Osimertinib induces the opposite effect of proliferation and migration in the drug resistance of EGFR-T790M non-small cell lung cancer cells

BACKGROUND

Lung cancer has become one of the leading causes of cancer incidence and mortality worldwide. Non-small cell lung carcinoma (NSCLC) is the most common type among all lung cancer cases. NSCLC patients contained high levels of activating epidermal growth factor receptor (EGFR) mutations, such as exon 19 deletion, L858R and T790M. Osimertinib, a third-generation of EGFR tyrosine kinase inhibitor (EGFR-TKI), has therapeutic efficacy on the EGFR-T790M mutation of NSCLC patients; however, treatment of osimertinib still can induce drug resistance in lung cancer patients. Therefore, investigation of the drug resistance mechanisms of osimertinib will provide novel strategies for lung cancer therapy.

METHODS

The H1975OR osimertinib-resistant cell line was established by prolonged exposure with osimertinib derived from the H1975 cells. The cell proliferation ability was evaluated by the cell viability and cell growth assays. The cell migration ability was determined by the Boyden chamber assays. The differential gene expression profile was analyzed by genome-wide RNA sequencing. The protein expression and location were analyzed by western blot and confocal microscopy.

RESULTS

In this study, we established the osimertinib-resistant H1975 (T790M/L858R) cancer cells, named the H1975OR cell line. The cell growth ability was decreased in the H1975OR cells by comparison with the H1975 parental cells. Conversely, the cell migration ability was elevated in the H1975OR cells. We found the differential gene expression profile of cell proliferation and migration pathways between the H1975OR and H1975 parental cells. Interestingly, the protein levels of phospho-EGFR, PD-L1, E-cadherin and β-catenin were decreased, but the survivin and N-cadherin proteins were increased in the H1975OR drug-resistant cells.

CONCLUSION

Osimertinib induces the opposite effect of proliferation and migration in the drug resistance of EGFR-T790M lung cancer cells. We suggest that differential gene and protein expressions in the cell proliferation and migration pathways may mediate the drug resistance of osimertinib in lung cancer cells. Understanding the molecular drug-resistant mechanisms of proliferation and migration pathways of osimertinib may provide novel targets and strategies for the clinical treatment of EGFR-TKIs in lung cancer patients.

A novel EGFR inhibitor suppresses survivin expression and tumor growth in human gefitinib-resistant EGFR-wild type and -T790M non-small cell lung cancer

Tyrosine kinase inhibitors of epidermal growth factor receptor (EGFR-TKIs) are currently used therapy for non-small cell lung cancer (NSCLC) patients; however, drug resistance during cancer treatment is a critical problem. Survivin is an anti-apoptosis protein, which promotes cell proliferation and tumor growth that highly expressed in various human cancers. Here, we show a novel synthetic compound derived from gefitinib, do-decyl-4-(4-(3-(4-(3-chloro-4-fluorophenylamino)-7-methoxyquinazolin-6-yloxy)propyl) piper-azin-1-yl)-4-oxobutanoate, which is named as SP101 that inhibits survivin expression and tumor growth in both the EGFR-wild type and -T790M of NSCLC. SP101 blocked EGFR kinase activity and induced apoptosis in the A549 (EGFR-wild type) and H1975 (EGFR-T790M) lung cancer cells. SP101 reduced survivin proteins and increased active caspase 3 for inducing apoptosis. Ectopic expression of survivin by a survivin-expressed vector attenuated the SP101-induced cell death in lung cancer cells. Moreover, SP101 inhibited the gefitinib-resistant tumor growth in the xenograft human H1975 lung tumors of nude mice. SP101 substantially reduced survivin proteins but conversely elicited active caspase 3 proteins in tumor tissues. Besides, SP101 exerted anticancer abilities in the gefitinib resistant cancer cells separated from pleural effusion of a clinical lung cancer patient. Consistently, SP101 decreased the survivin proteins and the patient-derived xenografted lung tumor growth in nude mice. Anti-tumor ability of SP101 was also confirmed in the murine lung cancer model harboring EGFR T790M-L858R. Together, SP101 is a new EGFR inhibitor with inhibiting survivin that can be developed for treating EGFR wild-type and EGFR-mutational gefitinib-resistance in human lung cancers.

Synthesis and biological assay of erlotinib analogues and BSA-conjugated erlotinib analogue

A series of erlotinib analogues that have structural modification at 6,7-alkoxyl positions is efficiently synthesized. The in vitro anti-tumor activity of synthesized compounds is studied in two non-small cell lung cancer (NSCLC) cell lines (A549 and H1975). Among the synthesized compounds, the iodo compound 6 (ETN-6) exhibits higher anti-cancer activity compared to erlotinib. An efficient method is developed for the conjugation of erlotinib analogue-4, alcohol compound, with protein, bovine serum albumin (BSA), via succinic acid linker. The in vitro anti-tumor activity of the protein attached erlotinib analogue, 8 (ETN-4-Suc-BSA), showed stronger inhibitory activity in both A549 and H1975 NSCLC cell lines.

Ubiquitin-coated nanodiamonds bind to autophagy receptors for entry into the selective autophagy pathway

Selective macroautophagy/autophagy plays a pivotal role in the processing of foreign pathogens and cellular components to maintain homeostasis in human cells. To date, numerous studies have demonstrated the uptake of nanoparticles by cells, but their intracellular processing through selective autophagy remains unclear. Here we show that carbon-based nanodiamonds (NDs) coated with ubiquitin (Ub) bind to autophagy receptors (SQSTM1 [sequestosome 1], OPTN [optineurin], and CALCOCO2/NDP52 [calcium binding and coiled-coil domain 2]) and are then linked to MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3) for entry into the selective autophagy pathway. NDs are ultimately delivered to lysosomes. Ectopically expressed SQSTM1-green fluorescence protein (GFP) could bind to the Ub-coated NDs. By contrast, the Ub-associated domain mutant of SQSTM1 (ΔUBA)-GFP did not bind to the Ub-coated NDs. Chloroquine, an autophagy inhibitor, prevented the ND-containing autophagosomes from fusing with lysosomes. Furthermore, autophagy receptors OPTN and CALCOCO2/NDP52, involved in the processing of bacteria, were found to be involved in the selective autophagy of NDs. However, ND particles located in the lysosomes of cells did not induce mitotic blockage, senescence, or cell death. Single ND clusters in the lysosomes of cells were observed in the xenografted human lung tumors of nude mice. This study demonstrated for the first time that Ub-coated nanoparticles bind to autophagy receptors for entry into the selective autophagy pathway, facilitating their delivery to lysosomes.

Cancer cell labeling and tracking using fluorescent and magnetic nanodiamond

Nanodiamond, a promising carbon nanomaterial, develops for biomedical applications such as cancer cell labeling and detection. Here, we establish the nanodiamond-bearing cancer cell lines using the fluorescent and magnetic nanodiamond (FMND). Treatment with FMND particles did not significantly induce cytotoxicity and growth inhibition in HFL-1 normal lung fibroblasts and A549 lung cancer cells. The fluorescence intensities and particle complexities were increased in a time- and concentration-dependent manner by treatment with FMND particles in lung cancer cells; however, the existence of FMND particles inside the cells did not alter cellular size distribution. The FMND-bearing lung cancer cells could be separated by the fluorescent and magnetic properties of FMNDs using the flow cytometer and magnetic device, respectively. The FMND-bearing cancer cells were identified by the existence of FMNDs using flow cytometer and confocal microscope analysis. More importantly, the cell morphology, viability, growth ability and total protein expression profiles in the FMND-bearing cells were similar to those of the parental cells. The separated FMND-bearing cells with various generations were cryopreservation for further applications. After re-thawing the FMND-bearing cancer cell lines, the cells still retained the cell survival and growth ability. Additionally, a variety of human cancer types including colon (RKO), breast (MCF-7), cervical (HeLa), and bladder (BFTC905) cancer cells could be used the same strategy to prepare the FMND-bearing cancer cells. These results show that the FMND-bearing cancer cell lines, which reserve the parental cell functions, can be applied for specific cancer cell labeling and tracking.

Covalent linkage of nanodiamond-paclitaxel for drug delivery and cancer therapy

A nanoparticle-conjugated cancer drug provides a novel strategy for cancer therapy. In this study, we manipulated nanodiamond (ND), a carbon nanomaterial, to covalently link paclitaxel for cancer drug delivery and therapy. Paclitaxel was bound to the surface of 3-5 nm sized ND through a succession of chemical modifications. The ND-paclitaxel conjugation was measured by atomic force microscope and nuclear magnetic resonance spectroscopy, and confirmed with infrared spectroscopy by the detection of deuterated paclitaxel. Treatment with 0.1-50 microg ml(-1) ND-paclitaxel for 48 h significantly reduced the cell viability in the A549 human lung carcinoma cells. ND-paclitaxel induced both mitotic arrest and apoptosis in A549 cells. However, ND alone or denatured ND-paclitaxel (after treatment with strong alkaline solution, 1 M NaOH) did not induce the damage effects on A549 cells. ND-paclitaxel was taken into lung cancer cells in a concentration-dependent manner using flow cytometer analysis. The ND-paclitaxel particles were located in the microtubules and cytoplasm of A549 cells observed by confocal microscopy. Furthermore, ND-paclitaxel markedly blocked the tumor growth and formation of lung cancer cells in xenograft SCID mice. Together, we provide a functional covalent conjugation of ND-paclitaxel, which can be delivered into lung carcinoma cells and preserves the anticancer activities on the induction of mitotic blockage, apoptosis and anti-tumorigenesis.

Alpha-bungarotoxin binding to target cell in a developing visual system by carboxylated nanodiamond

Biological molecules conjugating with nanoparticles are valuable for applications including bio-imaging, bio-detection, and bio-sensing. Nanometer-sized diamond particles have excellent electronic and chemical properties for bio-conjugation. In this study, we manipulated the carboxyl group produced on the surface of nanodiamond (carboxylated nanodiamond, cND) for conjugating with alpha-bungarotoxin (α-BTX), a neurotoxin derived from Bungarus multicinctus with specific blockade of alpha7-nicotinic acetylcholine receptor (α7-nAChR). The electrostatic binding of cND-α-BTX was mediated by the negative charge of the cND and the positive charge of the α-BTX in physiological pH conditions. Sodium dodecyl sulfate-polyacrylamide gel analysis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI/TOF-MS) spectra displayed that α-BTX proteins were conjugated with cND particles via non-covalent bindings. The green fluorescence of the cND particles combining with the red fluorescence of tetramethylrhodamine-labeled α-BTX presented a yellow color at the same location, which indicated that α-BTX proteins were conjugated with cND particles. Xenopus laevis's oocytes expressed the human α7-nAChR proteins by microinjection with α7-nAChR mRNA. The cND-α-BTX complexes were bound to α7-nAChR locating on the cell membrane of oocytes and human lung A549 cancer cells analyzed by laser scanning confocal microscopy. The choline-evoked α7-nAChR-mediated inward currents of the oocytes were blocked by cND-α-BTX complexes in a concentration-dependent manner using two-electrode voltage-clamp recording. Furthermore, the fluorescence intensity of cND-α-BTX binding on A549 cells could be quantified by flow cytometry. These results indicate that cND-conjugated α-BTX still preserves its biological activity in blocking the function of α7-nAChR, and provide a visual system showing the binding of α-BTX to α7-nAChR.

Nanomechanical characterization of red blood cells using optical tweezers

Deformation behaviours of red blood cells (RBCs) have been studied by applying stretching forces via optical tweezers. Combined with finite-element analyses (FEA), the RBCs' mechanical properties are determined quantitatively based on a best fitting between the experimental deformed geometries and the simulated counterparts. Experimentally, a silica beads attached erythrocyte is optical-mechanically stretched to different lengths. On the theoretical front, a large deformation model with Mooney-Rivlin constitutive equations has been simulated by using FEA to predict the cell deformation geometries. The numerically simulated transverse and longitudinal strains which are in a good agreement with the experimental measurements facilitate the determination of elastic constants of the cells.

Nanometer-sized diamond particle as a probe for biolabeling

A novel method is proposed using nanometer-sized diamond particles as detection probes for biolabeling. The advantages of nanodiamond's unique properties were demonstrated in its biocompatibility, nontoxicity, easily detected Raman signal, and intrinsic fluorescence from its natural defects without complicated pretreatments. Carboxylated nanodiamond's (cND's) penetration ability, noncytotoxicity, and visualization of cND-cell interactions are demonstrated on A549 human lung epithelial cells. Protein-targeted cell interaction visualization was demonstrated with cND-lysozyme complex interaction with bacteria Escherichia coli. It is shown that the developed biomolecule-cND complex preserves the original functions of the test protein. The easily detected natural fluorescent and Raman intrinsic signals, penetration ability, and low cytotoxicity of cNDs render them promising agents in multiple medical applications.

Avian influenza in Hong Kong 1997-2002

In 1997, a high-pathogenicity H5N1 avian influenza virus caused serious disease in both man and poultry in Hong Kong, China. Eighteen human cases of disease were recorded, six of which were fatal. This unique virus was eliminated through total depopulation of all poultry markets and chicken farms in December 1997. Other outbreaks of high-pathogenicity avian influenza (HPAI) caused by H5N1 viruses occurred in poultry in 2001 and 2002. These H5N1 viruses isolated had different internal gene constellations to those isolated in 1997. No new cases of infection or disease in man due to these or other H5N1 viruses have been reported. This paper provides an overview and chronology of the events in Hong Kong relating to avian influenza, covering the period from March 1997 to March 2002.

An Update on Avian Influenza in Hong Kong 2002

An outbreak of highly pathogenic avian influenza caused by multiple genotypes of H5N1 virus occurred in Hong Kong, commencing in January 2002. Infection in local chicken farms was preceded by the detection of virus in multiple retail markets and the main poultry wholesale market. The first case of this disease on a local farm was detected on February 1, 2002. By February 9, 2002, 15 farms were infected, and by late March a total of 22 infected farms had been identified. Three main clusters of infected farms were seen, suggesting multiple incursions of virus, and subsequent limited lateral spread to neighboring firms. Control of this disease has been effected through a combination of quarantine, tightening of biosecurity measures, and depopulation of infected and contact farms. About 950,000 birds have been destroyed. Vaccination using a killed H5 vaccine was introduced in April 2002 to farms in one zone where infection has persisted. None of the viruses isolated contained the internal genes found in the 1997 H5N1 virus.

Capsule-substrate contact deformation: determination of adhesion energy

A study is reported of a cellular entity (liquid-filled microcapsule) adhered on a flat glass substrate in response to changes in osmotic pressure and temperature. High-resolution reflection interference contrast microscopy (HR-RICM) and phase-contrast microscopy were developed for probing the adhesion contact area, capsule-substrate separation profile and adhesion energy of the adhering microcapsule. The new technique increased the detection limit of the measured capsule wall-substrate separation in the cohesive zone from 1 to 4.5 microm and improved the spatial resolution of the heterogeneous contact zones. A theoretical model was applied to correlate quantitatively the adhesion energy to the area of the contact zone. The work demonstrated the possibility of ascertaining the quantitative interfacial adhesion energy of a liquid-filled microcapsule using the present technique and represents the first step in extending this novel approach to study more complicated systems, such as cell-substrate interactions, in the future.

Contact mechanics of a thin-walled capsule adhered onto a rigid planar substrate

A thin-walled capsule, modelled as an incompressible liquid droplet contained in a thin flexible membrane, was allowed to adhere onto a rigid substrate. The contact mechanics were formulated, based on linear elasticity, to portray quantitatively the relationships between osmotic inflation, contact area and angle, membrane stretching and adhesion strength. The predicted results shed light on fundamental adhesive contact mechanics in a cell-substrate system.

Enzyme-catalyzed asymmetric deacylation for the preparation of lasofoxifene (CP-336156), a selective estrogen receptor modulator

[structure] selective estrogen receptor modulator (SERM), Lasofoxifene (CP-336156), was prepared by an enzyme-catalyzed asymmetric deacylation with high optical purity and excellent yield even though the hydrolytic site is remote from the chiral centers.

New model to characterise cell-substrate adhesion in the presence of osmosis

A simple model of cell-substrate adhesion, in response to osmosis change, is derived to describe quantitatively the interrelationships between osmotic inflation, contact area and angle, membrane stretching and adhesion strength. As the cell inflates, the contact area shrinks in dimension, until the cell is eventually lifted off the substrate. The theoretical prediction is consistent with other published data.

The use of laparoscopy in the management of adnexal pathologies in children

BACKGROUND

The authors' experience of using laparoscopy in the management of 23 girls (mean age: 8.9 years; range: 3 months-15 years) with various adnexal pathologies over a 3-year period is reviewed.

METHODS

Of the 23 patients, seven were evaluated for congenital gonadal pathologies, 15 presented with abdominal pain and one patient had an antenatally diagnosed adnexal mass. Detailed laparoscopic examination of the pelvic cavity and laparoscopic gonadectomy were successfully performed in all seven patients with congenital gonadal pathologies: mosaic Turner's syndrome (n = 2), gonadal dysgenesis (n = 3) and testicular feminization syndrome (n = 2). Of 15 patients presenting with abdominal pain, 11 had an adnexal mass, two had acute appendicitis and two had pelvic inflammatory disease.

RESULTS

Laparoscopic excision of the adnexal masses were successfully performed in 10 of 11 patients. Conversion to open surgery was required in one patient with a huge teratoma. Laparoscopic appendicectomy was successfully performed in both patients with acute appendicitis while diagnostic laparoscopy was the only procedure required in the two patients with pelvic inflammatory disease. Laparoscopy in the infant with an antenatally diagnosed adnexal mass confirmed this to be an omental cyst, which was successfully excised. All patients recovered without complications and good cosmetic result was universally achieved.

CONCLUSION

Laparoscopy is safe and effective in both diagnosis and treatment of adnexal pathologies in children.

Picrotoxin blockade of invertebrate glutamate-gated chloride channels: subunit dependence and evidence for binding within the pore

Glutamate-gated chloride channels have been described in nematodes, insects, crustaceans, and mollusks. Subunits from the nematode and insect channels have been cloned and are phylogenetically related to the GABA and glycine ligand-gated chloride channels. Ligand-gated chloride channels are blocked with variable potency by the nonselective blocker picrotoxin. The first two subunits of the glutamate-gated chloride channel family, GluClalpha and GluClbeta, were cloned from the free living nematode Caenorhabditis elegans. In this study, we analyze the blockade of these novel channels by picrotoxin. In vitro synthesized GluClalpha and GluClbeta RNAs were injected individually or coinjected into Xenopus oocytes. The EC50 values for picrotoxin block of homomeric GluClalpha and GluClbeta were 59 microM and 77 nM, respectively. Picrotoxin block of homomeric GluClbeta channels was promoted during activation of membrane current with glutamate. In addition, recovery from picrotoxin block was faster during current activation by glutamate. A chimeric channel between the N-terminal extracellular domain of GluClalpha and the C-terminal membrane-spanning domain of GluClbeta localized the higher affinity picrotoxin binding site to the membrane-spanning domains of GluClbeta. A point mutation within the M2 membrane-spanning domain of GluClbeta reduced picrotoxin sensitivity >10,000-fold. We conclude that picrotoxin blocks GluCl channels by binding to a site accessible when the channel is open.

Identification of a Drosophila melanogaster glutamate-gated chloride channel sensitive to the antiparasitic agent avermectin

Glutamate-gated chloride channels, members of the ligand-gated ion channel superfamily, have been shown in nematodes and in insects to be a target of the antiparasitic agent avermectin. Two subunits of the Caenorhabditis elegans glutamate-gated chloride channel have been cloned: GluCl-alpha and GluCl-beta. We report the cloning of a Drosophila melanogaster glutamate-gated chloride channel, DrosGluCl-alpha, which shares 48% amino acid and 60% nucleotide identity with the C. elegans GluCl channels. Expression of DrosGluCl-alpha in Xenopus oocytes produces a homomeric chloride channel that is gated by both glutamate and avermectin. The DrosGluCl-alpha channel has several unique characteristics not observed in C. elegans GluCl: dual gating by avermectin and glutamate, a rapidly desensitizing glutamate response, and a lack of potentiation of the glutamate response by avermectin. The pharmacological data support the hypothesis that the DrosGluCl-alpha channel represents the arthropod H-receptor and an important target for the avermectin class of insecticides.

A receptor in pituitary and hypothalamus that functions in growth hormone release

Small synthetic molecules termed growth hormone secretagogues (GHSs) act on the pituitary gland and the hypothalamus to stimulate and amplify pulsatile growth hormone (GH) release. A heterotrimeric GTP-binding protein (G protein)-coupled receptor (GPC-R) of the pituitary and arcuate ventro-medial and infundibular hypothalamus of swine and humans was cloned and was shown to be the target of the GHSs. On the basis of its pharmacological and molecular characterization, this GPC-R defines a neuroendocrine pathway for the control of pulsatile GH release and supports the notion that the GHSs mimic an undiscovered hormone.

An amino acid substitution in the pore region of a glutamate-gated chloride channel enables the coupling of ligand binding to channel gating

Many of the subunits of ligand-gated ion channels respond poorly, if at all, when expressed as homomeric channels in Xenopus oocytes. This lack of a ligand response has been thought to result from poor surface expression, poor assembly, or lack of an agonist binding domain. The Caenorhabditis elegans glutamate-gated chloride channel subunit GluClbeta responds to glutamate as a homomeric channel while the GluClalpha subunit is insensitive. A chimera between GluClalpha and GluClbeta was used to suggest that major determinants for glutamate binding are present on the GluClalpha N terminus. Amino acid substitutions in the presumed pore of GluClalpha conferred direct glutamate gating indicating that GluClalpha is deficient in coupling of ligand binding to channel gating. Heteromeric channels of GluClalpha+beta may differ from the prototypic muscle nicotinic acetylcholine receptor in that they have the potential to bind ligand to all of the subunits forming the channel.

Detection of intracellular calcium elevations in Xenopus laevis oocytes: aequorin luminescence versus electrophysiology

Detection of receptor expression in Xenopus oocytes often relies upon functional coupling to second messengers such as Ca2+ or cyclic adenosine monophosphate. To detect intracellular Ca2+, electrophysiological measurement of the endogenous Ca(2+)-activated chloride current (ICl(Ca)) is often used (Dascal, 1987). An alternative utilizes the Ca2+ sensing, bioluminescent protein aequorin (Parker and Miledi(1986) Proc. R. Soc. Lond. B, 228: 307-315; Giladi and Spindel (1991) BioTechniques, 10: 744-747). In the present study the sensitivities of aequorin and electrophysiology for detecting receptor-mediated Ca2+ transients were compared. Assays were performed on the same batches of oocytes using either animal serum or ligands of exogenous receptors to generate inositol 1,4,5-trisphosphate (InsP3) and ultimately elevate intracellular Ca2+. Signal amplitudes were controlled by titrating the concentration of animal serum, or titrating the amount of receptor mRNA injected. Both assays detected signals with high concentrations of animal serum, or with high receptor density. However, aequorin signals were not detected in experiments with average ICl(Ca) current amplitudes below 200 nA. To further evaluate the differences between these two techniques, membrane current and bioluminescence were measured simultaneously. Results of these studies suggest that the signals differ due to the spatial distribution of aequorin, the chloride channels, and the calcium release sites.

Ectopic ureter as a cause of wetting: the role of laparoscopy in its management

A diagnosis of wetting caused by an ectopic ureter usually can be made from the history because of the characteristic pattern of wetting. Localization of the origin of the ectopic ureter is important in guiding the surgical approach. This is usually not a problem for cases of ectopic ureter arising from a duplex system. However, the single ectopic ureter arising from a small dysplastic and often ectopic kidney may defy a long search. Videolaparoscopy, with its magnifying effect, can confirm the diagnosis, localize the dysplastic kidney and allow its removal using endoscopic equipment.

Video-assisted thoracoscopic surgery in the paediatric population

OBJECTIVE

Video-assisted thoracoscopic surgery (VATS) is now widely practised in adults but there are few publications on its application in the paediatric population.

METHODOLOGY

Retrospective review of the authors' experience with VATS in children under 16 years old during an 18 month period in a university teaching hospital.

RESULTS

From September 1993 to March 1994, VATS was attempted in 14 patients. Five were unsuccessful because of pleural symphysis or inability to collapse the upper lung. Ten cases of VATS were successfully performed in the remaining nine patients (eight males, one female; age range from 22 days to 15 years old). These included two drainages and limited decortications for loculated pleural effusion, one guided drainage of pericardial effusion, one thymectomy for thymic hyperplasia, three wedge resections for metastatic pulmonary osteosarcoma and three bleb excisions and pleurodesis for primary spontaneous pneumothoraces. There were no intra-operative complications. There was one death from dysrhythmia following an uneventful wedge resection. The mean duration of chest tube drainage was 1.4 days and postoperative hospital stay 2.6 days excluding two patients who stayed for further medical treatment.

CONCLUSION

VATS is a useful approach in selected cases but further development of this approach awaits refinement of anaesthetic technique and endoscopic instrumentation.

The mechanism of action of avermectins in Caenorhabditis elegans: correlation between activation of glutamate-sensitive chloride current, membrane binding, and biological activity

Xenopus laevis oocytes were injected with mRNA isolated from the free-living nematode Caenorhabditis elegans and the activation and potentiation of a glutamate-sensitive chloride current by a series of avermectin analogs and milbemycin D were determined. There was a strong correlation between the EC50 value determined for current activation in oocytes, the LD95 value for nematocidal activity, and also for the Ki value determined in a [3H]ivermectin competition binding assay. Four of the analogs were tested for potentiation of glutamate-sensitive current and the rank order for potentiation correlated with the EC50 for direct activation of current. We conclude that avermectins and milbemycins mediate their nematocidal effects on C. elegans via an interaction with a common receptor molecule, glutamate-gated chloride channels.

Cloning of an avermectin-sensitive glutamate-gated chloride channel from Caenorhabditis elegans

The avermectins are a family of macrocyclic lactones used in the control of nematode and arthropod parasites. Ivermectin (22,23-dihydroavermectin B1a) is widely used as an anthelmintic in veterinary medicine and is used to treat onchocerciasis or river blindness in humans. Abamectin (avermectin B1a) is a miticide and insecticide used in crop protection. Avermectins interact with vertebrate and invertebrate GABA receptors and invertebrate glutamate-gated chloride channels. The soil nematode Caenorhabditis elegans has served as a useful model to study the mechanism of action of avermectins. A C. elegans messenger RNA expressed in Xenopus oocytes encodes an avermectin-sensitive glutamate-gated chloride channel. To elucidate the structure and properties of this channel, we used Xenopus oocytes for expression cloning of two functional complementary DNAs encoding an avermectin-sensitive glutamate-gated chloride channel. We find that the electrophysiological and structural properties of these proteins indicate that they are new members of the ligand-gated ion channel superfamily.

Cloning, overexpression and isolation of the type II FDP aldolase from E. coli for specificity study and synthetic application

A stable overexpression E. coli strain containing the plasmid pKEN 2 for the production of the Zn(2+)-dependent FDP aldolase from E. coli has been developed. Approximately 14,000 U of the enzyme (specific activity = 23.3 U/mg) can be obtained from 4-L of growth medium. The enzyme was isolated, purified to homogeneity and used for the studies of stability, substrate specificity and metal ion replacement and dissociation. Crystals of the enzyme have been obtained for structural analysis. This E. coli strain was deposited with the American Type Culture Collection (ATCC #77472).

Sacrococcygeal teratoma in children: a diagnostic challenge

Sacrococcygeal teratoma is relatively rare. Its characteristic appearance, location and size usually leave little doubt as to the diagnosis, but the less obvious ones may occasionally give rise to diagnostic difficulty. Four cases of sacrococcygeal teratoma in children are reported. One neonate presented with a large protuberant swelling at the sacrococcygeal area, with no diagnostic difficulty. The second neonate presented with a small paraxial sacral swelling with an overlying haemangioma. The third patient presented with a small tail-like appendage at the natal cleft. A properly performed rectal examination in both the second and third patients disclosed the diagnosis. The fourth patient presented with an anocutaneous fistula and partial sacral agenesis with no external sacrococcygeal swelling. The diagnosis was confirmed with computerized tomography. While the diagnosis of the protuberant sacrococcygeal teratoma presents no difficulty, that of the less obvious cases requires a high index of clinical suspicion. A properly performed rectal examination supplemented with appropriate imaging allows the diagnosis to be made.

Expression of a glutamate-activated chloride current in Xenopus oocytes injected with Caenorhabditis elegans RNA: evidence for modulation by avermectin

Membrane currents were recorded from Xenopus laevis oocytes injected with C. elegans poly(A)+ RNA. In such oocytes glutamate activated an inward membrane current that desensitized in the continued presence of glutamate. Glutamate-receptor agonists quisqualate, kainate, and N-methyl-D-aspartate were inactive. The reversal potential of the glutamate-sensitive current was -22 mV, and exhibited a strong dependence on external chloride with a 48 mV change for a 10-fold change in chloride. The chloride channel blockers flufenamate and picrotoxin inhibited the glutamate-sensitive current. Ibotenate, a structural analog of glutamate, also activated a picrotoxin-sensitive chloride current. Ibotenate was inactive when current was partially desensitized with glutamate, and the responses to low concentrations of glutamate and ibotenate were additive. The anthelmintic/insecticide compound avermectin directly activated the glutamate-sensitive current. In addition, avermectin increased the response to submaximal concentrations of glutamate, shifted the glutamate concentration-response curve to lower concentrations, and slowed the desensitization of glutamate-sensitive current. We propose that the glutamate-sensitive chloride current and the avermectin-sensitive chloride current are mediated via the same channel.

Avermectin-sensitive chloride currents induced by Caenorhabditis elegans RNA in Xenopus oocytes

Avermectins are a family of potent broad-spectrum anthelmintic compounds, which bind with high affinity to membranes isolated from the free-living nematode Caenorhabditis elegans. Binding of avermectins is thought to modulate chloride channel activity, but the exact mechanism for anthelmintic activity remains to be determined. In this report, the properties of an avermectin-sensitive membrane current were evaluated in Xenopus laevis oocytes that were injected with poly(A)+ RNA from C. elegans. In such oocytes, avermectins increased inward membrane current at a holding potential of -80 mV. An avermectin analog without anthelmintic activity had no effect. Half-maximal activation of current was observed with 90 nM avermectin. The reversal potential for avermectin-sensitive current was -19.3 +/- 1.9 mV, and it shifted with external chloride, as expected for a chloride current. Avermectin increased membrane current in C. elegans-injected oocytes that were also injected with the Ca2+ chelator ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. The response to avermectin was greatest in the 1.0-2.5-kilobase class of size-fractionated C. elegans poly(A)+ RNA. Oocytes that responded to avermectin were insensitive to gamma-aminobutyric acid and the avermectin-induced current was blocked by picrotoxin.