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Biomedical subjects

P Johnson

Publications and source records attributed to P Johnson.

At least 217 records · Page 12Linked to original sources
PubMed1996

Development of an expert system for amino acid sequence identification.

An expert system for amino acid sequence identification has been developed. The algorithm uses heuristic rules developed by human experts in protein sequencing. The system is applied to the chromatographic data of phenylthiohydantoin-amino acids acquired from an automated sequencer. The peak intensities in the current cycle are compared with those in the previous cycle, while the calibration and succeeding cycles are used as ancillary identification criteria when necessary. The retention time for each chromatographic peak in each cycle is corrected by the corresponding peak in the calibration cycle at the same run. The main improvement of our system compared with the onboard software used by the Applied Biosystems 477A Protein/Peptide Sequencer is that each peak in each cycle is assigned an identification name according to the corrected retention time to be used for the comparison with different cycles. The system was developed from analyses of ribonuclease A and evaluated by runs of four other protein samples that were not used in rule development. This paper demonstrates that rules developed by human experts can be automatically applied to sequence assignment. The expert system performed more accurately than the onboard software of the protein sequencer, in that the misidentification rates for the expert system were around 7%, whereas those for the onboard software were between 13 and 21%.

Algorithms↗
PubMed1996

Grey horizons: who pays for old age in the 21st century?

"This article challenges pessimistic interpretations of the economic impact of population ageing that have been advanced by the World Bank and others. Common perceptions of an ¿old age crisis' are shown to result from a narrow reading of demographic data. Future changes in the age structure of the population will be no greater than those already experienced and accommodated in the last fifty years, and estimates of demographic dependency ratios provide an unreliable basis for future economic projections. Although population ageing will require a larger proportion of income to be transferred from years of work to years of retirement, this cost cannot be significantly reduced by shifting from public to private pension systems." The geographical focus is on Australia.

Adult↗
PubMed1996

Effect of methyl mercaptan on synthesis and degradation of collagen.

Measurements of the conversion of [14C]-proline to [14C]-hydroxyproline were employed to assess the effect of methyl mercaptan on intra- and extracellular metabolism of collagenous proteins in human gingival fibroblast cultures. Following a 30-min pulse, 10 ng of methyl mercaptan per ml of 95% air/5% CO2 head-space suppressed collagen synthesis by 39% and increased the intracellular degradation of newly synthesized collagen from 26% to 42%. Parallel cultures assayed for proline transport demonstrated a 29% inhibition of [14C]-proline uptake. A similar analysis of cultures exposed to methyl mercaptan for 12 h revealed an increase in intracellular degradation (20% control vs. 30% test) and a marked increase in extracellular collagenolysis (4% control vs. 55% test). While pulsing, collagen synthesis was decreased by 39%. Slab gel electrophoresis also demonstrated that treatment with methyl mercaptan caused reductions both in mature alpha 1 and alpha 2 chains of type I collagen and in type III procollagen. Identities of the procollagen species were confirmed by pepsin digestion. Reverse transcribed polymerase chain reaction was utilized to compare expression of alpha 1 chains of type I procollagen with type III procollagen and indicated suppression of mRNA synthesis for type III procollagen in cultures exposed to methyl mercaptan.

Cells, Cultured↗
PubMed1996

Inspiratory muscle endurance in patients with chronic heart failure.

OBJECTIVE: To assess the significance of changes in respiratory muscle endurance in relation to respiratory and limb muscle strength in patients with mild to moderate chronic heart failure using a threshold loading technique. SUBJECTS: 20 patients with chronic heart failure (17 male) aged 63.8 (SD 7.4) years and 10 healthy men aged 63.1 (5.6) years. Heart failure severity was New York Heart Association (NYHA) grade II (n = 11) and NYHA grade III/IV (n = 9). METHODS: Respiratory muscle strength was measured from mouth pressures during maximum inspiratory effort (MIP) at functional residual capacity (FRC) and limb muscle strength was measured using a hand grip dynamometer. Inspiratory muscle endurance was measured using a threshold loading technique. The total endurance duration, the maximum threshold pressure achieved (P-Max), and the inspiratory load (% ratio of P-Max/MIP) were recorded in all subjects. RESULTS: Inspiratory muscles were weaker in patients with heart failure than in the controls [MIP 53.6 (16.5) v 70.9 (20.2) cm H2O, P < 0.05]. Hand grip strength was similar in both subject groups [31.6 (SD) v 36.1 (15.9) dynes]. Total endurance duration was significantly reduced in the patient group [494 (223) v 996 (267) s, P < 0.01], as was the maximal threshold pressure achieved [P-Max 18.5 (6.4) v 30.7 (6.6) cm H2O, P < 0.01]. When expressed as a percentage of MIP, P-Max was also lower in the patients [35.2 (11.8) v 44.8 (11.4)%, P < 0.05]. There was no significant correlation between any measure of endurance and limb muscle strength. CONCLUSIONS: Respiratory muscle endurance is reduced in patients with chronic heart failure. These changes probably reflect a generalised skeletal myopathy and provide further evidence of respiratory muscle dysfunction in patients with this disease. Respiratory muscle endurance needs now to be related to symptoms and the effects of treatment and respiratory muscle training should also be explored.

Chronic Disease↗
PubMed1996

Alterations of lipolysis and lipoprotein lipase in chronically nicotine-treated rats.

These studies examined the cellular mechanisms for lower adiposity seen with nicotine ingestion. Rats were infused with nicotine or saline for 1 wk and adipocytes isolated from epididymal fat pads. Nicotine-infused rats gained 37% less weight and had 21% smaller fat pads. Basal lipolysis was 78% higher, whereas the maximal lipolytic response to isoproterenol was blunted in adipocytes from nicotine-infused rats. The antilipolytic actions of adenosine and the levels of serum catecholamines were unaffected by nicotine. The nicotine-induced alteration in lipolysis was not associated with any changes in hormone-sensitive lipase. Nicotine caused a 30% decrease in lipoprotein lipase (LPL) activity, without any changes in LPL mass or mRNA levels, in epididymal fat in the fed state. In contrast, LPL activity, mass, and mRNA levels in heart were increased by nicotine whether animals were fed or fasted. These studies provide evidence for multiple mechanistic events underlying nicotine-induced alterations in weight and suggest that nicotine diverts fat storage away from adipose tissue and toward utilization by muscle.

Adipose Tissue↗
PubMed1996

Remote continuous physiological monitoring in the home.

As part of a larger study we established a remote physiological monitoring network to investigate cardiorespiratory function during sleep in 400 infants in their homes. The objective of the study was to link measurements made at three weeks and three months of age with detailed measurements of maternal and fetal nutrition during pregnancy and subsequent outcome (growth, development and cardiorespiratory diseases). Five infants per night were monitored anywhere within a radius of 10 miles (16 km) of the remote hub. Of 800 overnight studies on 64 (of 400) infants, 99 were completed. Options allowed downloading data from monitor memory as well as review (on- and off-line) from the infants' or nurses' homes, the hub and the Oxford telemonitoring centre. The reasons for these measurements being made at home were to ensure physiological accuracy and to reduce cost. The network was effectively run by local community nurses; with the exception of the size and cost of the monitors, it had all the elements of a remote primary-care clinical service.

Community Health Services↗
PubMed1996

Early tumour response and treatment toxicity after hyperfractionated radiotherapy in nasopharyngeal carcinoma.

The aim of the present study was to undertake a planned interim analysis of a prospective randomized trial comparing the tumour response and the acute and subacute complications of hyperfractionated radiotherapy and conventional radiotherapy in non-metastatic nasopharyngeal carcinoma (NPC). 100 patients with newly diagnosed non-metastatic NPC were randomized to receive either conventional radiotherapy (Arm I) or hyperfractionated radiotherapy (Arm II). Stratification was done according to the T-Stage (modified Ho's T-Stage classification). The biological effective dose (10 Gy) to the primary and the upper cervical lymphatics were 75.0 and 73.1 for Arm I and 84.4 and 77.2 for Arm II, respectively. Hyperfractionated radiotherapy was associated with significant mucositis which is of higher grade than conventional radiotherapy (p = 0.0001), but the duration of mucositis was similar between the two Arms and all study patients completed radiotherapy on schedule without interruption of radiotherapy. Early survival and tumour recurrence rates were comparable between the Arms. The preliminary results indicate that the hyperfractionated radiotherapy has excellent patient compliance in Chinese patients, with acceptable acute and subacute toxicities and the local and regional complete tumour response rates being comparable with conventional radiotherapy. The significance of the time required after start of radiotherapy to achieve a complete tumour response is discussed.

Carcinoma↗
PubMed1996

Allele imbalance at tumour suppressor loci during the indolent phase of follicle centre cell lymphoma.

We have examined 41 cases of follicle centre cell lymphoma with fluorescent PCR of microsatellite repeats closely linked to or within six tumour suppressor gene loci (APC, DCC, P53, RB1, WT1 and NM23). These probes are highly informative with heterozygousity rates in the range of 57%-90%. In addition we have used four loci from chromosome 6 (D6S260, TNFa, D6S281 and D6S262) as control loci which are unlikely to be involved in the pathogenesis of lymphoma. Of 369 informative PCR reactions allele imbalance was identified in 38 (10%) and this was seen in 23 of the 41 cases. Looking at individual loci allele imbalance was seen in APC(1) 11%, APC(2) 12%, P53(1) 5%, P53 (2) 7%, WT1 5%, RB1 13%, DCC 18% and NM23 0%. This frequency of change was no different from that seen at the control loci D6S260 16%, TNFa 20%, D6S281 4% and D6S262 9%. In the indolent phase of germinal centre cell lymphoma there is therefore quite a high rate of allele imbalance at all loci but this is no higher in those loci linked to tumour suppressor genes.

Alleles↗
PubMed1996

Neonatal individualized predictive pathway (NIPP): a discharge planning tool for parents.

The development of clinical pathways has paralleled the national movement to control health care dollars. This movement is particularly intense in states with extensive managed care plans, such as Arizona. Early infant discharge with minimal home nursing support is a reality that forces parents to anticipate their discharge needs well in advance of the actual discharge date. The 59-bed NICU at Phoenix Children's Hospital uses neonatal individualized predictive pathways (NIPPs) as a discharge planning tool with parents of premature infants less than 32-weeks gestation. The NIPPs were developed after an extensive retrospective record review identified time frames for a variety of medical therapies and clinical milestones. Parent and nursing staff expectations are specified on a weekly basis opposite the medical therapies. This article discusses the positive parental response to the NIPP and identifies future areas for development.

Critical Pathways↗
PubMed1996

An intention-based language for representing clinical guidelines.

Automated support for guideline-based care would be enhanced considerably by a standard representation of clinical guidelines. To faciliate use and reuse, we suggest a representation that includes the explicit intentions of the guideline's author. These intentions include the desirable actions of the care provider and the patient states to be achieved before, during, and after the administration of the guideline. Intentions are temporal patterns of provider actions or patient states to be maintained, achieved, or avoided. We view automated support as a collaborative effort of the health-care provider and an automated assistant and involves several different tasks. We defined the syntax and, the semantics of a text-based language (ASBRU) for representation and annotation of clinical guidelines. The language supports maintenance of the automated assistant's knowledge base and could improve the quality and flexibility of the automated assistant's recommendations. In the ASGAARD project, we are developing reasoning mechanisms that use the ASBRU language for execution and critiquing tasks in conjunction with online electronic patient medical records.

Expert Systems↗
PubMed1995

Characterization of the subunit isoforms of duck salt gland Na/K adenosine triphosphatase.

The N-terminal sequences of the alpha and beta subunits from the Na/K-ATPase of duck salt gland have been determined by automated Edman degradation chemistry. These sequences were compared to sequences previously reported for Na/K-ATPase subunits from other sources in order to determine the subunit isoform composition of the salt gland enzyme. The comparisons indicate that the duck salt gland enzyme is composed of an alpha-1 subunit and a beta-1 subunit. This subunit isoform composition is consistent with the involvement of this enzyme in sodium excretion as Na/K-ATPases in other tissues involved in sodium excretion also have this subunit isoform composition.

Amino Acid Sequence↗
PubMed1995

Association of 75/80-kDa phosphoproteins and the tyrosine kinases Lyn, Fyn, and Lck with the B cell molecule CD20. Evidence against involvement of the cytoplasmic regions of CD20.

CD20, a non-glycosylated cell-surface protein expressed exclusively on B lymphocytes, is one of a family of 4-pass transmembrane molecules that also includes the beta chain of the high affinity receptor for IgE. The precise function of CD20 is unknown, although in vitro effects of CD20-specific antibodies on resting B cells indicate that it is able to transduce an extracellular signal affecting the G0/G1 cell cycle transition. Previous studies have demonstrated that CD20-initiated intracellular signals involve tyrosine kinase activation and that CD20 is tightly associated with both serine and tyrosine kinases. Here, analysis of CD20-associated molecules has revealed that CD20 is associated with the Src family tyrosine kinases p56/53lyn, p56lck, and p59fyn and with 75/80-kDa proteins phosphorylated in vivo on tyrosine residues. Mutagenesis of CD20 was performed to define regions of CD20 involved in intermolecular interactions. Mutants were analyzed in the human T lymphoblastoid cell line Molt-4, in which ectopically expressed wild-type CD20 associated with p59fyn, p56lck, and 75/80-kDa phosphoproteins. Deletion of major portions of the cytoplasmic regions of CD20 did not abolish its association with either p75/80 or tyrosine kinases. The interaction between CD20 and the Src-related kinases is therefore likely to be independent of CD20 cytoplasmic domains and may occur indirectly. The interaction may be mediated by the p75/80 phosphoproteins, which were found to be tightly associated with the Src family kinases isolated from the CD20 complex.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1995

Characterization of the interaction between CD45 and CD45-AP.

CD45, a leukocyte-specific transmembrane protein tyrosine phosphatase, is required for critical signal transduction pathways in immune responses. To elucidate the molecular interactions of CD45 with other proteins involved in CD45-mediated signal transduction pathways, we have recently cloned a 30-kDa phosphorylated protein, CD45-AP, which specifically associates with CD45. Binding analysis employing several deleted or chimeric forms of CD45-AP and CD45 demonstrated that the potential transmembrane segment of CD45-AP bound to the transmembrane portion of CD45. CD45-AP was found in particulate fractions of lymphocytes along with CD45, indicating that it is likely to be a transmembrane protein. In addition, CD45-AP was resistant to proteolysis by tosylphenylalanyl chloromethyl ketone-treated trypsin applied to intact cells. This is consistent with the most likely membrane orientation of CD45-AP predicted from the amino acid sequence, that is, only a short amino-terminal segment of CD45-AP is extracellular. We propose that CD45-AP interacts with CD45 at the plasma membrane and that the bulk of CD45-AP located in the cytoplasm act as an adapter which directs the interaction between CD45 and other molecules involved in CD45-mediated signal transduction pathways.

Animals↗
PubMed1995

Substrate-based inhibitors of lanosterol 14 alpha-methyl demethylase: II. Time-dependent enzyme inactivation by selected oxylanosterol analogs.

Selected 15-, 32-, and 15,32-substituted lanosterol analogs are shown here to display time-dependent inactivation and lanosterol 14 alpha-methyl demethylase. These molecules are competitive with respect to substrate and require NADPH and O2 in order to display time dependence, thus supporting the premise that they are mechanism-based inactivators. Structural features required for lanosterol demethylation by the lanosterol demethylase such as nuclear double bond location and availability of an abstractable 15 alpha-proton are also essential elements for time-dependent inactivation. 32-(S)-Vinyllanost-8-en-3 beta,32-diol is a potent time-dependent inactivator (Kinact/Ki = 0.36 min-1 microM-1), while the 32-(R)-vinyllanost-8-en-3 beta,32-diol functions solely as a competitive demethylase inhibitor. These results support the premise that stereoselective oxidation occurs during lanosterol demethylation and that the 32-pro-S proton is abstracted during the demethylation reaction.

Binding, Competitive↗
PubMed1995

Dopamine D2 receptor gene (DRD2) haplotypes and the defense style questionnaire in substance abuse, Tourette syndrome, and controls.

The defence style questionnaire (DSQ) was administered to Caucasian males consisting of 123 subjects from a V.A. addiction treatment unit (ATU), 42 Tourette syndrome (TS) subjects, and 49 controls. For the ATU and TS subjects, there was a significant decrease in the mean score for mature defenses and a significant increase in mean score for immature defenses compared to controls. Many of the individual subscores showed the same significant differences. Dopamine D2 receptor (DRD2) gene haplotypes, identified by allele specific polymerase chain reaction of two mutations (G/T and C/T) 241 base pairs apart, were determined in 57 of the ATU subjects and 42 of the controls. Subjects with the 1 haplotype tended to show a decrease in mature and an increase in neurotic and immature defense styles compared to those without the 1 haplotype. Of the eight times that the subscale scores were significant for haplotype 1 versus non-1, they were always in this direction. There results suggest that the DRD2 locus is one factors controlling defense styles. The difference in the mean scores between controls and substance abuse subjects indicates that other genes and environmental factors also play a role.

Alcoholism↗
PubMed1995

Non-radioactive method to measure CD45 protein tyrosine phosphatase activity isolated directly from cells.

Preparation of radioactive phosphorylated substrates is laborious, yields a limited amount of substrate with a short half-life and generates a low percentage of phosphorylated product which then has to be separated from non-phosphorylated material. These factors limit the usefulness of radioactive phosphorylated substrates in phosphatase assays and prohibit their use for kinetic analysis, which often requires large amounts of substrate. An alternative method for the kinetic analysis of purified or recombinant soluble phosphatases uses the malachite green reagent which can detect nanomoles of phosphate released from chemically synthesized phosphorylated peptides. In this report we describe a rapid and sensitive non-radioactive method that can be used to measure protein tyrosine phosphatase (PTP) activities of both transmembrane and soluble phosphatases immunoprecipitated directly from cells. This colorimetric microassay is performed in 96 well microtitre plates and can reliably detect 100 pmol of free phosphate released, using a standard microplate reader. The phosphatase activity of CD45, a transmembrane PTP, was determined from as few as 1 x 10(4) lymphoid cells. The development of this colorimetric assay to measure immunoprecipitated CD45 PTP activity isolated from very small numbers of cells has general applicability for other PTPs and will help identify the cellular situations and conditions that result in changes in PTP activity.

Amino Acid Sequence↗