Biomedical subjects

Y H Yang

Publications and source records attributed to Y H Yang.

At least 55 records · Page 3Linked to original sources

PubMed2001

A double-blind, placebo-controlled, and randomized study of loratadine (Clarityne) syrup for the treatment of allergic rhinitis in children aged 3 to 12 years.

Allergic rhinitis is a common disease in children, and antihistamines are the key medication. However, traditional tablets are not convenient and lead to low compliance in young children. The aim of this double-blind, placebo-controlled, parallel, randomized study was to evaluate the effectiveness and safety of loratadine syrup for the treatment of children aged 3 to 12 years with allergic rhinitis. Sixty children with allergic rhinitis due to dust mites were enrolled. They were randomized into 2 parallel groups: one group received loratadine syrup 5 mg or 10 mg daily for 3 weeks, and the other group received placebo. The patients returned to special clinics for symptoms evaluation at day 7 and day 21, and the parents were requested to record disease severity daily. Both evaluations, physician's and parents', were recorded with a 4-point scale for 5 symptoms: sneezing, rhinorrhea, nasal congestion, nasal itching and ocular symptoms. Forty-six patients completed the study, 22 in the loratadine group and 24 in the placebo group. At the initial visit, the total symptom score (TSS) in both groups was not significantly different (p = 0.39). The TSS of the loratadine syrup group at day 7 and day 21 was lower than those of the placebo group (p = 0.003, p = 0.06). The daily card scores in the experimental group were also significantly lower than those of the placebo group (week 1, p = 0.014; week 2, p = 0.029; week 3, p = 0.014). No adverse reactions were recorded in both groups. This study revealed that loratadine syrup 5 mg or 10 mg once a day improved symptom scores of children with allergic rhinitis effectively and safely.

Administration, Oral↗

PubMed2001

[Dynamic changes in collagen type I and collagen type III in rabbits infected with Schistosoma japonicum and the effect of gamma-interferon].

OBJECTIVE: To observe the dynamic changes in collagen type I and collagen type III in rabbits with schistosomiasis japonica and the treatment effect of gamma-interferon on the degradation of collagens in schistosomal hepatic fibrosis. METHODS: Each rabbit was infected with 80 +/- 1 S. japonicum cercariae. Liver operations were done at different time points after infection and the liver specimens were embedded with paraffin and stained with alpha-SMA, HE and picric acid-Sirius red. The stained slides were observed under polarizing microscope and different collagen areas calculated by computer imagine analysis system. At the 16th week after infection, the infected rabbits received a single dose of praziquantel and gamma-interferon for 8 weeks. RESULTS: The area percent of collagen type I at the 28th week after infection (40.14 +/- 17.00) increased about seven fold compared with the 8th week group (5.73 +/- 3.40). The area percent of collagen type III at the 28th week after infection (6.80 +/- 5.19) increased about six fold compared with the 8th week group (1.15 +/- 1.34). The alpha-SMA positive cells also increased significantly. After gamma-interferon treatment, the area percent of collagen type I and type III decreased significantly, from 18.51 +/- 7.52 and 4.63 +/- 3.64 (before treatment) to 3.09 +/- 1.54 and 0.40 +/- 0.37 (0 and 4 weeks after treatment) (P < 0.01). However, after the withdrawl of gamma-interferon treatment, the collagen degradation was reversible. CONCLUSION: Gamma-interferon is effective in the treatment of hepatic fibrosis in rabbits infected with S. japonicum, the effect being reversible.

Animals↗

PubMed2000

Cloning and characterization of two mouse genes with homology to the yeast Sir2 gene.

The yeast Sir2 gene encodes a protein (Sir2p) that plays an essential role in silencing regulation at mating-type loci, rDNA, and telomeres. Recent studies have also shown that the protein participates in cell cycle regulation, DNA double-strand break repair, meiotic checkpoint control, and histone deacetylation. Overexpression of wildtype Sir2p in yeast resulted in an extended life span but mutant Sir2p shortened the life span, suggesting its function in aging processes. Sir2p is evolutionarily conserved from prokaryotes to higher eukaryotes. However, its function(s) in mammals remains unknown. To investigate Sir2p function(s) in mice, we cloned and characterized two mouse Sir2-like genes. Our results revealed that the two mouse Sir2-like proteins (mSIR2L2 and mSIR2L3) are most similar to the human Sir2-like proteins SIR2L2 and SIR2L3, respectively. Sir2 core domains are highly conserved in the two proteins and yeast Sir2p; however, the intracellular localizations of both mSIR2L2 and mSIR2L3 differ from that of yeast Sir2p and from one another. The two mouse genes have completely different genomic structures but were mapped on the same chromosome. It seems that the two mouse proteins, though they have Sir2 conserved domains, may function differently than yeast Sir2p.

Amino Acid Sequence↗

PubMed2000

Effects of 17beta-estradiol and testosterone on hepatic mRNA/protein levels and catalytic activities of CYP2M1, CYP2K1, and CYP3A27 in rainbow trout (Oncorhynchus mykiss).

There is growing concern that exposure to chemicals in the environment can disrupt the endocrine systems of wildlife and humans, causing reproductive problems or other adverse effects. The expression of many cytochrome P450s (CYPs) is under hormonal control, hence, levels of these enzymes can be affected by exposure to endocrine-disrupting chemicals. Previous research has reported that treatment of fish and other animals with the estrogenic and androgenic hormones 17beta-estradiol (E2) and testosterone (T) alters the P450 content or enzyme activities in the treated animals. However, the results of many of these studies are either incomplete or in disagreement and in most cases the effect on specific P450 forms has not been determined. Therefore, to better understand the effects of gonadal hormones on the expression of P450s and their associated enzyme activities, it was of interest to undertake a comprehensive investigation of the transcriptional and translational expression of three constitutive hepatic P450s in the rainbow trout (Oncorhynchus mykiss) following hormone exposure. Accordingly, juvenile trout were injected intraperitoneally with propylene glycol vehicle and the most active estrogenic and androgenic hormones E2 (3 mg/kg) or T (3 mg/kg) on days 1, 4, 7, 13, and 15 and euthanized on day 19. After treatment with E2, hepatic microsomes showed significantly lower levels (percentage of control) in total P450 contents (52%), lauric acid hydroxylase (32%), and 6beta-progesterone hydroxylase activities (27%), [(3)H]aflatoxin-DNA binding (31%), and the protein levels of individual cytochrome P450s (CYPs) LMC1 (CYP2M1), LMC2, (CYP2K1), and LMC5 (CYP3A27) (average for three isoforms a reduction to 29% of control values) with only minor differences between sexes. Treatment with T had either no effect or resulted in small increases in total P450 in males (42%), in lauric acid hydroxylase in females (24%), and in 6beta-progesterone hydroxylase activity in males (21%). Biological variabilities among fish were high and a polymorphic or new LMC2-like form was detected at about 52 kDa in some liver microsomal samples after exposure of fish to either hormone. Female liver RNAs were analyzed through Northern blots and an average decrease of 94% in CYP2 M1, CYP2K1, and CYP3A27 mRNA levels occurred in the E2-treated trout. In livers from T-treated trout, the changes of mRNA levels of CYP2M1 and CYP3A27 were negligible, but CYP2K1 mRNA level decreased by about 60%. Additional CYP2K1 cDNA hybridizable mRNAs were seen in some fish as faint bands at about 2.8 kb for both hormone treatments. Results of this study, therefore, indicated that E2 down-regulated while T produced small but variable effects on the hepatic mRNA/protein levels of CYP2K1, CYP2M1, and CYP3A27 in juvenile rainbow trout. This study, therefore, suggests that exposure of fish and other wildlife to environmental endocrine disruptors, especially estrogen mimics, can adversely affect a number of physiological processes through mechanisms involving altered levels of expression of specific P450 isozymes.

Aflatoxin B1↗

PubMed2000

[The expression of p16 and Rb protein in the tissue of cervical squamous carcinoma].

OBJECTIVE: To study the aberrant expression and coexpression of protein p16 and Rb in cervical squamous carcinomas, and to evaluate whether these alterations provide causative information. METHODS: The expressions of p16 and Rb protein were detected by treptavidin-peroxidase(S-P) immunohistochemical methods. RESULTS: 1. The p16 protein expression was mainly found in cytoplasm. The positive rate in carcinoma, CIN and normal cervix were 43.1%(25/58), 62.5%(5/8) and 70%(14/20), respectively; the positive expression were decreased in lower grade and clinical advanced cases(P < 0.05). 2. The Rb protein expression was detected in nucleus. The positive rate of Rb protein were 37.9%(22/58), 75%(6/8) and 85(17/20) in tum. The difference of the expression of Rb protein between the cervical squamous carcinoma and the normal cervix was significant(P < 0.05). The positive expression were increased in lower grade cancers(P < 0.05), and decreased in advanced cases(P > 0.05). 3. The positive rates of p16 and Rb protein in cervical squamous carcinoma showed an inverse correlation (vs = -0.4301, P < 0.01). CONCLUSIONS: 1. The abnormal p16 and Rbn expression might play an important role in the tumor genesis and the development of cervical squamous carcinoma. 2. Loss of function of both tumor suppressor genes may be an advanced event in cervical squamous carcinomas and might involve a bad prognosis.

Carcinoma, Squamous Cell↗

PubMed2000

Diagnosis of Penaeus monodon-type baculovirus by PCR and by ELISA of occlusion bodies.

The black tiger prawn Penaeus monodon is a valuable aquaculture product in Taiwan. Two specific diagnostic methods were established for P. monodon-type baculovirus, one using polymerase chain reaction (PCR) technology and the other enzyme-linked immunosorbent assay (ELISA) technology. Monodon-type baculovirus (MBV) was purified by sucrose gradient centrifugation from occlusion bodies of MBV-infected postlarvae of P. monodon. MBV DNA was subsequently purified from the occlusion bodies and its presence was confirmed by PCR using primers of the polyhedrin gene. Based on conserved sequences of the DNA polymerase genes of Autographa californica nuclear polyhedrosis virus (AcMNPV) and Lymantria dispar nuclear polyhedrosis virus (LdMNPV), primers were designed and synthesized to yield a 714 bp PCR fragment from MBV. However, the sequence of this fragment revealed low homology with that of LdMNPV and AcMNPV. From the DNA sequence of this fragment, a second set of primers was designed, and using these primers, a 511 bp DNA fragment was amplified only when MBV DNA was the template. DNA templates from AcMNPV, white spot syndrome diseased shrimp, or PMO cells (a cell line derived from the Oka organ of Penaeus monodon) did not give any amplified DNA fragment. Therefore, this primer pair was specific for the diagnosis of MBV. By using intraspleenic immunization of rabbits with purified MBV occlusion bodies, a polyclonal rabbit antiserum against MBV was obtained. This antiserum could detect nanogram levels of MBV, but did not cross react with white spot syndrome virus (WSSV), homogenates of PMO cells, postlarvae, hepatopancreatic tissue or intestinal tissue of black tiger prawns by competitive ELISA. This sensitive method could detect MBV even in tissue homogenates.

Animals↗

PubMed2000

The conditional survival statistics for survivors with primary supratentorial astrocytic tumors.

BACKGROUND: Relative survival rates can offer a general description of tumor outcome and, traditionally, are used for surveillance and comparison purposes. However, they are not informative for individual tumor survivors. Conditional survival estimates can calculate the probability of surviving next some years given survival to a specific period of time after craniotomy for individual tumor survivors. However, clinically, they have not been used for predicting the tumor outcome. METHODS: We calculated conditional probabilities of survival within 6 years after craniotomy in 112 patients with primary supratentorial astrocytic tumors and evaluated factors affecting the survival time more than 2 years after craniotomy. RESULTS: Our data showed that the conditional probability of survival can predict yearly survival rate when patients survive for a specific period of time. The conditional survival rates within 6 years after craniotomy were always higher than those evaluated by relative survival rates. Overall, the longer the patients survived, the higher the conditional probabilities of surviving sixth year postoperatively were. CONCLUSION: Our study demonstrates the conditional probabilities of survival have good availability and are important estimates for individual tumor survivors.

Adolescent↗

PubMed2000

Comparison of serum specific IgE antibodies to staphylococcal enterotoxins between atopic children with and without atopic dermatitis.

BACKGROUND: The skin of patients with atopic dermatitis (AD) exhibits a striking susceptibility to colonization and infection by Staphylococcus aureus. The exotoxins secreted by S. aureus can act as superantigens and classic allergens, inducing the production of functionally relevant specific IgE antibodies. The aim of this study was to compare the levels and positive rates of serum staphylococcal enterotoxin A (SEA)- and staphylococcal enterotoxin B (SEB)-specific IgE between atopic children with and without AD. METHODS: Sixty children with AD, 55 children with respiratory allergy without AD, and 24 nonatopic healthy children were studied. The levels and positive rates of serum SEA- and SEB-specific IgE were compared among three groups. The correlation between the levels or positive rates of serum SEA/SEB-specific IgE and the severity of AD or the presence of previous skin infections was studied. RESULTS: The children with AD had significantly higher levels and positive rates of serum SEA- and SEB-specific IgE than the atopic children without AD (P < 0.001) and the nonatopic children (P < 0.001). There was no significant difference in the levels and positive rates of serum SEA- and SEB-specific IgE between the atopic children without AD and the nonatopic children. With or without adjustment for the potential confounding effect of total serum IgE levels, the levels and positive rates of serum SEA- and SEB-specific IgE were significantly correlated with severity of AD (P <0.005), but they were not significantly different between AD children with and without previous skin infections. CONCLUSIONS: SEA and SEB may contribute to chronic inflammation and exacerbation of AD through the IgE-mediated immune response.

Adolescent↗

PubMed2000

Increased transforming growth factor-beta (TGF-beta)-secreting T cells and IgA anti-cardiolipin antibody levels during acute stage of childhood Henoch-Schönlein purpura.

Henoch-Schönlein purpura (HSP) is a small vessel vasculitis characterized by increased serum IgA and IgA-dominant immune complex deposition in lesions. The involvement of IgA implies a probable role for TGF-beta, a major factor in IgA production, in the pathogenesis of HSP. Among IgA antibodies, serum IgA anti-cardiolipin antibodies (aCL) have been found in many diseases, including vasculitis. In addition to the clinical presentations and laboratory parameters, we further investigated the roles of IgA aCL and TGF-beta in childhood HSP. Twenty-six Chinese children with the diagnosis of HSP were enrolled. Blood samples from these patients were collected at both acute and convalescent stages. Intracellular staining of lymphocytes was performed to enumerate type 1 (interferon-gamma-secreting), type 2 (IL-4-secreting), and type 3 (TGF-beta-secreting) helper T cells. Serum levels of TGF-beta were detected by ELISA. Serum IgA aCL of 21 of 26 patients at the acute stage, 11 of them at the convalescent stage, were measured by ELISA. The data showed that IgA aCL serum levels were significantly elevated in patients compared with healthy controls (P < 0.001), and those patients at the convalescent stage (P < 0.001). In addition, TGF-beta-secreting T cells were significantly elevated during the acute stage, and decreased at the convalescent stage. Although more studies are needed, the high prevalence of IgA aCL and increased TGF-beta-secreting T cells in children with acute HSP revealed some points which should permit a better understanding of the pathogenesis of HSP.

Acute Disease↗

PubMed2000

Adverse pregnancy outcome following post-chorionic villus sampling amniocentesis compared to chorionic villus sampling.

OBJECTIVE: To assess the adverse pregnancy outcome of post-chorionic villus sampling (CVS) amniocentesis and chorionic villus sampling. METHODS: Adverse pregnancy outcomes of 32 post-CVS amniocentesis cases and 264 CVS only cases were compared. The base-line characteristics were comparable in the 2 groups. RESULTS: One (3.1%) chromosomal abnormality was detected in the post-CVS amniocentesis group, compared to 5 (1.8%) in the CVS only group (p > 0.05). The fetal loss rate (spontaneous abortions and stillbirths) among continuing pregnancies was 3.2% in the post-CVS amniocentesis group and 3.5% in the CVS only group (p > 0.05). No statistically significant difference was found in the incidence of neonatal death, preterm delivery, fetal growth restriction, or congenital anomalies between the 2 groups. CONCLUSION: Adverse pregnancy outcome occurred at a similar frequency in the post-CVS amniocentesis group as in the CVS only group. Therefore, a subsequent amniocentesis after CVS can be considered as a safe procedure that does not introduce any additional adverse pregnancy outcome compared to that of CVS only.

Adult↗

PubMed2000

Prenatal genetic diagnosis from maternal blood: simultaneous immunophenotyping and FISH of fetal nucleated erythrocytes isolated by negative and positive magnetic activated cell sorting.

Fetal nucleated red blood cells (nRBCs) are rare in maternal circulation, but their presence constitutes a potential source of non-invasive prenatal genetic diagnosis. This study was undertaken to establish a non-invasive prenatal genetic diagnosis method using isolated fetal nRBCs. A multi-step method including triple density gradient and magnetic activated cell sorting (MACS) using CD45 and CD71, cytospin centrifugation, K-B staining, and glycophorin A-immuno fluorescence in situ hybridization (GPA-immuno FISH) was performed. The study population included 65 patients from 8 to 41 weeks of gestation, and fetal nRBC was separated from all cases. The number of fetal nRBCs retrieved was 12.8 +/- 2.7 in 8 to 11 gestational weeks, 15.2 +/- 6.5 in 12 to 18 gestational weeks, 16.4 +/- 6.5 in 19 to 23 gestational weeks, 10.6 +/- 3.2 in 24 to 28 gestational weeks, and 5.5 +/- 1.9 in 35 to 41 gestational weeks: the mean number of nRBCs collected from 20 ml of maternal peripheral blood was 13.7 +/- 6.2. The highest value of yield was 45.6% from 12 to 18 weeks gestation. The fetal sex determination confirmed by amniocentesis or chorionic villus sampling showed 100% sensitivity and 91.7% specificity for males; 91.7% sensitivity and 100% specificity for females. We showed that fetal cells can be reliably enriched from maternal blood and that they can be used for detecting specific chromosomes by FISH with a specificity superior to current non-invasive methods.

Erythrocytes↗

PubMed2000

Hepatocellular carcinoma presenting as a pyogenic liver abscess in a patient with hemochromatosis.

Primary hemochromatosis is rare in Taiwan. Hepatocellular carcinoma (HCC) is endemic in Taiwan, but HCC with initial presentation as pyogenic liver abscess is unusual. We report a case of HCC presenting as pyogenic liver abscess in a hemochromatotic patient with cirrhosis. The patient underwent hepatectomy and had a smooth postoperative course. Unfortunately, he died of pneumonia eight months after surgery. HCC should be considered in the differential diagnosis in hemochromatotic patients with a pyogenic liver abscess.

Aged↗

PubMed2000

Acute pancreatitis associated with temporal lobectomy and intractable seizure.

We present a rare case of acute pancreatitis associated with temporal lobectomy due to intractable seizure in a 23-year-old man. The patient underwent elective right temporal lobectomy and hippocampectomy. Severe upper abdominal pain occurred just 10 hours after surgery. The diagnosis of acute pancreatitis was based on the elevation of serum amylase and lipase levels, and the findings of abdominal computerized tomography. Other possible causative factors of acute pancreatitis including alcohol, biliary tract stone, hypertriglyceridemia, hypercalcemia, hyperparathyroidism, biliary dysmotility and autoimmune disease were excluded by a series of examinations. The possibility of drug-induced pancreatitis was very low in this patient. The patient was discharged after supportive treatment. No recurrence of seizure or abdominal pain was noted in the three months after discharge. Acute abdominal pain after brain surgery deserves clinical evaluation for acute pancreatitis.

Acute Disease↗

PubMed2000

Childhood mixed connective tissue disease.

Two girls with mixed connective tissue disease (MCTD) were treated in our hospital in the past 5 years. Patient 1, a 10-year-old girl presenting with migratory arthralgia, had an initial diagnosis of juvenile rheumatoid arthritis. Muscle weakness with elevated levels of creatine kinase and liver enzymes, sclerodactyly, Raynaud's phenomenon and heliotrope sign developed subsequently in the following 3 years. Patient 2, a 13-year-old girl, had been treated for suspected systemic lupus erythematosus since 9 years of age. She presented with lymphadenopathy, arthralgia, pericardial effusion, and paralytic ileus. The symptoms waxed and waned. Sclerodactyly, Raynaud's phenomenon, proteinuria, and hypertension were also noted. Both patients had high serum titers of antinuclear antibody (speckled pattern, 1:5120) and were seropositive for antiribonuclear protein antibody. Intravenous immunoglobulin, prednisolone, cyclosporine A, and nonsteroidal anti-inflammatory drugs (NSAIDs) were given to patient 1. Patient 2 received cyclosporine A, prednisolone, and methylprednisolone pulse therapy. The disease has been well controlled for 2 years by low-dose immunosuppressants and NSAIDs. MCTD is a rare juvenile rheumatic disease: early identification and appropriate treatment can improve the disease outcome.

Adolescent↗

PubMed2000

Long-term effects of azathioprine therapy for juvenile rheumatoid arthritis.

BACKGROUND AND PURPOSE: Juvenile rheumatoid arthritis (JRA) can result in disability, growth disturbance, and systemic complications. This study investigated the efficacy and adverse effects of azathioprine (AZA) therapy in children with JRA. METHODS: Data from the medical records of 24 children with JRA treated with oral AZA during the period from 1988 to 1998 were retrospectively analyzed. All 24 patients had received two or more nonsteroidal anti-inflammatory drugs (NSAIDs) and 12 had received disease-modifying antirheumatic drugs (DMARDs) prior to the start of AZA. Of the 24 patients, 21 were corticosteroid-dependent prior to the onset of AZA therapy. The indication for AZA therapy was lack of efficacy of the current treatment regimen. The initial and maximal doses of AZA averaged 1.7 mg.kg-1.d-1 (range, 1-3 mg. kg-1.d-1) and 1.9 mg.kg-1.d-1 (range, 1-6 mg.kg-1.d-1), respectively. The mean duration of treatment was 13 months (range, 4-37 mo). The mean duration of follow-up was 45 months (range, 7-137 mo) from the start of AZA therapy. RESULTS: Fifteen children (62.5%) showed clinical improvement, while the other nine (37.5%) achieved clinical remission. AZA treatment resulted in a more than 50% reduction in the required corticosteroid dose in seven children and complete discontinuation of corticosteroid administration in eight children. None of the patients treated with AZA doses of 1 to 3 mg.kg-1.d-1 developed AZA-related side-effects. Two patients suffered from AZA-related adverse effects due to AZA overdose (6 mg.kg-1.d-1). Both experienced pancytopenia and disseminated infection, which resolved following reduction of the AZA dose to 3 mg.kg-1.d-1. CONCLUSIONS: AZA is an effective and well-tolerated steroid-sparing agent for JRA refractory to NSAIDs or DMARDs.

Adolescent↗

PubMed2000

Efficacy and safety of methotrexate therapy for juvenile rheumatoid arthritis.

BACKGROUND AND PURPOSE: Juvenile rheumatoid arthritis (JRA) can result in disability, growth disturbance, and systemic complications. This study investigated the efficacy and adverse effects of oral methotrexate (MTX) therapy in Taiwanese children with JRA. METHODS: The medical records of 52 Taiwanese children with JRA treated with oral MTX were retrospectively analyzed. The disease onset was polyarticular in 22 children, oligoarticular in 13, and systemic in 17. The indication for MTX therapy was lack of efficacy of previous drugs, including two or more nonsteroidal anti-inflammatory drugs, in all patients. In addition, three patients had received hydroxychloroquine and one had received sulfasalazine, without improvement. Corticosteroid dependency had developed in 27 patients prior to MTX therapy. The mean initial dose of MTX was 9.1 mg.m-2.wk-1 (range, 5-20 mg.m-2.wk-1), and the mean maximal dose was 10.2 mg.m-2.wk-1 (range, 5-20 mg.m-2.wk-1). The mean duration of treatment was 23 months (range, 6-96 mo), and the mean duration of follow-up was 52 months (range, 10-123 mo) from the start of MTX therapy. RESULTS: Thirty-six children (69%) showed clinical improvement and 25 children (48%) achieved clinical remission. The administration of MTX resulted in more than a 50% reduction in required corticosteroid dosage in six children, and complete discontinuation of corticosteroid in 10 children. MTX was discontinued in 18 patients following a mean of 8 months (range, 2-34 mo) of clinical remission. Relapse occurred in nine (50%) of these patients. Thirteen patients (25%) suffered from adverse effects associated with MTX treatment. All of these adverse effects resolved spontaneously, or subsided within 4 weeks following dosage reduction or discontinuation of MTX. CONCLUSIONS: Oral MTX therapy is effective and well-tolerated in Taiwanese children with JRA. It can serve as the first choice of second-line therapy in JRA.

Adolescent↗

PubMed2000

[Mutants of subtilisin E].

Ser 236, located in the surface of subtilisin E and at the end of alpha-helex with Ser221, is far from the active center (Asp32, His64, Ser221). The replacement of Ser236 with Cys via directed-mutagenesis should effect protease activity insignificantly and may be able to improve the stability of enzyme due to the potency to form disulfide across two molecules. The results indicated that BP-1 (Ser236Cys) was found to gain 150% activity (Kcat/Km value) of the wild-type subtilisin E and 3-fold increase in stability in aqueous solution at pH7.4 and 50 degrees C, compared to the wild-type enzyme. However, further mutations on BP-1 to introduce Ala15Asp/Gly20His (BU-1) or Ser24His/Lys27Asp (BW-1) was found negative effects on the activity and stability of subtilisin E.

Enzyme Stability↗

PubMed2000

[Glucose isomerase gene knock-out by denatured double-stranded DNA].

After Genetic background analysis of Streptomyces diastaticus No. 7 strain M1033, the modified conditions of M1033 protoplasts and transformation were established. Replacement plasmid for homologous recombination was also constructed by inserting tsr gene into glucose isomerase gene. The homologous recombination of GI gene in M1033 chromosomes was achieved by using denatured linearized DNA fragments and glucose isomerase deficient strain M1033LJ was obtained. It is basic for introducing mutation into M1033 chromosome and realizing site-directed molecular reformation.

Aldose-Ketose Isomerases↗