Biomedical subjects

J Tan

Publications and source records attributed to J Tan.

At least 199 records · Page 11Linked to original sources

PubMed1996

Use of unrefrigerated fresh whole blood in massive transfusion.

OBJECTIVE: To establish the efficacy of transfusion of fresh unrefrigerated whole blood in surgical patients with ongoing massive bleeding despite adequate blood-component replacement therapy and adequate surgical haemostasis. DESIGN: A retrospective review of patients who received fresh unrefrigerated whole-blood transfusions, noting blood usage and outcome. SETTING: A tertiary care teaching hospital with a major cardiac surgical and trauma service. PATIENTS: All patients (n=11) receiving fresh unrefrigerated whole-blood transfusions from March 1992 to February 1995. RESULTS: Mean blood usage in the 24 hours before the decision to transfuse fresh unrefrigerated whole blood was 16.5 units of packed cells (range, 6-27), 17.1 units of platelets (8-32), 14.5 units of fresh frozen plasma (6-26) and 13.5 units of cryoprecipitate (4-36). After the transfusion of fresh whole blood there was an immediate and substantial reduction in the rate and volume of blood loss in all patients. This was sustained in seven patients, who had a successful outcome; the other four patients died within 24 hours from recurrent uncontrollable haemorrhage. The reduction in blood usage in the 24 hours after the transfusion of fresh whole blood was statistically significant in the surviving patients but not in the patients who died. None of the surviving patients showed evidence of viral seroconversion six months after the transfusion. CONCLUSIONS: Our study provides preliminary evidence that there is a role for transfusion of fresh unrefrigerated whole blood in surgical patients with unresponsive life-threatening haemorrhage.

Adult↗

PubMed1996

Three new mutations of the pyruvate dehydrogenase alpha subunit: a point mutation (M181V), 3 bp deletion (-R282), and 16 bp insertion/frameshift (K358SVS-->TVDQS).

Three novel mutations in the coding region of E1 alpha gene were found in three PDC-deficient male patients, including a missense mutation (M181V), a 3 bp deletion (AGA, corresponding to R282), and a 16 bp insertion (CAGTGGATCAAGTTTA), causing a frameshift starting with lysine 358 and resulting in decrease of both E1 subunits.

Cells, Cultured↗

PubMed1996

Identification of two mutations in a compound heterozygous child with dihydrolipoamide dehydrogenase deficiency.

An infant girl with elevated blood lactate, pyruvate, and plasma branched-chain amino acids was diagnosed with dihydrolipoamide dehydrogenase (E3; dihydrolipoamide: NAD+ oxidoreductase, EC 1.8.1.4) deficiency. Activities of the pyruvate dehydrogenase complex and E3 from patient were 26 and 2% of controls in blood lymphocytes, and 11 and 14% in cultured skin fibroblasts, respectively. Western blot analysis demonstrated that the amount of E3 protein in fibroblasts from the patient and her father was about half of controls, while Northern blot analysis showed normal amounts of E3 RNA. DNA sequencing of cloned full-length E3 cDNAs from the patient revealed two mutations in separate alleles. One is a single base insertion of an extra adenine in the last codon of the leader peptide sequence (TAC-->TAAC) leading to a nonsense mutation which results in the premature termination of the precursor E3 polypeptide (Y35X). The other is a missense mutation due to substitution of guanine for adenine, causing an Arg-->Gly substitution at amino acid 460 of the mature protein (R460G) which triggers the loss of E3 activity probably by structural change in the E3 dimer. DNA sequencing of E3 cDNAs from the parents demonstrated that the nonsense mutation was inherited from the father and the missense mutation was inherited from the mother.

Alleles↗

PubMed1996

Operative laparoscopic management of adnexal cysts: initial experience at the Royal Women's Hospital 1991-1994.

The introduction of operative laparoscopic surgery for benign adnexal cysts had led to shorter postoperative hospitalization (mean stay of 2.0 days) in association with a low rate of major complications (1.6%). A planned laparoscopic approach was successful in 95.2% (179/188) of patients. The majority of women were premenopausal (93.6%) and the most common procedure performed was an ovarian cystectomy (73.5% of cysts). Three ovarian cysts that were thought to be benign by preoperative and intraoperative assessment were subsequently found to be ovarian tumours of low malignant potential after histological examination. Operative laparoscopy has become the preferred mode of treatment for benign adnexal cysts at the Royal Women's Hospital. It confers a wide range of benefits to patients, reduces health-care costs and appears to be a safe and effective treatment modality.

Adolescent↗

PubMed1996

Constant composition dissolution kinetics studies of human dentin.

The constant composition (CC) method has been used to study the dissolution kinetics of whole powdered human dentin as a function of calcium phosphate concentration at relative undersaturations with respect to hydroxyapatite (sigma HAP), ranging from +0.8 to -2.8, ionic strength from 0.05 to 0.30 mol/L-1 in sodium chloride or potassium nitrate, pH 4.00 to 5.50, and molar calcium/phosphate ratio in the reaction solutions from 0.05 to 11.1. The results suggest that human dentin behaves as a mixture of at least two calcium phosphate phases, HAP-like and octacalcium phosphate-like, OCP-like. Significant dissolution took place in solutions that were even supersaturated with respect to HAP, and the rates exhibited a striking insensitivity to relative undersaturation, while influenced by ionic strength, pH, and molar calcium/phosphate ratio in the reaction solutions. Although the dissolution was retarded in the presence of magnesium ion, the reaction rate showed the same insensitivity to undersaturation with respect to calcium phosphate.

Dentin↗

PubMed1996

Toxicity studies in thymidine kinase-deficient herpes simplex virus therapy for malignant astrocytoma.

Previous studies have shown that genetically engineered thymidine kinase (tk)-defective herpes simplex virus type 1 (HSV-1) can effectively and selectively destroy gliomas in animal models. The consequences of viral infection and tumor regression must be characterized before this therapy can be applied in human trials. To study the potential for long-term toxicity, immunocompetent rats harboring 9L gliosarcomas were injected intratumorally with a tk-defective HSV-1, KOS-SB, at titers that previously have been demonstrated to cause tumor regression. In animals surviving 3 months or longer following viral treatment, there was no evidence of persistent infection or inflammation in peritumoral brain tissue or in remote systemic organs studied with routine histological and immunocytochemical analyses. Polymerase chain reaction using primers specific for HSV-1 detected HSV-1 DNA in peritumoral tissue only in animals sacrificed within 3 months of viral injection. There was no evidence of HSV-1 DNA in systemic tissues at any time after treatment. We conclude that stereotactic intratumoral injection of tk-deficient HSV can be attempted for the treatment of brain tumors without risk of systemic infection or significant toxicity to normal brain or remote proliferating tissues.

Animals↗

PubMed1996

Mutations in the MGAT2 gene controlling complex N-glycan synthesis cause carbohydrate-deficient glycoprotein syndrome type II, an autosomal recessive disease with defective brain development.

Carbohydrate-deficient glycoprotein syndrome (CDGS) type II is a multisystemic congenital disease with severe involvement of the nervous system. Two unrelated CDGS type II patients are shown to have point mutations (one patient having Ser-->Phe and the other having His-->Arg) in the catalytic domain of the gene MGAT2, encoding UDP-GlcNAc:alpha-6-D-mannoside beta-1,2-N- acetylglucosaminyltransferase II (GnT II), an enzyme essential for biosynthesis of complex Asn-linked glycans. Both mutations caused both decreased expression of enzyme protein in a baculovirus/insect cell system and inactivation of enzyme activity. Restriction-endonuclease analysis of DNA from 23 blood relatives of one of these patients showed that 13 donors were heterozygotes; the other relatives and 21 unrelated donors were normal homozygotes. All heterozygotes showed a significant reduction (33%-68%) in mononuclear-cell GnT II activity. The data indicate that CDGS type II is an autosomal recessive disease and that complex Asn-linked glycans are essential for normal neurological development.

Blotting, Northern↗

PubMed1996

[Analysis of apolipoprotein gene family in codon space--non-random selection of nucleotide changes in evolution].

The choice of nucleotide changes in DNA evolution can be either selectively neutral or biased. To study how apolipoprotein gene selects the nucleotide substitutions in the course of evolution, a codon space is constructed in which its DNA sequence can be mapped as a matrix of nucleotide frequencies in three codon positions. Accordingly, a number of methods that measure the nonrandomness of nucleotide distribution in codon space are developed based on maximum entropy techniques to define the nature of nucleotide change selection in evolution. By these methods, we demonstrated that the nucleotide composition in 1st and 3rd codon position of apolipoprotein genes is highly nonrandom, which appears to be a result of non-neutral selection of codon positions by adenosine and thymidine. In addition, this paper is also concerned in the divergence of synonymos codon usage and its correlation to taxonomic distances among species. As a result, a codon usage clock was reported in apolipoprotein A-I. Our studies suggest that non-random selection of nucleotide changes in codon space may represent an evolutionary characteristics of apolipoprotein genes.

Animals↗

PubMed1996

[DNA typing for HLA-DR in donor-recipients of cadaveric transplantation].

OBJECTIVE: To accurately allocate donor-recipients of HLA-matching and improve long-term graft survival, genotyping method for HLA-DR alleles by polymerase chain reaction with sequence-specific primers (PCR-SSP) was established and applied to renal transplantation. METHODS: Thirty primers were designed and synthesized according to the HLA-DR nucleotide sequences. Genomic DNAs were prepared by a rapid salting-out method. A rapid genotyping method of PCR-SSP was set up by PCR technique and applied to HLA-DR typing in 14 cell lines DNA and 171 individuals of donor-recipients of cadaveric transplantation. The amplification was accomplished by 34 cycles consisting of denaturation at 94 degrees C for 30 seconds, annealing at 60 degrees C for 50 seconds, and extension at 72 degrees C for 40 seconds. The specificity of matching was determined against a panel of standard DNA, analysis with restriction endonucleases and Southern hybridization. RESULTS: HLA-DR alleles of all 171 samples and 14 cell line DNAs were able to be typed by PCR-SSP. The size of specific products was consistent with the size of calculation. The overall time of genotyping was only 5 hours. No false positive or false negative typing results were discovered. The typing results were confirmed by analysis with endonucleases and hybridization. The specificity and reproducibility were 100%. CONCLUSIONS: Genotyping for HLA-DR by PCR-SSP is a rapid and accurate matching technique, suitable for organ transplantation, especially allocation of donor-recipients of cadaveric transplantation.

Alleles↗

PubMed1996

[Immunohistochemical detection of antigen of human cytomegalovirus in hepatocyte].

The expression plasmid of human cytomegalovirus (HCMV) 52kd glycoprotein was induced and amplified, and the recombinant protein was extracted. The rabbit antiserum to the recombinant protein was prepared. The antiserum-reacted to the antigen of HCMV AD165, and the titer of antiserum was 1 : 3200 by using 125I-Protein A. Using Avidin-Biotinperoxidase complex technique (ABC method), we detected the HCMV 52 kd glycoprotein in the hapatic slides of 9 cases. Among them, one case (an infant died of congenital heart disease) was held as a negative control. The other 8 cases (patients with clinically diagnosed cytomegalic inclusion disease) had viral hepatitis histopathologically. Of these 8 cases, 7 had positive signals but found in the nucleus and cytomembrane of the hepatocytes, no positive signal was found in the hepatocytes of the control. The result showed that HCMV 52kd glycoprotein was located in the nucleus and on the membrane of the infected hepatocyte. The antibody prepared with the antigen of gene engineering could find the virus antigen and represent the virus gene state which was active or silent. ABC method is not only simple, sensitive and specific, but also effective in localization. It is of importance to clinical diagnosis, differential diagnosis and prognostication.

Cytomegalovirus↗

PubMed1996

[The influence of HX- I on rabbit thyroid allografts].

We studied the anti-rejection effect of HX- I, a preparation of traditional Chinese herbs, on rabbit thyroid allografts. The transplantations were performed on 28 rabbits after total thyroidectomies. The grafting sites were in their pretrachial muscles. These animals were divided into four groups, namely, Group I: homografts: Group I: allografts without medication; Group II: allografts with dexamethason (0.25 mg/(kg.d) intramuscularly), and Group IV: allografts with HX-I water solution, (5g/(kg.d), peros). The medication lasted 28 days. Blood samples were drawn every week postoperatively. Serum T3 and T4 were tested by RIA. The grafts were removed for histopathological evaluation on the 28th day postoperatively. The histopathology of rejection and survival were scored and classified. On the 7th and 14th days, serum T3 and T4 levels were almost the same between groups. On the 21st and 28th days, the T3 and T4 levels were higher in Groups I and IV than those in Group II (P < 0.05). The histopathological findings were; in Group I, damaged follicles with much lymphocytes infiltration and fibrosis, and 6 cases being rejected; in Group II, two deaths and three cases with damaged thyroid tissue and much lymphocytes infiltration; in Group IV, three cases with damaged thyroid tissue and four intact grafts. Our results indicate that HX-I and dexamethason both can inhibit rejection in thyroid allografts in rabbits, but dexamethason has more side effects HX-I has many components and the machanism of its early anti-rejection effect is worthy of further study.

Animals↗

PubMed1996

Rapid HLA-DR genotyping by PCR-amplification with sequence-specific primers.

OBJECTIVE: To establish a rapid genotyping for HLA-DR alleles by polymerase chain reaction with sequence-specific primers (PCR-SSP) for clinical application. MATERIAL AND METHODS: The subjects of study included 69 recipients, 43 unrelated donors and 5 cell lines. Genomic DNA was prepared from peripheral blood leukocytes by a salting-out method. Thirty primers were designed according to the HLA-DRB nucleotide sequences, and synthesized on a 391 DNA synthesizer. Twenty separate PCR reactions were performed for each sample. The amplification was accomplished by 34 cycles consisting of denaturation at 94 degrees C for 30 seconds, annealing at 60 degrees C for 50 seconds and extension at 72 degrees C for 40 seconds. The specificity of matching was determined by standard DNAs and Southern hybridization using DIG labeling probes. RESULTS: All 112 samples and 5 cell lines were able to be typed by PCR-SSP. No false positive or false negative typing results were obtained. The reproducibility was 100%. The size of the specific product was in concordance with the size of the designed primers. The overall time for genotyping was 4 hours. The typing results were confirmed by Southern hybridization. CONCLUSIONS: Genotyping for HLA-DR by PCR-SSP is a rapid and accurate matching technique suited for clinical application.

Alleles↗

PubMed1996

[Rapid genotyping for HLA-DR by PCR-amplification with sequence-specific primers and clinical practice].

Genotyping for HLA-DR alleles by polymerase chain reaction with sequence-specific primers (PCR-SSP) was first typed in 112 individuals of donor-recipients of cadaveric transplantation and 9 cell lines DNA. Twenty separate PCR reactions were performed per sample. The amplification was accomplished by 34 cycles consisting of denaturation at 94 degrees C for 30 sec, annealing at 60 degrees C for 50 sec and extension at 72 degrees C for 40 sec. HLA-DR alleles could be accurately distinguished. The overall time of genotyping was only 5 hours. The specificity of matching was determined against a panel of standard DNA, analysis with restriction endonucleases, and Southern hybridization using DIG oligonucleotide 3'- end labeling probes. The specificity and reproducibility were 100%. No false positive or false negative typing results were obtained. These showed genotyping by PCR-SSP was a rapid and accurate matching technique, suited for clinical practice.

Alleles↗

PubMed1996

[Priorities of disease control in China--analysis on mortality data of National Disease Surveillance Points System].

The leading health problems in the Chinese population are analyzed with indices as standard death rate, YPLL and DALY, using data from The Chinese Diseases Surveillance Points System (DSP). Disease pattern in China is different from that in the 1950's owing to demographic transition (aging of the population), decrease of both morbidity and mortality of communicable disease etc. That made chronic disease relatively more important the increase of some risk factors, directly cause the rising of mortality and morbidity of some chronic diseases and injuries related to lung cancer and transportation. At present the character of the disease pattern is as follows: there is still a long way to go to control communicable diseases, although the incidence rates and proportion have decreased. Meanwhile, chronic diseases and injuries are becoming major health issues. Hence, China is facing double challenges.

Accidents↗

PubMed1996

[Improvement in model of mesangial proliferative glomerulonephritis of rat].

To establish a model of mesangial proliferative glomerulonephritis (MsPGN), we gave Sprague-Dawley rats staphylococcal enterotoxin B (SEB) intravenously twice in different times, bovine serum albumine (BSA) through digestive tract every other day, and Freud's adjuvant subcutaneously twice in different times, respectively. The results showed that measangial cells and matrix in glomeruli of rats began to proliferate at the end of 6th week and this change became obvious at the end of 8th week. The duration of experiment was shorter than that using only SEB, and the change of pathomorphology was stable. The experiment confirms the thesis that mucosal immunization of gastroenteric tract plays an important role in the development of MsPGN.

Animals↗

PubMed1995

Synthesis of pentasaccharide analogues of the N-glycan substrates of N-acetylglucosaminyltransferases III, IV and V using tetrasaccharide precursors and recombinant beta-(1-->2)-N-acetylglucosaminyltransferase II.

Recombinant human UDP-GlcNAc: alpha-Man-(1-->6)R beta-(1-->2)-N-acetylglucosaminyltransferase II (EC 2.4.1.143, GlcNAc-T II) was produced in the Sf9 insect cell/baculovirus expression system as a fusion protein with a (His)6 tag and partially purified by affinity chromatography on a metal chelating column. The partially purified enzyme was used to catalyze the transfer of GlcNAc from UDP-GlcNAc to R-alpha-Man(1-->6)(beta-GlcNAc(1-->2)alpha-Man(1-->3))beta-Man-O-octyl to form beta-GlcNAc(1-->2)R-alpha-Man(1-->6)(beta-GlcNAc(1-->2)alpha- Man(1-->3))beta-Man-O-octyl where there is either no modification of the alpha-Man(1-->6) residue (7), or where R is 3-deoxy (8), 4-deoxy (9) or 6-deoxy (10). The yields ranged from 64-80%. Products were characterized by 1H and 13C nuclear magnetic resonance spectroscopy and fast atom bombardment mass spectrometry. Compounds 7-10 are pentasaccharide analogues of the biantennary N-glycan substrates of N-acetylglucosaminyltransferases III, IV and V.

Carbohydrate Conformation↗

PubMed1995

Long-range interaction between two promoters: activation of the leu-500 promoter by a distant upstream promoter.

The leu-500 mutation can be suppressed in S. typhimurium topA. Previous studies have demonstrated that the plasmid-borne leu-500 minimal promoter cannot be activated in topA mutants unless adjacent (< 250 bp) transcription occurs away from the leu-500 promoter (short-range promoter interaction). To search for a potential upstream promoter responsible for activation of leu-500 in the chromosomal context, we have identified the ilvlH promoter, located 1.9 kb upstream of leu-500 (long-range promoter interaction). Different from short-range promoter interaction, which is abolished by DNA sequence insertions, the long-range promoter interaction is mediated by the intervening DNA sequence. These studies suggest that the long-range interaction between a pair of divergently arrayed promoters is probably mediated by a complex process involving relay of DNA supercoiling by the DNA sequence located between the two promoters.

Base Sequence↗

PubMed1995

The human UDP-N-acetylglucosamine: alpha-6-D-mannoside-beta-1,2- N-acetylglucosaminyltransferase II gene (MGAT2). Cloning of genomic DNA, localization to chromosome 14q21, expression in insect cells and purification of the recombinant protein.

UDP-GlcNAc:alpha-6-D-mannoside [GlcNAc to Man alpha 1-6] beta-1,2-N-acetylglucosaminyltransferase II (GlcNAc-T II, EC 2.4.1.143) is a Golgi enzyme catalyzing an essential step in the conversion of oligomannose to complex N-glycans. A 1.2-kb probe from a rat liver cDNA encoding GlcNAc-T II was used to screen a human genomic DNA library in lambda EMBL3. Southern analysis of restriction endonuclease digests of positive phage clones identified two hybridizing fragments (3.0 and 3.5 kb) which were subcloned into pBlueScript. The inserts of the resulting plasmids (pHG30 and pHG36) are over-lapping clones containing 5.5 kb of genomic DNA. The pHG30 insert (3.0 kb) contains a 1341-bp open reading frame encoding a 447-amino-acid protein, 250 bp of G + C-rich 5'-upstream sequence and 1.4 kb of 3'-downstream sequence. The pHG36 insert (3.5 kb) contains 2.75 kb of 5'-upstream sequence and 750 bp of the 5'-end of the open reading frame. The protein sequence showed the domain structure typical of all previously cloned glycosyltransferases, i.e. a short 9-residue putative cytoplasmic N-terminal domain, a 20-residue hydrophobic non-cleavable putative signal-anchor domain and a 418-residue C-terminal catalytic domain. Northern analysis of human tissues showed a major message at 3 kb and minor signals at 2 and 4.5 kb. There is no sequence similarity to any previously cloned glycosyltransferases including human UDP-GlcNAc:alpha-3-D-mannoside [GlcNAc to Man alpha 1-3] beta-1,2-N-acetylglucosaminyltransferase I (GlcNAc-T I) which has 445 amino acids with a 418-residue C-terminal catalytic domain. The human GlcNAc-T I and II genes (MGAT1 and MGAT2) map to chromosome bands 5q35 and 14q21, respectively, by fluorescence in situ hybridization. The entire coding regions of human GlcNAc-T I and II are each on a single exon. There is 92% identity between the amino acid sequences of the catalytic domains of human and rat GlcNAc-T II. Southern analysis of restriction enzyme digests of human genomic DNA indicates that there is only a single copy of the MGAT2 gene. The full-length coding region of GlcNAc-T II has been expressed in the baculovirus/Sf9 insect cell system, the recombinant enzyme has been purified to near homogeneity with a specific activity of about 20 mumol.min-1.mg-1 and the product synthesized by the recombinant enzyme has been identified by high-resolution 1H-NMR spectroscopy and mass spectrometry.

Amino Acid Sequence↗