Search PubMed⌕ Search

Biomedical subjects

C Lewis

Publications and source records attributed to C Lewis.

At least 109 records · Page 6Linked to original sources
PubMed1997

The use of povidone iodine in exit site care for patients undergoing continuous peritoneal dialysis (CAPD).

Exit site infection is a major risk factor for the development of peritonitis in continuous ambulatory peritoneal dialysis. The frequency of infection can be reduced by scrupulous exit site care with or without topical antiseptics. A randomized trial was performed of 149 catheters in 130 patients to assess any additional benefits conferred by the use of povidine iodine dry powder spray at dressing changes over an existing strict protocol of exit care. Exit infections occurred in 14 (18%) of 77 patients using spray and in 15 (21%) of 72 patients not using spray. The risk of peritonitis was also similar in each group. The proportion of infections caused by Staphylococcus aureus was reduced in the spray group, but those caused by Pseudomonas aeruginosa were increased. Rash occurred in 6% of those using the spray. The use of the spray did not therefore seem justified.

Aged↗
PubMed1997

Application of NASA's advanced life support technologies in polar regions.

NASA's advanced life support technologies are being combined with Arctic science and engineering knowledge in the Advanced Life Systems for Extreme Environments (ALSEE) project. This project addresses treatment and reduction of waste, purification and recycling of water, and production of food in remote communities of Alaska. The project focus is a major issue in the state of Alaska and other areas of the Circumpolar North; the health and welfare of people, their lives and the subsistence lifestyle in remote communities, care for the environment, and economic opportunity through technology transfer. The challenge is to implement the technologies in a manner compatible with the social and economic structures of native communities, the state, and the commercial sector. NASA goals are technology selection, system design and methods development of regenerative life support systems for planetary and Lunar bases and other space exploration missions. The ALSEE project will provide similar advanced technologies to address the multiple problems facing the remote communities of Alaska and provide an extreme environment testbed for future space applications. These technologies have never been assembled for this purpose. They offer an integrated approach to solving pressing problems in remote communities.

Alaska↗
PubMed1997

Evaluation of a programming algorithm for the third tachycardia zone in a fourth-generation implantable cardioverter-defibrillator.

The clinical efficacy of electrical algorithms for termination of slow ventricular tachycardia (VT) and ventricular fibrillation (VF) in implantable cardioverter-defibrillators (ICDs) is well established. Such algorithms have not been equally well defined for fast VT reversion. We report the testing of a prospectively designed algorithm for ICDs to treat fast VT that is inherently less responsive to antitachycardia pacing than slow VT. Fourth-generation ICD devices were programmed to three prospectively defined tachycardia detection zones as follows: cycle lengths < or = 260 ms for VF, 270-330 ms for fast VT, and > 330 ms for slow VT. The initial selected therapy for the VF zone was a high-energy biphasic shock (> 15 J), while a 3- or 5-J biphasic shock was usually administered for fast VT, and antitachycardia pacing was initially attempted for slow VT. Initial therapy was followed by backup therapy with high-energy shocks. Twenty-eight patients, 24 of whom were males, all with organic heart disease, with a mean age of 65 +/- 9 years, received either a Medtronic 7219D (23 patients), 7219C (2 patients), 7218SP1 (2 patients), or 7218C (1 patient) ICD with a nonthoracotomy lead system. The defibrillation threshold was 10 +/- 5 J. At predischarge electrophysiologic testing, a single 3- or 5-J shock terminated all episodes of fast VT tested. During a follow-up of 18 +/- 9 months, there were four nonarrhythmic deaths. Fourteen patients (50%) had a total of 21 VF, 44 fast VT, and 202 slow VT episodes. Twenty-three of 24 (96%) VF, 33 of 39 (84%) fast VT, and 193 of 202 (95.5%) slow VT episodes were terminated with the first delivered therapy in each therapy algorithm (p = NS). The overall efficacy of the entire electrical therapy algorithm was 100% for VF, 100% for fast VT, and 98% for slow VT episodes (p = NS). No patient experienced syncope or presyncope during fast VT or VF in this study. We conclude that a third detection and therapy zone can be successfully programmed in ICDs to define a range of fast VT episodes that can be effectively terminated with lower energy cardioversion shocks with comparable success and freedom from arrhythmic symptoms to electrical therapies used for slow VT and VF.

Aged↗
PubMed1997

Value of an orthopaedic pre-admission clinic for total knee and hip replacements in a rural health service.

The emphasis on orthopaedic pre-admission clinics within hospital settings is very recent in Australia. Tamworth Base Hospital, a large rural hospital, started a compulsory clinic in mid-1995. The purpose of this study was to determine the value of orthopaedic education in a pre-admission clinic for patients who were undergoing total knee and total hip replacements. Regarding total knee replacement patients, the average length of stay for those who attended the clinic after it had become compulsory, compared with before, was 3.8 days shorter. For total hip replacement patients, the reduction was 1.1 days. This study found that the major value of the clinic was not so much in reduced lengths of stay, rather it related more to increased patient satisfaction, and perhaps more so in the rural setting where patients are disadvantaged in many cases by the large distances they travel for services.

Adult↗
PubMed1997

Interaction between electronic article surveillance systems and implantable defibrillators: insights from a fourth generation ICD.

We present a case report of an inappropriate discharge from a fourth generation implantable cardioverter defibrillator (ICD) as a result of exposure to electromagnetic interference. A 60-year-old man implanted with a Medtronic 7219D defibrillator experienced shocks without preceding symptoms while walking through an electronic surveillance system in a store. Though this has been reported, the mechanism of the interaction remains unexplained. The electrogram storage capabilities of this particular device enabled us to establish that this resulted from inappropriate sensing of the electromagnetic interference.

Defibrillators, Implantable↗
PubMed1996

Ionic permeability of, and divalent cation effects on, two ATP-gated cation channels (P2X receptors) expressed in mammalian cells.

1. Complementary DNAs for the ATP-gated ion channel subunits P2X1 (from human bladder) and P2X2 (from rat phaeochromocytoma (PC12) cells) were used to express the receptors in human embryonic kidney cells by stable transfection, and in Chinese hamster ovary cells by viral infection. 2. Membrane currents evoked by ATP were recorded by the whole-cell patch clamp method. The reversal potential of the current was measured with various intracellular and extracellular solutions and used to compute the relative permeability of the P2X receptor channels. 3. There was no difference between the two receptors with respect to their permeability to monovalent organic cations. The relative permeabilities (PX/PNa) were 2.3, 1.0, 1.0, 0.95, 0.72, 0.5, 0.29, 0.16, 0.04 and 0.03 for guanidinium, potassium, sodium, methylamine, caesium, dimethylamine, 2-methylethanolamine, tris(hydroxymethyl)-aminomethane, tetraethylammonium and N-methyl-D-glucamine, respectively (values for P2X2 receptor). 4. The calcium permeability of P2X1 receptors was greater than that of P2X2 receptors. Under biionic conditions (112 mM calcium outside, 154 mM sodium inside), PCa/PNa values were 3.9 and 2.2, respectively (corrected for ionic activities). 5. ATP-evoked currents in cells expressing the P2X2 receptor were strongly inhibited when the extracellular calcium concentration was increased (0.3-30 mM); the action of ATP could be restored by increasing the ATP concentration. ATP-evoked currents in cells expressing the P2X1 receptor were not inhibited by such increases in the extracellular calcium concentration.

Adenosine Triphosphate↗
PubMed1996

Folding of proteins with WD-repeats: comparison of six members of the WD-repeat superfamily to the G protein beta subunit.

The family of WD-repeat proteins comprises over 30 different proteins that share a highly conserved repeating motif [Neer, E. J., Schmidt, C. J., Nambudripad, R., & Smith, T. F. (1994) Nature 371, 297-300]. Members of this family include the signal-transducing G protein beta subunit, as well as other proteins that regulate signal transduction, transcription, pre-mRNA splicing, cytoskeletal organization, and vesicular fusion. The crystal structure of one WD-repeat protein (G beta) has now been solved (Wall et al., 1995; Sondek et al, 1996) and reveals that the seven repeating units form a circular, propeller-like structure with seven blades each made up of four beta strands. It is very likely that all WD-repeat proteins form a similar structure. If so, it will be possible to use information about important surface regions of one family member to predict properties of another. If WD proteins form structures similar to G beta, their hydrodynamic properties should be those of compact, globular proteins, and they should be resistant to cleavage by trypsin. However, the only studied example of a WD-repeat protein, G beta, synthesized in vitro in a rabbit reticulocyte lysate, is unable to fold into a native structure without its partner protein G gamma. The non-WD-repeat amino terminal alpha helix of G beta does not inhibit folding because G beta does not fold even when this region is removed. It is not known whether all WD-repeat proteins are unable to fold when synthesized in an in vitro system. We synthesized seven members of the family in a rabbit reticulocyte lysate, determined their Stokes radius, sedimentation coefficient, and frictional ratio, and assayed their stability to trypsin. Our working definition of folding was that the proteins from globular, trypsin-resistant structures because, except for G beta gamma, their functions are not known or cannot be assayed in reticulocyte lysates. We chose proteins that include amino and carboxyl extensions as well as proteins that are made up entirely of WD-repeats. We show that unlike G beta, several proteins with WD-repeats are able to fold into globular proteins in a rabbit reticulocyte lysate. One protein, beta Trcp, formed large aggregates like G beta, suggesting that it may also require a partner protein. Despite the presence of many potential tryptic cleavage sites, all of the proteins that did fold gave stable large products on tryptic proteolysis, as predicted on the basis of the structure of G beta. These studies suggest that other WD-repeat proteins are likely to form propeller structures similar to G beta.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1996

Maintenance of cellular levels of G-proteins: different efficiencies of alpha s and alpha o synthesis in GH3 cells.

G-proteins couple membrane-bound receptors to intracellular effectors. Each cell has a characteristic complement of G-protein alpha, beta and gamma subunits that partly determines the cell's response to external signals. Very little is known about the mechanisms that set and maintain cellular levels of G-proteins or about potential points of regulation. We have assayed the steady-state levels of mRNA and protein for two types of G-protein subunits, alpha s and alpha o, in rat brain, heart and GH3 cells, and found that in all these cases, it takes 9- to 20-fold more mRNA to produce a given amount of alpha s protein than to produce the same amount of alpha o protein. Such a situation could arise from a relatively rapid rate of alpha s protein degradation, requiring rapid protein synthesis to compensate, or from relatively inefficient translation of alpha s mRNA compared with alpha o mRNA. The latter appears to be the case in GH3 cells. These cells contain 94 times more mRNA for alpha s than for alpha o, yet the rate of alpha s protein synthesis is only 9 times greater than alpha o protein synthesis. The degradation rates of the two proteins are similar (13 h for alpha s and 18 h for alpha o). To begin to define the mechanism that accounts for the fact that it takes more mRNA to synthesize a given amount of alpha s than alpha o, we asked whether there is a pool of alpha s mRNA that does not participate in protein synthesis. We found that virtually all alpha s and alpha o mRNA is associated with ribosomes. Therefore, all the mRNA is likely to be capable of directing protein synthesis. Since the rate-limiting step in protein synthesis is usually binding of the ribosome to mRNA at initiation, our results suggest that the relatively slow rate of alpha s protein synthesis is regulated by a mechanism that acts beyond initiation at peptide elongation and/or termination.

Animals↗
PubMed1996

Stable transfer of intact high molecular weight DNA into plant chromosomes.

In conjunction with an enhanced system for Agrobacterium-mediated plant transformation, a new binary bacterial artificial chromosome (BIBAC) vector has been developed that is capable of transferring at least 150 kb of foreign DNA into a plant nuclear genome. The transferred DNA appears to be intact in the majority of transformed tobacco plants analyzed and is faithfully inherited in the progeny. The ability to introduce high molecular weight DNA into plant chromosomes should accelerate gene identification and genetic engineering of plants and may lead to new approaches in studies of genome organization.

Base Sequence↗
PubMed1996

P2X1 receptor activation in HL60 cells.

Recent cloning of the human P2X1 receptor revealed high levels of its messenger RNA in differentiated promyelocytes (HL60 cells). We found expression of P2X1 receptor protein in HL60 cells by radioligand binding, by immunohistochemistry, using a receptor specific antibody, and by electrophysiology. The currents elicited by adenosine triphosphate (ATP) had the expected properties of P2X1 receptors (rapid desensitization, mimicked by alpha,beta-methylene-ATP). However, these currents were only observed in cells that were pretreated with apyrase, which destroys extracellular ATP, or with suramin, a P2X receptor antagonist. This implies that HL60 cells release ATP, which chronically desensitizes the receptor. ATP release was detected by direct measurement, using the luciferin-luciferase assay. It is concluded that functional P2X1 receptors are present in the membrane of differentiated HL60 cells.

Adenosine Triphosphate↗
PubMed1996

An antagonist-insensitive P2X receptor expressed in epithelia and brain.

A cDNA was cloned which encodes a new ATP-gated ion channel (P2X4 receptor). ATP induces a cationic current in HEK293 cells transfected with the P2X4 receptor. However, the current is almost completely insensitive to antagonists effective at other P2X receptors. Sensitivity to two of these antagonists (pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid and pyridoxal 5-phosphate) is restored by replacement of Glu249 by lysine, which occurs at the equivalent position in P2X1 and P2X2 receptors. P2X4 RNA is found by in situ hybridization in the brain, peripheral ganglia and epithelia including serosal cells of salivary glands. Recordings from rat submandibular gland cells showed ATP-induced currents that are also insensitive to antagonists. These results define a further member of P2X receptor family, and they identify an amino acid residue involved in antagonist binding. They also introduce a new phenotype for ATP responses at P2X receptors--insensitivity to currently known antagonists.

Adenosine Triphosphate↗
PubMed1996

Altered expression of TGF alpha and TGF beta 1 in the mucosa of the functioning pelvic ileal pouch.

The mucosa of the functioning pelvic ileal pouch undergoes loss of villous height and an increase in crypt cell proliferation as an adaptive response to its new luminal environment. These changes can occur in the absence of inflammation and could be mediated by growth factors such as transforming growth factors alpha and beta 1 (TGF alpha and TGF beta 1). Expression of TGF alpha and TGF beta 1 messenger RNA (mRNA) and protein was determined by in situ hybridization and immunohistochemistry in sections of terminal ileum taken at the time of pouch formation and of subsequent pouch biopsies from 14 patients (total of 90 specimens). Crypt cell proliferation was assessed using the monoclonal antibody MIB-1. As ileal pouch mucosa underwent loss of villous height and crypt hyperplasia, epithelial expression of TGF alpha mRNA and protein decreased. In contrast, TGF beta 1 mRNA and protein were abundant in both normal and flat mucosa. Epithelial expression of TGF beta 1 protein was maximal in flat, inflamed biopsies. These results suggest that although altered expression of TGF alpha and TGF beta 1 mRNA and protein may play some part in the regulation of the adaptive response in ileal pouch mucosa, TGF alpha does not have a direct, positive role in the regulation of crypt cell proliferation.

Adult↗
PubMed1996

Reliability and changes in validity of self-reported cardiovascular disease risk factors using dual response: the behavioral risk factor survey.

The authors previously studied the validity of self-reported cardiovascular disease (CVD) risk factors assessed by telephone surveys, and found the validity low, especially for self-reported hypertension and hypercholesterolemia. One way to improve validity is to combine repeated measurements (dual response) into a single measure. The authors explored this and the reliability of self-reported CVD data collected by the Behavioral Risk Factor Survey in three New York counties from January 1989 to May 1990. Nine hundred and eleven subjects were interviewed by telephone to collect CVD risk factor and health behavior information. Interviewees were offered physical examination and laboratory testing to verify self-reported CVD risk factors; 628 participated. Subjects were also reinterviewed to assess the test-retest reliability of the survey, and to study how validity of self-reported CVD data changes by dual response. Reliability coefficients for CVD risk factors, preventive health practices, and knowledge of risk factor levels ranged from 0.42 to 0.99. Minimal improvement in sensitivity of self-reported risk factors was found using dual response, and it did not improve specificity. Also, for prevalence of risk factors, dual response minimally improved self-reported rates compared to objective estimates. Combining self-reported measurements causes minimal changes in the validity of these variables. Physiological assessment for hypertension and hypercholesterolemia, or correction for misclassification, is needed for valid individual measurement and for community prevalence estimates from telephone surveys. Self-reported cigarette smoking, obesity, and diabetes mellitus have better validity, but physiological assessment or correction for misclassification may supplement these self-reported risk factors.

Adult↗
PubMed1996

Implantation of multiple foldable acrylic posterior chamber lenses in the capsular bag for high hyperopia.

This case series describes the implantation of multiple acrylic intraocular lenses (IOLs) in the capsular bag of six eyes of three highly hyperopic patients (spherical equivalent +5.75 to +8.62) during cataract surgery. Two foldable acrylic lenses were placed in the capsular bag of each eye. Preoperative best corrected visual acuity (BCVA) ranged from 20/50 to 20/300. Postoperative uncorrected visual acuity ranged from 20/25 to 20/60, while BCVA ranged from 20/25 to 20/40. Multiple acrylic lenses were used successfully in cases in which a single IOL would have given inadequate correction.

Acrylates↗