The rising incidence of serious chloroquine overdose in Harare, Zimbabwe: emergency department surveillance in the developing world.
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Adolescent↗
Biomedical subjects
R J Lewis
Publications and source records attributed to R J Lewis.
Video-assisted thoracic surgical non-rib spreading simultaneously stapled lobectomy: a more patient-friendly oncologic resection.
OBJECTIVE: To evaluate the outcomes from a new surgical technique for lobectomy. PATIENTS: Two hundred fifty consecutive patients with an average age of 67.3 years underwent simultaneously stapled lobectomy. METHODS: Video-assisted thoracic surgical non-rib spreading lobectomy (VNSSL) is a new technique that has been evolving for approximately 6.5 years. During 1990, we began using video-assisted thoracic surgery (VATS) for simple, benign diseases. Throughout 1991, VATS was applied to malignant problems, ie, mediastinal masses, staging of lymph nodes, malignant effusions, and coin lesions. As experience was acquired, more complex procedures were attempted, such as lobectomy. On September 9, 1991, our first VATS lobectomy, using anatomic hilar dissection and lymph node sampling, was performed for primary carcinoma of the lung. One year later, we performed our first VNSSL using simultaneous stapling. RESULTS: Currently, 400 VNSSLs have been performed. In this entire series, there have been no surgical mortality, bronchopleural fistulas, port implantations, or transfusions. Bronchial stumps have averaged 4 mm in length, and all have been microscopically negative for neoplasm. In order to evaluate long-term survival for primary carcinoma of the lung in patients with an adequate duration of follow-up, the first 250 consecutive VNSSLs have been reviewed. There were 120 male and 130 female patients ranging in age from 20 to 92 years old who had 62 right upper lobe, 20 right middle lobe, 58 right lower lobe, 63 left upper lobe, and 33 left lower lobe lobectomies, and 14 bilobectomies. The lesions consisted of 214 primary carcinomas, 8 metastatic lesions, and 28 benign problems. Seven to 18 lymph nodes could be resected during staging of the primary neoplasms. The tumors ranged in size from 1 to 9 cm, and operating times averaged 78.6 min. Hospitalization averaged 2.83 days. No patient was admitted to the ICU. Intensive monitoring or narcotic analgesia were not needed. No epidural or intercostal anesthesia was used. Complications were infrequent and minor. Most patients returned to preoperative levels of physical activity within 7 to 10 days. Overall survival at a mean of 34 months, when all stages of neoplasms were combined, is 83%. For stage I, overall survival is 92%. The cost of VNSSL is approximately 50% less than the traditional open thoracotomy. CONCLUSIONS: VNSSL is an oncologic technique that has been clinically rewarding and economically beneficial for patients with malignant lesions. Long-term survival for primary carcinoma currently exceeds reports being published for the traditional open thoracotomy. Scientific reasons for this extraordinary survival are emerging. Complications, surgical mortality, pain, and length of stay have all been reduced. Patient recovery, comfort, and satisfaction have been extraordinary.
Adult↗
Differential actions of pacific ciguatoxin-1 on sodium channel subtypes in mammalian sensory neurons.
Pacific ciguatoxin-1 (P-CTX-1), is a highly lipophilic cyclic polyether molecule originating from the marine dinoflagellate Gambierdiscus toxicus. Its effects were investigated on sodium channel subtypes present in acutely dissociated rat dorsal root ganglion neurons, using whole-cell patch clamp techniques. Concentrations of P-CTX-1 ranging from 0.2 to 20 nM had no effect on the kinetics of tetrodotoxin-sensitive (TTX-S) or tetrodotoxin-resistant (TTX-R) sodium channel activation and inactivation, however, a concentration-dependent reduction in peak current amplitude occurred in both channel types. The main actions of 5 nM P-CTX-1 on TTX-S sodium channels were a 13-mV hyperpolarizing shift in the voltage dependence of sodium channel activation and a 22-mV hyperpolarizing shift in steady-state inactivation (hinfinity). In addition, P-CTX-1 caused a rapid rise in the membrane leakage current in cells expressing TTX-S sodium channels. This effect was blocked by 200 nM TTX, indicating an action mediated through TTX-S sodium channels. In contrast, the main action of P-CTX-1 (5 nM) on TTX-R sodium channels was a significant increase in the rate of recovery from sodium channel inactivation. These results indicate that P-CTX-1 acts to modify voltage-gated sodium channels present in peripheral sensory neurons consistent with its action to increase nerve excitability. This provides an explanation for the sensory neurological disturbances associated with ciguatera fish poisoning.
Animals↗
An evolutionary link between sporulation and prophage induction in the structure of a repressor:anti-repressor complex.
Spore formation is an extreme response of some bacteria to adversity. In Bacillus subtilis the proteins of the sin, sporulation inhibition, region form a component of an elaborate molecular circuitry that regulates the commitment to sporulation. SinR is a tetrameric repressor protein that binds to the promoters of genes essential for entry into sporulation and prevents their transcription. This repression is overcome through the activity of SinI, which disrupts the SinR tetramer through the formation of a SinI-SinR heterodimer. The interactions governing this curious quaternary transition are revealed in the crystal structure of the SinI-SinR complex. The most striking, and unexpected, finding is that the tertiary structure of the DNA-binding domain of SinR is identical with that of the corresponding domains of the repressor proteins, CI and Cro, of bacteriophage 434 that regulate lysis/lysogeny. This structural similarity greatly exceeds that between SinR and any bacterial protein or between the 434 repressor proteins and their homologues in the closely related bacteriophage lambda. The close evolutionary relationship implied by the structures of SinR and the 434 repressors provokes both comparison of their functions and a speculative consideration of the intriguing possibility of an evolutionary link between the two adaptive responses, sporulation and prophage induction.
Amino Acid Sequence↗
Structure of d(TGCGCA)2 and a comparison to other DNA hexamers.
The X-ray crystal structure of d(TGCGCA)2 has been determined at 120 K to a resolution of 1.3 A. Hexamer duplexes, in the Z-DNA conformation, pack in an arrangement similar to the 'pure spermine form' [Egli et al. (1991). Biochemistry, 30, 11388-11402] but with significantly different cell dimensions. The phosphate backbone exists in two equally populated discrete conformations at one nucleotide step, around phosphate 11. The structure contains two ordered cobalt hexammine molecules which have roles in stabilization of both the Z-DNA conformation of the duplex and in crystal packing. A comparison of d(TGCGCA)2 with other Z-DNA hexamer structures available in the Nucleic Acid Database illustrates the elusive nature of crystal packing. A review of the interactions with the metal cations Na+, Mg2+ and Co3+ reveals a relatively small proportion of phosphate binding and that close contacts between metal ions are common. A prediction of the water structure is compared with the observed pattern in the reported structure.
Binding Sites↗
Bacillus subtilis regulatory protein GerE.
GerE is the latest-acting of a series of factors which regulate gene expression in the mother cell during sporulation in Bacillus. The gene encoding GerE has been cloned from B. subtilis and overexpressed in Escherichia coli. Purified GerE has been crystallized by the hanging-drop vapour-diffusion method using polyethylene glycol as a precipitant. The small plate-like crystals belong to the monoclinic space group C2 and diffract beyond 2.2 A resolution with a synchrotron radiation X-ray source.
Bacillus subtilis↗
The 1.1 A resolution crystal structure of [Tyr15]EpI, a novel alpha-conotoxin from Conus episcopatus, solved by direct methods.
Conotoxins are valuable probes of receptors and ion channels because of their small size and highly selective activity. alpha-Conotoxin EpI, a 16-residue peptide from the mollusk-hunting Conus episcopatus, has the amino acid sequence GCCSDPRCNMNNPDY(SO3H)C-NH2 and appears to be an extremely potent and selective inhibitor of the alpha3beta2 and alpha3beta4 neuronal subtypes of the nicotinic acetylcholine receptor (nAChR). The desulfated form of EpI ([Tyr15]EpI) has a potency and selectivity for the nAChR receptor similar to those of EpI. Here we describe the crystal structure of [Tyr15]EpI solved at a resolution of 1.1 A using SnB. The asymmetric unit has a total of 284 non-hydrogen atoms, making this one of the largest structures solved de novo by direct methods. The [Tyr15]EpI structure brings to six the number of alpha-conotoxin structures that have been determined to date. Four of these, [Tyr15]EpI, PnIA, PnIB, and MII, have an alpha4/7 cysteine framework and are selective for the neuronal subtype of the nAChR. The structure of [Tyr15]EpI has the same backbone fold as the other alpha4/7-conotoxin structures, supporting the notion that this conotoxin cysteine framework and spacing give rise to a conserved fold. The surface charge distribution of [Tyr15]EpI is similar to that of PnIA and PnIB but is likely to be different from that of MII, suggesting that [Tyr15]EpI and MII may have different binding modes for the same receptor subtype.
Amino Acid Sequence↗
The Bacillus subtilis regulator SinR inhibits spoIIG promoter transcription in vitro without displacing RNA polymerase.
Initiation of sporulation in Bacillus subtilis is controlled by several regulators which affect activation by phosphorylation of the key response regulator Spo0A or transcription of Spo0A-P-dependent genes. In vivo overexpression of one of these regulators, sinR , results in suppression of transcription from the Spo0A-P-dependent promoters of spo0A , spoIIA , spoIIE and spoIIG and in vitro SinR binds to the promoters of the spoIIA operon and the spo0A gene. In this study we have demonstrated that in vitro SinR directly repressed Spo0A- P-dependent transcription by B.subtilis RNA polymerase from the spoIIG operon promoter. SinR inhibited transcription prior to formation of heparin-resistant complexes but did not displace RNA polymerase from the spoIIG promoter. DNase I protection studies demonstrated that SinR protected a large region of the spoIIG promoter and induced DNase I hypersensitive sites, particularly around the 0A boxes, at the same positions as those induced by zinc. Since binding of zinc induces bends in the DNA, we concluded that SinR binding also altered the conformation of the spoIIG promoter. We propose that SinR-induced conformational changes in Spo0A-dependent promoters prevent activation of trans-cription by Spo0A-P.
Bacillus subtilis↗
Ciguatoxin (CTX-1) modulates single tetrodotoxin-sensitive sodium channels in rat parasympathetic neurones.
The actions of the marine neurotoxin, ciguatoxin-1 (CTX-1), were investigated in isolated parasympathetic neurones from neonatal rat intracardiac ganglia using patch-clamp recording techniques. Under current clamp conditions, bath application of 1-10 nM CTX-1 caused gradual membrane depolarization and tonic action potential firing. Action potential firing ceased with depolarization beyond approximately -35 mV and application of 300 nM tetrodotoxin (TTX) repolarized the cell to its control resting potential. In cell-attached membrane patches, 1-10 nM CTX-1 in the patch pipette markedly increased the open probability of single TTX-sensitive Na+ channels in response to depolarizing voltage steps but did not alter the unitary conductance (10 pS) or reversal potential. Under steady-state conditions, CTX-1 caused spontaneous opening of single Na+ channels which did not inactivate at hyperpolarized membrane potentials. CTX-1 increases neuronal excitability by shifting the voltage of activation of TTX-sensitive Na+ channels to more negative potentials.
Action Potentials↗
alpha-conotoxin EpI, a novel sulfated peptide from Conus episcopatus that selectively targets neuronal nicotinic acetylcholine receptors.
We have isolated and characterized alpha-conotoxin EpI, a novel sulfated peptide from the venom of the molluscivorous snail, Conus episcopatus. The peptide was classified as an alpha-conotoxin based on sequence, disulfide connectivity, and pharmacological target. EpI has homology to sequences of previously described alpha-conotoxins, particularly PnIA, PnIB, and ImI. However, EpI differs from previously reported conotoxins in that it has a sulfotyrosine residue, identified by amino acid analysis and mass spectrometry. Native EpI was shown to coelute with synthetic EpI. The peptide sequence is consistent with most, but not all, recognized criteria for predicting tyrosine sulfation sites in proteins and peptides. The activities of synthetic EpI and its unsulfated analogue [Tyr15]EpI were similar. Both peptides caused competitive inhibition of nicotine action on bovine adrenal chromaffin cells (neuronal nicotinic ACh receptors) but had no effect on the rat phrenic nerve-diaphragm (muscle nicotinic ACh receptors). Both EpI and [Tyr15]EpI partly inhibited acetylcholine-evoked currents in isolated parasympathetic neurons of rat intracardiac ganglia. These results indicate that EpI and [Tyr15]EpI selectively inhibit alpha3beta2 and alpha3 beta4 nicotinic acetylcholine receptors.
Amino Acid Sequence↗
Supporting emergency medicine research: developing the infrastructure.
The long-term goals of developing research within the specialty of emergency medicine include the following: (1) to continue to improve the quality and quantity of emergency patient care; (2) to maximize the research potential of emergency health care professionals to develop new emergency research talent and enthusiasm; and (3) to establish the academic research credentials of the specialty of emergency medicine to become competitive for federal research funding, and further improve emergency patient care. This article addresses the process by which the infrastructure for emergency medicine research can be developed at academic medical centers and provides recommendations. The roles of the academic chair, research director, senior researcher, and departmental faculty are discussed.
Academic Medical Centers↗
Video-assisted thoracic surgical non-rib spreading simultaneously stapled lobectomy (VATS(n)SSL).
Two hundred consecutive patients underwent a video-assisted thoracic surgical non-rib spreading simultaneously stapled lobectomy (VATS(n)SSL). Ninety-three were males and 107 were females, ranging in age from 20 to 92 years. Lesions consisted of 171 primary lung carcinomas, 7 metastatic tumors, and 22 benign lesions. Resections included 47 right upper lobe, 18 right middle lobe, 46 right lower lobe, 52 left upper lobe, 26 left lower lobe and 11 bilobectomies, ie, 9 right upper and middle lobes and 2 right middle and lower lobes. Operating time averaged 79.5 minutes, and no patient received a transfusion. Tumors ranged from 1 cm to 9 cm, bronchial stumps were 4 to 5 mm, and length of hospitalization averaged 3.07 days. Complications were minimal, and there was no surgical mortality. No patient developed a bronchopleural fistula or neoplastic port implant. Twenty-four patients have died of metastases. At a median follow-up of 34 months for all stages of carcinoma, there is an overall survival rate of 86%. Survival rate is 92% for stage I. VATS(n)SSL is a new technique for lobectomy that has proven to be beneficial for patients needing resection.
Adult↗
Material properties and biosynthetic activity of articular cartilage from the bovine carpo-metacarpal joint.
OBJECTIVE: To determine the site variation of material properties and cellular biosynthetic activity, and to compare these at each site, of articular cartilage from the bovine carpo-metacarpal joint in order to test its usefulness as a model system for investigating the metabolic effects of mechanical stimuli. DESIGN: The mechanical properties and composition of full-depth biopsies of articular cartilage were measured at defined sites in bovine carpometacarpal joints. Metabolic activity at the same sites was assessed by incubating further biopsies in medium containing 35S-sulfate and 3H-leucine then measuring the incorporated radioisotope and cell density. These results were compared with an estimate of the distribution of forces across the joint. RESULTS: Topographical variation of water content, stiffness, cell count or incorporated radioisotope was not significant whereas collagen and glycosaminoglycan varied in different ways. A moderate correlation was found between water and collagen contents, but the correlation between water and glycosaminoglycan contents was poor. Neither compressive stiffness nor creep compliance was predicted strongly by any of the composition measurements. A negative correlation was found between metabolic activity and cell density. CONCLUSIONS: Defining the variation of tissue properties across the bovine carpometacarpal joint and the lack of variation in biosynthetic activity will enable proper matching of experimental and control groups of biopsies in studies of the effects of mechanical stimuli on the composition and mechanical properties of articular cartilage. In addition, the lack of correlation between stiffness, water and glycosaminoglycan contents is further evidence that the mechanical properties of the tissue depend significantly on factors other than these broad measures of composition.
Animals↗
Comparative pharmacodynamics of meropenem using an in-vitro model to simulate once, twice and three times daily dosing in humans.
An in-vitro pharmacokinetic model was used to study the antibacterial activity of meropenem. Strains of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus were exposed to meropenem concentrations likely to be produced in an adult by rapid iv infusion of 3 g once a day (q24h regimen), 1.5 g twice a day (ql2h regimen) or 1 g three times a day (q8h regimen). Each of these three dosing regimens produced a rapid reduction in viable bacterial count over the first 16 h after dosing. There were no differences in the pattern of reduction in viable count with the q24h, q12h or q8h regimens with any of the three bacterial strains tested over the first 16 h. However, reduction in viable counts was poorer at 24 h with the q24h than q12h or q8h regimens. A simulation lasting 48 h of the q24h dosing regimen indicated a reduction in bacterial count below the limit of detection from the model with E. coli but not with P. aeruginosa or S. aureus. The time for which the meropenem concentration was higher than the MIC for the bacteria correlated best with the reduction in viable bacterial count at 24 h. The AUC for the bacterial time-kill curve, which may be a better measure of antibacterial efficacy, was not related to the length of time for which the concentration was above the MIC or the peak concentration/MIC ratio. The antibacterial effect of the conventional q8h dosing simulation was indistinguishable from that given by the q12h simulation, and both the q8h and q12h regimens offered minor advantages over a q24h regimen. Dosing of meropenem 12 hourly or 24 hourly in humans should be investigated.
Adult↗
Environmental poisoning: presentation and management.
Environmental poisoning is most commonly associated with chronic long-term exposure to toxins rather than to acute exposure. Such repeated exposure to sublethal doses of compounds and elements presents problems in risk assessment. This is primarily because the data are unavailable to describe relationships between dose and effect at lower levels of exposure to toxins. Bioavailability of toxins also presents a problem because the data on bioavailability are sparse and seldom as high as the default of 100% bioavailability commonly used in risk assessment. Examples are presented of two toxins: arsenic as an elemental anthropogenic and geologic poison and ciguatoxin, a polyether ladder compound, as a toxin produced naturally by dinoflagellates. Bioavailability drives the toxicity of arsenic from contaminated sites, whereas tissue accumulation drives the toxicity of ciguatoxin. Considerable benefit is derived from the harmonization of regulatory processes where there is linkage of health and environmental factors in the derivation of credible risk assessment.
Arsenic↗
Inappropriate sensing of atrial stimuli in patients with third-generation defibrillators and DDD pacemakers.
Although the problem of ICD sensing of paced ventricular stimuli has been resolved by incorporation of VVI pacing into current ICDs, many patients required separate DDD pacemakers. We report a problematic PM-ICD interaction: the inability to prevent sensing of paced atrial stimuli ("atrial sensing") leading to double-counting in DDD-PM-requiring patients with transvenous (TV) ICDs with aggressive autogain sensing (CPI Ventak PRxII or III). Four of eight patients receiving both transvenous DDD PMs and ICDs (CPI Endotak lead, at the RV apex), had atrial sensing, leading to double counting, despite intraoperative testing of multiple atrial locations with an active fixation lead. Five patients had a PRxII/III ICD, four with atrial sensing (80%), and three a PRx without atrial sensing. Patients with atrial sensing were not distinguished by any clinical or device related variable. In patients with atrial sensing (all with heart block), the PM was programmed to VDD mode. No patient has received inappropriate therapy or failed to sense VF in follow-up. In many patients with TV ICDs who required DDD pacing, no atrial position can be found without ICD sensing of atrial stimuli. While in patients with heart block this problem can be circumvented by programming to the VDD mode, in patients with sinus incompetence it may only be resolved by the combination ICD-DDD PM, currently in development.
Aged↗
Supporting emergency medicine research: developing the infrastructure.
The long-term goals of developing research within the specialty of emergency medicine (EM) include the following: 1) to continue to improve the quality and quantity of EM research in order to ultimately improve emergency patient care; 2) to maximize the research potential of emergency health care professionals in order to develop new emergency research talent and enthusiasm; and 3) to establish the academic research credentials of the specialty of EM in order to become competitive for federal research funding, and further improve emergency patient care. This article addresses the process by which the infrastructure for EM research can be developed at academic medical centers and provides recommendations. The roles of the academic chair, research director, senior researcher, and departmental faculty are discussed.
Academic Medical Centers↗
Parametric statistical tests: unnecessary assumptions, computers, and the search for the trustworthy p-value.
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Computers↗