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S M Chan

Publications and source records attributed to S M Chan.

At least 37 records · Page 2Linked to original sources
PubMed1999

Characterization of the shrimp eyestalk cDNA encoding a novel fushi tarazu-factor 1 (FTZ-F1).

To study the role of ecdysone and the ecdysone inducible gene in the regulation of molting and development in crustaceans, we have cloned a cDNA encoding an orphan nuclear receptor family member from the eyestalk of the shrimp Metapenaeus ensis. The size of the cDNA is 4.3 kb with the longest open reading frame (ORF) encoding a protein of 545 amino acid residues. The deduced amino acid sequence of the shrimp cDNA consists of regions that are characteristic of those of the nuclear hormone receptors. It shows a high degree of amino acid sequence identity in the DNA binding domain, ligand binding domain and the FTZ box as compared to those of invertebrates and vertebrates. Unlike the insects Drosophila melanogaster and Bombyx mori, an AF2 transactivation domain was present in the shrimp FTZ-F1. Northern blot analysis using total RNA indicated that the FTZ-F1 mRNA could also be detected in the mature ovary. Northern blot analysis and RT-PCR analysis showed that the shrimp FTZ-F1 transcripts could be detected in the ovary, newly hatched nauplius, testis, eyestalk and epidermis of the adult shrimp. Although the cDNA clone was isolated from the eyestalk library, the shrimp FTZ-F1 appeared to express most abundantly in the mature oocytes. The presence of abundant FTZ-F1 specific maternal message in the late vitellogenic ovary and early nauplius indicates that it may be important for the early embryonic and larval development of the shrimp. Interestingly, shrimp FTZ-F1 can also be found in testis of the male shrimp. The presence of FTZ-F1 in other tissues such as epidermis suggests that it may also be involved in other physiological processes such as molting.

Amino Acid Sequence↗
PubMed1999

Covalent linkage to beta2-microglobulin enhances the MHC stability and antigenicity of suboptimal CTL epitopes.

Many CTL epitopes of clinical importance, particularly those derived from tumor Ags, display relatively poor MHC binding affinity and stability. Because in vivo immunogenicity, and thus the efficacy of peptide-based vaccines, is thought to be determined by MHC/peptide complex stability, there is a need to develop a simple strategy for enhancing the binding of suboptimal epitopes. Toward this goal, the ability to enhance suboptimal peptides through covalent linkage to beta2-microglobulin (beta2m) was explored. Two suboptimal variants of a high-affinity Db-restricted influenza nucleoprotein peptide were covalently linked, via a polypeptide spacer, to the amino terminus of human beta2m and the recombinant fusion proteins expressed in Escherichia coli. When compared with their uncoupled counterparts, the beta2m-linked epitopes display enhanced MHC stabilization and antigenicity. Thus, tethering epitopes to beta2m provides a simple method for augmenting the biological activity of suboptimal peptides and could be useful in the design of peptide-based vaccines or immunotherapeutics.

Animals↗
PubMed1999

Effect of carbamide peroxide bleaching on the shear bond strength of composite to dental bonding agent enhanced enamel.

STATEMENT OF PROBLEM: Carbamide peroxide bleaching has been implicated in adversely affecting the bond strength of composite to enamel. PURPOSE: This in vitro study evaluated the effect of 3 dental bonding agents (OptiBond, All-Bond 2, One-Step) on the shear bond strength of a hybrid composite to enamel which was treated by a 10% carbamide peroxide bleaching system. MATERIAL AND METHODS: Cylinders of composite were bonded to carbamide peroxide-treated enamel on extracted human teeth using 3 dental bonding agents. After thermocycling, shear bond strengths were determined with a universal testing machine. RESULTS: OptiBond aided bond strengths were 23.7 +/- 5.6 MPa to bleached and 19.6 +/- 2.9 MPa to unbleached enamel. For All-Bond 2, bleached enamel exhibited bond strengths of 14.9 +/- 4.0 MPa and unbleached enamel exhibited a bond strength value of 20. 4 +/- 2.3 MPa. The composite bond strength for One-Step was 13.6 +/- 5.9 MPa to bleached and 23.0 +/- 3.9 MPa to unbleached enamel. There was no statistical difference between OptiBond (alcohol base) aided bond strengths for bleached and unbleached enamel; however, the bond strength of composite to bleached enamel with All-Bond 2 or One-Step (acetone base) was significantly lower than unbleached controls. CONCLUSION: The effect of bonding agent usage on composite bond strength to enamel bleached with a particular carbamide peroxide was dependent on the bonding agent used.

Analysis of Variance↗
PubMed1998

The shrimp hyperglycemic hormone-like neuropeptide is encoded by multiple copies of genes arranged in a cluster.

The crustacean hyperglycemic hormone (CHH) plays an important role in the regulation of glucose metabolism. We have cloned and sequenced several cDNAs encoding the preproCHH-like of the shrimp, Metapenaeus ensis. The preproCHH-like peptide of the shrimp consists of a signal peptide, a CHH precursor-like peptide (CPRP) and the CHH-like peptide. Comparative analysis revealed that the signal peptide and the CPRP of the shrimp peptide are the shortest among all the CHHs reported. MeCHH-like is expressed in the eyestalk, but it is not expressed in the heart, hepatopancreas, muscle, nerve cord and pre-hatch embryo. To study the structural organization of the shrimp CHH-like gene, we have screened the genomic DNA library constructed from one shrimp. Three groups of overlapping genomic clones have been isolated. The results from both genomic Southern blot analysis and library screening indicate that the shrimp genome contains at least six copies of the CHH-like genes arranged in a cluster on the chromosome. The size of the CHH-like genes is 1.5-2.1 kb. DNA sequence determinations indicate that the CHH-like genes share 98-100% amino acid sequence identity. There are three exons and two introns in each CHH-like gene. The first intron separates the signal peptide and the second intron separates the mature peptide in the coding region. The 150-200 bp of the upstream 5' flanking region of the CHH-like genes contains promoters with characteristics similar to most eukaryotic genes. Several putative cis-acting elements are also identified in the first 400 bp 5' end upstream region. The organization of the shrimp CHH-like genes is similar to that of the molt inhibiting hormone gene of the same shrimp and the crab, Charybdis feriatus.

Amino Acid Sequence↗
PubMed1998

PCR cloning and expression of the molt-inhibiting hormone gene for the crab (Charybdis feriatus).

A PCR-based genomic DNA walking technique was used to clone the gene for the molt-inhibiting hormone of the crab, Charybdis feriatus. Several overlapping genomic clones were isolated, and the MIH gene for the crab was reconstructed. DNA sequence determination of the overlapping clone reveals that the MIH gene spans 4.3kb and consists of three exons and two introns. Exons 1 and 2 carry a coding sequence for the signal peptide, and exons 2 and 3 consist of coding sequence for the mature peptide. The exon-intron boundary of the crab MIH gene also follows the 'GT-AG rule' for the splice donor and acceptor. The deduced amino acid sequence of MIH shows the highest overall similarity to those of the crabs, Callinectes sapidus and Carcinus maenas, and the gonad-inhibiting hormone (GIH) of the lobster. The putative polyadenylation signal is approximately 1.0kb 3' downstream of the termination codon (TGA). Genomic Southern blot analysis indicates that few genomic fragments were hybridized to the cDNA probe. The 5' flanking region contains a putative promoter with several putative cis elements similar to some vertebrate neuropeptide genes. The 530-bp flanking region was subcloned separately to two promoterless reporter plasmids carrying either the Green Fluorescent Protein gene (GFP) or the Choramphenicol Acetyltransferase gene (CAT). The DNA constructs were transfected into insect cells (Sf21) and mouse pituitary cells (GH4ZR7), respectively. Green fluorescent protein was detected in some of the transfected insect cells, and expression of the CAT was detected in cells transfected with DNA constructs containing the crab promoter. By RT-PCR, MIH transcripts can be detected in the eyestalk of shrimp in intermolt, early premolt, late premolt stages and females that brood their eggs. It can also be found in the brain, but not in the ovary, hepatopancreas, muscle and epidermis. During early larval development, MIH mRNA can be detected in the pre-hatched and the newly hatched larvae. Unlike the adult, the expression of the MIH in the larvae is exclusively in the brain.

Amino Acid Sequence↗
PubMed1998

Cloning of a shrimp (Metapanaeus ensis) cDNA encoding a nuclear receptor superfamily member: an insect homologue of E75 gene.

Degenerate primers were derived from the amino acid sequence in the DNA binding domain of the Drosophila ecdysone receptor (DmEcR). Several partial cDNAs were amplified from the shrimp epidermis by reverse transcription polymerase chain reaction (RT-PCR). One of these fragments shows the highest amino acid sequence homology to the insect ecdysone inducible gene E75. This partial cDNA was used as a probe to screen the swimming leg cDNA library of the shrimp, Metapenaeus ensis. A 3.6 kb cDNA clone was obtained. The longest open reading frame of this cDNA consists of 606 amino acids and its deduced amino acid sequence has all five domains typical of a nuclear receptor. The putative polyadenylation signal is located at about 400 bp 3' to the stop signal. The deduced amino acid sequence of this cDNA shows the highest identity to that of the E75A reported in Manduca sexta, Galleria melonella, Drosophila melanogaster, and Choristoneura fumiferana. Based on the amino acid sequence comparison, the shrimp nuclear receptor is considered the insect homologue of E75A. Northern blot analysis shows that the shrimp E75 is expressed in the epidermis, eyestalk and the nerve cord of the pre-molt shrimp. Moreover, E75 transcripts can be detected in the epidermal tissues of early pre-molt shrimp by in situ hybridization. To determine whether the shrimp could also express other E75s like the insects, 5' end RACE and RT-PCR were performed on epidermal cDNA of a single shrimp. Subcloning and DNA sequence determination of the PCR products confirmed the presence of two other forms of E75 (tentatively called E75C and E75D) in shrimp. By RT-PCR, different levels of E75 expression can be detected in the epidermis, nerve cord and the eyestalk of early pre-molt shrimp. In addition to the different levels of expression of the shrimp E75s in the epidermis, the pattern of their expression is also different during the molting cycle. This is the first report on the cloning of a shrimp nuclear receptor superfamily member.

Amino Acid Sequence↗
PubMed1998

Bilateral choroidal metastases as the initial presentation of a small breast carcinoma: a case report.

Most ocular tumors metastasize from systemic origins in breast carcinoma in females, and bronchial carcinoma in males. Here, we report a case of choroidal carcinoma metastasis from the breast with visual problems being the only initial manifestations. In this case, both eyes were involved at almost the same time, with initial manifestation of blurred vision which progressed to complete visual loss. At first, the patient was diagnosed with malignant melanoma, and enucleation of the right eye was performed in another hospital. However, the tumor had already metastasized rapidly to numerous organs, including the lungs, brain and bone, although it had not affected the liver. Clinical presentations were, therefore, not compatible with those of malignant melanoma, which has usually been reported to metastasize to the liver. Persistent hypercalcemia and raised carcinoembryonic antigen (CEA) concentrations prompted investigations into the possibility of systemic malignancy. A very small breast nodule was finally located by thorough physical examination, and a lumpectomy was performed. A detailed review of the histopathology showed the tumors from the breast and the right eye to have the same origin. Simultaneous bilateral choroidal metastases from other malignancies is not uncommon; however, it is quite rare for breast carcinoma to present with visual problems as a first manifestation. Detailed history taking and physical examination are therefore essential when searching for a primary tumor, so that appropriate therapy can be given earlier.

Adult↗
PubMed1998

Cloning of a cDNA encoding a putative molt-inhibiting hormone from the eyestalk of the sand shrimp Metapenaeus ensis.

Degenerate primers were designed from the amino acid sequence of the neuropeptide Pej-SGP-IV of the shrimp Penaeus japonicus. Reverse transcriptase-polymerase chain reaction (RT-PCR) was performed using eyestalk complementary DNA of the sand shrimp Metapenaeus ensis. A partial cDNA that codes for a protein homologous to the neuropeptide Pej-SG-IV was cloned. The partial cDNA was used as a probe to screen the eyestalk cDNA library. Several cDNA clones with nucleotide sequence identical to the partial cDNA were isolated. The largest cDNA is 957 bp with an open reading frame consisting of a coding sequence 315 bp in length. The deduced amino acid of the neuropeptide consists of 77 amino acids and is preceded by a signal peptide of 28 amino acids. Because the deduced amino acid sequence of the shrimp cDNA is highly homologous to the Pej-SGP-IV of P. japonicus (which is molt inhibiting) and to other crustaceans' molt-inhibiting hormones (MIHs), the shrimp neuropeptide is tentatively called MeMIH. Northern blot analysis and RT-PCR showed that MeMIH is expressed in the postmolt, intermolt, and premolt stages of the shrimp eyestalks and the brain. Moreover, RNA message can also be detected in the nervous tissues of newly developed larvae. MeMIH is, however, not found in the muscle, swimming leg, and hepatopancreas. Results from genomic Southern blot analysis and amplification of the shrimp genomic DNA by polymerase chain reaction (PCR) suggest that a single copy of the MIH gene is present in the genome. The structural organization of the gene for the shrimp putative MIH is similar to that of the crab Charybdis feriatus.

Amino Acid Sequence↗
PubMed1997

Randomized controlled trial to evaluate flush and reperfusion techniques in liver transplantation.

To determine the impact of different flush and reperfusion techniques on postreperfusion syndrome (PRS) and postoperative graft function, 100 transplants were randomly assigned into four groups as follows: group 1 (n=31), portal vein flush, no vena caval venting; group 2 (n=21), hepatic arterial flush, no vena caval venting; group 3 (n=29), portal vein flush with vena caval venting; and group 4 (n=19), hepatic artery flush with vena caval venting. Donor and recipient characteristics were similar. Extensive intraoperative and postoperative monitoring was performed and measurements were documented immediately before reperfusion and at 1, 5, 15, and 30 min after reperfusion. PRS was defined by three criteria: mean arterial pressure (MAP) <60 mmHg at 1 min after reperfusion, MAP <60 mmHg at 5 min after reperfusion, and a decrease of 30% or more for the MAP percent area under the curve during the initial 5 min after reperfusion (%AUC). Using these definitions, the overall incidence of PRS was 21%, 8%, and 43%, respectively. Group 1 was the most hemodynamically stable; the incidence of PRS in group 1 was 2/31 (7%) at 1 min and 8/31 (25%) using %AUC criteria compared with 7/21 (33%) at 1 min and 12/21 (57%) using %AUC criteria for group 2 (P<0.05). The patients in groups 3 and 4 (vena caval venting) demonstrated smaller percentage increases in serum potassium levels (as determined by %AUC; 4.3+/-6.8 and 0.3+/-5.4, vs. 15.1+/-8.1 for group 1 and 22.9+/-8.2 for group 2). The difference between group 4 and group 2 was statistically significant (P<0.05). The increases in serum potassium did not translate into increased cardiac or hemodynamic instability. Combining all data obtained over the first 30 min after reperfusion, there was no statistically significant difference in hemodynamic or biochemical changes noted among the four groups. Postoperative liver function was similar among the four groups. We conclude that portal vein flush without vena caval venting provided a lower incidence of PRS than any other technique. Vena caval venting decreased the release of potassium into the circulation. Postoperative graft function was not significantly affected by flush and reperfusion techniques.

Adult↗
PubMed1996

Characterization and inhibition of a cholecystokinin-inactivating serine peptidase.

A cholecystokinin (CCK)-inactivating peptidase was purified and identified as a membrane-bound isoform of tripeptidyl peptidase II (EC 3.4.14.10), a cytosolic subtilisin-like peptidase of previously unknown functions. The peptidase was found in neurons responding to cholecystokinin, as well as in non-neuronal cells. Butabindide, a potent and specific inhibitor, was designed and shown to protect endogenous cholecystokinin from inactivation and to display pro-satiating effects mediated by the CCKA receptor.

Amino Acid Sequence↗
PubMed1992

SpCOUP-TF: a sea urchin member of the steroid/thyroid hormone receptor family.

Embryonic nuclear proteins from the sea urchin Strongylocentrotus purpuratus bind in vitro to a cis-acting element that lies upstream of the actin gene CyIIIb and consists of two direct repeats homologous to steroid hormone response elements. This sea urchin element is specifically recognized by transcription factor COUP-TF from HeLa cell nuclear extracts as well. A sea urchin gene homologous to the human COUP-TF1 gene was detected by blot hybridization to S. purpuratus genomic DNA. Screening of a genomic DNA library with a human COUP-TF1 cDNA probe produced overlapping genomic clones that carry the S. purpuratus gene. Our results indicate that the sea urchin homologue has a structure similar to the human COUP-TF1 gene, i.e., conserved intron positions characteristic of this subgroup of steroid hormone receptors. Sequencing of the exons that encode the DNA- and ligand-binding domains of the sea urchin protein revealed 96% and 92% amino acid identity to the domains of the human protein, respectively. Transcripts derived from the S. purpuratus COUP-TF homologous gene were detected in ovarian and embryonic RNAs from various stages.

Actins↗
PubMed1991

Effects of flow on recombinant tissue plasminogen activator-induced pulmonary thrombolysis.

We employed a canine model of pulmonary embolism induced by injection of radioactive blood clots to investigate effects of changes in cardiac output (CO) on recombinant tissue plasminogen activator- (rtPA) induced pulmonary thrombolysis. Rate and extent of thrombolysis were assessed with a gamma camera. Eighteen dogs were studied. Emboli increased mean pulmonary arterial pressure and decreased CO from 2.6 to 1.9 l/min (P less than 0.001). Subsequently, dogs were randomly divided into three groups: group 1 received 0.5 mg/kg of rtPA over 30 min; 30 min before the same dose regimen of rtPA, in the six group 2 dogs, mean CO was increased to approximately 3.25 l/min by opening one systemic arteriovenous fistula; in the six group 3 dogs, before rtPA, mean CO was increased to approximately 4.5 l/min by opening two or three fistulas. After embolization, CO remained low in group 1; the mean 2-h time-averaged CO was 1.8 l/min. CO was much higher in groups 2 and 3 (3.3 and 4.6 l/min, respectively; both P less than 0.001 compared with group 1; and P less than 0.001, group 2 vs. group 3). Compared with group 1, corresponding to the increased flow in groups 2 and 3, rate and extent of pulmonary thrombolysis significantly increased. These results indicate that an increase in flow per se augments rtPA-induced pulmonary thrombolysis. Also, because thrombolysis was similar between groups 2 and 3, these results define an upper limit to the flow-thrombolytic relationship with rtPA.

Animals↗