151
|
Wong KK, Chang S, Weiler SR, Ganesan S, Chaudhuri J, Zhu C, Artandi SE, Rudolph KL, Gottlieb GJ, Chin L, Alt FW, DePinho RA. Telomere dysfunction impairs DNA repair and enhances sensitivity to ionizing radiation. Nat Genet 2000; 26:85-8. [PMID: 10973255 DOI: 10.1038/79232] [Citation(s) in RCA: 247] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Telomeres are specialized nucleoprotein complexes that serve as protective caps of linear eukaryotic chromosomes. Loss of telomere function is associated with rampant genetic instability and loss of cellular viability and renewal potential. The telomere also participates in processes of chromosomal repair, as evidenced by the 'capture' or de novo synthesis of telomere repeats at double-stranded breaks and by the capacity of yeast telomeres to serve as repositories of essential components of the DNA repair machinery, particularly those involved in non-homologous end-joining (NHEJ). Here we used the telomerase-deficient mouse, null for the essential telomerase RNA gene (Terc), to assess the role of telomerase and telomere function on the cellular and organismal response to ionizing radiation. Although the loss of telomerase activity per se had no discernable impact on the response to ionizing radiation, the emergence of telomere dysfunction in late-generation Terc-/- mice imparted a radiosensitivity syndrome associated with accelerated mortality. On the cellular level, the gastrointestinal crypt stem cells and primary thymocytes showed increased rates of apoptosis, and mouse embryonic fibroblasts (MEFs) showed diminished dose-dependent clonogenic survival. The radiosensitivity of telomere dysfunctional cells correlated with delayed DNA break repair kinetics, persistent chromosomal breaks and cytogenetic profiles characterized by complex chromosomal aberrations and massive fragmentation. Our findings establish a intimate relationship between functionally intact telomeres and the genomic, cellular and organismal response to ionizing radiation.
Collapse
|
152
|
Bardeesy N, Wong KK, DePinho RA, Chin L. Animal models of melanoma: recent advances and future prospects. Adv Cancer Res 2000; 79:123-56. [PMID: 10818679 DOI: 10.1016/s0065-230x(00)79004-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
MESH Headings
- Animals
- Cell Cycle Proteins/genetics
- Cell Cycle Proteins/physiology
- Chromosomes, Human, Pair 9/genetics
- Cricetinae
- Cyprinodontiformes
- Disease Progression
- Forecasting
- Genes, p16
- Genes, ras
- Growth Substances/physiology
- Humans
- Loss of Heterozygosity
- Melanocytes/metabolism
- Melanocytes/pathology
- Melanoma, Experimental/epidemiology
- Melanoma, Experimental/genetics
- Melanoma, Experimental/metabolism
- Melanoma, Experimental/pathology
- Mesocricetus
- Mice
- Mice, Transgenic
- Mutation
- Neoplasm Proteins/genetics
- Neoplasm Proteins/physiology
- Neoplasms, Radiation-Induced/epidemiology
- Neoplasms, Radiation-Induced/genetics
- Opossums
- Proteins/genetics
- Receptor Protein-Tyrosine Kinases/genetics
- Receptor Protein-Tyrosine Kinases/physiology
- Receptors, Growth Factor/genetics
- Receptors, Growth Factor/physiology
- Species Specificity
- Tumor Suppressor Protein p14ARF
Collapse
|
153
|
Ang P, Chia KH, Teoh MK, Wong KK. Use of a peripherally implanted subcutaneous permanent central venous access device for chemotherapy--the Singapore General Hospital experience. AUSTRALIAN AND NEW ZEALAND JOURNAL OF MEDICINE 2000; 30:470-4. [PMID: 10985513 DOI: 10.1111/j.1445-5994.2000.tb02054.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Venous access for chemotherapy patients at the Singapore General Hospital has conventionally been via an externalised (Hickman) catheter. A peripherally implanted permanent subcutaneous central venous access device (P.A.S.Port) was introduced in 1996. AIMS We review its use, complications and cost competitiveness with other chemotherapy delivery systems. METHODS A retrospective study of clinical records was conducted with follow up interviews of patients and nursing staff. RESULTS Twelve patients had the P.A.S.Port inserted for administration of chemotherapy as an outpatient procedure. Immediate complications were pain (8%) and bruising (8%). One port-related infection (8%) one week following insertion was reported and one patient complained of interference with elbow movement as a late complication. Cost analysis was favourable for P.A.S.Port over an externalised Hickman catheter or chest-placed port at one year. Patient and nursing staff acceptance was high. CONCLUSION P.A.S.Port insertion is a safe outpatient procedure and is an alternative for permanent venous access.
Collapse
|
154
|
Nademanee A, Molina A, Dagis A, Snyder DS, O'Donnell MR, Parker P, Stein A, Smith E, Planas I, Kashyap A, Spielberger R, Fung H, Krishnan A, Bhatia R, Wong KK, Somlo G, Margolin K, Chow W, Sniecinski I, Vora N, Slovak M, Niland JC, Forman SJ. Autologous stem-cell transplantation for poor-risk and relapsed intermediate- and high-grade non-Hodgkin's lymphoma. CLINICAL LYMPHOMA 2000; 1:46-54. [PMID: 11707813 DOI: 10.3816/clm.2000.n.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The primary objective of this study was to evaluate the outcome of patients treated with high-dose chemo-/radiotherapy or high-dose chemotherapy and autologous stem-cell transplant (ASCT) for relapsed, refractory, or poor-risk intermediate-grade (IG) and high-grade (HG) non-Hodgkin's lymphoma (NHL). The secondary objectives were to determine prognostic factors for relapse and survival. Between February 1987 and August 1998, 264 patients, 169 (64%) IG and 95 (36%) HG, underwent high-dose therapy and ASCT at City of Hope National Medical Center (COHNMC). There were 157 (59%) males and 107 (41%) females with a median age of 44 years (range, 5-69 years). The median number of prior chemotherapy regimens was 2 (range, 1-4), and 71 (27%) had received prior radiation as part of induction or as salvage therapy. The median time from diagnosis to ASCT was 10.8 months (range, 3-158 months). Ninety-four patients (36%) underwent transplantation in first complete/partial remission (CR/PR), 40 (15%) in induction failure, and 130 (49%) in relapse or subsequent remission. Two preparative regimens were used: total body irradiation/high-dose etoposide/cyclophosphamide (TBI/VP/CY) in 208 patients (79%) and carmustine/etoposide/cyclophosphamide (BCNU/VP/CY) in 56 patients (21%). One hundred sixty-three patients (62%) received peripheral blood stem cells (PBSC) and 101 (38%) received bone marrow (BM) alone or BM plus PBSC. At a median follow-up of 4.43 years for surviving patients (range, 1-12.8 years), the 5-year Kaplan-Meier estimates of probability of overall survival (OS), progression-free survival (PFS), and relapse for all patients are 55% (95% confidence interval [CI]: 49%-61%), 47% (95% CI: 40%-53%), and 47% (95% CI: 40%-54%), respectively. There were 27 deaths (10%) from nonrelapse mortality, including seven (3%) patients who developed second malignancies (five with myelodysplasia/acute myelogenous leukemia and two with solid tumors). By stepwise Cox regression analysis, disease status at ASCT was the only prognostic factor that predicted for both relapse and survival. The 5-year probability of PFS for patients transplanted in first CR/PR was 73% (95% CI: 62%-81%) as compared to 30% (95% CI: 16%-45%) for induction failure and 34% (95% CI: 26%-42%) for relapsed patients. Our results further support the role of high-dose therapy and ASCT during first CR/PR for patients with poor-risk intermediate- and high-grade NHL. Early transplant is recommended for patients failing initial induction therapy or relapsing after chemotherapy-induced remission. Relapse continues to be the most common cause of treatment failure. An alternative approach to prevent relapse, the incorporation of radioimmunotherapy into the high-dose regimen, is being investigated. The development of a second malignancy is a serious complication of high-dose therapy, which requires close surveillance.
Collapse
|
155
|
Wong KK, Hancock RE. Insertion mutagenesis and membrane topology model of the Pseudomonas aeruginosa outer membrane protein OprM. J Bacteriol 2000; 182:2402-10. [PMID: 10762238 PMCID: PMC111300 DOI: 10.1128/jb.182.9.2402-2410.2000] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa OprM is a protein involved in multiple-antibiotic resistance as the outer membrane component for the MexA-MexB-OprM efflux system. Planar lipid bilayer experiments showed that OprM had channel-forming activity with an average single-channel conductance of only about 80 pS in 1 M KCl. The gene encoding OprM was subjected to insertion mutagenesis by cloning of a foreign epitope from the circumsporozoite form of the malarial parasite Plasmodium falciparum into 11 sites. In Escherichia coli, 8 of the 11 insertion mutant genes expressed proteins at levels comparable to those obtained with the wild-type gene and the inserted malarial epitopes were surface accessible as assessed by indirect immunofluorescence. When moved to a P. aeruginosa OprM-deficient strain, seven of the insertion mutant genes expressed proteins at variable levels comparable to that of wild-type OprM and three of these reconstituted MIC profiles resembling those of the wild-type protein, while the other mutant forms showed variable MIC results. Utilizing the data from these experiments, in conjunction with multiple sequence alignments and structure predictions, an OprM topology model with 16 beta strands was proposed.
Collapse
|
156
|
Jensen PK, Pasa-Tolić L, Peden KK, Martinović S, Lipton MS, Anderson GA, Tolić N, Wong KK, Smith RD. Mass spectrometric detection for capillary isoelectric focusing separations of complex protein mixtures. Electrophoresis 2000; 21:1372-80. [PMID: 10826683 DOI: 10.1002/(sici)1522-2683(20000401)21:7<1372::aid-elps1372>3.0.co;2-y] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Capillary isoelectric focusing (CIEF) can provide high-resolution separations of complex protein mixtures, but until recently it has primarily been used with conventional UV detection. This technique would be greatly enhanced by much more information-rich detection methods that can aid in protein characterization. We describe progress in the development of the combination of CIEF with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry and its application to proteome characterization. Studies have revealed 400-1000 putative proteins in the mass range of 2-100 kDa from total injections of approximately 300 ng protein in single CIEF-FTICR analyses of cell lysates for both Escherichia coli (E. coli) and Deinococcus radiodurans (D. radiodurans). We also demonstrate the use of isotope labeling of the cell growth media to improve mass measurement accuracy and provide a means for quantitative proteome-wide measurements of protein expression. The ability to make such comprehensive and precise measurements of differences in protein expression in response to cellular perturbations should provide new insights into complex cellular processes.
Collapse
|
157
|
Wong KK, Pompliano DL. Peptidoglycan biosynthesis. Unexploited antibacterial targets within a familiar pathway. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1999; 456:197-217. [PMID: 10549370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
|
158
|
Fermann ME, Galvanauskas A, Stock ML, Wong KK, Harter D, Goldberg L. Ultrawide tunable Er soliton fiber laser amplified in Yb-doped fiber. OPTICS LETTERS 1999; 24:1428-1430. [PMID: 18079824 DOI: 10.1364/ol.24.001428] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A Raman-shifted and frequency-doubled high-power Er-fiber soliton laser for seeding an efficient high-power Yb fiber femtosecond amplifier is demonstrated. The Raman-shifted and frequency-doubled Er-soliton laser is tunable from 1.00 to 1.070microm and produces bandwidth-limited 24-pJ pulses at a repetition rate of 50 MHz with a FWHM pulse width of 170 fs at 1.040microm . The Yb(3+) amplifier has a slope efficiency of 52% and generates 3-ps linearly chirped pulses with an average power of 0.8 W at 1.05microm . After pulse compression, 74-fs bandwidth-limited pulses with an average power of 0.4 W and a pulse energy of 8 nJ are generated.
Collapse
|
159
|
Leppänen VM, Merckel MC, Ollis DL, Wong KK, Kozarich JW, Goldman A. Pyruvate formate lyase is structurally homologous to type I ribonucleotide reductase. Structure 1999; 7:733-44. [PMID: 10425676 DOI: 10.1016/s0969-2126(99)80098-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND Pyruvate formate lyase (PFL) catalyses a key step in Escherichia coli anaerobic glycolysis by converting pyruvate and CoA to formate and acetylCoA. The PFL mechanism involves an unusual radical cleavage of pyruvate, involving an essential C alpha radical of Gly734 and two cysteine residues, Cys418 and Cys419, which may form thiyl radicals required for catalysis. We undertook this study to understand the structural basis for catalysis. RESULTS The first structure of a fragment of PFL (residues 1-624) at 2.8 A resolution shows an unusual barrel-like structure, with a catalytic beta finger carrying Cys418 and Cys419 inserted into the centre of the barrel. Several residues near the active-site cysteines can be ascribed roles in the catalytic mechanism: Arg176 and Arg435 are positioned near Cys419 and may bind pyruvate/formate and Trp333 partially buries Cys418. Both cysteine residues are accessible to each other owing to their cis relationship at the tip of the beta finger. Finally, two clefts that may serve as binding sites for CoA and pyruvate have been identified. CONCLUSIONS PFL has striking structural homology to the aerobic ribonucleotide reductase (RNR): the superposition of PFL and RNR includes eight of the ten strands in the unusual RNR alpha/beta barrel as well as the beta finger, which carries key catalytic residues in both enzymes. This provides the first structural proof that RNRs and PFLs are related by divergent evolution from a common ancestor.
Collapse
|
160
|
Mi J, Chatterjee S, Wong KK, Forbes C, Lawless G, Tobin AJ. Recombinant adeno-associated virus (AAV) drives constitutive production of glutamate decarboxylase in neural cell lines. J Neurosci Res 1999; 57:137-48. [PMID: 10397644 DOI: 10.1002/(sici)1097-4547(19990701)57:1<137::aid-jnr15>3.0.co;2-d] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Many neurological disorders result directly or indirectly from the loss of inhibitory function. Engineering the production of GABA, an inhibitory neurotransmitter, may therefore be able at least partly to restore the lost inhibition seen in epilepsy, Parkinson's disease, or Huntington's disease. In this article, we describe a set of recombinant adeno-associated viruses (AAVs) that can deliver cDNAs encoding the GABA-producing enzyme, glutamate decarboxylase (GAD), directly into neural cells. We have characterized these recombinant AAVs in several cell lines derived from the CNS. These recombinant AAVs effectively transduced all neural cell lines, although with different efficiencies. Transduction occurred in both proliferating and nonproliferating cells, but actively proliferating cell lines had approximately six times greater transduction efficiency than nonproliferating cells. Furthermore, these AAVs maintained long-term expression of GAD in an astrocytic cell line for at least seven passages. These recombinant AAVs are promising vehicles for investigating the potential therapeutic effects of GABA in animal models of epilepsy and neurodegenerative diseases.
Collapse
|
161
|
Wong RM, Wong KK, Benson NR, McClelland M. Sample sequencing of a Salmonella typhimurium LT2 lambda library: comparison to the Escherichia coli K12 genome. FEMS Microbiol Lett 1999; 173:411-23. [PMID: 10227170 DOI: 10.1111/j.1574-6968.1999.tb13533.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
As part of the ongoing sequencing of the complete Salmonella typhimurium LT2 genome, a partly ordered set of 416 lambda clones has been developed, representing over 90% of the genome. The average insert size is 17 kb. Sequences were obtained from both ends of each clone in this set. A total of over 600 kb of sequence has been deposited in the genome survey sequence section of GenBank. This resource of clones is available from the Salmonella Genome Stock Center. A preliminary comparison with the Escherichia coli K12 genome indicates that there are likely to be many hundred insertion deletion events, encompassing more than one gene, that distinguish these genomes. Fully 30% of the S. typhimurium sequences have no close homologs in the GenBank database.
Collapse
|
162
|
Chatterjee S, Li W, Wong CA, Fisher-Adams G, Lu D, Guha M, Macer JA, Forman SJ, Wong KK. Transduction of primitive human marrow and cord blood-derived hematopoietic progenitor cells with adeno-associated virus vectors. Blood 1999; 93:1882-94. [PMID: 10068661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023] Open
Abstract
We evaluated the capacity of adeno-associated virus (AAV) vectors to transduce primitive human myeloid progenitor cells derived from marrow and cord blood in long-term cultures and long-term culture-initiating cell (LTC-IC) assays. Single-colony analyses showed that AAV vectors transduced CD34(+) and CD34(+)38(-) clonogenic cells in long-term culture. Gene transfer was readily observed in LTC-ICs derived from 5-, 8-, and 10-week cultures. Recombinant AAV (rAAV) transduction was observed in every donor analyzed, although a wide range of gene transfer frequencies (5% to 100%) was noted. AAV transduction of LTC-ICs was stable, with week-8 and -10 LTC-ICs showing comparable or better transduction relative to week-5 LTC-ICs. Fluorescence in situ hybridization (FISH) analyses performed to determine the fate of AAV vectors in transduced cells showed that 9% to 28% of CD34(+) and CD34(+)38(-) cells showed stable vector integration as evidenced by chromosome-associated signals in metaphase spreads. Comparisons of interphase and metaphase FISH suggested that a fraction of cells also contained episomal vector at early time points after transduction. Despite the apparent loss of the episomal forms with continued culture, the number of metaphases containing integrated vector genomes remained stable long term. Transgene transcription and placental alkaline phosphatase (PLAP) expression was observed in CD34(+), CD34(+)38(-) LTC-ICs in the absence of selective pressure. These results suggest that primitive myeloid progenitors are amenable to genetic modification with AAV vectors.
Collapse
|
163
|
Leung C, Poon W, Lam J, Wong CW, Wai S, Ma HK, Wong KK, Kwok S, Lau FL. Neurosurgical emergencies in patients who are unfit for transfer: Is a mobile neurosurgeon a feasible option? J Telemed Telecare 1999. [DOI: 10.1258/1357633991933260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
164
|
Romine MF, Stillwell LC, Wong KK, Thurston SJ, Sisk EC, Sensen C, Gaasterland T, Fredrickson JK, Saffer JD. Complete sequence of a 184-kilobase catabolic plasmid from Sphingomonas aromaticivorans F199. J Bacteriol 1999; 181:1585-602. [PMID: 10049392 PMCID: PMC93550 DOI: 10.1128/jb.181.5.1585-1602.1999] [Citation(s) in RCA: 238] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The complete 184,457-bp sequence of the aromatic catabolic plasmid, pNL1, from Sphingomonas aromaticivorans F199 has been determined. A total of 186 open reading frames (ORFs) are predicted to encode proteins, of which 79 are likely directly associated with catabolism or transport of aromatic compounds. Genes that encode enzymes associated with the degradation of biphenyl, naphthalene, m-xylene, and p-cresol are predicted to be distributed among 15 gene clusters. The unusual coclustering of genes associated with different pathways appears to have evolved in response to similarities in biochemical mechanisms required for the degradation of intermediates in different pathways. A putative efflux pump and several hypothetical membrane-associated proteins were identified and predicted to be involved in the transport of aromatic compounds and/or intermediates in catabolism across the cell wall. Several genes associated with integration and recombination, including two group II intron-associated maturases, were identified in the replication region, suggesting that pNL1 is able to undergo integration and excision events with the chromosome and/or other portions of the plasmid. Conjugative transfer of pNL1 to another Sphingomonas sp. was demonstrated, and genes associated with this function were found in two large clusters. Approximately one-third of the ORFs (59 of them) have no obvious homology to known genes.
Collapse
|
165
|
Leong MKH, Wong KK, Leung CKM, Wong C, Tang W, Tang F. Successful pregnancy in a case of azoospermic infertility by using testicular sperm for intracytoplasmic injection into the oocyte. Hong Kong Med J 1999; 5:69-71. [PMID: 11821571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Abstract
Non-obstructive azoospermia used to be considered an untreatable cause of infertility. By the microinjection technique, however, sperm that has been surgically extracted from the testis can be injected into the oocyte cytoplasm. The injected eggs can be transferred to the uterus or fallopian tubes to initiate a pregnancy. A healthy baby boy conceived by using this method was delivered in November 1997. This micromanipulation technique offers couples in which the man has non-obstructive azoospermia the chance of having their own offspring. The methodology used and a brief discussion of its merits are presented.
Collapse
|
166
|
Leppänen VM, Parast CV, Wong KK, Kozarich JW, Goldman A. Purification and crystallization of a proteolytic fragment of Escherichia coli pyruvate formate-lyase. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 1999; 55:531-3. [PMID: 10089368 DOI: 10.1107/s0907444998011056] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Under anaerobic conditions, the reaction catalysed by pyruvate formate-lyase (PFL) is the first reaction after the production of pyruvate in the glycolytic pathway. Crystallization trials with Escherichia coli PFL were unsuccessful and therefore limited proteolysis was used to produce a stable crystallizable N--terminal protein fragment by trypsin cleavage. The molecular weight of this cleavage product was found to be 69.6 kDa by MALDI MS analysis, and the DNA sequence corresponding to this fragment was cloned. The recombinant protein fragment was crystallized by sitting-drop vapour diffusion using polyethylene glycol 1000 as precipitant. The crystals, which grew to 2 mm in length and 0.2 mm in cross section, belong to the hexagonal space group P61 or P65 with cell dimensions a = b = 140.4, c = 215.3 A and two molecules per asymmetric unit. X--ray diffraction data were collected from 20 to 3.2 A resolution from a single frozen crystal on a synchrotron-radiation beamline.
Collapse
|
167
|
Wong KK, Zhao XB. The Influence of Bureaucratic Behavior on Land Apportionment in China: The Informal Process. ACTA ACUST UNITED AC 1999. [DOI: 10.1068/c170113] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
In the early 1990s China experienced phenomenal, massive, speculative land development that had long range impacts on China's sustainable development. The authors attempt to examine the administrative framework of the current land-apportionment system from the perspectives both of formal or legal and of informal or quasi-legal processes. In particular, they focus on the detrimental consequences of the informal process of land apportionment, which has virtually overridden the formal process in recent years. They also cautiously scrutinize the underlying reasons for land misapportionment. They argue that the informal process is difficult to control and it will continue to impede the normal and healthy development of China's land market in the foreseeable future.
Collapse
|
168
|
Wong KK. Lack of significant alteration of histamine-induced response in aorta from diabetic rats induced by streptozocin. ARTERY 1999; 22:287-92. [PMID: 9921404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Effect of histamine on aortic contraction between age-matched control and diabetic rats induced by streptozocin were compared in vitro. It was shown that the aortic response to histamine in 12-week diabetic rats remained unchanged, even though the methoxamine-induced contraction was potentiated significantly in diabetic aorta. The significant potentiation of the methoxamine-induced aortic contraction implies that the diabetes-induced change in aortic response to drugs has occurred in 12-week diabetic aorta. Since histamine is an endothelium dependent vasoactive agent, the lack of change of the histamine-induced response in 12-week diabetic aorta suggests that the histamine receptors in the endothelium are unlikely modified after 12 weeks of diabetic development.
Collapse
|
169
|
Markillie LM, Varnum SM, Hradecky P, Wong KK. Targeted mutagenesis by duplication insertion in the radioresistant bacterium Deinococcus radiodurans: radiation sensitivities of catalase (katA) and superoxide dismutase (sodA) mutants. J Bacteriol 1999; 181:666-9. [PMID: 9882685 PMCID: PMC93425 DOI: 10.1128/jb.181.2.666-669.1999] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Deinococcus radiodurans R1 is extremely resistant to both oxidative stress and ionizing radiation. A simple and general targeted mutagenesis method was developed to generate catalase (katA) and superoxide dismutase (sodA) mutants. Both mutants were shown to be more sensitive to ionizing radiation than the wild type.
Collapse
|
170
|
Cheng F, Ip M, Wong KK, Yan WW. Critical care ethics in Hong Kong: cross-cultural conflicts as east meets west. THE JOURNAL OF MEDICINE AND PHILOSOPHY 1998; 23:616-27. [PMID: 10190844 DOI: 10.1076/jmep.23.6.616.2554] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The practice of critical care medicine has long been a difficult task for most critical care physicians in the densely populated city of Hong Kong, where we face limited resources and a limited number of intensive care beds. Our triage decisions are largely based on the potential of functional reversibility of the patients. Provision of graded care beds may help to relieve some of the demands on the intensive care beds. Decisions to forego futile medical treatment are frequently physician-guided family-based decisions, which is quite contrary to the Western focus on patient autonomy. However, as people acquire knowledge about health care and they become more aware of individual rights, our critical care doctors will be able to narrow the gaps between the different concepts of medical ethics among our professionals as well as in our society. An open and caring attitude from our intensivists will be important in minimizing the cross-cultural conflict on the complex issue of medical futility.
Collapse
|
171
|
Wong KK. Mechanism of the aortic relaxation induced by low concentrations of berberine. PLANTA MEDICA 1998; 64:756-757. [PMID: 9933995 DOI: 10.1055/s-2006-957575] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The mechanism of the aortic relaxation induced by a low concentration of berberine was investigated in rat isolated aorta. It was found that the aortic relaxation induced by berberine below 1 x 10(-6) M was solely endothelium dependent. Denuded aorta and methylene blue pretreated aorta did not demonstrate aortic relaxation with such berberine concentrations. Higher concentrations (above 1 x 10(-6) M berberine), however, induced aortic relaxation irrespective of the presence of intact endothelium or methylene blue pretreatment. Since methylene blue is known as a direct inhibitor of nitric oxide synthase beside being a nonspecific guanylyl cyclase inhibitor, the present data suggest that the mechanism of the aortic relaxation induced by a low berberine concentration is solely dependent on the presence of endothelium.
Collapse
|
172
|
Wong KK. Differential effect of tetrandrine on aortic relaxation and chronotropic activity in rat isolated aorta and atria. PLANTA MEDICA 1998; 64:663-665. [PMID: 9810276 DOI: 10.1055/s-2006-957546] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Tetrandrine is known as a calcium blocker which can induce bradycardia as well as hypotension. It was however reported that the heart rate was unchanged during tetrandrine-induced hypotension. The possibility of different tissue sensitivity to various concentrations of tetrandrine was therefore investigated using the rat isolated aorta and atria. It was found that tetrandrine (1 x 10(-5) M) was sufficient to suppress more than 90% of the aortic contraction induced by norepinephrine (1 x 10(-8) M) or KCl (50 mM). However, only 10% of the initial heart rate was suppressed by 1 x 10(-5) M tetrandrine. It was therefore concluded that the aorta and atria might have different sensitivity to tetrandrine.
Collapse
|
173
|
Au WY, Chan AC, Wong KK, Leung CY, Liang R, Kwong YL. Multiple osseous metastases from occult paraganglioma: a diagnostic pitfall. Histopathology 1998; 33:287-8. [PMID: 9777399 DOI: 10.1046/j.1365-2559.1998.0482d.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
174
|
Gegnas LD, Waddell ST, Chabin RM, Reddy S, Wong KK. Inhibitors of the bacterial cell wall biosynthesis enzyme MurD. Bioorg Med Chem Lett 1998; 8:1643-8. [PMID: 9873406 DOI: 10.1016/s0960-894x(98)00285-6] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of transition-state analog inhibitors of the D-glutamic acid-adding enzyme (MurD) of bacterial peptidoglycan biosynthesis has been synthesized and evaluated for inhibition of the E. coli enzyme.
Collapse
|
175
|
Wong KK, McClelland M, Stillwell LC, Sisk EC, Thurston SJ, Saffer JD. Identification and sequence analysis of a 27-kilobase chromosomal fragment containing a Salmonella pathogenicity island located at 92 minutes on the chromosome map of Salmonella enterica serovar typhimurium LT2. Infect Immun 1998; 66:3365-71. [PMID: 9632606 PMCID: PMC108353 DOI: 10.1128/iai.66.7.3365-3371.1998] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/1998] [Accepted: 04/30/1998] [Indexed: 02/07/2023] Open
Abstract
Using a genomic approach, we have identified a new Salmonella pathogenicity island, SPI-4, which is the fourth Salmonella pathogenicity island to be identified. SPI-4 was located at 92 min on the chromosome map and was flanked by the ssb and soxSR loci. The DNA sequence covering the entire SPI-4 and both boundaries was determined. The size of SPI-4 was about 25 kb and it contains 18 putative open reading frames (ORFs). Three of these ORFs encode proteins that have significant homology with proteins involved in toxin secretion. Another five ORFs encode proteins that have significant homology with hypothetical proteins from Synechocystis sp. strain PCC6803 or Acinetobacter calcoaceticus. The rest of the ORFs encode novel proteins, one of which has five membrane-spanning domains. SPI-4 is likely to carry a type I secretion system involved in toxin secretion. Furthermore, a previously identified locus (ims98), which is required for intramacrophage survival, was also mapped within the SPI-4 region. These findings suggested that SPI-4 is needed for intramacrophage survival.
Collapse
|