Biomedical subjects

H W Ren

Publications and source records attributed to H W Ren.

6 recordsLinked to original sources

PubMed2006

Characterization of metallothioneins (MT-I and MT-II) in the yak.

The cDNA-encoding sequences for yak metallothionein isoforms I (MT-I) and II (MT-II) were amplified and cloned by reverse-transcription PCR to characterize the nucleotide sequence and protein structure of metallothionein in the yak. The cDNA sequences of MT-I and MT-II were subjected to BLAST searching at the National Center for Biotechnology Information, and the results indicated that the nucleotide sequences of yak MT-I and MT-II, when compared among different species of mammals, are highly conserved. The yak open reading frames have a length of 183 nucleotides, which encode for yak MT-I and MT-II proteins of 61 AA, respectively. Analysis of hydrophobicity, trans-membrane region, and signal peptides suggested that metallothioneins of the yak are nonsecretory proteins. There were several conserved tripeptide sequences, such as C-X-C, C-C-X-C-C, and C-X-X-C (X designates AA excluding cysteine in MT-I and MT-II), and they are highly conserved in their evolution. By homologous comparative modeling, we predicted the molecular spatial structures of yak MT-I and MT-II, which are composed of alpha- and beta-domains that are linked by the conserved tripeptide Lys(30)-Lys(31)-Ser(32) (KKS).

Amino Acid Sequence↗

PubMed2001

Fluorescence intermittency in self-assembled InP quantum dots.

Fluorescence intermittency in InP self-assembled dots is investigated by means of far field imaging and single dot spectroscopy. Based on our observation that blinking dots are found in the vicinity of scratches and the blinking frequency is drastically enhanced under a near-infrared laser irradiation, we attribute the origin of the fluorescence intermittency to a local electric field due to a carrier trapped at a deep localized center in the Ga0.5In0.5P matrix. The validity of this explanation is confirmed by a thermal activation-type behavior of the switching rate and artificial reproduction of the blinking phenomenon by an external electric field.

Journal Article↗

PubMed2001

Expression of Human Trefoil Factor 3 in Pichia pastoris and Its Biological Activity Analysis.

The human TFF3 (trefoil factor 3) DNA fragment was amplified by polymerase chain reaction (PCR) from human fetal placenta cDNA. The gene was cloned into the Pichia pastoris expression vector pPIC9K containing AOX 1 promoter and alpha-factor leader sequence. Multi-copies insertion transformants were screened on G418 plates. After the induction by 2% methanol for 48 hours, the expression of dimeric hTFF3 came up to 45% of total proteins in medium, as identified by SDS-PAGE and Western blot assay. The recombinant protein was further purified by S-Sepharose, Q-Sepharose ion-exchange chromatography and Sephacryl-S-100 gel filtration chromatography to the 95% purity, as shown by densitometric scanning. The N-terminus and molecular weight of the recombinant hTFF3 was in good agreement with the native hTFF3. The recombinant protein was proved to have good biological activity of preventing rats from the gastric ulcer induced by hydrochloric acid.

Journal Article↗

PubMed2000

Two metallothioneins in the fresh-water fish, crucian carp (Carassius cuvieri): cDNA cloning and assignment of their expression isoforms.

Two metallothionein cDNAs (MT-A and MT-B) in the fresh-water fish crucian carp (Carassius cuvieri Temminck et Schlegel) were cloned. Sequence analysis of both cDNAs gave the structure of a coding region corresponding to 60 amino acid residues. The homology of their deduced amino acid sequences was completely conserved at the positions of the cysteine residue, but a significant difference existed in the size of their 3'-untranslated regions (130 base pairs for MT-A and 280 base pairs for MT-B). Direct amino acid sequencing of the MT-II isoform purified by HPLC was accomplished for up to 30 residues and its sequence was identical to that deduced from MT-B cDNA. This is the first case in vertebrates that N-terminal methionine in crucian carp MT-II was not blocked. By northern blot analysis, basal and cadmium chloride- or dexamethasone-induced MT-B (MT-II) mRNAs were detected time dependently after treatment. On the other hand, the expression of MT-A mRNA was extremely low. These results indicate that the MT isoform II in crucian carp is coded by the MT-B gene, and that the MT-B-dominant expression of mRNA in crucian carp may be due to the difference in the 3'-untranslated regions of MT mRNAs.

Amino Acid Sequence↗

PubMed1999

Induction of two major isoforms of metallothionein in crucian carp (Carassius cuvieri) by air-pumping stress, dexamethasone, and metals.

The induction of metallothionein (MT) by physical and chemical stress was assessed using the fresh-water fish, crucian carp (Carassius cuvieri Temminck et Schlegel). The fish exposed to violent air-pumping stress for 6 days revealed time-dependent induction of MT-like metal-binding proteins in both their livers and kidneys. Their hepatic contents after exposure to stress were elevated to twice the basal level with 24 h, resulting in more than a 3-fold increase at 144 h, whereas their renal contents gradually increased after 24 h and reached the same level as that in the liver around 96 h. Two major inducible proteins were purified from livers of fish exposed to stress and were shown to be MT based upon their chromatographic behavior, UV absorption spectra and their molecular weights. Consequently, they were termed ccMT-1 and ccMT-2, according to their elution sequence upon anion-exchange chromatography. Both proteins mainly bound zinc in their endogenous forms and showed different immunogenicity to rat and rabbit MTs. Dexamethasone, a potent inducer for MT synthesis in mammals, induced the production of both isoforms in crucian carp, whereas cadmium and zinc ions prominently induced the synthesis of ccMT-2. These results indicate that crucian carp have the ability to produce MTs in response to various kinds of environmental stress and that violent air-pumping stress in crucian carp may induce MT synthesis, in part, via the release of endogenous factor(s), such as glucocorticoids.

Air↗

PubMed1999

The application of in vivo confocal microscopy and tear LDH measurement in assessing corneal response to contact lens and contact lens solutions.

PURPOSE: To evaluate differences in corneal response to daily wear (DW) of soft contact lens (CL) wear with different CL solutions and to assess the ability of in vivo confocal microscopy (CM) and tear lactate dehydrogenase (LDH) measurement to detect such differences in NZW rabbits. METHODS: Daily treatment of lenses consisted of a rub and rinse cleaning, then overnight soak in one of five solutions: Sauflon All in One (ALL), Compound A (CoA), OPTI-FREE((R) )Rinsing, Disinfecting, and Storage Solution (OPT), ReNu((R)) <?Pub Caret>Multipurpose Solution (REN), and UNISOL( (R)) Saline Solution (UNI). Rabbits (4/test group) wore 71% H( 2)O/type4 soft lenses approximately 7 hours daily. On days 0, 1, 3 and 7, slit lamp examination, tear LDH measurement, and in vivo CM were performed after removal of lenses. Using in vivo CM, epithelial thickness, epithelial cell area, and stromal thickness were measured, both centrally and peripherally. RESULTS: Epithelial thickness in ALL, CoA, and UNI-treated eyes showed a significant decrease of 15.6%, 13. 3%, and 10.6% (p < 0.05 in all groups), centrally, while CoA, OPT, and UNI showed a significant decrease of 9.3%, 7.1%, and 4.4% (p < 0. 05 in all groups), peripherally. ALL showed a significant 9.5% (p < 0.05) decrease of central cell area, while CoA showed a significant 21.5% (p < 0.01) decrease peripherally. UNI demonstrated a significant 3.2% (p < 0.05) decrease in central stromal thickness. ALL, CoA, and UNI showed a significant increase in LDH level of 152. 1%, 192.1%, and 308.2% (p < 0.05 in all groups) at day 3, respectively, but values declined at day 7. Significant changes in basal epithelial morphology were also observed with CoA on day 7 on in vivo CM. CONCLUSIONS: Overall, lens care solutions in combination with CL wear may interact to cause increased epithelial desquamation leading to decreased surface cell area and epithelial thickness. The clinical significance of these changes will require further investigation. In vivo CM combined with tear LDH assay is a quantitative, objective, non-invasive method of assessing CL wear and CL disinfecting solution effects on the cornea, and is able to detect differences in corneal response to different CL solutions.

Animals↗