Biomedical subjects
G L Tan
Publications and source records attributed to G L Tan.
[A nasopharyngeal carcinoma negatively related EST on 7q32].
To isolate and clone the tumor suppressor gene on chromosomal region 7q32 that corelated with the occurrence of human NPC, we detected the genotype of polymorphic microsatellite markers on 7q32 in 24 nasopharyngeal carcinoma biopsies and matched normal lymphocyte DNA. LOH was found in 30% biopsies. Using differential RT-PCR and Northern hybridization we compared the expression level of 20 EST on 7q32 between NPC cell line HNE1 and primary culture of normal nasopharyngeal epithelial cell, and found AA070437 EST expressed high in primary culture of normal nasopharyngeal epithelial cell, but very low in HNE1. Differential RT-PCR (dRT-PCR) analysis showed that the expression level of AA070437 was lower in 30.7% NPC biopses than in normal cell. Differential PCR (dPCR) showed that allelic loss of AA070437 was observed in 29.1% NPC biopses. This EST is a part of sequence of a new gene compared with GeneBank database. Our results showed that AA070437 EST negatively related with the occurrence of human NPC is a candidate of tumor suppressor gene of NPC on 7q32.
Ergonomic task analysis in electronics industries: some case studies.
The analyses of a few tasks were carried out in an electronics factory. The main objectives are to identify the ergonomic and biomechanical hazards of problem work tasks, to analyze each task systematically in order to evaluate the workers' exposures to the risk factors of force, posture pressure and repetition and to make recommendations to reduce the risks and hazards. The methodology includes objective measures--detailed analysis by going through training manuals, job description and production records. Subjective measures include interviewing the operator and supervisors informally, the operators were also required to fill in a structured questionnaire. The paper concludes by making recommendations to reduce the ergonomic hazards by engineering solutions, redesign or administrative controls or the implementation of procedures.
[A study of T-lymphocyte subsets, IL-2 production and IL-2 receptor expression in peripheral blood lymphocytes in patients with nasopharyngeal carcinoma].
T lymphocyte subsets, IL-2 production and IL-2 receptor expression were detected in PBLs of 31 NPC patients and 28 normal subjects and of normal PBLs populations under the influence of serum of NPC patients. The results were as follows: CD4+ and IL-2 receptor expression, CD4+:CD8+ ratios and IL-2 production were significantly depressed and CD8+-significantly elevated in PBLs of NPC patients before radiation and of normal PBLs populations under the influence of the serum of NPC patients. CD8+ was significantly decreased and CD4+, IL-2 production and IL-2 receptor expression were depressed in patients after radiation. These suggest that cellular immunity and immunoregulation are impaired in NPC patients before and after radiation.
G-protein-linked serotonin receptors in mouse kidney exhibit identical properties to 5-HT1b receptors in brain.
The serotonin 1b (5-HT1b) receptor is thought to mediate both pre- and postsynaptic actions of serotonin. Until recently 5-HT1b sites were thought to be present only in rodent brain. We now report the presence of high-affinity [125I]iodocyanopindolol [( 125I] ICYP) binding sites in the mouse renal medulla with properties identical to those of brain 5-HT1b receptors. In vitro receptor autoradiography demonstrates that [125I]ICYP binding is highly localized to the outer stripe of the renal medulla. Association and dissociation kinetics, saturation analysis and competition displacement analyses indicate that renal medullary [125I]ICYP binding sites exhibit identical properties with brain 5-HT1b receptors. Incubation of renal medullary or brain membranes with guanylimidodiphosphate results in a decreased affinity of 5-HT1b sites for 5-HT and [125I]ICYP; this can be reversed by the addition of a purified mixture of G proteins (Gi/Go). Treatment of brain or kidney membranes with N-ethylmaleimide results in a decrease in 5-HT1b binding which can also be restored by reconstitution with purified G proteins. Adenylyl cyclase from renal medullary homogenates or minces can be stimulated more than 3-fold by forskolin and attenuated by 5-HT. These results indicate that mouse kidney contains high-affinity 5-HT1b receptors with identical properties to those found in brain. These are localized in the outer stripe of the renal medulla and are functionally coupled to adenylyl cyclase inhibitor (Gi) G-proteins.
G protein dependent alterations in [125I]iodocyanopindolol and +/- cyanopindolol binding at 5-HT1B binding sites in rat brain membranes.
Several manipulations that affect G protein/receptor coupling also alter the binding of [125I]iodocyanopindolol ([125I]ICYP) and [corrected] +/- cyanopindolol (+/- CYP) to rat brain 5-HT1B binding sites in radioligand binding assays. Inclusion of 5 mM MgSO4 in these assays results in a small but significant increase in the affinity of [125I]ICYP (from KD = 0.046 nM to KD = 0.037 nM). In contrast, 100 microM Gpp(NH)p, GTP, or GDP reduce [125I]ICYP affinity (KD = 0.056 nM with GTP) while ATP and GMP are less effective. +/- CYP affinity for 5-HT1B sites labeled by [3H]dihydroergotamine [( 3H]DE) also displays a small but significant reduction (from Ki = 1.4 nM to Ki = 3.5nM) by the inclusion of 100 microM GTP. Pre-treatment of the brain membranes with N-ethylmaleimide (NEM) in concentrations known to inactivate many G proteins reduces 5-HT1B specific binding of [125I]ICYP. The NEM induced reduction in [125I]ICYP binding can be reversed by reconstitution with purified exogenous G proteins (Go and Gi), demonstrating directly that high affinity binding of [125I]ICYP to 5-HT1B sites is dependent on G proteins. The effects of Mg2+ ion, guanine nucleotides, NEM and G protein reconstitution on [125I]ICYP and +/- CYP binding are all hallmarks of agonist binding to G protein linked receptors. The effect of GTP, however, is quantitatively much less for the binding of these pindolol derivatives than for the binding of 5-HT, a presumed full agonist at 5-HT1B sites.(ABSTRACT TRUNCATED AT 250 WORDS)
Differential inactivation and G protein reconstitution of subtypes of [3H]5-hydroxytryptamine binding sites in brain.
The sulfhydryl reagents p-chloromercuribenzoate and N-ethylmaleimide (NEM) inactivate high affinity [3H]serotonin [( 3H]5-HT) binding to bovine and rat brain membranes in a concentration-dependent manner. In both species, 15-25% of total specific high affinity [3H]5-HT binding is relatively insensitive to NEM. This study examines the NEM sensitivity of the various high affinity [3H]5-HT binding subtypes, using selective ligands, tissues, and pharmacological masks to study each subtype. Reconstitution of NEM-inactivated binding by addition of GTP-binding proteins (G proteins, Gi and Go) is also described. Agonist binding to 5-HT1A, 5-HT1B, and 5-HT1D sites in rat brain and to 5-HT1A and 5-HT1D sites in bovine brain is sensitive to NEM. Binding of [3H]dihydroergotamine and [125I]iodocyanopindolol, both of which are weak partial agonists to 5-HT1B sites is relatively insensitive to NEM. Binding of [3H]5-HT to 5-HT1C sites in rat and bovine brain and choroid plexus is relatively insensitive to NEM. In the presence of spiperone to mask binding of 5-HT2 sites, binding of antagonist [( 3H]mesulergine) to 5-HT1C sites is also insensitive to NEM. Likewise, binding of the agonist [3H]4-bromo-2,5-dimethoxyphenylisopropylamine and of the antagonist [3H]ketanserin to 5-HT2 sites is not inhibited by NEM treatment of membranes. These findings suggest that agonist binding to 5-HT1A, 5-HT1B, and 5-HT1D sites is sensitive to NEM alkylation. Binding of neither agonist nor antagonist to 5-HT1C and 5-HT2 sites is sensitive to NEM. Inability of high concentrations of a variety of ligands to protect the sensitive binding sites against NEM inactivation indicates that the critical sulfhydryl group(s) are not located in the ligand binding domain of the NEM-sensitive binding sites. When membranes are treated with NEM, displacement of [125I]iodocyanopindolol by 5-HT is no longer sensitive to 5'-guanylyl imidodiphosphate (Gpp(NH)p). Gpp(NH)p sensitivity of agonist displacement of 5-HT1B binding to NEM-treated membranes is restored by addition of purified guanine nucleotide binding proteins (Gi plus Go). In addition, NEM-inactivated binding to 5-HT1A and 5-HT1D sites can be restored by addition of Gi plus Go. These data suggest that NEM exerts its effects on 5-HT1A, 5-HT1B, and 5-HT1D binding sites by inactivating the G protein(s) associated with the 5-HT receptor subtypes.
Ascorbic acid prevents nonreceptor "specific" binding of [3H]-5-hydroxytryptamine to bovine cerebral cortex membranes.
[3H]-5-Hydroxytryptamine ([3H]-5-HT) decomposes rapidly when exposed to air in solution at physiological pH if antioxidants are not present. The decomposition products appear to bind to two saturable sites on brain membranes (apparent Kd values = 1-2 and 100-1000 nM). This binding mimics "specific" ligand/receptor binding in that it is inhibited by 10 microM unlabeled 5-HT. This inhibition is not competitive, but rather is due to the prevention of [3H]-5-HT breakdown by excess unlabeled 5-HT. Unlike genuine ligand/receptor binding, the binding of [3H]-5-HT breakdown products is essentially irreversible and does not display a tissue distribution consistent with binding to authentic 5-HT receptors. [3H]-5-HT decomposition can be eliminated by the inclusion of 0.05 to 5 mM ascorbic acid. At these concentrations ascorbic acid is not deleterious to reversible [3H]-5-HT binding. When [3H] 5-HT exposure to air occurs in the presence of brain membranes, the apparent antioxidant activity of brain membranes themselves affords protection against [3H]-5-HT degradation equal to ascorbic acid. This protection is effective below final [3H]-5-HT concentrations of 10 nM. Above 10 nM [3H]-5-HT, addition of ascorbic acid or other antioxidants is necessary to avoid the occurrence of additional low affinity (apparent Kd = 15-2000 nM) binding sites that are specific but nonetheless irreversible. When care is taken to limit [3H]-5-HT oxidation, the only reversible and saturable specific binding sites observed are of the 5-HT1 high affinity (Kd = 1-2 nM) type. Radioligand oxidation artifacts may be involved in previous reports of low affinity (Kd = 15-250 nM) [3H]-5-HT binding sites in brain membrane preparations.
Screening of urine cultures by three automated systems.
A study was conducted to compare three automated systems and the Gram stain for their ability to detect significant bacteriuria. A total of 1,000 urine specimens were evaluated by Autobac MTS (General Diagnostics), Auto Microbic system (AMS; Vitek Systems, Inc.), and MS-2 (Abbott Laboratories) and compared with a semiquantitative culture plate method. Two hundred thirty-nine (23.9%) specimens had colony counts of >10(5) colony-forming units (CFU)/ml by the culture plate method (group I). Of these, 204 (85.3%) were positive by Autobac, 198 (82.8%) were positive by AMS, and 179 (74.9%) were positive by MS-2. When pure cultures of diphtheroids, lactobacilli, and viridans streptococci not group D were considered contaminants and therefore excluded, there were 118 specimens containing pure cultures of probable pathogens. The percentage of significant isolates detected was 97.4% (115 of 118) by the Gram stain, 96.6% (114 of 118) by Autobac, and 95.8% (113 of 118) by AMS and MS-2. The average detection time for all organisms was 2.2 h by Autobac, 6.1 h by AMS, and 1.8 h by MS-2; therefore, all three methods were more rapid than the 18- to 24-h standard plate culture method. One hundred sixty-one (16.1%) specimens had colony counts of 10(4) to 10(5) CFU/ml (group II). The probable pathogens not detected in this group were two (1.2%) by Autobac and MS-2 and three by AMS (1.9%). The average detection time for group II was 4.2 h by Autobac, 8.9 h by AMS, and 3.8 h by MS-2. Six hundred specimens had colony counts of <10(4) CFU/ml. Of these, 188 had colony counts equal to 10(3) and <10(4) CFU/ml (group III), and 412 cultures were below detectable limits by the standard plate method (group IV). Less than 37 and 15% of groups III and IV, respectively, were detected by instrumentation. Average detection times for groups III and IV were 4.6 and 4.8 h by Autobac, 10 and 11 h by AMS, and 4.2 and 4.4 h by MS-2. The cost of supplies and technical time with Gram stain, Autobac, and MS-2, when used as screening methods, were comparable and considerably less expensive than for the reference method. The AMS was the least expensive system when the cost for identifying probable pathogens was included.
A respirometer for use in the field for the measurement of oxygen consumption. 'The Miser', a miniature, indicating and sampling electronic respirometer.
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The cost of work on a vehicle assembly line.
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