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Biomedical subjects

P Tang

Publications and source records attributed to P Tang.

At least 73 records · Page 4Linked to original sources
PubMed1998

[Salvage surgery for nasopharyngeal carcinoma after irradiation failure].

OBJECTIVE: To study the salvage surgery for nasopharyngeal carcinoma after irradiation failure. METHODS: One hundred and twenty-one full-dose-irradiation-uncontrolled cases of nasopharyngeal carcinoma had undergone salvage surgery since 1965 till 1992, in which 41 had primary lesion and 80 neck lesion. All patients received radiation before surgery with the dose of 60Gy-145Gy. The patient selection for this report limited to those with recurrent tumors at the primary sites with no apparent bony involvement and no cranial nerve palsy, or cases with resectable neck recurrences. RESULTS: It showed that palatal fenestration was the best choice of approach for recurrent tumors located at the vault of the nasopharyngeal cavity. When the tumor invaded the parapharyngeal space or, owing to the after-effect of radiotherapy, the patient presented with severe occlusion of the mandible, we preferred the lateral approach through partial mandi-bulectomy. The lateral rhinotomy was only indicated for cases with tumor remnant at the posterior nares. Lymph node excision was performed for cases with single movable node on the neck, and RND for the cases with multiple nodes. The complication rate of after surgery was low (10%), considering the heavy dose of irradiation. The three- and five-year survival rate were 49% (59/121) and 38% (38/100) respectively. CONCLUSION: It suggests that the surgery should be considered as a salvage procedure for cases of nasopharyngeal cancer after irradiation failure. Because of high rate of distant metastasis (62 cases or 45% died after surgery), chemotherapy or other measures should be adopted after local treatment.

Adolescent↗
PubMed1998

[Prevention and management of chylous fistula after neck dissection].

OBJECTIVE: To evaluate the effect of treatment for chylous fistulas after neck dissection, as a means of reasonable option of therapeutic measures. METHODS: Of 37 chylous fistulas, 30 were left-sided and 7 were right-sided. Conservative therapy which included closed-wound drainage and local pressure dressing and/or low-fat nutritional support was employed in 26 cases, and 50% glucose was injected into the neck basic wound bed in 2 cases, to promoto the chylous fistula healing up. Operative ligation was performed in 7 cases. Open-wound and packing in 4 cases. RESULTS: Eighty-six percent chylous fistula occured from 1 to 3 postoperative days. Of 26 chylous fistulas with conservative management, 15 cases were successfully treated, the mean duration for healing was 9.7 (4-30) days, the remaining 11 cases failed to had and were further treated surgically. Seven cases with operative ligation were successful, and the other 4 cases with open-wound and packing had delayed healing, the mean duration was 8.5 (7-10) days. CONCLUSION: The majority of patients with chylous fistulas could be treated reasonablly without increasing the hospital days. The conservative therapy should be employed in cases with a maximal production of chyle below 500 ml a day. Operative ligation should be done early in cases with a maximal production exceeding 500 ml a day and with conservative treatment failure for a few days. The open-wound and packing should be used in chylous fistulas persisting for more then 7 days.

Adolescent↗
PubMed1998

[The extended indications of near-total laryngectomy].

OBJECTIVE: To evaluate near-total laryngectomy in treatment of laryngeal cancers. METHODS: Fifty-seven near-total laryngectomies were reviewed, among them 40 were T3 or T4 laryngeal cancers due to tumor invasion to the base of tongue or subglottic region. RESULTS: In these patients, there were 11 cases of T3 pyriform sinus cancers, 5 cervical esophageal cancers, 1 case with adenoid cystic carcinoma involving the base of the tongue and oropharynx. Speech function had been preserved in 93% of cases with normal swallowing. Three year survival rates were 67.5% in laryngeal cancer and 50% in hypopharyngeal cancer. Local recurrence rate was only 3.5%. CONCLUSION: The authors believed that near-total laryngectomy is safe and beneficial to the patients with the above types of cancers. The quality of life may improve if speech function is preserved.

Aged↗
PubMed1998

[Visceral voice training for laryngectomy after hypopharyngectomy and visceral transplant].

OBJECTIVE: To establish a way to visceral voice after stomach or colon transplantation for patients with hypopharyngeal or cervical esophageal cancer. METHODS: Esophageal voice training was used and modified according to the compliance of the patients. Twenty laryngectomies with replacement of the hypopharynx and esophagus by stomach(13 cases), colon(6 cases) and jejunum (1 case) were trained for voice rehabilitation at the Department of Head and Neck Surgery. RESULTS: The patients with an artificial esophagus from vicera were easy to gain an influx of certain volume of gas into their artificial esophagus (stomach or colon) and to learn to speak. But on the whole the quality of voice was not so satisfactory. In this series nineteen out of 20 patients (95%) could express their idea by speech after a training course of three weeks. CONCLUSION: The literature has emphasized role of cricopharyngeus muscle in the training of esophageal voice. Owing to the fact that this series of patients who had had their cricopharyngeus removed, could easily get their voice rehabilitated, it seems this muscle played no major role in the voice rehabilitation.

Aged↗
PubMed1998

[Preoperative radiation plus surgery vs. operation alone for laryngeal carcinoma].

OBJECTIVE: To study the validity of preoperative radiation in improving the survival rate of laryngocarcinoma. METHODS: A prospective randomized clinical trial was conducted with preoperative radiation plus surgery (RS) as one group and surgery alone (SA) as the other group. The ages of the patients were less than 75 years, and the operative types were decided after clinical examination. The patients were divided into SA or RS group by random. Doses of preoperative irradiation was 40 Gy. Three hundred and seventy patients with laryngocarcinoma were treated, 215 in the SA group; 155 in the RS group. All patients were followed up over three years. RESULTS: In SA group, 3 years survival rate was 83.3%, 5-year survival rate 82.6%, 10-year survival rate 80.3%. In RS group, 3-year survival rate was 78.9%, 5-year survival rate 76.4%, 10-year survival rate 68.6%. There is no statistically significant difference in survival rates between the groups (P = 0.1); but, the 10-year survival rate in SA group was better than that in RS group for the stage III and IV supraglottic carcinomas, the former was 73.6% and the latter 63.5% (P = 0.003). The 10-year survival rate for the patients with T3 and T4 supraglottic carcinomas who underwent total laryngectomy in SA group was better than that in RS group. The former was 68% and the latter 50% (P = 0.0001). CONCLUSION: Preoperative radiotherapy with 40 Gy didn't increase the survival rate of laryngeal carcinoma. The 10-year survival of stages III and IV supraglottic carcinoma in combined treatment group was lower than that in the surgery alone group.

Adult↗
PubMed1997

Amphiphilic sites for general anesthetic action? Evidence from 129Xe-[1H] intermolecular nuclear Overhauser effects.

Because a strong correlation exists between the potency of general anesthetics and their ability to dissolve in oil, a lipophilic site of action is often assumed. We show here that a lipophilic molecule may preferentially target less lipophilic sites after interaction with a membrane takes place. Xenon, a chemically inert and structureless general anesthetic, was chosen as an unbiased molecular probe for assessment of its dynamic distribution. Site-selective intermolecular 129Xe-[1H] nuclear Overhauser effects were used to measure the specific interaction between xenon and protons in different regions in a phosphatidylcholine lipid membrane. It was evident that xenon-membrane interaction was directed toward the amphiphilic head region, with significant involvement of interfacial water, despite xenon's apolar and highly lipophilic nature in the gas phase. This result may suggest the importance of amphiphilicity in association with anesthetic action.

Anesthetics, General↗
PubMed1997

Easy fabrication of a tunable high-pass birdcage resonator.

A practical design for a high-pass birdcage resonator is presented. Precision seamless telescoping tubes were used for easy tuning of resonant frequency by adjusting the length of the coils. Three probes, of 4.4, 5.0, and 25.0 cm in diameter, respectively, were constructed and tested. An empirical formula is given that can be used to calculate the capacitance needed for a given frequency when the desired physical dimension and the number of elements of the coll are specified. A simple three-step procedure is suggested for easy fabrication of resonators that are routinely tunable over tens of megahertz.

Magnetic Resonance Imaging↗
PubMed1997

Different distribution of fluorinated anesthetics and nonanesthetics in model membrane: a 19F NMR study.

Despite their structural resemblance, a pair of cyclic halogenated compounds, 1-chloro-1,2,2-trifluorocyclobutane (F3) and 1,2-dichlorohexafluorocyclobutane (F6), exhibit completely different anesthetic properties. Whereas the former is a potent general anesthetic, the latter produces no anesthesia. Two linear compounds, isoflurane and 2,3-dichlorooctofluorobutane (F8), although not a structural pair, also show the same anesthetic discrepancy. Using 19F nuclear magnetic spectroscopy, we investigated the time-averaged submolecular distribution of these compounds in a vesicle suspension of phosphatidylcholine lipids. A two-site exchange model was used to interpret the observed changes in resonance frequencies as a function of the solubilization of these compounds in membrane and in water. At clinically relevant concentrations, the anesthetics F3 and isoflurane distributed preferentially to regions of the membrane that permit easy contact with water. The frequency changes of these two anesthetics can be well characterized by the two-site exchange model. In contrast, the nonanesthetics F6 and F8 solubilized deeply into the lipid core, and their frequency change significantly deviated from the prediction of the model. It is concluded that although anesthetics and nonanesthetics may show similar hydrophobicity in bulk solvents such as olive oil, their distributions in various regions in biomembranes, and hence their effective concentrations at different submolecular sites, may differ significantly.

Anesthetics↗
PubMed1997

The autocrine loop of TGF-alpha/EGFR and brain tumors.

Malignant human gliomas are the most common forms of primary tumors in the central nerve system. Due to their location and invasive nature, treatment so far has been mainly palliative. Thus, understanding the molecular detail of tumor transformation and progression is crucial for developing effective therapeutic strategy for this fetal tumor. Among the genetic alternations found in these tumors, p53 inactivation and PDGF/PDGFR activation represent the early events, and the loss of chromosome 10 and gene amplification and rearrangement of EGFR represent the late events. Studies with both glioma cell lines and primary tumor tissues have strongly suggested that TGF-alpha and EGFR function as an important autocrine loop in supporting proliferation of human glioma, especially in high grade glioma, since elevated TGF-alpha expression is also found in these high grade tumors. Furthermore, down regulation of the expression of TGF-alpha by antisense constructs has been shown to inhibit several types of human tumor cell growth including glioma. Other means of therapeutic approaches using this autocrine loop as a target also include the use of monoclonal antibodies and their cytotoxic conjugated. Considerable understanding of the EGFR-mediated signal transduction pathways has become available recently, which including GRB2/mSOS1 mediated MAP kinase activation; JAK/STATs pathway; PLC-gamma pathway. However, much work still needs to be done before a specific component of these pathways can be applied for effective control of tumor growth in the clinic.

Animals↗
PubMed1997

[RU486 reverses dexamethasone-mediated suppression of IL-2 receptor expressions in lymphocytes of rat spleen].

Experiments were designed to investigate whether glucocorticoid-mediated immunosuppression are involved in glucocorticoid receptor activation. It was shown that RU486, a blocker of glucocorticoid, reversed dexamethasone (DEX)-mediated suppression of CD25 antigen expressions on ConA-stimulated lymphocytes, as determined with anti-CD25 monoclonal antibody. By means of radioligand binding assay, changes in high affinity IL-2 receptor were examined. The data indicated that RU486 alone was unable to affect high affinity IL-2 receptor expressions, but antagonized DEX-mediated down regulation of high affinity IL-2 receptor on cellular surface. The maximal binding capacities of IL-receptor were 10.0 +/- 0.7, 10.4 +/- 2.1, 6.5 +/- 0.8 and 12.1 +/- 2.7 fmol/10(7) cell respectively in four groups of the normal, RU486, DEX, and DEX plus RU486. The results suggest that such effects of DEX may be mediated through glucocorticoid receptor in lymphocytes.

Animals↗
PubMed1997

[Morphological and cytochemitry features of CD34+ hematopoietic cells isolated from human bone marrow].

OBJECTIVE: To explore the cytomorphological and cytochemitry features of CD34+ hematopoietic cells. METHODS: Highly purified CD34+ hematopoietic cells isolated from human bone marrow by a two-step method of immunomagnetic beads-FACS sorting were comprehensively examined. RESULTS AND CONCLUSION: CD34+ hematopoietic cells could be sorted into three types in light of morphology and cytochemical staining. Type I was considered as candidates for stem cells,which were most blastlike in morphology and slightly larger than lymphocytes in size with negative reactions to all cytochemical stainings. Type II was considered as multipotent progenitor cells, with sizes similar to small lymphocytes and negative reactions to all cytochemical stainings. Type III was identified as committed progenitor cells whose sizes were heterogeneous and whose reactions to cytochemical stainings ranged from +/- to + +.

Antigens, CD34↗
PubMed1997

[The effect of interleukin (IL) 12 on hemopoiesis in irradiated mice].

OBJECTIVE: To investigate the regulating effect of IL-12 on hemopoiesis. METHODS: cDNA coding for the two subunits of murine IL-12 were cloned into two different eukaryotic expression vectors and transduced into a same NIH3T3 cell line, resulting in two engineered fibroblast clones secreting IL-12. Cells were mixed with collagens and inoculated into the peritoneal cavities of whole-body-irradiated mice. RESULTS: On day 10 after treatment, endogenous splenic colony-forming-unit (CFU-S) counts in mice treated with IL-12-secreting NIH3T3 cells were higher than those of mice accepting parental cells or untreated irradiated mice. This difference was statistically significant in both 6.0 Gy irradiated mice and 7.0 Gy group mice. Histopathological studies showed that NIH3T3-secreted IL-12 alleviates the injuries caused by irradiation in both bone marrow and spleen, activates hemopoietic cells, increases the number and scale of hemopoietic clusters, hence enhancing hemopoietic function including erythropoiesis, granulopoiesis, and megakaryocytopoiesis. CONCLUSION: IL-12 up-regulates and promotes the recovery of hemopoietic function in irradiated mice.

3T3 Cells↗
PubMed1996

Human pro-tumor necrosis factor is a homotrimer.

The structure of human transmembrane pro-TNF-alpha was studied both in intact cell systems and in an in vitro translation system. In intact cell systems (LPS-induced THP-1 and TNF cDNA-transfected COS-7), a trimer of pro-TNF was detected after chemical cross-linking based on its molecular weight in Western blotting analysis. The trimer was shown to be a TNF-specific protein and could be partially cleaved to 26-kDa pro-TNF monomers by cleaving the cross-linkers. The trimeric structure was assembled intracellularly, because it could be detected in both the in vitro microsomal translation system and in THP-1 cells coincident with the appearance of pro-TNF in the cell lysate, prior to secretion of mature TNF. To further analyze the relationship between the trimeric structure and the biological activity of pro-TNF, we characterized several noncleavable pro-TNF deletion mutants. We observed a correlation between expression of TNF cytotoxicity in a juxtacrine fashion and detection of trimer. Thus, human pro-TNF-alpha, like the secreted mature TNF-alpha, has trimeric structure which is assembled intracellularly before transport to the cell surface and is apparently required for mediating its biologic activity.

Animals↗
PubMed1996

Length of the linking domain of human pro-tumor necrosis factor determines the cleavage processing.

Several studies have indicated that only one cleavage site (Ala-1/Val+1) is involved in the release of mature TNF from human pro-TNF, whereas others have suggested that the linking sequence (residues -20 to -1) may be important. We previously demonstrated that a pro-TNF deletion mutant, delta -20- -1, was able to form a trimeric structure and mediate TNF cytotoxicity in a juxtacrine fashion without releasing mature TNF. We constructed seven mutants with smaller deletions within this region. Three 15-residue deletion mutants, delta -20- -6, delta -15- -1 and delta -20- -16, -10- -1, were noncleavable, although able to form a trimer and to mediate cytotoxicity through cell-to-cell contact. Three five- or ten-residue deletion mutants, delta -20- -16, delta -10- -1, and delta -5-, -1, behaved like the wild-type TNF; all formed a trimer and released mature TNF. These results suggested that in pro-TNF (1) the number of residues between the base of the trimer and the plasma membrane determines accessibility of the cleavage site to the pro-TNF processing enzyme(s) since small deletions did not block cleavage whereas large ones did regardless of the presence of the native cleavage site (-1/+1), (2) the native cleavage site is not sufficient for releasing mature TNF because mutant delta -20- -6, in which the native cleavage site was intact, was noncleavable, and (3) alternative cleavage site(s) may exist since mutants delta -10- -1 and delta -5- -1, which lack the native cleavage site, were cleavable.

Amino Acid Sequence↗
PubMed1996

19F nuclear magnetic resonance investigation of stereoselective binding of isoflurane to bovine serum albumin.

Whether proteins or lipids are the primary target sites for general anesthetic action has engendered considerable debate. Recent in vivo studies have shown that the S(+) and R(-) enantiomers of isoflurane are not equipotent, implying involvement of proteins. Bovine serum albumin (BSA), a soluble protein devoid of lipid, contains specific binding sites for isoflurane and other anesthetics. We therefore conducted 19F nuclear magnetic resonance measurements to determine whether binding of isoflurane to BSA was stereoselective. Isoflurane chemical shifts were measured as a function of BSA concentration to determine the chemical shift differences between the free and bound isoflurane. KD was determined by measuring the 19F transverse relaxation times (T2) as a function of isoflurane concentration. The binding duration was determined by assessing increases in 1/T2 as a result of isoflurane exchanging between the free and bound states. The S(+) and R(-) enantiomers exhibited no stereoselectivity in chemical shifts and KD values (KD = 1.3 +/- 0.2 mM, mean +/- SE, for S(+), R(-), and the racemic mixture). Nonetheless, stereoselectivity was observed in dynamic binding parameters; the S(+) enantiomer bound with slower association and dissociation rates than the R(-).

Anesthetics, Inhalation↗
PubMed1996

Interaction of polyethyleneglycol-phospholipid conjugates with cholesterol-phosphatidylcholine mixtures: sterically stabilized liposome formulations.

PURPOSE: The purpose of this study was to investigate polyethyleneglycol (PEG)-phosphatidylethanolamine (PE) conjugate interaction with cholesterol-phospholipid mixtures in an attempt to explain the effect of cholesterol on liposome circulation time. METHODS: Differential scanning calorimetry, NMR, electron microscopy, dynamic light scattering and fluorescence spectroscopy were the major methods used. RESULTS: Studies performed in the absence of cholesterol indicated the formation of three distinct physical states depending on the chain length of PEG in PEG-PE. Mixed micelle formation was observed at concentrations of PEG(1,000)-DPPE above 7 mol-% of lipid. Phase separated lamellae were observed at all concentrations of PEG( 12,000)-DPPE (Bedu-Addo et al. Pharm. Res. 13:710-717 (1996)). Upon incorporation of high concentrations of cholesterol >30 mol% into the lipid bilayer, the formation of phase separated lamellae was completely inhibited and the formation of mixed micelles significantly reduced. At high concentrations of PEG(1,000)-PE, solubilization of the bilayer occurred with preferential solubilization of cholesterol over phosphatidylcholine. Maximum steric stabilization (surface protection) was observed with low concentrations of short chain PEG-PE and high concentrations of cholesterol. CONCLUSIONS: The study provides a physical mechanism for the following observations: the blood circulation time is significantly increased or decreased with liposomes highly enriched with cholesterol or PEG-PE respectively.

Calorimetry, Differential Scanning↗