapped people, especially those with few reliable voluntary movements. Such movements must be harnessed efficiently to provide control over all aspects of life including communication, mobility and the immediate environment. To highlight the role of microtechnology in the day to day life of a severely handicapped person living at home, a case study is presented. The systems Mary uses for communication and environmental control are described and their limitations discussed. Adaptive man-machine interfaces are proposed and foreseeable developments in the fields of speech technology and robotics are considered. Successful introduction of high technology devices requires a full appreciation of medical and social factors as well as those relating to the technology. This is achieved through close partnership between the clinical engineer and the rehabilitation consultant to the benefit of the severely handicapped person.
Sequence and organization of genes encoding the human 27 kDa heat shock protein.
The 27 kDa human heat shock protein (hsp27) is encoded by a gene family of 4 members. Two genomic fragments hybridizing to cDNA encoding hsp27 have been isolated, characterized, and sequenced. One clone is a member of a cluster of three genes linked within a 14-18 kb region of the genome and encodes a transcript interrupted by two intervening sequences. A single open reading frame encodes a polypeptide of 22,300 deduced molecular weight. The 5' flanking region contains two transcription start sites and sequences homologous to the Drosophila consensus heat inducible control element. Induction of both potential transcripts follows heat shock in vivo. Accurate heat inducible transcription occurs at both start sites after injection into Xenopus oocytes. The second genomic clone is a processed pseudogene lacking promoter elements and is unlinked with the other members of the hsp27 gene family. The amino acid sequence of human hsp27 shows striking homology with mammalian alpha crystallin, and contains a region towards the carboxy terminus which shares homology with the small hsp of Drosophila and other organisms.
Beer potomania: an unusual cause of symptomatic hyponatremia.
A 43-year-old woman presented to the emergency department with acute agitation, confusion, and tonic seizures. She had a history of drug abuse, most notably beer, which constituted her major dietary intake. The patient's seizures were at first thought to be factitious in association with an acute psychosis; however, her serum sodium concentration was 110 mEq/L and urine sodium was 14 mEq/L. The patient responded to IV hypertonic saline and subsequently recovered completely. Beer potomania, the most likely etiology for this patient's hyponatremia, is a rare disorder in which dietary sodium and protein insufficiency lead to dilutional hyponatremia.
Ventilatory function computer.
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Angiographic measurements of blood vessel calibers.
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Report on a symposium on monitoring drug concentrations in neuropsychiatry London, July 3-5, 1979.
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Fluoride distribution in teeth using a silicate model.
The fluoride determinations were done on enamel biopsies taken before and after restoration of extracted teeth with silicate cement. Two sites, one near the restoration and one 3 mm or more away from the restoration, were assayed. No difference was noted in pre- and post-restoration biopsies when teeth were restored with a fluoride-free silicate. Post-restoration biopsies at sites near and away from the restoration were significantly higher in fluoride as compared to pre-restoration biopsies when the teeth were restored with a fluoride-containing silicate.
Sensitometry of films for nuclear medicine.
A method is described for the determination of characteristic curves for films used in nuclear medicine imaging. Such characteristic curves are presented for a number of commercially available film types and their significance is discussed.