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Biomedical subjects

P Peng

Publications and source records attributed to P Peng.

At least 19 recordsLinked to original sources
PubMed2005

Femtosecond spectroscopy of carrier relaxation dynamics in type II CdSe/CdTe tetrapod heteronanostructures.

Branched nanocrystal heterostructures synthesized from CdSe and CdTe exhibit a type II band structure alignment that induces separation of charge upon photoexcitation and localizes carriers to different regions of the tetrahedral geometry. The dynamics of carrier relaxation examined with femtosecond pump-probe spectroscopy showed heterostructures having rise times and biexponential decays longer than those of nanorods with similar dimensions. This is attributed to weaker interactions with surface states and nonradiative relaxation channels afforded by the type II alignment.

Journal Article↗
PubMed2001

[Application of video laryngoscope in diagnosis and treatment of laryngeal diseases].

OBJECTIVE: To investigate the value of video laryngoscope in diagnosis of laryngeal diseases. To study the effect of video laryngoscope in treatment of laryngeal diseases. METHOD: Pentax VNL-1530T and Olympus BF-240T video laryngoscope were used in diagnosis of 3628 cases of laryngeal diseases and in treatment of 1221 cases of laryngeal diseases. RESULT: 3628 cases were examined by video laryngoscope, and correct diagnosis was made. 768 cases of vocal cord polyp and 249 cases of vocal cord node were excised, 113 cases of foreign bodies in hypopharynx or larynx were removed. 91 cases of other laryngeal diseases were treated under video laryngoscope. CONCLUSION: Video laryngoscope is a new excellent instrument in diagnosis and treatment of laryngeal disease.

Adolescent↗
PubMed2000

Determination of porphyrin carbon isotopic composition using gas chromatography-isotope ratio monitoring mass spectrometry.

Carbon isotopic compositions of aetio I occurring in the form of free-base, nickel, demetallation, dihydroxysilicon(IV) and bis(tert.-butyldimethylsiloxy)silicon(IV) [(tBDMSO)2Si(IV)] have shown that it has experienced no obvious isotope fractionation during the synthesis of [(tBDMSO)2Si(IV)] porphyrin from aetio I. Here, aetio I porphyrin species such as free-base, nickel, demetallated and dihydroxysilicon were analyzed by the conventional method, namely it is combusted in sealed system, and followed by isotope ratio monitoring mass spectrometric analysis. [(tBDMSO)2Si(IV)] aetio I was assayed by gas chromatography-isotope ratio monitoring mass spectrometry (GC-IRMS). A porphyrin mixture of [(tBDMSO)2Si(IV)] aetio I and octaethylporphyrin was also prepared. Their carbon isotopic compositions measured by GC-IRMS indicate that no isotope exchange took place between the porphyrins during the synthesis of [(tBDMSO)2Si(IV)] porphyrins. This method is employed for delta13C determination of geoporphyrins from the Maoming and Jianghan oil shales.

Carbon Isotopes↗
PubMed2000

Determining minimum effective anesthetic concentration of hyperbaric bupivacaine for spinal anesthesia.

We determined the minimum effective anesthetic concentration (MEAC) of bupivacaine for spinal anesthesia, defined as the median effective concentration at which a spinal anesthetic produces surgically equivalent anesthesia within 20 min of administration in 50% of human subjects. Two doses of spinal bupivacaine (7.5 mg and 10 mg) were administered to 45 volunteers (19-39 yr) in a randomized, double-blinded fashion. Hyperbaric bupivacaine solutions of 0.1% to 0.75% containing 8.25% dextrose were administered intrathecally and MEAC established by using the Dixon's up-and-down method. Complete anesthesia was defined as: 1) pinprick anesthesia at or higher than T12; 2) anesthesia to transcutaneous tetanic electric stimulation (50 Hz at 60 mA for 5 s) in the knees; and 3) complete leg paralysis, all occurring in both lower extremities within 20 min of intrathecal injection. We found that the MEAC of spinal bupivacaine was 0.43% (95% confidence interval 0.24-0.62) when 10 mg was administered. At this dose, a concentration as low as 0.1% could provide complete anesthesia, but consistent blockade was obtained only with the 0.7% solution. The 7.5-mg dose failed to provide complete anesthesia consistently, even in the presence of 0.75% (maximum). The current commercially available 0.75% concentration of hyperbaric bupivacaine seems to be clinically optimal when 10 mg is used if complete bilateral lower extremity blockade is desired.

Adult↗
PubMed2000

Photoyellowing inhibition of bleached high yield pulps using novel water-soluble UV screens.

To address the deficiencies of benzophenone UV screens for preventing brightness reversion in high yield mechanical papers, we synthesized a new series of such materials with enhanced water solubility and compatibility with the lignocellulosic substrate. A series of 2,4-dihydroxybenzophenones (DHB) were synthesized containing various Mannich bases at the C3 position of one of its rings. They possess the UV-screening ability of o-hydroxylbenzophenones, and they also contain tertiary nitrogen atoms that may function as radical scavengers. Aqueous solutions of the hydrochloride salt of 3-(dimethylaminomethylene)-2,4-dihydroxylbenzophenone (1), when applied on bleached chemithermomechanical pulp (CTMP) sheets, were significantly more efficient in preventing photoyellowing than the original DHB applied on the sheets from ethanol-water solutions. This confirmed our original hypothesis that increasing the compatibility of the UV screen with the lignocellulosic matrix would increase its efficiency in preventing photoyellowing. Compound 1, however, was found to be somewhat more effective than its hydrochloride salt toward preventing photoyellowing. This was attributed to the synergistic action of the free tertiary aminic center attached on the molecule with its UV-screening ability. To comprehend further the various parameters that influence the photoyellowing inhibition performance of these compounds and DHB with bleached CTMP pulp fibers, a series of handsheets were prepared at different pH. The interactions of the protonated compound 1 with pulp fibers were then evaluated by studying their kinetics of absorption and desorption to and from the fiber matrix. This part of our study found that the adsorption of protonated Mannich derivatives of DHB onto pulp is most likely governed by a cation-exchange mechanism involving the cationic amine group with the sulfonic and carboxylic acid groups located on the surface of the fibers. The pH the paper sheet was made from was also found to affect profoundly the adsorption and retention characteristics of these compounds onto the lignocellulosic matrix.

Benzophenones↗
PubMed2000

[Detection of the asymptomatic infection by human papillomavirus in pregnant women and neonates].

OBJECTIVE: To investigate the state of human papillomavirus (HPV) infection in similar average-aged pregnant women of different gestational periods, in the puerperium and neonates. METHODS: Polymerase chain reaction (PCR) assay was employed to detect HPV-6, 11, 16 and 18 DNA in 30 pregnant women in the first trimester, 42 in the second and 31 in the third (who were followed up to their puerperium), and 30 non-pregnant women asking for intrauterine device in our out-patient clinic were taken as controls. Average age in the four groups showed no significant difference (P > 0.05). Samples from cervical, vaginal exfoliated cells, maternal peripheral blood and nasopharyngeal secretion of the newborns were examined respectively. RESULTS: (1) In the first trimester, HPV-DNA was detected in the cervical, vaginal exfoliated cells of 5 cases and in the maternal peripheral blood of 7 cases. (2) In the second trimester, HPV-DNA was detected in the cervical, vaginal exfoliated cells of 12 cases and in the maternal peripheral blood of 11 cases. (3) In the third trimester, HPV-DNA was detected in the cervical, vaginal exfoliated cells of 23 cases and in the maternal peripheral blood of 18 cases. (4) In the puerperium, HPV-DNA was detected in samples of cervical, vaginal exfoliated cells of 8 cases and maternal peripheral blood of 7 cases. (5) In the control group, HPV-DNA was detected in the cervical, vaginal exfoliated cells of 8 cases and in the maternal peripheral blood of 6 cases. (6) Consecutive examinations were carried out in 31 pregnant women from the third trimester, through labor to 6 weeks of postpartum. HPV-DNA was positive in the cervical, vaginal samples of 17, 21 and 8 cases, respectively, according to the perinatal periods, and in the maternal peripheral blood of 14, 13 and 7 cases, respectively. The result through the above gestational stages was fluctuated in the cervical, vaginal samples of 6 cases and in the maternal peripheral blood of 7 cases. (7) Successive examinations in infants at time of birth, 48-72 h and 6 weeks after birth showed positive HPV-DNA in the nasopharyngeal secretion of 13, 6 cases and 1 case with respect to the examining periods. (8) The positive cases were mainly infected by HPV-16, 18. CONCLUSIONS: (1) Infective rate of HPV is statistically significant in the third trimester, but no significant difference exists among the first trimester, the second trimester, the puerperium or the non-pregnancies. (2) Examining consecutively, the HPV positive rate is found to be decreased after delivery, the positive expression of HPV during the gestational periods exhibited fluctuation. (3) Infective rate of HPV in the neonatal nasopharyngeal specimens tends to decrease with time after delivery.

Adult↗
PubMed1999

Association of peptides with heat shock protein gp96 occurs in vivo and not after cell lysis.

Immunization of mice and rats with gp96 preparations isolated from syngeneic cancers has been shown to elicit protective immunity to a number of cancers. The specific immunogenicity of gp96 preparations derives from the antigenic peptides chaperoned by the gp96 molecule and not from gp96 molecules per se. Studies reported here demonstrate that the association of peptides with gp96 occurs in vivo and is not a procedural artifact which occurs in vitro after cell lysis. This demonstration has a bearing on the proposed functional role of HSP peptide association in antigen processing and presentation by MHC I molecules.

Animals↗
PubMed1999

An uncommon mechanism of brachial plexus injury. A case report.

PURPOSE: To report a case of brachial plexus injury occurring on the contralateral side in a patient undergoing surgery for acoustic neuroma through translabrynthine approach. CLINICAL FEATURES: A 51-yr-old woman underwent surgery for acoustic neuroma through translabrynthine approach in the left retroauricular area. She had a short neck with a BMI of 32. Under anesthesia, she was placed in supine position with Sugita pins for head fixation. The head was turned 45 degrees to the right side and the neck was slightly flexed for access to the left retroauricular area, with both arms tucked by the side of the body. Postoperatively, she developed weakness in the right upper extremity comparable with palsy of the upper trunk of the brachial plexus. Hematoma at the right internal jugular vein cannulation site was ruled out by CAT scan and MRI. The only remarkable finding was considerable swelling of the right sternocleidomastoid and scalene muscle group, with some retropharyngeal edema. An EMG confirmed neuropraxia of the upper trunk of brachial plexus. She made a complete recovery of sensory and motor power in the affected limb over the next three months with conservative treatment and physiotherapy. CONCLUSIONS: Brachial plexus injury is still seen during anesthesia despite the awareness about its etiology. Malpositioning of the neck during prolonged surgery could lead to compression of scalene muscles and venous drainage impedance. The resultant swelling in the structures surrounding the brachial plexus may result in a severe compression.

Brachial Plexus↗
PubMed1999

Femoral nerve block and ketorolac in patients undergoing anterior cruciate ligament reconstruction.

PURPOSE: The primary objective was to evaluate the analgesic effectiveness of femoral nerve block and ketorolac following ACL reconstruction. The secondary objective was to examine their effects on recovery milestones. METHODS: Prior to standard general anesthesia, 90 patients were randomized into three groups of preoperative treatment: 1) femoral nerve block (15 mL bupivacaine 0.5%) and 1 mL normal saline i.v. (FNB group); 2) placebo femoral nerve block (15 mL normal saline) and 30 mg (1 mL) ketorolac i.v. (KT group); 3) placebo femoral nerve block (15 mL normal saline) and 1 mL normal saline i.v. (PL group). Postoperatively, pain was assessed by visual analogue score, demand and consumption of morphine via patient-controlled analgesia pump. The times for patients to tolerate oral fluid, food, sit up, ambulate and void were also noted. RESULTS: Morphine consumption within one hour, three hours and until POD 1 in the FNB group was lower than the PL group (7 +/- 6, 11 +/- 9, 27 +/- 23 mg vs 13 +/- 5, 20 +/- 9, 49 +/- 28 mg respectively), whereas only that within one hour in the KT group was lower than the PL group. Pain score was lower in FNB and KT groups in the first postoperative hour than in the PL group (P < 0.05). There were no differences among the three groups in the times to meet recovery milestone and discharge criteria. CONCLUSION: Femoral nerve block provides superior analgesia than placebo for ACL reconstruction but was insufficient to facilitate early recovery.

Adolescent↗
PubMed1999

Neurophysiology of Cancer Pain: From the Laboratory to the Clinic.

Pain is one of the most distressing symptoms associated with cancer. Basic science research has provided much insight into the mechanisms of peripheral and central pain and the actions of new drugs. Despite these advances, pain accompanying malignancy can be difficult to treat. Pain most commonly presents when the tumor has invaded somatic,visceral, or neural structures. An understanding of pain mechanisms is essential when deciding on the appropriate treatment. New therapeutic options have been developed and will hopefully provide clinicians with tools to successfully alleviate cancer pain.

Journal Article↗
PubMed1997

Elevations in cathepsin B protein content and enzyme activity occur independently of glycosylation during colorectal tumor progression.

Western blots, enzyme assays, protein glycosylation studies, and immunohistochemical staining were used to characterize cathepsin B expression at successive stages of colorectal tumor progression. In normal colon mucosa and premalignant adenomas, cathepsin B expression was predominantly due to mature two-chain protein detected on Western blots as the nonglycosylated 27-kDa form, with overexpression of this protein occurring in only 4 of 18 adenomas. Overexpression increased significantly in Dukes A and B carcinomas (26 of 37 cases), with cathepsin B protein generally detectable in carcinomas as a combination of both 27-kDa nonglycosylated and 28-kDa glycosylated mature two-chain forms. Glycosylated cathepsin B protein in carcinoma extracts was sensitive to PNGase F but resistant to Endo H, indicating a pattern consistent with complex rather than high mannose type glycosylation. When sorted by advancing tumor stage, peak expression of cathepsin B protein occurred in carcinomas involved in local invasion compared with adenomas or metastatic cancers. At all stages, cathepsin B activity correlated significantly with the levels of heavy chain mature cathepsin B protein (r = 0.6682, p < 0.0001) irrespective of glycosylation. Immunohistochemical staining of cathepsin B protein revealed fine diffuse cytoplasmic staining in both adenomas and carcinomas compared with coarse granular cytoplasmic staining (typical of lysosomes) seen in matched normal mucosa. Our results demonstrate several sequential, apparently independent changes in cathepsin B expression during colorectal tumor progression including early changes in subcellular localization, up-regulation of cathepsin B protein and activity in invasive cancers, and altered protein glycosylation detected in malignant tumors at all stages.

Adenoma↗
PubMed1997

Immunotherapy of tumors with autologous tumor-derived heat shock protein preparations.

Immunotherapy of mice with preexisting cancers with heat shock protein preparations derived from autologous cancer resulted in retarded progression of the primary cancer, a reduced metastatic load, and prolongation of life-span. Treatment with heat shock protein preparations derived from cancers other than the autologous cancer did not provide significant protection. Spontaneous cancers (lung cancer and melanoma), chemically induced cancers (fibrosarcoma and colon carcinoma), and an ultraviolet radiation-induced spindle cell carcinoma were tested, and the results support the efficacy of autologous cancer-derived heat shock protein-peptide complexes in immunotherapy of cancers without the need to identify specific tumor antigenic epitopes.

Animals↗