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Biomedical subjects

Q Peng

Publications and source records attributed to Q Peng.

At least 55 records · Page 3Linked to original sources
PubMed2000

Surgical prevention of posterior capsule opacification. Part 2: Enhancement of cortical cleanup by focusing on hydrodissection.

PURPOSE: To experimentally analyze the role and efficacy of hydrodissection in achieving maximal cortical cleanup. SETTING: Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: Phacoemulsification and irrigation/aspiration were performed in 10 pairs of human eyes (20 eyes) obtained postmortem. Ten eyes had previous hydrodissection and 10 eyes, no hydrodissection. The time (seconds) required for complete lens substance removal in each procedure was measured. In addition, a qualitative evaluation of difficulty of surgery was noted. RESULTS: Phacoemulsification required 28.6% less time in eyes with previous hydrodissection than in those without. Irrigation/aspiration time was reduced by 50.9% when hydrodissection was performed. The total time of each procedure required for complete evacuation of the capsular bag was reduced by an average of 37.7% in eyes with hydrodissection. Furthermore, qualitatively the procedure was far easier, less stressful, and caused less posterior capsule stress or rupture when copious hydrodissection was performed. CONCLUSIONS: Hydrodissection enhances the general safety and efficiency of cortical cleanup, especially at 12 o'clock. Hydrodissection is the best available, practical, immediately implementable, and inexpensive means to help remove equatorial E-cells and thus alleviate the incidence of posterior capsule opacification.

Aged↗
PubMed2000

Creating cataracts of varying hardness to practice extracapsular cataract extraction and phacoemulsification(2).

We describe a method to harden the nucleus of crystalline lenses in postmortem human globes by intralenticular injection of a mixture of paraformaldehyde and glutaraldehyde (Karnovsky's solution). Evaluation of the nuclear manipulations, using the Miyake-Apple posterior video/photographic technique, shows that the method provides suitable specimens for practicing extracapsular cataract extraction and phacoemulsification.

Cataract↗
PubMed2000

Interlenticular opacification: clinicopathological correlation of a complication of posterior chamber piggyback intraocular lenses.

PURPOSE: To present a clinicopathological correlation of 2 pairs of piggyback posterior chamber intraocular lenses (PC IOLs) explanted because of opacification between the lens optics. SETTING: Gayton Health Center, Eyesight Associates of Middle Georgia, Warner Robins, Georgia, and Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: Two pairs of piggyback AcrySof lenses were explanted from 2 patients with significant visual loss related to opacification between the optics. They were submitted for pathological analysis. Gross and histopathological examinations were performed, and photomicroscopy was used to document the results. RESULTS: Gross examination showed accumulation of a membrane-like white material between the lenses. Histopathological examination revealed that the tissue consisted of retained/proliferative lens epithelial cells (bladder cells or pearls) mixed with lens cortical material. CONCLUSION: Piggyback PC IOLs were explanted in 2 cases because of a newly described complication, interlenticular opacification. Three surgical means may help prevent this complication: meticulous cortical cleanup, especially in the equatorial region; creation of a relatively large continuous curvilinear capsulorhexis to sequester retained cells peripheral to the IOL optic within the equatorial fornix; insertion of the posterior IOL in the capsular bag and the anterior IOL in the ciliary sulcus to isolate retained cells from the interlenticular space.

Acrylic Resins↗
PubMed2000

Pycnogenol protects vascular endothelial cells from beta-amyloid-induced injury.

The neuropathological hallmarks of Alzheimer's disease (AD) are senile plaques, cerebrovascular beta-amyloidosis, neurofibrillary tangles, and selective neuronal loss. Beta-amyloid (Abeta) has been shown to cause vascular damage mediated by generation of reactive oxygen species and this damage is considered an early event in the development of AD. In this study, we determined the effect of pyenogenol, a potent antioxidant phytochemical, on Abeta-induced cellular injury. Pulmonary artery endothelial cells (PAEC) were exposed to Abeta for 24 h. Cell injury was assessed by measuring cell viability with methylthiazol tetrazolium (MTT) assay, and by determining the release of intracellular lactate dehydrogenase (LDH). Lipid peroxidation products of PAEC were determined by measuring thiobarbituric acid-reactive substances (TBARS). Exposure of PAEC to Abeta resulted in a decrease in cell viability, an increase of LDH release indicating membrane damage, and an elevated level of TBARS. Preincubation of PAEC with pycnogenol significantly minimized these changes. This study demonstrated that pycnogenol can protect vascular endothelial cells from Abeta-induced injury. The data suggest that pycnogenol may be useful for the prevention and/or treatment of vascular or neurodegenerative diseases associated with Abeta toxicity.

Alzheimer Disease↗
PubMed2000

[The effective dielectric function of porous SiO2 glass].

In this paper, we discussed the effective dielectric function of porous SiO2 glass with pore size 7.5 nm. We briefly discussed different formulae proposed by different theoretical models of porous systems, and compared the relationship of effective dielectric functions changing with different porosity of porous SiO2 of each formula. Through comparing the experimental spectra and the theoretical spectra of each formula, we found the equation ln epsilon e = theta 1 ln epsilon 1 + theta 2 + theta 2 ln epsilon 2 best indicates the effective dielectric function of porous SiO2. This work is helpful in selecting special absorption materials.

English Abstract↗
PubMed1999

Update on fixation of rigid and foldable posterior chamber intraocular lenses. Part I: Elimination of fixation-induced decentration to achieve precise optical correction and visual rehabilitation.

PURPOSE: Realizing that precise posterior chamber intraocular lens (PC-IOL) centration is needed to consistently achieve good optical results and visual rehabilitation after modern cataract surgery, the authors assessed the status and success rate of lens haptic fixation and its correlation with lens optic centration-decentration in a large series of eyes with PC-IOLs obtained postmortem. DESIGN: Prospective analysis of pseudophakic eyes obtained postmortem. PARTICIPANTS: A total of 3493 human eyes obtained postmortem, the largest database of such specimens available to date. METHODS: Miyake-Apple posterior photographic technique. MAIN OUTCOME MEASURES: The amount of decentration of rigid PC-IOLs and small-incision foldable PC-IOLs was analyzed, and the results were correlated with the type of fixation that had been achieved in each case. RESULTS: Determination of mean values revealed that capsular bag fixation was achieved in 52.05% of eyes, asymmetric bag-sulcus fixation in 34.21 % of eyes, and sulcus-sulcus fixation in 13.74% of eyes. Asymmetrically fixed lenses consistently showed significant decentration. During the past 5 years (1993-98), the overall rate of in-the-bag fixation increased to 59.2%; by 1998 it had increased to 64%. Most significantly, success in achieving bag-bag fixation of foldable IOLs implanted in association with modern capsular surgery with small incisions has surged to 90% over the past 4 years. CONCLUSIONS: The authors found a direct correlation of decentration in eyes with asymmetric fixation, and the results underscore the need for careful in-the-bag haptic placement. Although few surgeons today would dispute the goal to implanting haptics in the capsular bag, these findings show that the overall success rate over the years has, while improving, remained surprisingly low. The overall success rate of about 60% seen with all lens designs is probably as good as can be expected with classic large-incision extracapsular techniques. However, and most important and encouraging, the success rate of haptic fixation in cases with foldable lenses has improved dramatically during the past 4 years (up to the 90% range). This coincides with the present emphasis on modern capsular surgery and small-incision techniques used to insert these lenses.

Acrylic Resins↗
PubMed1999

Update on fixation of rigid and foldable posterior chamber intraocular lenses. Part II: Choosing the correct haptic fixation and intraocular lens design to help eradicate posterior capsule opacification.

PURPOSE: Posterior capsule opacification (PCO) is one of the most common complications of cataract surgery, and there is an urgent need to reduce its incidence. Its main treatment, neodymium:YAG (Nd:YAG) laser posterior capsulotomy, may be associated with significant morbidity and is expensive. In this study, the authors ascertain the effect of posterior chamber intraocular lens (PC-IOL) fixation and various IOL designs (rigid polymethyl methacrylate [PMMA] optic and small-incision foldable designs) on the pathogenesis of PCO. DESIGN: Prospective analysis of pseudophakic eyes obtained postmortem. PARTICIPANTS: A total of 3493 eyes with PC-IOLs obtained postmortem and received between 1984 and 1998. METHODS: Miyake-Apple posterior photographic technique. MAIN OUTCOME MEASURES: Peripheral Soemmering's ring, central PCO in the visual axis, and eyes that have had Nd:YAG laser posterior capsulotomy were analyzed and scored, and these findings were correlated with the type of fixation and IOL design. RESULTS: The degree of formation of peripheral Soemmering's ring was not influenced by IOL fixation. The acrylic design revealed relatively low Soemmering's ring scores. In contrast, central PCO and Nd:YAG laser capsulotomy scores were consistently influenced by fixation. The scores were significantly lower in eyes with in-the-bag fixation. The bag-bag fixated acrylic-PMMA design and the three modern silicone IOL designs analyzed in this study had less central PCO and lower posterior capsulotomy scores than did the PMMA IOLs. CONCLUSIONS: The formation of peripheral PCO (the Soemmering's ring), the precursor of clinically significant, vision-threatening PCO, is not significantly influenced by the haptic fixation pattern. It is much more dependent on the quality and thoroughness of surgical cortical cleanup. Reduction of Soemmering's ring is an important goal because the retained regenerative cortical cells within this lesion are the cells of origin of PCO. The acrylic IOL design was associated with a lessor amount of peripheral Soemmering's ring as compared with all other designs. In sharp contrast to peripheral PCO, fixation of the IOL was a highly significant factor affecting the formation and quantity of central PCO-the clinically significant opacity behind the IOL optic, measured in this series either by scoring an intact retro-optical membrane or by documenting the presence of a Nd:YAG laser posterior capsulotomy orifice. The quantity of central PCO was consistently much lower in eyes with in-the-bag fixated IOLs compared with lenses with one or both haptics out of the bag. This is best explained by the fact that secure in-the-bag fixation positions the IOL optic in the best possible position to create a barrier effect. The lowest PCO rates were generally noted with the acrylic and modern silicone IOL designs.

Acrylic Resins↗
PubMed1999

Ginkgo biloba inhibits hydrogen peroxide-induced activation of nuclear factor kappa B in vascular endothelial cells.

The present study determined the effects of Ginkgo biloba extract (GBE) on the activation of nuclear factor kappa B (NF-kappaB) and the level of hydrogen peroxide (H2O2) in bovine pulmonary artery endothelial cells (PAEC). H2O2 showed a concentration-dependent activation of NF-kappaB. GBE demonstrated a concentration-dependent suppression of NF-kappaB activated by H2O2. GBE directly scavenged H2O2 in a cell-free system; it also decreased H2O2 levels in PAEC. These results suggest that the inhibitory effect of GBE on H2O2-induced NF-kappaB activation may be caused by its scavenging and suppression of H2O2. Our experiments demonstrate that GBE can inhibit NF-kappaB activation induced by H2O2 and may thus be effective for the prevention or treatment of atherosclerosis and other disorders related to NF-kappaB activation.

Animals↗
PubMed1999

Pathological examination of an explanted phakic posterior chamber intraocular lens.

PURPOSE: To report the clinicopathological correlation of an explanted phakic posterior chamber intraocular lens (PPC IOL) and to study the conformation of this lens implanted into human eyes obtained postmortem. SETTING: Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: Three silicone PPC IOLs were explanted. One lens, explanted from a 38-year-old woman with complicated cataract, was submitted for pathological analysis. In addition to gross and scanning electron microscopy (SEM), the lens was studied after experimental implantation in human eyes obtained postmortem using frontal, posterior, and side-view techniques. RESULTS: Although gross and SEM showed that the IOL was well polished, examination of the lens in human cadaver eyes showed it was oversized and poorly fixated. It was relatively bulky in its anterior-posterior dimension and revealed evidence of significant contact with the iris and crystalline lens. CONCLUSIONS: This study illustrates many pitfalls to be avoided in the design of a plate PPC IOL. The lens in this report was too large, and instead of ciliary sulcus fixation, it showed poor fixation through the zonules onto the posterior face of the pars plicata. Present and future PPC IOLs should be submitted for similar preclinical studies to clarify the type and site of fixation.

Adult↗
PubMed1999

Different apoptotic pathways are induced from various intracellular sites by tetraphenylporphyrins and light.

The induction of apoptosis from different intracellular sites was studied by exposing V79 Chinese hamster fibroblasts to photodynamic therapy (PDT) with various porphyrins and light. The effects of two lipophilic, intracellular membrane-localized porphyrins, tetra(3-hydroxyphenyl)porphyrin (3THPP) and Photofrin, were compared with that of two sulphonated meso-tetraphenylporphines (TPPS2a and TPPS4), which are taken up into lysosomes by endocytosis. Apoptotic fractions induced by the various dyes and light were quantified by flow cytometry using the terminal deoxynucleotidyl transferase (TdT) assay. Cell fragmentation was measured in parallel, while the nuclear morphology of apoptotic cells was studied by fluorescence microscopy. Different kinetics were found for the induction of DNA strand breaks characteristic of apoptotic cells. PDT-induced damage to membranes resulted in an increasing number of apoptotic cells for about 12 h after PDT After damage to lysosomes, apoptotic cells were not detected until more than 12 h after PDT. Furthermore, apoptotic bodies were not observed after PDT-induced damage to intracellular membranes, whereas apoptosis induced from lysosomal sites was characterized by extensive cell fragmentation. Cell fragmentation occurred in combination with or in the absence of nuclear fragmentation. The results support the idea that the degradation phase of apoptosis can consist of a sequence of independent steps rather than a common final pathway.

Animals↗
PubMed1999

[p16 gene suppresses growth of human esophageal carcinoma cells].

OBJECTIVE: To explore the effect of p16 gene on the growth inhibition of esophageal carcinoma cell line NEC. METHODS: The full length of wild-type p16 cDNA was transfected into the esophageal carcinoma cell line of human fetus induced by N-methyl-N-benzylnitrosamine (NMBzA). In these esophageal carcinoma cell, p16 gene was homozygously deleted. RESULTS: Expression of exogenous p16 gene in NEC cells was identified by dot blot and Western blot analyses. The growth rate of NEC transfected with p16 gene (NEC-p16) was markedly suppressed. Colony formation in soft agar was also decreased significantly. Cell cycle analysis by flow cytometry showed that the number of cells in G1-G0 phase of NEC-p16 cells was significantly increased while cells in S and G2 + M phase was decreased compared to that of the control NEC cells. CONCLUSION: Transduction of wild type p16 gene into p16 gene-depleted esophageal cancer cells can restore its suppressive effect on cell growth by arrest of cell cycle at G1 phase.

Esophageal Neoplasms↗
PubMed1999

[Transplantation of neural retina after photic injury of retina in mice].

OBJECTIVE: To examine the possibility of retinal photoreceptors rescued after photic injury by allogeneic neural retinal transplantation. METHODS: The retinal photic injury model was established by a light-damage trunk designed by ourselves. After photo-illumination, 60 mice were divided into two groups: Group I (n = 20) was the photic injury group and group II (n = 40), the retinal transplantation group; then group II was subdivided into II(A) (n = 20) and II(B) (n = 20) subgroups. External approach for neural retinal transplantation was performed at 24hr (group II(A)) and day 7 (group II(B)) after photic injury respectively. The recipients were sacrificed at day 6, day 12, day 18 and day 30 post-operatively to examine whether the graft could rescue the injured retinal photoreceptors. RESULTS: In group I, the inner and outer segment showed edema, disorganization and vesiculation, the outer nuclear layer became very thin and disorganized, and the cell nuclear chromatin showed pyknosis and margination. In group II, the graft survival rate in group II(A) was 50% (10/20) and in group II(B) was 80% (16/20), the difference being significant (chi(2) = 3.956, P < 0.05). Among the graft survival samples, we compared the rescue rate of photoreceptors between group II(A) 40% (4/10) and group II(B) 50% (8/16), the difference being not significant (P = 0.702). CONCLUSION: The retinal photic injury may result in photoreceptor degeneration that can be rescued by retinal transplantation, and the successful rate of the transplantation performed at day 7 is higher than that at 24-hr after injury.

Animals↗
PubMed1999

[Synthetic assessment of health impact of cerebrovascular diseases on potential health days of life lost].

OBJECTIVE: To assess synthetically the impact on population health caused by cerebrovascular diseases. METHODS: Incidence, duration of disease, disabilities and deaths of cerebrovascular diseases were analyzed with potential health days of life lost (PHDLL) as an indicator in urban areas of Changsha, Hunan Province. RESULTS: The PHDLL caused by cerebrovascular disease totaled 2 624.94 days per thousand of population, 33.01% of them attributed to deaths and 53.44% to chronic disability. CONCLUSION: Hemorrhagic cerebrovascular disease mainly lead to death and ischemic one caused chronic disability.

Adolescent↗
PubMed1999

[Antihypertensive study of xingnao qingxuan recipe].

OBJECTIVE: To observe the effect of decreasing blood pressure of Xingnao Qingxuan Casuples. METHOD: The blood pressure in normal and anesthetised cats was examined with direct method, the blood pressure in the conscious SHR was obtained by indirect method. RESULTS: Duodenuos administration(id) of XQC of 2.8 g/kg produced a decrease of blood pressure in normal cats; XQC of 1.4, 2.8 and 5.6 g/kg once a day for 14 days produced a dose-dependent reduction of blood pressure in SHR, 3-4 days after administration the blood pressure returned to the level before but the change was not significant. With gastric administration of XQC of 2.8 and 5.6 g/kg for 3 times, the incubation period of eyeball tremor induced by chloroform by dropping into the ear was prolonged by 14.4% and 13.0%, and the keeping time shortened by about 33.3% and 23.3% respectively. Brain basic arterial spasm induced by KCl or 5-HT in dog was relaxed obviously by XQC in vitro experiment. CONCLUSION: XQC has the effect of reducing blood pressure resisting dizziness, which is related to the diastole of brain blood vessel.

Animals↗
PubMed1998

Production of protoporphyrin IX induced by 5-aminolevulinic acid in transplanted human colon adenocarcinoma of nude mice can be increased by ultrasound.

BALB/c nude mice bearing WiDr human colon adenocarcinoma were used to determine the effect of ultrasound on the production of 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) both in the tumors and in skin overlying the tumors. Ultrasound (1 MHz) with pulsed irradiation at an average intensity of 3 W/cm2 was given 10 min to the tumor area 10 min after administration of ALA (20% in an oil-in-water emulsion applied topically on the surface of the tumor for 30 min to 3 hr). An approximately 45% increase in the amount of PpIX produced by ALA in the tumors was obtained within 1 to 2 hr following ultrasound treatment. In particular, 1 hr after ultrasound treatment, the amount of PpIX in the tumors was at the same level as that 3 hr after ALA application alone. However, pulsed ultrasound irradiation for 5 min or continuous irradiation for 5 or 10 min had no significant effect on the production of PpIX by the tumor 1 hr after topical ALA application. Furthermore, in most cases, the amount of PpIX in the tumors was significantly decreased when ultrasound was given immediately before ALA application. There was no significant change in the ratio of the amount of PpIX in tumor to that in skin after ultrasound treatment. Most likely, the distribution of PpIX fluorescence in the tumors treated with ultrasound was more homogeneous than that in the tumors given ALA only. Our results provide a theoretical basis for possible clinical use of ultrasound-combined ALA or ALA based photodynamic therapy.

Adenocarcinoma↗
PubMed1998

Photodynamic therapy.

Photodynamic therapy involves administration of a tumor-localizing photosensitizing agent, which may require metabolic synthesis (i.e., a prodrug), followed by activation of the agent by light of a specific wavelength. This therapy results in a sequence of photochemical and photobiologic processes that cause irreversible photodamage to tumor tissues. Results from preclinical and clinical studies conducted worldwide over a 25-year period have established photodynamic therapy as a useful treatment approach for some cancers. Since 1993, regulatory approval for photodynamic therapy involving use of a partially purified, commercially available hematoporphyrin derivative compound (Photofrin) in patients with early and advanced stage cancer of the lung, digestive tract, and genitourinary tract has been obtained in Canada, The Netherlands, France, Germany, Japan, and the United States. We have attempted to conduct and present a comprehensive review of this rapidly expanding field. Mechanisms of subcellular and tumor localization of photosensitizing agents, as well as of molecular, cellular, and tumor responses associated with photodynamic therapy, are discussed. Technical issues regarding light dosimetry are also considered.

Antineoplastic Agents↗