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Biomedical subjects

P P Lin

Publications and source records attributed to P P Lin.

At least 19 recordsLinked to original sources
PubMed2005

Bioanalytical method development and validation for a large peptide HIV fusion inhibitor (Enfuvirtide, T-20) and its metabolite in human plasma using LC-MS/MS.

A method for measuring a human immunodeficiency virus (HIV) cell membrane fusion inhibitor (T-20/Ro 29-9800) and its metabolite (M-20/Ro 50-6343) in human plasma by liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed. The relatively large peptide analytes and their corresponding deuterated (d(10)) peptides used as internal standard were isolated from plasma by protein precipitation with two volumes of acetonitrile to plasma. A large pore size reversed-phase C(18) column was employed to elute the peptides. A triple quadrupole mass spectrometer with electrospray interface operating in positive ion and multiple reaction monitoring modes with transitions m/z 1124-->1343 for both T-20 and M-20 was utilized for peak detection. The advantages of the method were a simple sample preparation, specific and sensitive MS/MS detection, and a wide dynamic range of 10-2000 ng/ml for T-20. The method was validated and used for analyzing samples from clinical studies to provide pharmacokinetic profiles of the HIV fusion inhibitor peptide drug and its metabolite.

Adsorption↗
PubMed2001

Gender difference in DNA adduct levels among nonsmoking lung cancer patients.

Lung cancer is the leading cause of cancer mortality in Taiwanese women. Cigarette smoking cannot explain the high lung cancer mortality in this population because less than 10% of women in Taiwan are smokers. Therefore, environmental factors other than smoking may play an important role in lung cancer development in female nonsmokers. The purpose of this study was to elucidate the role of environmental carcinogen exposure in lung cancer development in Taiwanese female nonsmokers, based on DNA adduct formation. We collected nontumorous lung tissues resected from 62 nonsmoking lung cancer patients and 20 noncancer controls to investigate whether differences in susceptibility to DNA adduct formation exist between men and women. (32)P-postlabeling and ELISA (enzyme-linked immunosorbent assay) with polyclonal antibody against BPDE (7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene)-DNA adduct were used to evaluate DNA adduct levels in lung tissues of study subjects. Our data showed that the DNA adduct levels of lung cancer patients determined by both assays were significantly higher than those of noncancer controls (P = 0.0001 for (32)P-postlabeling; P = 0.01 for ELISA). Moreover, DNA adduct levels in females were markedly greater than those in males (P = 0.014 for (32)P-postlabeling; P = 0.001 for ELISA). The difference in DNA adduct levels could not be explained by genetic polymorphisms of cytochrome P-4501A1 (CYP1A1) or glutathione S-transferase (GSTM1), as determined by polymerase chain reaction and restriction fragment length polymorphism. These results demonstrate that lung cancer patients have a higher susceptibility to DNA damage than that of noncancer controls. In addition, differences in susceptibility to DNA damage derived from environmental carcinogen exposure were observed between male and female nonsmokers. In conclusion, high susceptibility to DNA damage in females may partially explain the high mortality rate of lung cancer in nonsmoking Taiwanese women.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1999

Simultaneous assay of morphine, morphine-3-glucuronide and morphine-6-glucuronide in human plasma using normal-phase liquid chromatography-tandem mass spectrometry with a silica column and an aqueous organic mobile phase.

Morphine (MOR) is an opioid analgesic used for the treatment of moderate to severe pain. MOR is extensively metabolized to morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). A rapid and sensitive method that was able to reliably detect at least 0.5 ng/ml of MOR and 1.0 ng/ml of M6G was required to define their pharmacokinetic profiles. An LC-MS-MS method was developed in our laboratory to quantify all three analytes with the required sensitivity and a rapid turnaround time. A solid-phase extraction (SPE) was used to isolate MOR, M3G, M6G, and their corresponding deuterated internal standards from heparinized plasma. The extract was injected on a LC tandem mass spectrometer with a turbo ion-spray interface. Baseline chromatographic separation among MOR, M3G, and M6G peaks was achieved on a silica column with an aqueous organic mobile phase consisting of formic acid, water, and acetonitrile. The total chromatographic run time was 3 min per injection, with retention times of 1.5, 1.9 and 2.4 min for MOR, M6G, and M3G, respectively. Chromatographic separation of M3G and M6G from MOR was paramount in establishing the LC-MS-MS method selectivity because of fragmentation of M3G and M6G to MOR at the LC-MS interface. The standard curve range in plasma was 0.5-50 ng/ml for MOR, 1.0-100 ng/ml for M6G, and 10-1000 ng/ml for M3G. The inter-day precision and accuracy of the quality control (QC) samples were <7% relative standard deviation (RSD) and <6% relative error (R.E.) for MOR, <9% RSD and <5% R.E. for M6G, and <3% RSD and <6% R.E. for M3G. Analyte stability during sample processing and storage were established. Method ruggedness was demonstrated by the reproducible performance from multiple analysts using several LC-MS-MS systems to analyze over one thousand samples from clinical trials.

Chromatography, Liquid↗
PubMed1999

Differential transactivation by alternative EWS-FLI1 fusion proteins correlates with clinical heterogeneity in Ewing's sarcoma.

The t(11;22)(q24;q12) translocation is present in up to 95% of cases of Ewing's sarcoma and results in the formation of an EWS-FLI1 fusion gene which encodes a chimeric transcription factor. The proximate role of EWS-FLI1 in the pathogenesis of Ewing's sarcoma is thought to involve the activation of as yet largely unknown target genes. Many alternative forms of EWS-FLI1 exist because of variations in the locations of the EWS and FLI1 genomic breakpoints. The most common form, designated "type 1," consists of the first seven exons of EWS joined to exons 6-9 of FLI1 and accounts for approximately 60% of cases. The "type 2" EWS-FLI1 fusion also includes FLI1 exon 5 and is present in another 25%. We and others have observed previously that the type 1 fusion is associated with a significantly better prognosis than the other fusion types. Because EWS-FLI1 is an aberrant transcription factor, we investigated whether these differences in clinical behavior may be correlated to functional differences by comparing transactivation by the type 1 EWS-FLI1 with other types in both heterologous cells (HeLa, NIH3T3) and homologous cells (Ewing's sarcoma cell lines). In a panel of seven Ewing's sarcoma cell lines, we found transactivation of a transiently transfected FLI1-responsive reporter construct to be significantly lower in cell lines with the type 1 fusion than in cell lines with the type 2 fusion (P = 0.003). Cotransfection of the same reporter construct with each of a series of seven EWS-FLI1 expression constructs (corresponding to the two major fusion types and five less common types) also showed that type 1 EWS-FLI1 was a significantly weaker transactivator than the type 2 product in both HeLa and NIH3T3 cells (P = 0.003, and P = 0.033, respectively). Electromobility shift assays showed equivalent binding of the type 1 and type 2 EWS-FLI1 to the consensus FLI1-responsive binding site, indicating that differences in transactivation were not due simply to differences in DNA binding affinity. The finding that the type 1 EWS-FLI1 fusion, associated with less aggressive clinical behavior, encodes a less active chimeric transcription factor may provide the basis for a molecular explanation of clinical heterogeneity in Ewing's sarcoma.

3T3 Cells↗
PubMed1999

Relationship between magnitude of resection, complication, and prosthetic survival after prosthetic knee reconstructions for distal femoral tumors.

BACKGROUND AND OBJECTIVES: Limb-sparing surgery has become the preferred surgical treatment of malignant bone tumors. The objective of this study was to evaluate factors that influence the morbidity and outcome of prosthetic knee replacement after resection of malignant tumors of the distal femur. METHODS: Eighty-two patients who had a resection of malignant tumor of the distal femur and implantation of a segmental knee prosthesis (minimum follow-up, 2 years) were retrospectively reviewed. RESULTS: Twenty-nine patients (35%) underwent 32 prosthetic revisions, 6 from perioperative wound complications, 13 from aseptic loosening, and 13 from other complications. The 3-, 5-, and 10-year Kaplan-Meier prosthetic survival rates were 82%, 71%, and 50%, respectively. On univariate analysis, patients who had more than 40% resection of the distal femur (P = 0.010) and those who had all their vasti muscles resected (P = 0.011) had significantly worse prosthetic survivals than the others. On multivariate analysis, resection of more than 40% of the distal femur was a significant negative prognostic factor for prosthetic survival (P = 0.017). Aseptic loosening was the primary cause of late prosthetic failure. Differences in the magnitude of resection influenced prosthetic survivorship more than prosthetic design. CONCLUSIONS: In the distal femoral endoprosthetic replacement, higher short- and long-term complications were found after extensive resections. Aseptic loosening was the primary cause of prosthetic failure.

Adolescent↗
PubMed1998

Pathologic femoral fracture after periosteal excision and radiation for the treatment of soft tissue sarcoma.

BACKGROUND: Surgical resection and adjuvant radiation therapy are standard therapy for soft tissue sarcomas. When the tumor approximates bone, periosteal excision may be necessary. It was hypothesized that periosteal stripping and radiation therapy would increase the rate of pathologic fracture. METHODS: The soft tissue sarcoma data base at the Memorial Sloan-Kettering Cancer Center was used to identify a consecutive series of 205 patients who were treated over a 15-year period (1982-1997). All patients had a soft tissue sarcoma of the thigh, which was managed by limb-sparing surgery and radiation therapy. Patients who had bone invasion by tumor or bone resection were not included. RESULTS: Nine patients, including eight women and one man, developed a femoral fracture in an area of previous radiation and surgery. All nine patients had undergone periosteal excision. The risk of fracture, by Kaplan-Meier survivorship, was 29% at 5 years if the resection included periosteum (P < 0.0001). Cox multiple regression analysis showed that periosteal excision was the only independent prognostic factor for the entire set of 205 patients at risk. However, for the subset of 54 patients who had periosteal stripping, two factors were also found to be prognostically important: female gender (P=0.022) and chemotherapy (P=0.020). The risk of fracture was 47% and 45%, respectively. The treatment of the fractures was difficult. There were four nonunions and three delayed unions. CONCLUSIONS: Periosteal stripping and radiation therapy places the femur at high risk of pathologic fractures, especially for female patients and patients undergoing chemotherapy. When practical, the combination of periosteal stripping and radiation should be avoided.

Adult↗
PubMed1998

Prognostic factors for patients with sarcomas of the pelvic bones.

BACKGROUND: Treatment of malignant tumors of the pelvis represents one of the most difficult problems in musculoskeletal oncology. However, factors that influence the local and systemic control of the disease remain ill-defined. METHODS: One hundred and two patients with localized pelvic sarcomas who underwent a surgical excision of the tumors were analyzed. The tumor diagnosis was chondrosarcoma in 49 patients, osteosarcoma in 26 patients, Ewing's sarcoma in 20 patients, and other tumors in 7 patients. The tumor was located in the ilium in 65 patients, the pubis in 21 patients, the ischium in 8 patients, and the sacrum in 8 patients. Eighty-three patients underwent a limb-sparing surgery and 19 patients underwent hemipelvectomy. Prognostic factors for local recurrence, metastasis, and survival were analyzed. RESULTS: At last follow-up, 47 patients were disease free, 7 were alive with disease, and 48 had died. The 5-year survival rate was 55% (chondrosarcoma: 65%, osteosarcoma: 47%, and Ewing's sarcoma: 52%). Inadequate surgical margin emerged as the only independent adverse prognostic factor for local recurrence. For distant metastasis, surgical stage remained as an independent prognostic factor. Patients who underwent a hemipelvectomy and those who had an inadequate surgical margin had significantly poorer survivals. CONCLUSIONS: Pelvic sarcomas remain diseases with a poor prognosis. Independent prognostic factors are few; an adequate surgical margin is critical to prevent local recurrence, and the surgical stage is related to the risk of distant metastasis. Surgical margins and hemipelvectomy were predictors of survival, but the patients who underwent hemipelvectomy also tended to have the largest, most advanced tumors. Hemipelvectomy should be considered when there is sacral involvement.

Adolescent↗
PubMed1998

Deep venous thrombosis after orthopedic surgery in adult cancer patients.

BACKGROUND AND OBJECTIVES: Patients with cancer and patients undergoing major orthopedic procedures are two groups at risk of deep venous thrombosis (DVT). The objective was to determine the rate of venous thromboembolic disease in patients with a malignant neoplasm and major orthopaedic surgery of the lower limb. METHODS: The study included 169 patients. All patients were given knee-high intermittent pneumatic compression devices for prophylaxis. Postoperative surveillance for thrombosis was performed on all patients with venous duplex doppler ultrasonography. RESULTS: Proximal DVT occurred in 24 of 169 patients (14.2%). One patient (0.6%) developed a symptomatic, nonfatal pulmonary embolus (PE). The development of DVT was not associated with age, sex, type of surgery, type of neoplasm, location, or pathologic fracture. The addition of anticoagulant medication such as warfarin did not significantly reduce the rate of DVT in a subset of 54 patients. In three patients, the DVT occurred only in the contralateral limb, and in four patients, there were bilateral DVTs. CONCLUSIONS: When intermittent compression boots were used for prophylaxis in conjunction with ultrasound screening, the risk of proximal DVT was substantial (14.2%), but the rate of symptomatic PE was low (0.6%).

Adult↗
PubMed1998

In vivo acetylation identified at lysine 70 of human lens alphaA-crystallin.

Posttranslational modification of protein lysyl residues that change the net charge of the molecule may alter the protein conformation. Such modifications are of particular significance among lens proteins, because conformational changes are associated with the development of cataract. A previously unidentified acetylated form of alphaA-crystallin has been isolated from the water-soluble portion of human lenses. The alphaA-crystallins were fractionated by anion exchange HPLC into seven peaks, each containing more than one form of alphaA-crystallin. The previously reported deamidated and phosphorylated forms were identified by their molecular masses, determined by electrospray ionization mass spectrometry. In addition to these modifications, approximately 5% of alphaA-crystallin had a modification that decreased the charge by one and increased the molecular mass by 42 u. This modification, identified as acetylation, was located uniquely at Lys 70. Like any modification that alters the surface charge, acetylation may affect protein conformation and intermolecular interactions, thereby altering the solubility or chaperone properties of alphaA-crystallin. Acetylation of lysine 70 is potentially significant since it is located in a region that has been implicated in the chaperone activity of alphaA-crystallin.

Acetylation↗
PubMed1998

Treatment of femoral fractures after irradiation.

Twelve fractures of the femur occurred after irradiation in 12 patients during the past 15 years. All 12 patients had excision of a soft tissue sarcoma of the thigh. The periosteum was stripped in every case. The fractures had a deceptively innocuous radiographic appearance, which showed minimal comminution, displacement, and shortening. Treatment of the fractures was difficult and demanding. At a mean followup of 37 months, bony union was achieved in only four patients, and in all four cases union was delayed beyond 12 months. Because fracture healing typically is delayed, a loadsharing device such as an intramedullary nail may be preferable in treating these fractures. Primary or delayed bone grafting may be necessary, for no fracture united without bone graft. For elderly patients with low supracondylar fractures, primary endoprosthetic replacement may effect quicker rehabilitation. The possibility of local recurrence of tumor should be ruled out before definitive surgical treatment of the fracture. Closed, antegrade nailing in the presence of recurrent tumor may contaminate the flap for a salvage procedure such as hemipelvectomy and may compromise chances for cure.

Bone Transplantation↗
PubMed1998

Placement of screws in the sustentaculum tali. A calcaneal fracture model.

Current methods of treating calcaneus fractures vary greatly, and many techniques of internal fixation have been described. The study of these fractures has been limited in part by the lack of a suitable laboratory model. In this study, a new cadaveric model of calcaneus fractures was developed, using a combination of osteotomies and impaction. The model allows a pattern of intraarticular injury to be reproduced consistently. The model was used to examine one aspect of internal fixation. It was hypothesized that fixation would be more stable if the screws supporting the posterior facet were incorporated into the lateral plate, as opposed to being separate from the plate. Six pairs of anatomic specimen legs were used, and each pair was divided randomly between two experimental groups. In Group A (screws out), the posterior facet screws were outside the plate, and in Group B (screws in), the screws were incorporated into the plate. The strength of the reconstructed calcanei were evaluated by axial loading of the limb through the tibia. Stiffness and energy to failure were significantly greater and Bohler's angle significantly less compromised in Group B. It was concluded that the position of the articular fragment of comminuted calcaneal fractures will be maintained at higher loads when the screws in the posterior facet are incorporated into the lateral plate. The model of calcaneal fractures described in this study may be suitable for examining other aspects of fixation.

Bone Plates↗
PubMed1998

Expression of proteoglycan epitopes in articular cartilage repair tissue.

To determine if expression of specific proteoglycan epitopes distinguishes articular cartilage repair tissue from normal articular cartilage, we used seven monoclonal antibodies to examine normal articular cartilage and cartilage repair tissue from osteochondral defects 3.2 mm in diameter and 4.0 mm deep in the medial femoral condyles of 27 New Zealand white rabbits and seven cynomolgus monkeys. Following creation of the osteochondral defects, one limb of each animal was treated with cast immobilization while the other limb was treated with passive motion for two weeks. Rabbit knees were examined at eight (13 animals, 26 knees) and 36 weeks (14 animals, 28 knees) and monkey knees at eight weeks (seven animals, 14 knees) following surgery. Staining for six of the antibodies did not differ between repair cartilage and normal articular cartilage, but an antibody that recognizes atypical glycosaminoglycan structures in developing tissues (MAb 7D4) consistently distinguished repair cartilage from normal cartilage in rabbits and monkeys. Repair tissue consisting of hyaline toluidine blue-staining matrix containing chondrocytic cells uniformly showed strong 7D4 staining. In contrast, normal articular cartilage and fibrous repair tissue showed inconsistent weak 7D4 staining. At eight weeks following surgery, rabbit cartilage repair tissue stained more intensely for 7D4 than monkey cartilage repair tissue; in rabbits, cartilage repair tissue stained more intensely for 7D4 at eight weeks than at 36 weeks following surgery. Repair tissue staining for 7D4 did not differ between osteochondral defects treated with passive motion and those treated with immobilization in rabbits and monkeys. These results indicate that expression of a high level of proteoglycan epitope 7D4 distinguishes hyaline articular cartilage repair tissue from normal articular cartilage and fibrous cartilage repair tissue in the early stages of osteochondral healing, and that as hyaline articular cartilage repair tissue matures expression of 7D4 decreases. The ability to characterize repair cartilage proteoglycans with monoclonal antibodies may aid in the evaluation of the quality and maturity of cartilage repair tissue and thereby facilitate improvements in procedures for resurfacing joints.

Animals↗
PubMed1996

Bis(2-chloroethyl)sulfide (BCES) disturbs the progression of rat keratinocytes through the cell cycle.

Epidermal basal keratinocytes are the primary target in BCES-induced cutaneous injury. DNA synthesis is inhibited by exposure to BCES which could relate to the mustard's cytotoxic effect. The effects of BCES on the cell cycle in keratinocytes synchronized by aphidicolin were investigated. Primary keratinocytes synchronized at the G1/S boundary entered the S, G2, M, and G1 phases at successive times after release from the block. When cells were exposed to 1, 10, or 50 microM BCES in different phases of the cell cycle, cells in the S phase were more sensitive to BCES than cells in the other phases. Keratinocytes exposed to 1 microM BCES at the G1/S boundary exhibited a prolongation of the S phase and a block in the G2 phase. When these cells were exposed to 10 or 50 microM BCES, they did not enter the S phase for up to 12h and the incorporation of thymidine into DNA was inhibited. These results suggest that the blocks in the G2 and G1 phases relate to the cytotoxic effect of BCES on the germinative population of epidermal keratinocytes.

Animals↗
PubMed1996

Bone mineralization in the affected extremities of children with spastic hemiplegia.

To assess the impact of neurologic involvement on bone mineralization, dual-energy X-ray absorptiometry was used to quantitate bone mineral content (BMC), bone mineral density (BMD), fat and lean muscle mass in the limbs of 19 children with spastic hemiplegic cerebral palsy. The BMC in the affected limb was on average 26.5% lower (upper limbs) and 15.6% lower (lower limbs) than in the corresponding uninvolved limb. Lean muscle mass was reduced by 15% and BMD by 6% in the involved limbs and did not differ significantly between upper and lower limbs. The fat content of involved and uninvolved limbs did not differ. Children with poor hand function had greater reductions in BMC (39.3%), BMD (11.3%) and lean muscle mass (22.5%) than did children with better hand function. Thus, bone size and density decrease with increasing neurologic involvement, and weight bearing may slightly lessen the effect.

Adolescent↗
PubMed1995

Bone-mineral density in children and adolescents who have spastic cerebral palsy.

Bone-mineral density was studied in a heterogeneous group of 139 children (mean age, nine years; range, three to fifteen years) who had spastic cerebral palsy. The evaluation included serum analyses and a nutritional assessment based on a dietary history and anthropometric measurements. The bone-mineral density of the proximal parts of the femora and the lumbar spine was measured with dual-energy x-ray absorptiometry and was normalized for age against a series of ninety-five normal children and adolescents who served as controls. Bone-mineral density varied greatly but averaged nearly one standard deviation below the age-matched normal means for both the proximal parts of the femora (-0.92 standard deviation) and the lumbar spine (-0.80 standard deviation). Ambulatory status was the factor that best correlated with bone-mineral density. Nutritional status, assessed on the basis of caloric intake, skinfolds, and body-mass index, was the second most significant variable. The pattern of involvement, durations of immobilization in a cast, and a calcium intake of less than 500 milligrams per day were additional factors of less significance. The age when the child first walked, previous fractures, use of anticonvulsants, and serum vitamin-D levels did not correlate with bone-mineral density after adjustment for covariance with the ambulatory status and the nutritional status. Serum levels of calcium, phosphate, alkaline phosphatase, and osteocalcin were not reliable indicators of low bone-mineral density.

Adolescent↗
PubMed1993

Impact of axillary lymph node dissection on the therapy of breast cancer patients.

PURPOSE: We studied a series of 283 breast cancer patients retrospectively to determine the actual benefits of axillary lymph node dissection (ALND) for these patients. PATIENTS AND METHODS: The records of 283 women with invasive breast cancer treated between 1988 and 1990 were reviewed for histologic status of the axillary lymph nodes, tumor size, DNA content, hormone-receptor values, and actual adjuvant treatments received. RESULTS: ALND was of possible therapeutic benefit for the 15% (43 of 283) of patients who had clinically positive nodes. Nodal metastases were found in 86% (37 of 43) of patients in this subgroup. ALND alone determined the indication for standard adjuvant therapy for a group of 31% (88 of 283) of patients who had favorable primary biopsy findings and clinically negative axillary nodes; ALND proved that 13% (11 of 88) of these latter patients had positive nodes. For 54% (152 of 283) of patients who had clinically negative nodes and unfavorable biopsies, ALND played no role in the decision as to whether standard adjuvant therapy was indicated. Only 5% (seven of 152) and 3% (four of 152) of these latter patients received radiation therapy and/or high-dose adjuvant chemotherapy, respectively, because of ALND. CONCLUSION: The benefits of ALND vary greatly for different groups of breast cancer patients, and controlled studies may be needed to determine whether ALND is necessary for all breast cancer patients.

Adult↗
PubMed1992

Reliability of a facebow transfer procedure.

The three-dimensional orientation of a maxillary cast mounting from a simulated-kinematic facebow transfer was evaluated in multiple trials among three operators on a single subject. The anterior and posterior anatomic facial reference points were marked on the subject. Each operator performed a separate series of trials to reset the anterior facebow component, the two posterior facebow components, and a control series with no resetting of any facebow components relative to the subject. The x, y, and z coordinates of three reference points on the maxillary cast were determined with a machinist microscope relative to a fixed reference after each facebow transfer. A range of differences between mountings of the maxillary cast were found between trials with all three methods used. These mounting errors were due to setting of the instrument and would be expected in routine clinical use of this instrument.

Analysis of Variance↗