Biomedical subjects

C C Yu

Publications and source records attributed to C C Yu.

At least 37 records · Page 2Linked to original sources

PubMed1999

Genetic manipulation to identify limiting steps and develop strategies for high-level expression of penicillin acylase in Escherichia coli.

We have identified the bottleneck steps limiting expression of penicillin acylase (PAC) through comparison of the expression performance for various PAC-expression vectors constructed by genetically modulating the efficiencies of transcription and/or translation of the pac gene. To our knowledge, this is the first report demonstrating that expression of PAC could be limited by various steps, such as transcription, translation, and post-translational steps (i.e. translocation and periplasmic processing), depending on the host/vector systems. Results also indicate that the structure of the wild-type pac gene might not be optimal for direct use in production of PAC using recombinant DNA technology. To improve the gene expression, transcription was enhanced by manipulating certain DNA bases in the pac regulatory region, whereas translation was enhanced by enlarging the spacing between the ribosome binding site and the ATG initiation codon to increase the initiation efficiency. The information is useful in terms of developing genetic strategies for overproduction of recombinant PAC in Escherichia coli.

Cloning, Molecular↗

PubMed1999

Manipulation of carbon assimilation with respect to expression of the pac gene for improving production of penicillin acylase in Escherichia coli.

A strategy of genetically manipulating carbon assimilation with respect to expression of the pac gene was employed for overproduction of recombinant penicillin acylase (PAC). Two expression plasmids of pCLL2902 and pCLL3201, which contain the pac coding region but differ in the pac regulatory region, were constructed for the production experiments. Expression of the pac gene was subjected to phenyl acetic acid (PAA-) induction and glucose catabolite repression for pCLL3201, whereas it was subjected to neither of the two transcriptional regulations for pCLL2902. The specific PAC activity for strains harboring pCLL2902 was significantly higher than that for strains harboring pCLL3201 due to an improved transcription efficiency. In addition, no inclusion bodies were observed upon production of PAC using the current expression systems. The results suggest that using the native pac promoter instead of a strong promoter such as tac for regulation is a feasible approach for production of PAC. The impact of the current expression systems is also significant from a process viewpoint since, using strains harboring pCLL2902, not only could glucose replace PAA as a carbon source of Escherichia coli cultures for production of PAC but also the volumetric PAC activity was highly improved.

Cloning, Molecular↗

PubMed1999

Chelation therapy for patients with elevated body lead burden and progressive renal insufficiency. A randomized, controlled trial.

BACKGROUND: Nephropathy is known to occur in persons exposed to high levels of lead, but the question of whether long-term exposure to low levels of environmental lead is associated with impaired renal function remains controversial. OBJECTIVE: To examine whether chelation therapy slows the progression of renal insufficiency in patients with mildly elevated body lead burden. DESIGN: Randomized, controlled trial. SETTING: Academic medical center in Taiwan. PATIENTS: 32 patients with chronic renal insufficiency (serum creatinine level > 132.6 micromol/L [1.5 mg/dL] and < 353.8 micromol/L [4.0 mg/dL]), mildly elevated body lead burden (> 0.72 micromol [150 microg] of lead per 72-hour urine collection and < 2.90 micromol [600 microg] of lead per 72-hour urine collection [EDTA mobilization tests]), and no history of heavy lead exposure. INTERVENTION: The treatment group received 2 months of chelation therapy; the control group received no therapy. MEASUREMENTS: The reciprocal of serum creatinine (1/Cr) was used as an index of progressive renal insufficiency. RESULTS: Rates of progression of renal insufficiency were similar in the treatment group and the control group during a 12-month baseline observation period (1/Cr, 0.000054 L/micromol per month compared with 0.000046 L/micromol per month; P > 0.2). After the 2-month treatment period, improvement in renal function was greater in the treatment group than in the control group. In the 12 months after the treatment period, renal insufficiency progressed more slowly in the treatment group than in the control group (1/Cr, 0.000033 +/- 0.00038 L/micromol per month compared with 0.000045 +/- 0.000038 L/micromol per month; P = 0.0030). CONCLUSION: Chelation therapy seems to slow the progression of renal insufficiency in patients with mildly elevated body lead burden. This implies that long-term exposure to low levels of environmental lead may be associated with impaired renal function in patients with chronic renal disease.

Adult↗

PubMed1999

Risk of gonadoblastoma in female patients with Y chromosome abnormalities and dysgenetic gonads.

We report two female patients with gonadal dysgenesis and sex chromosome mosaicism involving the Y chromosome. Conventional karyotyping was supplemented with fluorescent in situ hybridisation techniques in order to confirm the presence of Y chromosomes. One patient is a phenotypic female with karyotype 45,X/46,X,idic(Y)(q11.2). She underwent a laparoscopic gonadectomy at which streak ovaries without evidence of gonadoblastoma were removed. The second patient presented as a virilised female with karyotype 45,X/47,XYY. At laparoscopy, she was found to have mixed gonadal dysgenesis with a gonadoblastoma in situ. We recommend early gonadectomy in female children presenting with gonadal dysgenesis and the presence of a Y chromosome although once the gonadoblastoma locus on Y chromosome gene has been cloned it may be possible to identify those patients who have a low risk of developing gonadoblastoma.

Child, Preschool↗

PubMed1999

Pre-dialysis glycemic control is an independent predictor of mortality in type II diabetic patients on continuous ambulatory peritoneal dialysis.

OBJECTIVE: To evaluate the impact of pre-dialysis glycemic control on clinical outcomes for type II diabetic patients on continuous ambulatory peritoneal dialysis (CAPD). MATERIALS AND METHODS: One hundred and one type II diabetic patients receiving CAPD for at least 3 months were enrolled in a single institute. The patients were classified into two groups according to status of glycemic control. In the good glycemic control group, more than 50% of blood glucose determinations were within 3.3-11.0 mmol/L and glycosylated hemoglobin (HbA1C) levels were within 5%-10% at all times. In the poor glycemic control group, less than 50% of blood glucose determinations were within 3.3-11.0 mmol/L, or HbA1C levels were above 10% at least 6 months before peritoneal dialysis was started. In addition to glycemic control status, pre-dialysis serum albumin, cholesterol levels, residual renal function, peritoneal membrane function, and modes of glycemic control were also recorded. RESULTS: The patients with good glycemic control had significantly better survival than those with poor glycemic control (p < 0.01). There was no significant difference in pre-dialysis morbidity between two groups. No significant differences were observed in patient survival between patients with serum albumin above 30 g/L and those with serum albumin under 30 g/L; between those with cholesterol levels above or below 5.2 mmol/L; and between those with different peritoneal membrane solute transport characteristics as evaluated by a peritoneal equilibration test (PET). Furthermore, there was no significant difference in survival between patients who controlled blood sugar by diet and those who controlled it by insulin. Cardiovascular disease and infection are the major causes of death in both groups. Although good glycemic control predicts better survival, it does not change the pattern of mortality in diabetic patients maintained on CAPD. CONCLUSIONS: Glycemic control before starting dialysis is a predictor of survival for type II diabetic patients on CAPD. Patients with poor glycemic control predialysis are associated with increased morbidity and shortened survival.

Blood Glucose↗

PubMed1999

Local supplementation of ketoprofen reduces the incidence of low back pain after lumbar epidural anesthesia.

BACKGROUND: Backache is a common postoperative complaint after lumbar epidural anesthesia. Our study was aimed to compare the effect of the local addition of ketoprofen on the incidence of postepidural backache after nonobstetric surgery. METHODS: One thousand patients scheduled for hemorrhoidectomy were randomly given 4 ml of 1% lidocaine with ketoprofen 1:400 (ketoprofen group) or without ketoprofen (control group) for local skin infiltration prior to epidural needle placement. Each of them received a single epidural injection of 25 ml 2% lidocaine with epinephrine 1:200000, and was interviewed 24, 48, and 72 hours postoperatively using a standard visual analog scale (VAS) for evaluation of postepidural backache. RESULTS: The incidence of postepidural backache in the ketoprofen-group patients for the 3 days was 9.8%, 4.6%, and 1.8%, all rates which were significantly less than those observed in the control-group patients (22.8%, 17.4%, and 9.2%, p < 0.001). There was also a significant association between postepidural backache and multiple attempts at epidural needle insertion. CONCLUSION: In summary, the local addition of ketoprofen reduced the incidence and severity of postepidural backache.

Adult↗

PubMed1998

Differential usage of VH gene segments is mediated by cis elements.

Ig diversity is generated in large part by the combinatorial joining of the Ig gene segments, VH, D, and JH, that together encode the variable domain of Ig. The final Ig repertoire, however, not only reflects the diversity generated through V(D)J recombinatorial joining, but it is also the product of a number of developmental restraints and selections. To avoid such restrictions and assess the recombination potential of individual Ig gene segments, we constructed Ig heavy (H) chain microlocus plasmids, each of which contain germline coding, recombination signal, and flanking sequences of a VH, D, and JH gene segment. These plasmids allow us to assess the recombination potential of the segments in the context of their natural flanking DNA sequences, but in the absence of any higher order chromatin structure or cellular selection. We found that the frequency and extent of deletions and additions at the recombination breakpoints are similar to those observed at rearranged Ig H chain loci in intact animals. The relative frequencies of the types of rearrangements--VD-J, V-DJ, VinvD-J (invD = inverted D), and VDJ--however, differ strongly. Moreover, V81x, the most used VH gene segment in intact mice, also is overused in this plasmid assay, 15 to 30 times that of another VH segment. This result indicates that the overuse of V81x in the early B cell repertoire can be a consequence of its DNA sequence and not of cellular activities.

Animals↗

PubMed1998

Aminoguanidine reduces glomerular inducible nitric oxide synthase (iNOS) and transforming growth factor-beta 1 (TGF-beta1) mRNA expression and diminishes glomerulosclerosis in NZB/W F1 mice.

Over-expression of iNOS is implicated in the pathogenesis of glomerulonephritis in animal models of systemic lupus erythematosus. The aim of this study was to evaluate the effect of aminoguanidine, a selective inhibitor of iNOS, for the protection from glomerulosclerosis in NZB/W F1 mice. Female NZB/W F1 mice (n = 8) were treated with aminoguanidine (1 g/l) in drinking water for 4 months starting at age 2 months before the onset of glomerulonephritis. Controls were age- and sex-matched mice (n = 10) without aminoguanidine treatment. By glomerular microdissection and reverse-transcription competitive polymerase chain reaction, we found that glomerular iNOS/beta-actin and TGF-beta1/beta-actin mRNA ratios were reduced 15.1% (P<0.05) and 61.3% (P<0.01), respectively, in aminoguanidine-treated mice. Aminoguanidine significantly reduced the glomerular iNOS staining, urinary nitrite production and degree of glomerulosclerosis. In addition, the glomerular volume and mean glomerular cell number were reduced 33.2% (P<0.01) and 32.8% (P<0.01), respectively. Likewise, the urinary proteinuria was also significantly reduced by aminoguanidine. These results indicate that administration of aminoguanidine may reduce the progression of glomerulosclerosis in NZB/W F1 mice, possibly through inhibition of glomerular nitric oxide production.

Animals↗

PubMed1998

Multifocal retroperitoneal malignant fibrous histiocytoma: a case report.

This report concerns a 67-year-old male with malignant fibrous histiocytoma arising from the psoas muscle and perirenal soft tissue. The tumor was considered a mesenchymal neoplasm. These are generally clinically and radiologically indistinguishable from other retroperitoneal tumors. This patient received en bloc resection of the retroperitoneal tumor and radical nephrectomy without adjuvant therapy. He underwent excision of a retroperitoneal cystic mass complicated with lymph leakage one year postoperatively. Discharged in a stable condition after one week of total parenteral nutrition, the patient remains disease-free 16 months postoperatively.

Aged↗

PubMed1997

Poor pre-dialysis glycaemic control is a predictor of mortality in type II diabetic patients on maintenance haemodialysis.

BACKGROUND: In type II diabetic patients, a better glycaemic control has been reported to slow down the progression of nephropathy. The effect of pre-dialysis glycaemic control on the long term prognosis in type II diabetics on haemodialysis is still uncertain. The purpose of this study is to evaluate the effect of glycaemic control before starting maintenance haemodialysis on the clinical outcome in type II diabetic haemodialysis patients. METHODS: One hundred and thirty-seven type II diabetics receiving regular haemodialysis in a single university hospital were enrolled. The patients were classified as either good or poor glycaemic control group according to their glycaemic control within 6 months before starting haemodialysis. Serum albumin, haematocrit, cholesterol, triglyceride, residual renal function, diabetic complications, and patient survival were analysed in both groups. RESULTS: There was no significant difference in age, gender, predialysis albumin level, cholesterol level, triglyceride level, and residual renal function between the two groups. The 1-year (94.5% vs 80.0%), 3-year (82.9% vs 58.1%), and 5-year (75.8% vs 21.8%) cumulative survival rates were lower in the poor glycaemic control group than in the good glycaemic control group (P < 0.001). The poor glycaemic control group also had more cardiovascular morbidity during the period of dialysis (P < 0.001). The increase in cardiovascular complications also accounted for the increased mortality during the course of haemodialysis. CONCLUSIONS: We conclude that poor glycaemic control before starting dialysis is a strong predictor of cardiovascular morbidity and survival for type II diabetics on haemodialysis. These results imply that better glycaemic control before dialysis might be important in improving the long-term prognosis in type II diabetics on haemodialysis.

Aged↗

PubMed1997

Radiolabelling leukocytes with 99Tcm-stannous chloride colloid for the detection of inflammatory lesions.

Freshly prepared 99Tcm-stannous chloride colloid (99Tcm-SCC) was used to label human leukocytes. The radiolabelled leukocytes were then injected intravenously into rats bearing carrageenan-induced inflammation in their hindlimbs. Scintigraphic imaging (n = 3) and biodistribution studies (n = 4) 4 h post-injection were performed. The ratio of radioactivity (cpm/pixel) accumulated in the inflammation site to that in the corresponding area of the contralateral limb was 2.9 +/- 0.8, as calculated by region-of-interest analyses of the planar images. The distribution of radioactivity in the dissected tissue showed that the ratio of radioactivity (cpm/g) of infected tissue to that of a normal sample obtained from the contralateral limb was 2.6 +/- 0.5. The biodistribution study of dissected organs showed high uptake in liver (58.9 +/- 8.2%), spleen (4.3 +/- 1.8%) and lungs (6.3 +/- 2.4%). The results of this preliminary study indicate that 99Tcm-SCC can be used as an alternative agent for radiolabelling leukocytes for the detection of inflammatory lesions.

Animals↗

PubMed1996

B and T cells are not required for the viable motheaten phenotype.

Hematopoietic cell phosphatase (HCP), encoded by the hcph gene, (also called PTP1C, SHP, SH-PTP1, and PTPN6) is deficient in motheaten (me/me), and the allelic viable motheaten (me(v)/me(v)) mice. Since HCP is expressed in many cell types and protein phosphorylation is a major mechanism of regulating protein function, it is not surprising that the motheaten phenotype is pleiotropic. It is commonly thought that immune system involvement causes this disease. If so, the motheaten disease ought to be alleviated when the recombination activation gene-1 (RAG-1) is disrupted because there will be no V(D)J rearrangement and thus impaired development of B and T cells. We bred homozygous, double-mutant me(v)/me(v) x RAG 1 -/- mice and found that, in fact, inflamed paws, and splenomegaly with elevated myelopoiesis. Thus, except for autoantibodies, the motheaten phenotype does not depend on the presence of B and T cells. This observation cautions the use of motheaten mice as a model of autoimmune disease.

Animals↗

PubMed1996

Peritoneal nitric oxide is a marker of peritonitis in patients on continuous ambulatory peritoneal dialysis.

Nitric oxide plays an important role in mediating the inflammatory process. The aim of this study was to evaluate if nitric oxide production was increased during peritonitis in patients receiving continuous ambulatory peritoneal dialysis (CAPD), and the association with the prognosis. The study population comprised 21 patients with 22 episodes of peritonitis. Fifteen patients without peritonitis were controls. Nitrate was measured by HPLC and nitrite by the Griess method, to reflect nitric oxide production. Peritoneal dialysate effluent and plasma were collected from six patients during peritonitis and 1 week after treatment to study changes in dialysate:plasma ratio. In 15 patients, nitrite was measured during peritonitis and every 3 days for 2 weeks or until normalized for evolutional changes. The dialysate:plasma ratios of nitrate and nitrite during peritonitis were reduced 26% and 41.5%, respectively, after 1 week of treatment, indicating the peritoneal production of nitric oxide during peritonitis. In the evolutional study, a 5.1-fold increase of peak nitrite levels in bacterial peritonitis (n = 13) and a 2.5-fold increase in fungal peritonitis (n = 3) were observed compared to controls. Nitrite gradually declined to control levels (9.3 +/- 7.2 days) after effective antibiotic treatment, but took longer than to normalize leukocyte count in the peritoneal dialysate effluent (3.9 +/- 1.9 days). In four patients with refractory peritonitis (Candida infection in three, Acinetobacter infection in one), the nitrite levels remained elevated 2-fold despite treatment, and the catheters were removed. It is concluded that nitrite levels in peritoneal dialysate effluent may serve as a marker to assess treatment efficacy in CAPD patients with peritonitis.

Acinetobacter Infections↗

PubMed1996

Propofol inhibits cardiac L-type calcium current in guinea pig ventricular myocytes.

BACKGROUND: Propofol may exert negative inotropic and chronotropic actions in the heart. Single-channel studies show that propofol affects the kinetics of opening and closing of cardiac L-type calcium channels (ICa(L)) without altering channel conductance. The aim of this study was to investigate the mechanisms of depressant effects of propofol on cardiac whole-cell ICa(L). METHODS: Single ventricular myocytes were freshly dissciated from guinea pig hearts using enzymatic isolation. One-suction electrode voltage-clamp technique (whole-cell mode) was used. LCa(L) was separated from other contaminated ionic currents. Propofol was applied in the commercial 10% Intralipid emulsion formula (Zeneca, UK). RESULTS: In isolated cardiomyocytes, propofol significantly inhibited whole-cell ICa(L) in a concentration-dependent manner (K D = 52.0 microM; Hill coefficient = 1.3). The solvent (Intralipid) did not affect ICa(L). Propofol decreased ICa(L) at all potentials tested along the voltage axis and reduced the slope conductance. The threshold potential for activation and the peak potential of the current-voltage relationship were not changed by propofol. The steady-state activation curves overlapped in the absence and the presence of 56 microM propofol. In contrast, the steady-state inactivation curve was shifted in the hyperpolarizing direction. The time course of the recovery from inactivation was delayed by 56 microM propofol. The blocking action on ICa(L) of propofol shows marked resting block and use-dependent block. Propofol caused more pronounced inhibition at a higher stimulation frequency. The effect of propofol on the inactivation process was even more clear on ICa(L). CONCLUSIONS: The authors conclude tha propofol, at supratherapeutic concentrations, inhibits cardiac ICa(L). This inhibition is mainly due to a shift of inactivation curve and a reduction in slope conductance.

Anesthetics, Intravenous↗

PubMed1996

Functional and urodynamic characteristics of Camey II ileal neobladder.

The object of this study is to evaluate the functional and urodynamic characteristics of 16 patients who had undergone the Camey II orthotopic bladder replacement after radical cystoprostatectomy. Questionnaires regarding the voiding pattern and urinary continence were answered by 14 patients. Daytime continence was achieved in 13 of 14 patients (93%) at a mean interval of 3 months postoperatively. Eight patients (62%) attained their nighttime continence at an average interval of 10 months. Six of these 8 patients had to void to keep dry at night. Urodynamic studies were completed in 13 patients at an average of 11 months (range 6-23) postoperatively. Patients with nighttime continence had a significantly higher cystometric filling capacity (323 vs. 196 ml, p < 0.001), lower basal pouch pressure (24.5 vs. 35.2 cm water, p = 0.04), lower maximal voiding pressure (62.1 vs. 88.0 cm water, p = 0.01) and higher maximal urethral closure pressure (65.5 vs. 44.0 cm water, p = 0.03). There is no significant difference among the parameters of the age at operation, the amount of residual urine and the functional profile length between these two groups of patients. The antireflux procedure was successful in 11 of 12 patients (92%). We conclude that the Camey II operation could fulfill all the criteria of ideal bladder substitution with adequate volume, low resting pressure, satisfactory continence rate and antireflux characteristic.

Cystectomy↗

PubMed1995

Characterization of the 3' untranslated region of the mouse homeobox gene HoxB5.

The mouse pre-B cell line, 70Z/3, expresses multiple transcripts of the homeobox gene, HoxB5. We show here that this heterogeneity is due, at least in part, to the usage of alternative poly-A addition sites in the 3' untranslated region (UT) of the primary HoxB5 transcript. Furthermore, upon analysis of the subcellular distribution of the different HoxB5 RNA species, we found that the transcripts are present mainly in the nucleus, with two-to-five-fold less RNA present in the cytoplasm. These studies suggest that multiple post-transcriptional regulatory mechanisms are involved in the expression of HoxB5 RNA.

Animals↗

PubMed1995

Reduction of transiently expressed acetylcholinesterase activity in developing thalamocortical projections does not affect the mature pattern of basal forebrain projections to visual cortex.

Experiments tested the hypothesis that acetylcholinesterase (AChE) activity, expressed transiently in developing thalamocortical projections, serves to limit the growth of basal forebrain cholinergic projections into thalamocortical recipient zones. Newborn rats were subjected to enucleation, a procedure that eliminates transient AChE activity in developing visual cortex. After 3-8 weeks survival, AChE histochemical techniques revealed no alteration in the pattern of AChE positive basal forebrain axons in visual cortex. These data indicate that transient AChE activity in developing sensory cortex does not limit ingrowth of basal forebrain cholinergic axons.

Acetylcholinesterase↗

PubMed1995

Electropharmacological actions of propofol on calcium current in guinea-pig ventricular myocytes.

Propofol, a widely-used intravenous anesthetic, causes bradycardia, depression in contractility and hypotension. The cellular mechanisms responsible for these cardiac toxicity remain unclear. In this study, we examined the cellular electropharmacological actions of propofol on calcium current in guinea-pig heart. Single ventricular myocytes were freshly isolated from guinea-pig using modified enzymatic method. Whole-cell voltage-clamp technique was applied with one suction pipette. Transmembrane L-type calcium current (ICa(L)) was separated from other ionic currents by voltage-control, ionic channel blockers and ion substitution methods. Our results show that propofol decreased ICa(L) in a concentration-dependent manner (KD = 54.2 microM). Slope conductance of current-voltage relation was decreased by 56 microM propofol. Propofol did not affect the steady-state activation curve, but shifted the inactivation curve to hyperpolarizing direction. Recovery from inactivation was slowed down by propofol. Marked resting block and use-dependent block were noted. In conclusion, our results indicate that propofol inhibits cardiac L-type calcium current mainly by shifting inactivation curve and retarding the recovery from inactivation.

Anesthetics, Intravenous↗