Biomedical subjects

Hongqi Li

Publications and source records attributed to Hongqi Li.

5 recordsLinked to original sources

PubMed2006

Promising clinical outcome of stereotactic body radiation therapy for patients with inoperable Stage I/II non-small-cell lung cancer.

PURPOSE: To evaluate the efficacy and toxicity of hypofractionated stereotactic body radiotherapy in patients with Stage I/II non-small-cell lung cancer. METHODS AND MATERIALS: Forty-three patients with inoperable Stage I/II non-small-cell lung cancer underwent treatment prospectively using the stereotactic gamma-ray whole-body therapeutic system (body gamma-knife radiosurgery) with 30 rotary conical-surface Co(60) sources focused on the target volume. Low-speed computed tomography simulation was conducted, which was followed by three-dimensional conformal radiotherapy planning. A total dose of 50 Gy was delivered at 5 Gy/fraction to the 50% isodose line covering the planning target volume, whereas a total dose of 70 Gy was delivered at 7 Gy/fraction to the gross target volume. The median follow-up duration was 27 months. RESULTS: Three to 6 months after treatment, the complete response rate for body-gamma knife radiosurgery was 63%, and the overall response rate was 95%. The 1-year, 2-year, and 3-year local control rates were all 95% in all patients. The 1-year, 2-year, and 3-year overall survival rates were 100%, 91%, and 91%, respectively, in patients with Stage I disease and 73%, 64%, and 64%, respectively, in those with Stage II disease. Only 2.3% (1/43) of the patients had Grade 3 pneumonitis. CONCLUSION: Our highly focused stereotactic body radiotherapy method resulted in promising local control and survival with minimal toxicity.

Adenocarcinoma↗

PubMed2006

Mechanical behavior of bulk amorphous alloys reinforced by ductile particles at cryogenic temperatures.

The mechanical behavior of Zr-based bulk amorphous alloy composites (BAACs) was investigated at 77 K. The 5 vol. % Ta-BAAC maintained large plastic strains of approximately 13% with a 16% strength increase, when compared with that at 298 K. The interaction between shear bands and particles shows that shear extension in particles has limited penetration, and shear bands build up around particles. In addition to on the failure surface of the amorphous matrix, molten characteristics were also found on the surface of sheared particles. Pair distribution function studies were performed to understand the mechanical behavior.

Journal Article↗

PubMed2004

Effects of autolysis on properties of mu- and m-calpain.

Although the biochemical changes that occur during autolysis of mu- and m-calpain are well characterized, there have been few studies on properties of the autolyzed calpain molecules themselves. The present study shows that both autolyzed mu- and m-calpain lose 50-55% of their proteolytic activity within 5 min during incubation at pH 7.5 in 300 mM or higher salt and at a slower rate in 100 mM salt. This loss of activity is not reversed by dialysis for 18 h against a low-ionic-strength buffer at pH 7.5. Proteolytic activity of the unautolyzed calpains is not affected by incubation for 45 min at ionic strengths up to 1000 mM. Size-exclusion chromatography shows that ionic strengths of 100 mM or above cause dissociation of the two subunits of autolyzed calpains and that the dissociated large subunits (76- or 78-kDa) aggregate to form dimers and trimers, which are proteolytically inactive. Hence, instability of autolyzed calpains is due to aggregation of dissociated heavy chains. Autolysis removes the N-terminal 19 (m-calpain) or 27 (mu-calpain) amino acids from the large subunit and approximately 90 amino acids from the N-terminus of the small subunit. These regions form contacts between the two subunits in unautolyzed calpains, and their removal leaves only contacts between domain IV in the large subunit and domain VI in the small subunit. Although many of these contacts are hydrophobic in nature, ionic-strength-induced dissociation of the two subunits in the autolyzed calpains indicates that salt bridges have an important, possibly indirect, role in the domain IV/domain VI interaction.

Animals↗

PubMed2003

The calpain system.

The calpain system originally comprised three molecules: two Ca2+-dependent proteases, mu-calpain and m-calpain, and a third polypeptide, calpastatin, whose only known function is to inhibit the two calpains. Both mu- and m-calpain are heterodimers containing an identical 28-kDa subunit and an 80-kDa subunit that shares 55-65% sequence homology between the two proteases. The crystallographic structure of m-calpain reveals six "domains" in the 80-kDa subunit: 1). a 19-amino acid NH2-terminal sequence; 2). and 3). two domains that constitute the active site, IIa and IIb; 4). domain III; 5). an 18-amino acid extended sequence linking domain III to domain IV; and 6). domain IV, which resembles the penta EF-hand family of polypeptides. The single calpastatin gene can produce eight or more calpastatin polypeptides ranging from 17 to 85 kDa by use of different promoters and alternative splicing events. The physiological significance of these different calpastatins is unclear, although all bind to three different places on the calpain molecule; binding to at least two of the sites is Ca2+ dependent. Since 1989, cDNA cloning has identified 12 additional mRNAs in mammals that encode polypeptides homologous to domains IIa and IIb of the 80-kDa subunit of mu- and m-calpain, and calpain-like mRNAs have been identified in other organisms. The molecules encoded by these mRNAs have not been isolated, so little is known about their properties. How calpain activity is regulated in cells is still unclear, but the calpains ostensibly participate in a variety of cellular processes including remodeling of cytoskeletal/membrane attachments, different signal transduction pathways, and apoptosis. Deregulated calpain activity following loss of Ca2+ homeostasis results in tissue damage in response to events such as myocardial infarcts, stroke, and brain trauma.

Animals↗

PubMed2002

Immunoaffinity purification of calpastatin and calpastatin constructs.

It has been difficult to purify calpastatin without using a step involving heating to 90-100 degrees C. Preparations of calpastatin obtained after heating often contain several polypeptides that have been ascribed to proteolytic degradation. Because calpastatin is highly susceptible to proteolytic degradation and several different calpastatin isoforms can be produced by using different start sites of transcription/translation and/or alternative splicing from the single calpastatin gene, it is not clear whether the different polypeptides observed in purified calpastatin preparations are proteolytic fragments or calpastatin isoforms. It would be useful, therefore, to have a method for purifying calpastatin that does not involve heating. At low ionic strength, calpastatin from skeletal muscle extracts binds quantitatively to an immunoaffinity column made by coupling a monoclonal antibody (MAb) to the C-terminal end of calpastatin (epitope between amino acids 707 and 786) to agarose; the bound calpastatin can be eluted at pH 2.5. The C-terminal end of the calpastatin polypeptide was used because the known isoforms of calpastatin all contain domain IV. The eluted calpastatin, which retains all its calpain inhibitory activity, consists largely of a 125 kDa polypeptide (70%), and several smaller polypeptides that are labeled with a MAb to calpastatin. Expressed calpastatin constructs representing the full-length XL-IV calpastatin and domains L-IV, II-IV, III-IV, and IV also bind to the immunoaffinity column and can be purified. The immunoaffinity column is especially useful for purifying calpastatin from small tissue samples in a single step.

Animals↗