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D T Chiu

Publications and source records attributed to D T Chiu.

At least 37 records · Page 2Linked to original sources
PubMed2000

Characterization of single-cell electroporation by using patch-clamp and fluorescence microscopy.

Electroporation of single NG108-15 cells with carbon-fiber microelectrodes was characterized by patch-clamp recordings and fluorescence microscopy. To minimize adverse capacitive charging effects, the patch-clamp pipette was sealed on the cell at a 90(o) angle with respect to the microelectrodes where the applied potential reaches a minimum. From transmembrane current responses, we determined the electric field strengths necessary for ion-permeable pore formation and investigated the kinetics of pore opening and closing as well as pore open times. From both patch-clamp and fluorescence microscopy experiments, the threshold transmembrane potentials for dielectric breakdown of NG108-15 cells, using 1-ms rectangular waveform pulses, was approximately 250 mV. The electroporation pulse preceded pore formation, and analyte entry into the cells was dictated by concentration, and membrane resting potential driving forces. By stepwise moving a cell out of the focused field while measuring the transmembrane current response during a supramaximal pulse, we show that cells at a distance of approximately 30 microm from the focused field were not permeabilized.

Animals↗
PubMed2000

Treatment of painful neuromas: a case report.

The authors report a 15-year history of management of multiple recurrent neuromas in a patient with an amputated arm. Various surgical modalities were employed, including burying the nerve ends in muscle and bone. In addition, they also treated successfully one of the neuromas in this patient by capping the transected nerve with an extended autologous vein graft. This application of the extended autologous venous nerve conduit may be a novel alternative in the treatment of this challenging problem.

Adult↗
PubMed1999

Chemical transformations in individual ultrasmall biomimetic containers.

Individual phospholipid vesicles, 1 to 5 micrometers in diameter, containing a single reagent or a complete reaction system, were immobilized with an infrared laser optical trap or by adhesion to modified borosilicate glass surfaces. Chemical transformations were initiated either by electroporation or by electrofusion, in each case through application of a short (10-microsecond), intense (20 to 50 kilovolts per centimeter) electric pulse delivered across ultramicroelectrodes. Product formation was monitored by far-field laser fluorescence microscopy. The ultrasmall characteristic of this reaction volume led to rapid diffusional mixing that permits the study of fast chemical kinetics. This technique is also well suited for the study of reaction dynamics of biological molecules within lipid-enclosed nanoenvironments that mimic cell membranes.

Alkaline Phosphatase↗
PubMed1999

Humic acid-mediated oxidative damages to human erythrocytes: a possible mechanism leading to anemia in Blackfoot disease.

Humic acid (HA) has been proposed as a factor that causes Blackfoot disease, an endemic peripheral vascular disease prevailing in the southwest coast of Taiwan. However, the relationship between HA and anemia associated with Blackfoot disease remains unclear. In this study, we showed that HA imposed damages on human red blood cells (RBCs), which were manifested as reduction in deformability of RBCs and hemolysis. At concentrations ranging from 10 to 100 microg/ml, HA caused lipid peroxidation in a dose-dependent manner. Such changes were accompanied by a depletion of glutathione and a reduction in activities of the antioxidant enzymes including catalase, superoxide dismutase, and glucose-6-phosphate dehydrogenase. These results indicate that HA initiates oxidative stress on RBCs and results in their dysfunction. Consistent with our previous findings, the present study supports the notion that HA plays an important role in the pathogenesis of Blackfoot disease.

Anemia↗
PubMed1999

The pinwheel technique: an adjunct to the periareolar approach in gynecomastia resection.

The most common surgical approach to gynecomastia is through Webster's intra-areolar incision. The authors have modified the excisional phase of the operation to facilitate the delivery of a large mass of breast tissue through a relatively small incision. The essential features of this procedure are (1) delineation of the perimeter of the breast on the pectoral fascia; (2) elevation of the anterior chest wall skin and subcutaneous tissues over the entire breast mass; (3) serial application of Kocher clamps at the perimeter of the breast and, with gentle traction, sequential lysis of the peripheral and posterior attachments of the breast mass; and (4) delivery of the the mass simultaneously through the periareolar incision, as the dissection proceeds, until the entire specimen is exteriorized. The specimen then consists of the entire breast mass encircled by a pinwheel-like arrangement of Kocher clamps. Thirty-one patients (61 gynecomastic breasts) were operated using this method. En bloc tissue specimens weighing as much as 285 g were removed without the need for dividing the specimen or extending the single incision. The authors recommend this technique, which is straightforward and efficacious with minimal blood loss and good postoperative cosmesis.

Adult↗
PubMed1999

Autogenous venous nerve conduits. A review.

Autogenous venous nerve conduit (AVNC) has evolved from an experimental idea to a clinical reality over the last two decades. The effectiveness of AVNC for reconstruction of a peripheral nerve with a nerve gap of less than 3 cm has been established and confirmed. An exciting application of this technique in the near future is to use the conduit as a vehicle for moderation and modulation of the cellular and molecular ambience for nerve regeneration.

Animals↗
PubMed1999

Painful neuromas: a review of treatment modalities.

There are numerous methods cited in the literature on the treatment of painful neuroma. Nonsurgical methods range from injections with various materials into the nerve end to desensitization of nerve pain conduction pathways. Some surgical treatments aim to alter the environment of the amputated nerve end by transposing it into muscle or bone, others have designed various flaps to protect truncated nerve ends from scar tissue, and still others try to "cap" the nerve with silicon, a nerve graft, or epineurium to prevent nerve regeneration. All of these methods have proved efficient. However, none of these methods work universally. The authors review the common treatments for painful neuromas. In addition, they review the preliminary results of the extended autologous venous nerve conduit as a novel technique of treating painful neuromas. They also report recent investigations into the pathophysiology of injured nerves.

Animals↗
PubMed1998

Impaired production of nitric oxide, superoxide, and hydrogen peroxide in glucose 6-phosphate-dehydrogenase-deficient granulocytes.

Since the generation of superoxide and hydrogen peroxide by NADPH oxidase and nitric oxide (NO) by NO synthase (NOS) in granulocytes is NADPH-dependent, we investigated the production of NO, superoxide and H2O2 in glucose 6-phosphate dehydrogenase (G6PD)-deficient human granulocytes. Our results showed that upon stimulation with either 5 microg/ml of lipopolysaccharide (LPS) or 10 microM of phorbol 12-myristate 13-acetate (PMA), the production of nitrite in normal granulocytes was elevated, 252 +/- 135% and 239 +/- 72%, respectively, compared to the resting stage. In contrast, G6PD-deficient granulocytes did not produce more nitrite upon stimulation with either LPS or PMA compared to the resting stage. Western blot analysis indicated a normal expression pattern of inducible NOS in G6PD-deficient granulocytes. In addition, the production of H2O2 and superoxide was also significantly impaired in G6PD-deficient granulocytes compared to control cells. These data demonstrate that G6PD deficiency causes an impairment in the production of NO, superoxide and H2O2.

Erythrocytes↗
PubMed1998

Separation and characterization of amines from individual atrial gland vesicles of Aplysia californica.

Several amine-containing components of individual vesicles from the atrial gland of Aplysia californica were identified with capillary electrophoresis (CE). On-line derivatization with naphthalene-2,3-dicarboxaldehyde was performed, and the derivatized amine-containing components were detected with laser-induced fluorescence (LIF). Amino acids, including taurine, that had not been determined previously in atrial gland vesicles were observed by using CE-LIF, and their identities were confirmed with CE, HPLC, NMR, and electrospray ionization mass spectrometry. The finding that taurine is packaged and stored into secretory vesicles supports the hypothesis that taurine may exhibit neuromodulatory activity. The bioactive peptides, well-known to be in atrial gland vesicles, were detected in lysed vesicle samples fractionated with HPLC and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. These peptides were also observed in single-vesicle runs with CE-LIF. The atrial gland vesicles (ranging from 0.5 to 2 microns diameter and 65 aL to 4 fL volume, respectively) studied in this work represent the smallest biological entities to be analyzed chemically on an individual basis.

Amines↗
PubMed1998

Probing single secretory vesicles with capillary electrophoresis.

Secretory vesicles obtained from the atrial gland of the gastropod mollusk Aplysia californica were chemically analyzed individually with a combination of optical trapping, capillary electrophoresis separation, and a laser-induced fluorescence detection. With the use of optical trapping, a single vesicle that had attoliters (10(-18) liters) of volume was introduced into the tapered inlet of a separation capillary. Once the vesicle was injected, it was lysed, and its components were fluorescently labeled with naphthalene-2, 3-dicarboxaldehyde before separation. The resultant electropherograms indicated distinct variations in the contents of single vesicles.

Amines↗
PubMed1998

Effect of optical temperature feedback control on patency in laser-soldered microvascular anastomosis.

Feedback control has been postulated to improve the efficacy of laser welding in microsurgery, but alteration of outcome has not been clearly shown. The authors evaluated the ability of an optical closed loop temperature feedback control to improve patency, aneurysm rate, and to histologically limit thermal damage. Rat femoral artery anastomoses were performed under operating microscope magnification. One hundred and twenty-four anastomoses were performed in five groups using 1) free-hand (FH) 1.9-microm laser soldering without feedback; 2) temperature controlled (TC) 1.9-microm laser soldering with optical feedback; 3) FH 808 nm laser; 4) TC 808 nm laser soldering; and 5) 10-0 nylon suture control. In Groups 2 and 4, an optical feedback system controlling laser exposure to produce a preset temperature was used. Anastomotic time was significantly less for all laser groups (p < 0.05). Late patency for all 1.9-microm laser anastomoses was almost 0. Temperature controlled 808-nm anastomoses showed no significant difference from sutures in terms of patency (88 percent vs. 96 percent), bursting pressure, and aneurysm rate, while freehand 808-nm anastomoses had a significantly lower patency (71 percent) and more tissue damage (ANOVA, p < 0.05). The authors conclude that temperature control improves outcome in microvascular anastomosis by reducing transmural thermal injury caused by variations in surgeon technique.

Anastomosis, Surgical↗
PubMed1997

Injection of ultrasmall samples and single molecules into tapered capillaries.

A novel injection scheme is described in which ultrasmall samples in the attoliter (10(-18) L) and low femtoliter (10(-15) L) range, or even single molecules, are controllably introduced into a tapered capillary so that electrophoretic separation can be carried out. To match the dimensions of the capillary inlet with that of the sample, capillary tips are tapered to an inside diameter ranging from hundreds of nanometers to a few micrometers. To inject an ultrasmall sample, optical trapping is used to immobilize and manipulate the sample in order to place it inside or next to the capillary inlet. A small controlled suction results in the loading of the sample into the capillary.

Chemistry Techniques, Analytical↗
PubMed1997

Palladium or platinum exacerbates hydroxyl radical mediated DNA damage.

Strand breakage of supercoiled pBR322 DNA by a Fenton system is increased in the presence of palladium or platinum (Pt) ions. Neither Pd nor Pt ions can substitute for iron in the Fenton system. We have obtained several lines of evidence that Pd and Pt ions in the presence of a Fenton system can augment the production of OH., as monitored by a spectrophotometric method quantifying hydroxylated salicylate or by a fluorometric method quantifying catechol production. Furthermore, the promoting effect of both metal ions on OH. production was substantiated by the identification of multiple hydroxylated products of salicylate [2,3-dihydroxybenzoate (A), 2,5-dihydroxybenzoate (B), and catechol (C)] using HPLC. The concentrations of A, B, and C produced in the control were 4.5, 8.0, and 2.0 microM, respectively; whereas, their respective concentrations increased to 23.6, 42.0 and 10.0 microM with the addition of Pd ions. The observed phenomenon was further confirmed by the identification of HO-DMPO spin adducts using ESR spectroscopy. Taken together, our data suggest that the mechanism of Pd or Pt ion-mediated exacerbation of DNA damage by a Fenton system is due to the promotion of OH. production by these metal ions.

DNA Damage↗
PubMed1997

Hemin-induced membrane sulfhydryl oxidation: possible involvement of thiyl radicals.

Sublytic levels (microM) of hemin destabilized RBC membrane as indicated by ghost fragmentation pattern using a laser viscodiffractometer. Furthermore, electron microscopic study shows that 5 microM of hemin induced echinocytic transformation whereas higher hemin concentration (40 microM) induced spherocytic transformation. In addition, hemin oxidized sulfhydryl groups in a dose dependent fashion and Electron Spin Resonance study suggests that such oxidation may involve a thiyl radical. Moreover, sulfhydryl compounds enhanced hemin-induced lipid peroxidation. Desferroxamine could prevent hemin-induced sulfhydryl oxidation as well as hemin-induced decrease in membrane stability. In contrast, vitamin E could effectively prevent hemin-induced lipid peroxidation but could not prevent hemin-mediated membrane destabilization.

Deferoxamine↗
PubMed1996

Rapid preparation of giant unilamellar vesicles.

We report here a rapid evaporation method that produces in high yield giant unilamellar vesicles up to 50 microns in diameter. The vesicles are obtained after only 2 min and can be prepared from different phospholipids, including L-alpha-phosphatidylcholine (lecithin), dipalmitoleoyl L-alpha-phosphatidylcholine, and beta-arachidonoyl gamma-palmitoyl L-alpha-phosphatidylcholine. Vesicles can be produced in distilled water and in Hepes, phosphate, and borate buffers in the pH range of 7.0 to 11.5 with ionic strengths up to 50 mM. The short preparation time allows encapsulation of labile molecular targets or enzymes with high catalytic activities. Cell-sized proteoliposomes have been prepared in which gamma-glutamyltransferase (EC 2.3.2.2) was functionally incorporated into the membrane wall.

Drug Stability↗
PubMed1996

Microsurgery in a rat lung transplant model: analysis of benefit.

With the use of microsurgery, we have developed a method of measuring hemodynamic parameters in a rat not possible with previous technology. Three groups of rats were studied: a chemically induced pulmonary hypertensive group (PH); a chemically induced pulmonary hypertensive group treated with single lung transplantation (LT); and an untreated, control group (C). Cardiac output, heart rate, and pulmonary vascular resistance were then calculated in each group from data obtained by 1 mm high fidelity micromanometers and an ultrasonic flow probe. The results show that the data collected from the rodent model are reproducible within each group, and data quality is comparable to large animal models. With this new method, data can be collected in a small animal model at a fraction of the time and cost of large animal studies. Additionally, the complications of graft rejection in large animal studies are eliminated in an isogenic rodent model.

Animals↗