Biomedical subjects

H C Lee

Publications and source records attributed to H C Lee.

At least 37 records · Page 2Linked to original sources

PubMed2003

Quantitative polymerase chain reaction assay for serum hepatitis B virus DNA as a predictive factor for post-treatment relapse after lamivudine induced hepatitis B e antigen loss or seroconversion.

BACKGROUND AND AIMS: Lamivudine induces favourable virological and biochemical responses but post-treatment relapses are frequent, even in patients with hepatitis B e antigen (HBeAg) loss or seroconversion. The aim of this study was to determine whether extended lamivudine therapy for up to 12 months after HBeAg loss/seroconversion could decrease the risk of post-treatment virological relapse. In addition, we monitored serum hepatitis B virus (HBV) DNA levels using a quantitative polymerase chain reaction (PCR) assay during extended lamivudine therapy and analysed predictive factors for post-treatment relapse. PATIENTS AND METHODS: A total of 49 patients who exhibited HBeAg loss/seroconversion during lamivudine therapy received extended lamivudine therapy for six months (group 1, n=23) or 12 months (group 2, n=26) after HBeAg loss/seroconversion. Serum HBV DNA levels were quantified by a PCR based assay at the time of HBeAg loss/seroconversion, and at cessation of therapy. RESULTS: Post-treatment virological relapse rates at two years were 59% in group 1 and 50% in group 2. Age, time interval to HBeAg loss/seroconversion, and serum HBV DNA levels at the time of cessation of therapy were independent predictive factors for post-treatment relapse. The post-treatment relapse rate was 37% at two years in patients with serum HBV DNA levels of <200 copies/ml but 73% in those with > or =10(3) copies/ml. CONCLUSIONS: Extended lamivudine therapy for up to 12 months did not decrease the rate of post-treatment virological relapse, and monitoring of serum HBV DNA by a quantitative PCR method was helpful in predicting post-treatment relapse.

Adult↗

PubMed2003

Fixation of distal radius fractures using AO titanium volar distal radius plate.

This study is to assess the effectiveness and outcome of the AO titanium volar distal radius plate (Synthes) in the treatment of peri-articular volar rim fractures of the distal radius. It was conducted on 22 patients with distal radius fractures who underwent open reduction, internal fixation using the AO titanium volar distal radius plate between July 1998 and December 1999 at the Changi General Hospital. The radiographs of the patients were analysed upon fracture union and assessment of wrist function was done using Gartland and Werley criteria. There were four extra-articular AO Type A2(1) and A3(3): the remaining 18 intra-articular fractures consisted of AO B3(2), AO C1(11), AO C2(2) and AO C3(3). The average follow-up period was 12.6 months (range 7-23). Radiological review showed bone healing in 21 patients (95.5%) and good articular congruity for all intra-articular fractures with less than 2 mm step-off. Three patients defaulted follow-up. Complications were few with one wound infection, one tendon rupture and three neuropraxia of the superficial radial nerve. Wrist function was excellent in three patients, good in 12 and fair in four. The AO titanium plate with its distal buttressing ability is an effective treatment modality in patients with distal radius fractures involving the peri-articular volar rim.

Adult↗

PubMed2003

Gluteal compartment syndrome misdiagnosed as deep vein thrombosis.

Gluteal compartment syndrome usually occurs secondary to prolonged immobility and recumbency following alcohol and drug abuse. The resultant pain and swelling in the lower limb may be misdiagnosed as deep vein thrombosis. Once compartment syndrome is diagnosed, urgent decompression fasciotomy is required. The outcome is poor if the diagnosis is missed or delayed. We report such a case.

Buttocks↗

PubMed2003

Open reduction and internal fixation of fractures of the acetabulum--local experience.

INTRODUCTION: It is now widely accepted that open reduction and internal fixation of displaced acetabular fractures should be the standard of care. This paper reports a case series of acetabular fracture fixation performed at the Changi General Hospital by a single trauma surgeon. PATIENTS AND METHODS: A retrospective study was conducted of 15 consecutive cases of displaced acetabular fracture fixation between February 1996 and September 1999. Outcome was assessed radiologically and functionally with the use of a hip scoring system used by Matta. RESULTS: The patients' age had a mean of 34.9 years. All fractures were a result of high energy trauma. The median duration to operation upon admission was eight days. The mean hospital stay was 24.9 days and the mean medical hospitalisation leave was 159 days. Bony union was achieved in all patients. Two patients (13.3%) had a residual displacement of 1 mm. Four patients (26.6%) had a residual displacement of 2 mm. Of these four patients with 2 mm displacement, two eventually developed osteoarthritis. Subsequently, one of the two with OA required revision to a total hip arthroplasty two years post fracture. Other complications include 1 (6%) wound infection and 2 (13%) deep vein thrombosis. There were no complications of heterotopic ossification or sciatic nerve injury. Functional scores with a minimum follow up of one year and a mean of 22.6 months follow-up were excellent in 13.3%, good in 66.7%, fair in 13.3% and poor in 6.7%. CONCLUSION: The number of cases in this paper is insufficient to produce any statisticallly significant outcome predictors but accuracy of reduction is an important factor. A good to excellent result was attained in 80% of the patients which confirms that open reduction and internal fixation is the treatment of choice for displaced and acetabular fractures.

Acetabulum↗

PubMed2002

Geometric and statistical properties of the mean-field hydrophobic-polar model, the large-small model, and real protein sequences.

Lattice models, for their coarse-grained nature, are best suited for the study of the "designability problem," the phenomenon in which most of the about 16 000 proteins of known structure have their native conformations concentrated in a relatively small number of about 500 topological classes of conformations. Here it is shown that on a lattice the most highly designable simulated protein structures are those that have the largest number of surface-core switchbacks. A combination of physical, mathematical, and biological reasons that causes the phenomenon is given. By comparing the most foldable model peptides with protein sequences in the Protein Data Bank, it is shown that whereas different models may yield similar designabilities, predicted foldable peptides will simulate natural proteins only when the model incorporates the correct physics and biology, in this case if the main folding force arises from the differing hydrophobicity of the residues, but does not originate, say, from the steric hindrance effect caused by the differing sizes of the residues.

Amino Acid Sequence↗

PubMed2002

(AC)(n) polymorphism of aldose reductase gene and diabetic microvascular complications in type 2 diabetes mellitus.

Recent studies suggest that the gene encoding aldose reductase, the enzyme that converts glucose to sorbitol, may confer susceptibility to microvascular disease. The aim of this study therefore, was to investigate the relationship between the aldose reductase gene and type 2 diabetic microvascular complications such as diabetic nephropathy and retinopathy. DNA from 127 Korean patients with type 2 diabetes was typed for an (AC)(n) dinucleotide repeat polymorphic marker at the 5'-end of the aldose reductase gene using polymerase chain reaction. No significant difference in the frequency of the putative risk allele Z-2 was found in patients of nephropathy and retinopathy groups compared with the uncomplicated group (32.2, 34.1 vs. 25.1%, respectively, P>0.05). Similarly, no difference was found in the frequency of the putative protective allele Z+2 among any of the study groups. In conclusion, the results of the study in Korean type 2 diabetic patients do not support the hypothesis that polymorphism at the 5' end of the aldose reductase gene contributes to the susceptibility to diabetic microvascular complications.

Aged↗

PubMed2002

Relationship between changes in interferon-gamma production by peripheral blood T cells and changes in peak expiratory flow rate in patients with chronic stable asthma.

BACKGROUND: Cytokines production by T helper lymphocytes (Th cells), which orchestrate the interplay of the different cells involved in airway inflammation of asthma, may be reflected in peripheral blood. Some studies have suggested that the Th cell cytokines by peripheral blood T cells correlate with asthma severity. OBJECTIVE: To investigate the relationship between changes in IFN-gamma production by peripheral blood T cells and changes in lung function in chronic stable asthmatics. METHODS: Sixteen patients with chronic stable moderate asthma aged 35-65 years (nine women) were recruited. Morning and evening peak expiratory flow rates (PEFR) monitoring and blood sampling for peripheral blood T cell culture, total IgE and blood eosinophils were performed at baseline and week 12. Levels of IFN-gamma, IL-4 and IL-5 in culture supernatants of peripheral blood T cell were determined by using enzyme-linked immunosorbent assay (ELISA) kits. RESULTS: Patients with increased IFN-gamma changes from baseline showed significantly increased changes in morning (P = 0.02) and evening (P < 0.05) PEFR compared with those with decreased IFN-gamma changes. The changes in IFN-gamma production and IFN-gamma: IL-4 ratio significantly correlated with the changes in morning PEFR (Rs = 0.59, P < 0.02; Rs = 0.63, P < 0.01, respectively) and tended to correlate with the changes in evening PEFR (Rs = 0.45, P = 0.08; Rs = 0.5, P = 0.05, respectively). The changes in IL-4 and IL-5 did not correlate with the changes in IgE and blood eosinophils, respectively. CONCLUSIONS: These findings suggest that IFN-gamma may be associated with the alteration of lung function in asthmatics and play a role in the pathophysiology of chronic stable asthma.

Adult↗

PubMed2002

Relationships of urinary phyto-oestrogen excretion to BMD in postmenopausal women.

OBJECTIVE: Phyto-oestrogens are plant compounds with both oestrogenic and anti-oestrogenic properties. However, it is not known whether natural phyto-oestrogens are beneficial or harmful in human osteoporosis. This study was performed to investigate the relationships between urinary phyto-oestrogens and bone mineral density (BMD) in Korean postmenopausal women. DESIGN: The subjects were classified into osteoporotic, osteopenic and normal groups according to their BMD as defined by WHO criteria. We compared the urinary phyto-oestrogens of each group and studied whether urinary phyto-oestrogens correlate with BMD. PATIENTS: The subjects were 75 Korean postmenopausal women with ages ranging from 52 to 65 years (mean 58 +/- 1.1 years). Mean number of years after menopause was 7.3 +/- 1.3. MEASUREMENTS: Twenty-four-hour urinary phyto-oestrogens were measured by gas chromatography-mass spectrometry (GCMS) and BMD by dual-energy X-ray absorptiometry (DXA, Lunar Expert-XL, Lunar Co., WI, USA). RESULTS: In Korean postmenopausal women, urinary enterolactone (1.46 +/- 1.11 micromol/day) was lower and daidzein (2.59 +/- 3.25 micromol/day) was higher than in western women, and both levels were comparable to those in Japanese women. Daily urinary excretion of genistein and apigenin were 1.09 +/- 0.912 and 0.48 +/- 0.40 micromol/day, respectively. In subjects with osteoporosis, urinary enterolactone was lower (P < 0.05) but apigenin was significantly higher (P < 0.05) than in the controls. BMD of L2-L4 correlated positively with urinary enterolactone (r = 0.388, P < 0.01), and BMD of the femoral neck and Ward's triangle correlated positively with urinary enterolactone (r = 0.271, P < 0.05 and r = 0.322, P < 0.05) but negatively with apigenin (r = -0.412, P < 0.01 and r = -0.395, P < 0.01). By multiple stepwise regression, the variables associated with spinal BMD were age, the amount of urinary apigenin and body mass index (BMI). The variables associated with femoral neck BMD were age and urinary apigenin. CONCLUSIONS: From these results, we conclude that urinary phyto-oestrogens, especially enterolactone and apigenin, are related to BMD in Korean postmenopausal women. Our results also suggest the possibility that phyto-oestrogens have differential effects on bone density. Further studies are needed to clarify the exact biological roles of phyto-oestrogenic components on bone metabolism.

4-Butyrolactone↗

PubMed2002

Clinical characteristics, GAD antibody (GADA) and change of C-peptide in Korean young age of onset diabetic patients.

AIMS: To investigate the association of clinical and immunological markers with diabetes classification in newly diagnosed young diabetic patients at disease onset. METHODS: Eighty-two diabetic patients recruited within 1 year of onset (mean age 23.0 +/- 7.1, M:F = 46:36) were divided into three groups, namely: a low fasting C-peptide (FC) level at baseline group (the low FC group (n = 14, FC < 0.18 nmol/l)), an intermediate FC group (n = 29, 0.18 nmol/l < or = FC < 0.37 nmol/l), and a high FC group (n = 39, 0.37 nmol/l < or = FC). Patients were reclassified at follow-up (mean follow-up period 3.7 +/- 1.4 years) in the same manner as described above into low FC group (n = 31), intermediate FC group (n = 20), and high FC group (n = 31). The clinical characteristics and prevalence of GADA were compared. RESULTS: Patients in the high FC group at baseline had a higher body mass index (BMI), a higher frequency of a family history of diabetes, a higher meal-stimulated C-peptide increment, a lower frequency of ketonuria, a lower frequency of history of diabetic ketoacidosis, and a lower frequency of insulin therapy at diagnosis than those in the low and intermediate FC groups at baseline. Insulin secretory capacity, which was represented by fasting C-peptide, was affected by BMI at diagnosis and the presence of GADA. All the patients of the low FC group on follow-up were finally classified as having Type 1 diabetes; moreover, the factors that determined the type of diabetes were lower BMI at onset, GADA positivity, insulin therapy, lower fasting C-peptide level and lower meal-stimulated C-peptide increment at initial admission. CONCLUSIONS: Our study suggests that follow-up involving C-peptide and GADA measurements in combination with clinical characteristics is useful for discriminating between the types of diabetes in these groups.

Adolescent↗

PubMed2002

Does race protect an oriental population from developing lipodystrophy in HIV-infected individuals on HAART?

OBJECTIVES: Lipodystrophy, hyperlipidaemia and hyperinsulinaemia are common metabolic complications of highly active antiretroviral therapy (HAART) in human immunodeficiency virus (HIV)-infected Caucasians. We questioned whether such complications also occur in other races. METHODS: A cross-sectional analysis was performed in an outpatient clinic of a university teaching hospital with 156 Koreans, divided into HIV-infected subjects receiving HAART (n=57, group 1), HAART-naïve subjects (n=42, group 2), and healthy controls (n=57, group 3). Lipodystrophy was assessed by physical examination and questionnaire and body composition by dual-energy X-ray absorptiometry. Fasting triglyceride, total cholesterol, low-density (LDL) and high-density lipoprotein (HDL) cholesterol, free fatty acid (FFA), Apolipoprotein A1 (ApoA1), Apolipoprotein B (ApoB), glucose, insulin, c-peptide, leptin, cortisol, dehydroepiandrosterone (DHEA), CD4, CD8 lymphocyte counts and HIV RNA load were measured. RESULTS: Lipodystrophy was observed in only 3.5% of HAART-treated HIV-infected Koreans. No statistical difference in regional fat accumulation or peripheral fat wasting was observed between groups 1, 2 and 3. No statistical difference in triglyceride, total cholesterol, LDL cholesterol, FFA, ApoA1, ApoB, glucose, insulin, C-peptide, leptin, cortisol, and DHEA were observed between groups 1, 2 and 3. HDL cholesterol was significantly lower in HIV-infected individuals compared to controls. CONCLUSIONS: Lipodystrophy, hyperlipidaemia, and insulin resistance are rare metabolic complications of HAART in an oriental HIV-infected group of individuals. These findings warrant further race-specific metabolic complication studies in HIV-infected subjects receiving HAART.

Absorptiometry, Photon↗

PubMed2002

The effects of recombinant human parathyroid hormone, rhPTH(1-84), on bone mass in undernourished rats.

Energy intake restriction reduces bone formation both in protein-energy malnourished children and in undernourished rats, and such conditions might cause partial or irreversible bone loss. Because the use of anti-resorptive agents in this situation is seemingly limited, we examined the effect of the anabolic agent, recombinant human parathyroid hormone (rhPTH(1-84)), on bones in undernourished conditions. First, the osteopenic changes of rat bones with 40% restricted diet for 4 weeks were confirmed. Subsequently, another set of the rats were randomized into four groups and studied for 8 weeks: the freely fed group (control group); the restricted diet, then freely fed group (restriction-ad libitum group); the restricted diet-vehicle-treated group (restriction-vehicle group); and the restricted diet-PTH-treated group (restriction-PTH group). In the restriction-vehicle group, total femoral bone mineral density (BMD) was lower and femoral length was shorter than the control group by 15.4% and 8.1% respectively (P<0.05). In the restriction-ad libitum group, these parameters recovered fully to those of the control group. In the case of intermittent PTH treatment in the persistent undernourished state, the BMD of total femur caught up with those of the control or the restriction-ad libitum group. However, the femoral length remained shorter than those of the other groups. Serum osteocalcin was significantly reduced in continuously undernourished rats, whereas it was elevated in the restriction-PTH group. In conclusion, BMD of total femur was low in undernourished rats. However, it increased after re-feeding ad libitum or intermittent PTH treatment. We suggest that rhPTH(1-84) may be a possible therapeutic agent for ongoing bone loss, especially in patients in a chronically undernourished condition.

Anabolic Agents↗

PubMed2002

Physiological characteristics of Singapore national water polo team players.

BACKGROUND: The purpose of this study is to describe the physiological characteristics of members of the Singapore national water polo team. METHODS EXPERIMENTAL DESIGN: a descriptive study on the physiological characteristics of members of a winning water polo team. SETTING: the study was conducted at the Sports Medicine and Research Centre. PARTICIPANTS: 13 male players (22.5+/-7.2 yrs; 178.5+/-3.9 cm and 71.0+/-8.4 kg). MEASURES: players completed body fat measurements, a submaximal cycling test to determine aerobic fitness and all-out maximal efforts (of arm-cranking and cycling) for 10 and 30 sec duration to determine anaerobic peak power, alactic and lactic acid work capacity for the upper and lower body. RESULTS: The physical measurements were compared with data of national players of various countries. The exercise test results were compared with available published data. CONCLUSIONS: Compared with elite water polo players from other countries, the Singapore water polo players are smaller in stature with a lower body mass. Relative to the limited published data, they are shown to possess a high level of aerobic fitness and anaerobic power and capacity for short-term work.

Adolescent↗

PubMed2001

Activation of ATP-sensitive K(+) channels by epoxyeicosatrienoic acids in rat cardiac ventricular myocytes.

1. We examined the effects of epoxyeicosatrienoic acids (EETs), which are cytochrome P450 metabolites of arachidonic acid (AA), on the activities of the ATP-sensitive K(+) (K(ATP)) channels of rat cardiac myocytes, using the inside-out patch-clamp technique. 2. In the presence of 100 microM cytoplasmic ATP, the K(ATP) channel open probability (P(o)) was increased by 240 +/- 60 % with 0.1 microM 11,12-EET and by 400 +/- 54 % with 5 microM 11,12-EET (n = 5-10, P < 0.05 vs. control), whereas neither 5 microM AA nor 5 microM 11,12-dihydroxyeicosatrienoic acid (DHET), which is the epoxide hydrolysis product of 11,12-EET, had any effect on P(o). 3. The half-maximal activating concentration (EC(50)) was 18.9 +/- 2.6 nM for 11,12-EET (n = 5) and 19.1 +/- 4.8 nM for 8,9-EET (n = 5, P = n.s. vs. 11,12-EET). Furthermore, 11,12-EET failed to alter the inhibition of K(ATP) channels by glyburide. 4. Application of 11,12-EET markedly decreased the channel sensitivity to cytoplasmic ATP. The half-maximal inhibitory concentration of ATP (IC(50)) was increased from 21.2 +/- 2.0 microM at baseline to 240 +/- 60 microM with 0.1 microM 11,12-EET (n = 5, P < 0.05 vs. control) and to 780 +/- 30 microM with 5 microM 11,12-EET (n = 11, P < 0.05 vs. control). 5. Increasing the ATP concentration increased the number of kinetically distinguishable closed states, promoting prolonged closure durations. 11,12-EET antagonized the effects of ATP on the kinetics of the K(ATP) channels in a dose- and voltage-dependent manner. 11,12-EET (1 microM) reduced the apparent association rate constant of ATP to the channel by 135-fold. 6. Application of 5 microM 11,12-EET resulted in hyperpolarization of the resting membrane potential in isolated cardiac myocytes, which could be blocked by glyburide. 7. These results suggest that EETs are potent activators of the cardiac K(ATP) channels, modulating channel behaviour by reducing the channel sensitivity to ATP. Thus, EETs could be important endogenous regulators of cardiac electrical excitability.

8,11,14-Eicosatrienoic Acid↗

PubMed2001

Induction of apoptotic cell death by a p53-independent pathway in neuronal SK-N-MC cells after treatment with 2,2',5,5'-tetrachlorobiphenyl.

Apoptotic cell death is an active process, which is a critical feature of the regulated development of multicellular organisms. Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants, some of which may be neurotoxic. This study investigates the 2,2', 5,5'-tetrachlorobiphenyl (PCB 52) induced apoptosis in human neuronal SK-N-MC cells, and the role of p53 in this response. Upon treatments with PCB 52, time- and concentration-dependent inhibition of the cell viability was observed. PCB 52 also caused apoptosis, as measured by cell morphology and DNA fragmentation. The capability of PCB 52 to induce apoptosis was associated with the proteolytic cleavage of specific target proteins, such as poly(ADP-ribose) polymerase (PARP) and beta-catenin proteins, suggesting the possible involvement of caspases. In general, DNA-damaging agents induce accumulation of the tumor suppressor protein p53, leading cells to either growth arrest in G1, or apoptosis. However, our data showed that both p53 and Bcl-2 protein levels were decreased in a time-dependent manner during apoptosis after exposure to PCB 52. These results suggest that PCB 52 induced a p53-independent apoptosis in these cells.

Apoptosis↗

PubMed2001

Molecular engineering. 8. Kinetic and conformational studies of resorcin [4]arene-based C4 tetraoxatetrathiahemicarceplexes: carceroisomerism and twistomerism.

New C(4v) tetraoxatetrathiahemicarcerands and their six hemicarceplexes containing DMF, DMA, DMSO, or NMP were synthesized and characterized. Their conformations, kinetic properties, carceroisomerism, and twistomerism were studied by VT, 2D COSY, NOESY, and ROESY (1)H NMR experiments. The decomplexation rates of DMF or DMA were very slow with high activation energy barriers (73 and 104 kJ mol(-1), respectively) and the complexed guests feel more constriction than their free liquid state. The largest isomerization energy barrier of carceroisomers was 15.4 kcal mol(-1), and the isomerization energy barriers of twistomers are significantly larger than those of carceroisomers.

Journal Article↗

PubMed2001

Differential roles of cytokine receptors in the development of epidermal gamma delta T cells.

IL-7 and IL-15 play important roles in gammadelta T cell development. These receptors transmit proliferation and/or survival signals in gammadelta T cells. In addition, the IL-7R promotes recombination and transcription in the TCR gamma locus. To clarify the role of the cytokine receptors in the development of epidermal gammadelta T cells, we introduced a Vgamma3/Vdelta1 TCR transgene, derived from Thy-1+ dendritic epidermal T cells (DETC), into IL-7Ralpha-deficient mice, and we found that they partly rescued gammadelta T cells in the adult thymus but not in the spleen. Introduction of an additional Bcl-2 transgene had a minimal effect on gammadelta T cells in the adult thymus of these mice. In contrast to the adult thymus, the introduction of the Vgamma3/Vdelta1 TCR transgene into IL-7Ralpha-/- mice completely restored Vgamma3+ T cells in the fetal thymus and DETC in the adult skin. On the contrary, the same Vgamma3/Vdelta1 TCR transgene failed to rescue DETC in the skin of IL-2Rbeta-deficient mice, even with the additional Bcl-2 transgene. These results suggest that the IL-2/IL-15R, rather than the IL-7R, plays an essential role in proliferation and survival of DETC in the fetal thymus and the skin. In contrast, the IL-7R is probably essential in the induction of V-J recombination of TCRgamma genes. Thus, this study proves that IL-7R and IL-2/IL-15R serve differential functions in epidermal gammadelta T cell development.

Aging↗

PubMed2001

Dihydroxyeicosatrienoic acids are potent activators of Ca(2+)-activated K(+) channels in isolated rat coronary arterial myocytes.

1. Dihydroxyeicosatrienoic acids (DHETs), which are metabolites of arachidonic acid (AA) and epoxyeicosatrienoic acids (EETs), have been identified as highly potent endogenous vasodilators, but the mechanisms by which DHETs induce relaxation of vascular smooth muscle are unknown. Using inside-out patch clamp techniques, we examined the effects of DHETs on the large conductance Ca(2+)-activated K(+) (BK) channels in smooth muscle cells from rat small coronary arteries (150-300 microM diameter). 2. 11,12-DHET potently activated BK channels with an EC(50) of 1.87 +/- 0.57 nM (n = 5). Moreover, the three other regioisomers 5,6-, 8,9- and 14,15-DHET were equipotent with 11,12-DHET in activating BK channels. The efficacy of 11,12-DHET in opening BK channels was much greater than that of its immediate precursor 11,12-EET. In contrast, AA did not significantly affect BK channel activity. 3. The voltage dependence of BK channels was dramatically modulated by 11,12-DHET. With physiological concentrations of cytoplasmic Ca(2+) (200 nM), the voltage at which the channel open probability was half-maximal (V(1/2)) was shifted from a baseline of 115.6 +/- 6.5 mV to 95.0 +/- 10.1 mV with 5 nM 11,12-DHET, and to 60.0 +/- 8.4 mV with 50 nM 11,12-DHET. 4. 11,12-DHET also enhanced the sensitivity of BK channels to Ca(2+) but did not activate the channels in the absence of Ca(2+). 11,12-DHET (50 nM) reduced the Ca(2+) EC(50) of BK channels from a baseline of 1.02 +/- 0.07 microM to 0.42 +/- 0.11 microM. 5. Single channel kinetic analysis indicated that 11,12-DHET did not alter BK channel conductance but did reduce the first latency of BK channel openings in response to a voltage step. 11,12-DHET dose-dependently increased the open dwell times, abbreviated the closed dwell times, and decreased the transition rates from open to closed states. 6. We conclude that DHETs hyperpolarize vascular smooth muscle cells through modulation of the BK channel gating behaviour, and by enhancing the channel sensitivities to Ca(2+) and voltage. Hence, like EETs, DHETs may function as endothelium-derived hyperpolarizing factors.

8,11,14-Eicosatrienoic Acid↗

PubMed2001

Induction of germline transcription in the human TCR gamma locus by STAT5.

TCR and Ig genes are assembled by V(D)J recombination during lymphocyte development. The enhancer and the germline promoter control the accessibility of each locus for the common recombinase activity. In the mouse TCRgamma locus, STAT5 proteins activated by the IL-7R interact with consensus motifs in 5' regions of Jgamma segments and induce germline transcription. To evaluate the role of STAT5 in controlling the accessibility of the TCRgamma locus, we characterized the germline transcription of human TCRgamma genes and compared it with mouse. We first demonstrated that Jgamma-Cgamma germline transcripts are induced in a cytokine-dependent human erythroleukemia cell line. STAT consensus motifs are present in 5' regions of Jgamma1.1 and Jgamma2.1 gene segments, and activated STAT5 binds to these motifs. By using a reporter assay, we showed that the Jgamma1.1 germline promoter is transactivated by STAT5 and that mutations in any of the two STAT motifs abrogate this activity. Thus, this study demonstrates that STAT5 induces germline transcription in the TCRgamma locus of both mouse and human and suggests the possibility that this mechanism may play an essential role in controlling the TCRgamma locus accessibility. In addition, STAT motifs are conserved among 5' Jgamma germline promoters, 3' enhancers, and a locus control region-like element, HsA, in both mouse and human TCRgamma loci, indicating the possibility that IL-7R/STAT5 signaling probably controls the locus-wide accessibility through these elements.

5' Untranslated Regions↗