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Biomedical subjects

J Chai

Publications and source records attributed to J Chai.

At least 19 recordsLinked to original sources
PubMed2000

Structural and biochemical basis of apoptotic activation by Smac/DIABLO.

Apoptosis (programmed cell death), an essential process in the development and homeostasis of metazoans, is carried out by caspases. The mitochondrial protein Smac/DIABLO performs a critical function in apoptosis by eliminating the inhibitory effect of IAPs (inhibitor of apoptosis proteins) on caspases. Here we show that Smac/DIABLO promotes not only the proteolytic activation of procaspase-3 but also the enzymatic activity of mature caspase-3, both of which depend upon its ability to interact physically with IAPs. The crystal structure of Smac/DIABLO at 2.2 A resolution reveals that it homodimerizes through an extensive hydrophobic interface. Missense mutations inactivating this dimeric interface significantly compromise the function of Smac/DIABLO. As in the Drosophila proteins Reaper, Grim and Hid, the amino-terminal amino acids of Smac/DIABLO are indispensable for its function, and a seven-residue peptide derived from the amino terminus promotes procaspase-3 activation in vitro. These results establish an evolutionarily conserved structural and biochemical basis for the activation of apoptosis by Smac/DIABLO.

Amino Acid Sequence↗
PubMed2000

Heparin-free hemodialysis in the treatment of hypernatremia in severely burned patients.

BACKGROUND: Hypernatremia in severely burned patients is associated with high morbidity and mortality rates. As the causes of hypernatremia in major burn patients are still not clear, hemodialysis is the method of choice for the treatment. While hemodialysis is effective for the control of hypernatremia, it can cause bleeding complications that may be fatal for burn patients with extensive wounds and potential gastro-intestinal mucosal damage. CLINICAL DATA: In the present study heparin-free hemodialysis in which the heparin is firmly absorbed to the haemofiltration membrane, hemophan, dispensed with systemic use of heparin. In two extensively burned patients with burn area of 100% TBSA and 98% TBSA respectively and hypernatremia with serum sodium concentration as high as 169 and 158 mmol/l respectively, heparin-free hemodialysis was performed five times and three times each. RESULTS: Hypernatremia was satisfactorily corrected with no interference to the coagulation system in the two patients as indicated by clinical observation and biochemical analysis. The patient with burn area of 98% TBSA survived and the patient with burn area of 100% TBSA died of wound coverage failure 6 weeks after injury because of non-availability of autograft. CONCLUSION: Heparin-free hemodialysis is an effective and safe method in the treatment of hypernatremia in extensively burned patients.

Adult↗
PubMed2000

Photophysical processes of a copolymer containing naphthalene and carbazole rings.

The photophysical processes of copolymer formed by copolymerization of beta-naphthyl-methacrylate (NMA) with vinylcarbazole (VCZ) were studied. The results show that when the solution of copolymer (NMA-VCZ) in THF is located in a low concentration range (about 10(-8) mol/l), the fluorescence emission is in good agreement with that of NMA monomer and the excimer is formed with gradual increase in concentration of copolymer (NMA-VCZ). The fluorescence of copolymer (NMA-VCZ) can be efficiently quenched both by electron donors and acceptors where the quenching effects follow the Stern-Volmer equation. The dimolecular exciplex between copolymer (NMA-VCZ) and N,N-dimethylaniline (DMA) is formed and the triple exciplex is also observed in the same system.

Carbazoles↗
PubMed2000

[Exclusive mapping on polydactyly with markers on chromosome 7 and 2 in a Chinese kindred].

OBJECTIVE: This study was aimed at mapping polydactyly related genes in a Chinese kindred. METHODS: Linkage analysis was performed using 7 markers on chromosome 7 and 1 marker on chromosome 2. RESULTS: Pairwise linkage analysis showed no linkage between the markers and polydactyly related gene in the kindred. CONCLUSION: The polydactyly related gene in this kindred may be located on a new locus.

Chromosome Mapping↗
PubMed1998

MHCWeb: converting a WWW database into a knowledge-based collaborative environment.

The World Wide Web (WWW) is useful for distributing scientific data. Most existing web data resources organize their information either in structured flat files or relational databases with basic retrieval capabilities. For databases with one or a few simple relations, these approaches are successful, but they can be cumbersome when there is a data model involving multiple relations between complex data. We believe that knowledge-based resources offer a solution in these cases. Knowledge bases have explicit declarations of the concepts in the domain, along with the relations between them. They are usually organized hierarchically, and provide a global data model with a controlled vocabulary. We have created the OWEB architecture for building online scientific data resources using knowledge bases. OWEB provides a shell for structuring data, providing secure and shared access, and creating computational modules for processing and displaying data. In this paper, we describe the translation of the online immunological database MHCPEP into an OWEB system called MHCWeb. This effort involved building a conceptual model for the data, creating a controlled terminology for the legal values for different types of data, and then translating the original data into the new structure. The OWEB environment allows for flexible access to the data by both users and computer programs.

Artificial Intelligence↗
PubMed1997

A multicenter longitudinal clinical trial of a new system for restorations.

STATEMENT OF PROBLEM: A new method for fabrication of crowns and fixed partial dentures (Procera system) that involves electric discharge machining and copy milling has been developed. The metal used is unalloyed titanium, which can be processed as a single coping or multiple units joined to a pontic by laser welding. PURPOSE: The single-unit coping or the fixed partial denture (FPD) substructure is then veneered with a low-fusing porcelain. MATERIAL AND METHODS: In this article the clinical application of this technique was evaluated by six major universities in the United States. A total of 114 patients participated in this study, which involved 126 restorations (55 maxillary and 71 mandibular prostheses). There were 179 abutments, of which 73 were crowns and 53 were three-unit FPDs. Surface and color, anatomic form, and margin integrity were assessed 1 month after cementation and at 1 year with the California Dental Association (CDA) quality assessment evaluation system. RESULTS: No statistically significant differences in CDA scores between the 1 month evaluations and the 1 year assessments were found for surface and color (p = 0.68), anatomic form (p > 0.99), or margin integrity (p = 0.57). By use of the lowest ranking in the three categories as the overall quality of the restoration, only 3.3% (two crowns and two FPDs) were not acceptable at the 1-month visit and 4.5% (two crowns and three FPDs) were not acceptable at the 1-year evaluation. At-the 1-month visit 96.6% (114) of the restorations were considered to be satisfactory, whereas 95.5% (107 restorations) were evaluated similarly at the 1-year evaluation. CONCLUSIONS: The Procera system demonstrated, by use of the CDA criteria, its capability to produce quality prostheses that were rated satisfactory more than 95% of the time after insertion and maintained this high rating at least for 1 year.

Adolescent↗
PubMed1997

Isolation of specific DNA probes for detection of Cryptococcus neoformans.

We report the construction of a genomic library and isolation of repetitive DNA probes from Cr. neoformans that are species- and variety-specific. The inserts of the genomic library were in a range of 0.3-1.8 kb, which were in normal distribution in length. Among 592 clones of the genomic library, there were 400(67.6%) clones inserted repetitive DNA sequence and 192(32.4%) inserted single copy DNA sequence of the Cr. neoformans genome. From the library, three specific probes were identified. Clone pCNIIA6 was serotype A-specific, pCNIIB5 species-specific, and pCNIIIG1 variety-specific (var. neoformans). On the basis of the high specificity and sensitivity of the signals observed by hybridization, we suggest that these probes provide a means for both biotyping and early diagnosis of Cr. neoformans.

Cryptococcus neoformans↗
PubMed1997

Oxygen free radical injury and its relation to bacterial and endotoxin translocation after delayed fluid resuscitation: clinical and experimental study.

OBJECTIVE: To examine whether there is generation of oxygen free radicals (OFR) and lipid peroxidation of cell membrane after volume replacement for burn shock, and to study the relationship between OFR injury and enterogenous endotoxemia. METHODS: Forty-seven burn patients were involved in this study. Among them, 18 had delayed fluid resuscitation (DR) and the others had early fluid resuscitation (ER) within 6 hours postburn. Sixty-six gnotobiotic rats were used in a collaborating experiment as burn models. They were divided into 4 groups: sham injury (n = 6), early resuscitation (n = 24), late resuscitation (n = 24) and vitamins E and C treatment group (n = 12). All the rats, except those in the sham injury group, were inflicted with 40% total body surface area (TBSA) third-degree burns. OFR was determined in the blood of patients with electron spin resonance (ESR). S/W ratio and tau c values of patients' erythrocytes were measured with ESR spectrometer. Blood superoxide dismutase (SOD) and glutathione peroxidase (GSHPx) activities, malondialdehyde contents and plasma endotoxin levels were assayed. Rats were sacrificed at the 12th, 24th, 48th and 72nd hour after injury. Plasma endotoxin levels, mucosal SOD, GSHPx and malondialdehyde (MDA), as well as diamine oxidase activity of ileum were determined. Cultures of mesenteric lymph nodes (MLN), liver, spleen, heart, lung, kidney and blood were done. RESULTS: A significant increase in blood OFR contents and plasma MDA, and a significant decline in blood SOD and GSHPx were found after resuscitation in DR group as compared with those in ER group. Both strong to weak spectra component (S/W) ratio and tau c value were higher in DR group in contrast with those in ER group. Higher elevation in plasma endotoxin level in DR group was seen. In DR group, plasma MDA content was correlated with S/W ratio, tau c value and plasma endotoxin level. In rats, the level of mucosal MDA, plasma endotoxin and incidence of bacterial translocation (BT) were significantly higher. Mucosal SOD, GSHPx and diamine oxidase (DAO) activity were significantly lower in DR group as compared with those in ER group. In DR group, mucosal MDA content was negatively correlated with mucosal DAO activity, while the latter was negatively correlated with BT. After treatment with vitamins E and C, mucosal MDA content decreased, plasma endotoxin and BT significantly declined and mucosal DAO heightened. CONCLUSIONS: Tissue reperfusion might induce the production of OFR, resulting in lipid peroxidation injury, especially to intestinal mucosa, and resulting in disruption of mucosal barrier function followed by endotoxemia and BT.

Adolescent↗
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

[Isolation of specific DNA probes from Cryptococcus neoformans].

OBJECTIVE: To construct plasmid library and screen specific DNA probes for Cryptococcus neoformans. METHODS: Serotype A Cryptococcus neoformans was used as the study strain, plasmid pUC18 as vector, and Escherichia coli JM103 as host cell. The plasmid library of cryptococcus neoformans was constructed (pCN). Other pathogenes causing affection diseases which should be distinguished from cryptococcusis clinically, and other fungi similar to Cryptococcus neoformans with physiological and biochemical characteristics were used as a distinguishing system, specific colonies were screened by hibridization in double steps. RESULTS: The inserts of the library were 280 to 1800 base pairs and 580 base pairs in average length. Repeated sequence was 32.43% and single copy sequence was 67.57% in genome of cryptococcus neoformans respectively. Three specific colonies were isolated from the library. Colony pCNII A6 was serotype A specific, pCNII B5 species specific and pCNIII G1-specific for var. neoformans. CONCLUSION: A rapid diagnosis of Cryptococcus neoformans infection at early stage can be made by using species-specific probe, and serotype and variaty of neoformans and gattii be distinguished in epidemic study.

Cloning, Molecular↗
PubMed1996

[The sequences of intron 50 and 51 of DMD gene and the deletion mechanism of 51st exon].

OBJECTIVE: To investigate the relationship between the structural characters of 50th and 51st introns and deletion mechanisms of 51st exon of DMD gene. METHODS: We cloned the 3.1 Kb-Hind I human genome DNA fragment containing the 50 and 51 introns of DMD gene, sequenced the fragment completely, and analysed the character of the sequences with computer. RESULTS: The length of the fragment was 3179, including the entire 51st exon and partial 50th and 51st intron sequences. There were 36 short tandom repeats, 22 direct and inverted repeats, and 8 homologous sequences in the 50th and 51st introns. A TATA box was found in the intron 50 and it may be another new promotor of DMD gene. CONCLUSION: The hypothesis, which the recombination of repeat sequences may result in the deletion of 51st exon, is put forward.

Base Sequence↗
PubMed1996

Characterization of pathogenic fungi genomes using pulsed field gel electrophoresis.

Pulsed field gel electrophoresis (PFGE) has been firstly introduced in characterization of the pathogenic fungi Penicillium marneffei and Exophiala dermatitidis genomes. The numbers and sizes of their chromosomes have been detected. Polymorphism was identified on the smallest chromosome of E. dermatitidis. The result shows that PFGE for characterization of large molecular DNA pathogenic fungi is very suitable, it is more simple and more efficacy. The result also shows the diversity of pathogenic fungi is relative common even in rare occurred pathogenic fungi such as E. dermatitidis.

DNA, Fungal↗
PubMed1995

Bonding characteristics of low-fusing porcelain bonded to pure titanium and palladium-copper alloy.

This study compared bond strengths among palladium-copper alloy/VMK 68 porcelain, cast titanium/Duceratin porcelain, and machine-milled titanium/Procera porcelain combinations and investigated the mode of bond failure of these combinations. The effect of multiple firings on the bond strength of porcelain bonded to machine-milled pure titanium was then examined. A uniform thickness of 1 mm of porcelain was applied along an 8 mm length in the central portion of metal specimens measured 25 x 3 x 0.5 mm. The specimens were subjected to a three-point bending test on a load-testing machine with a span distance of 20 mm, and the load of bond failure was recorded and statistically analyzed. Two completely debonded specimens and two longitudinally sectioned specimens of each group were studied with a scanning electron microscope to determine the mode of bond failure. The bond strength of Pd-Cu/VMK 68 porcelain was significantly greater than two titanium/porcelain combinations. There was no significant difference in the bond strengths of porcelain bonded to machine-milled pure titanium among the five porcelain firing schedules.

Copper↗
PubMed1995

[Protective effects of vitamin E on impaired neutrophil phagocytic function in patients with severe burn].

The protective effects of vitamin E on impaired neutrophil phagocytic function were observed in 22 patients with severe burn. The results showed that lowering of SOD values, elevation of MDA values significantly elevated and impairment of neutrophil phagocytic function were all more marked in the patients who did not receive vitamin E than that of vitamin E treated groups and the healthy control. It was also found that there was a significant inverse correlation between MDA values of blood plasma and neutrophil phagocyte rate and phagocyte index in the patients without vitamin E treatment. The results suggested that in severely burned patients the use of free radical scavenger and antioxidant could protect the neutrophil function to certain extent. The optimal dosage of vitamin E will be further assessed.

Adolescent↗
PubMed1995

Some myths and legends about dental implants.

Dental practitioners are faced with difficulties in the interpretation of claims of superior properties of a dental system by a manufacturer at times. These difficulties stemmed from either insufficient information, inconsistent findings, lack of validity of the experiments, misinterpreted results or erroneous conclusions. The author attempted to address several frequently visited issues in the selection of a dental implant system. These issues included biocompatibility, the surface properties of titanium and its alloys, the efficacy of hydroxylapatite and calcium phosphate compounds, and the meaning of success rates.

Biocompatible Materials↗
PubMed1995

[Detection of hypermethylation in affected males with fragile X syndrome by PCR assay].

PCR technique was applied to detect hypermethylation at BssH II recognition sites within CpG island of FMR-1 gene in normal, affected, and clinically suspected males with fragile X syndrome. Hypermethylation was found to occur in all 7 affected and 5 of 26 suspected, but none of 15 normal males. The results of PCR assay are in good coincidence with those of Southern blot and cytogenetic assays. This PCR assay will be a promising method in the diagnosis of fragile X syndrome in males with mental retardation.

Base Sequence↗
PubMed1995

[Study on skin storage at -20 degrees C].

Small pieces of fresh guinea pig or cadaveric skin, 0.3mm in thickness, were soaked in cryoprotective solution for 30 min, then were put into plastic bags and kept in -20 degrees C refrigerator. Before and after 14, 30, 45, 60, 75 days storage, the skin were sent for succinae dehydrogenase assay (modified Hershey's method) and oxygen consumption determination (microelectrolyte method). The average viabilities measured by succinated dehydrogenase and oxygen consumption were nearly 50% after 60 days storage and 30% after 75 days storage in both guinea pig and cadaveric skin. 37 times of autologous skin stored at -20 degrees C for 1-26 days were grafted on the granulation wounds with good results. Skin can be preserved viably at -20 degrees C for 45 days but not longer than 60 days. This method may be helpful for hospital which has no -80 degrees C deep freezer or liquid nitrogen container.

Animals↗