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H T Chang

Publications and source records attributed to H T Chang.

At least 73 records · Page 4Linked to original sources
PubMed1995

Kinetics of substrate oxidation by whole cells and cell membranes of Helicobacter pylori.

Oxygen uptake by Helicobacter pylori cells and membranes was determined. Cells from stirred broth cultures or agar plates, suspended in buffer, possessed a variable and apparently endogenous respiration which could be sustained for several hours. In contrast, oxygen consumption by cells from statically incubated broth cultures, in the absence of added substrate, was transient or undetectable. These latter cells, however, oxidised ethanol, fumarate, glucose, D-lactate, pyruvate and succinate, though glucose-oxidising ability declined rapidly. The Kms for D-lactate, pyruvate and succinate metabolism were low (< or = 20 microM) and oxygen uptake was approximately 1.5, 2 and 2 mol per mol substrate respectively, indicating metabolism beyond acetate plus CO2 and implying the presence of tricarboxylic acid cycle activity. Cell membranes oxidised fumarate, D-lactate, NADH, NADPH and succinate. NADPH oxidation was six times more rapid than that of NADH. Rates of oxygen uptake by cells suspended in buffer with metabolisable substrate were < 20% of those for cells suspended in a brain heart infusion medium. Uninoculated medium consumed significant quantities of oxygen.

Cell Membrane↗
PubMed1995

Determination of catecholamines in single adrenal medullary cells by capillary electrophoresis and laser-induced native fluorescence.

The present study demonstrates that native fluorescence detection combined with capillary electrophoresis separation at low pH provides high sensitivity (down to nanomolar), high resolution, high speed, and low interference for the analysis of catecholamines. Further, this method has been employed successfully for the measurement of the amounts of epinephrine and norepinephrine in individual bovine adrenal medullary cells. Application of this method to the study of neurochemistry is promising.

Adrenal Medulla↗
PubMed1995

Dispersion coefficients of a protein and DNA fragment in polyacrylamide gel electrophoresis as a function of parameters defining the effective gel pore size and particle size.

The dispersion coefficient, D', of the representative homogeneous protein, conalbumin, decreases linearly as the polyacrylamide concentration increases from 4 to 14%T (2%C), and varies in a biphasic fashion as %C (Bis) is increased from 2 to 20%, with a broad peak between 5 and 15%C. D' increases linearly with the concentration of the initiator, potassium persulfate, in the range of 0.01-0.15%. D' remains constant when the field strength is varied from 5 to 15 V/cm. A DNA fragment (1857 bp) exhibits a constant D' in 4-6% polyacrylamide (2%C) at a field strength of 1 V/cm, and a linearly increasing D' at 5 V/cm, in analogy to its previously observed behavior in agarose gels. In solutions of uncrosslinked polyacrylamide, the decrease of the D' of conalbumin with polymer concentration is not significantly different from that in 2% N, N'-methylenebisacrylamide-crosslinked gels in the range of 4-14%T, while the decrease of mobility with polyacrylamide concentration is much steeper in 2% crosslinked compared to uncrosslinked polymer. Finally, delta (log D')/ delta T was found to be proportional to the retardation coefficient, KR (= -delta (log mu)/ delta T), in polyacrylamide gels. The ratio of -delta (log D')/ delta T over KR increases with field strength in the range of 5-15 V/cm.

Conalbumin↗
PubMed1995

Horizontal gel electrophoresis with sample volumes up to 1.5 mL, using a discontinuous buffer system and automated apparatus.

Horizontal gel electrophoresis has previously suffered from lack of an instrumental design that would allow for application of large sample volumes. A recently introduced commercial apparatus (HPGE-1000, LabIntelligence) remedies that problem in application to gel electrophoresis with intermittent scanning of fluorescence by using the concentrator module of that apparatus as a stacking gel reservoir. By using this technique and a 3 mL stacking gel, protein samples of up to 1.5 mL yield bands in the horizontal resolving gel that are independent of sample volume in their width, area and migration rate. A remaining procedural problem relates to the apparent nonsimultaneity of dye and protein entrance into the resolving gel, which necessitates peak characterization by absolute rather than relative mobilities.

Automation↗
PubMed1995

Dynamic control to improve the separation performance in capillary electrophoresis.

Dynamic control in capillary electrophoresis (CE) is able to provide better resolution, shorter separation time, reduced band broadening and better reproducibility for the separations of organic and inorganic ions and large molecules such as proteins and DNA. This article provides an overview of dynamic control in CE by several techniques: pH, temperature, external electric field, and field amplification. These techniques take advantage of the changes in electroosmotic flow coefficient, electrophoretic mobilities of the analytes due to changes in equilibrium, viscosity of the buffer solution, and/or electric field strength. The basic theories and applications to the improvement of the separation performance for standard samples in CE by using these dynamic control techniques are presented. Finally, the advantages and shortcomings of these techniques and the future trends of dynamic control for the separations of real samples are discussed.

Electric Conductivity↗
PubMed1995

GABAergic axons in the ventral forebrain of the rat: an electron microscopic study.

The ventral forebrain, including the ventral striatum, the ventral pallidum and the substantia innominata, is an important region involved in the functions of the basal ganglia and the limbic system, as well as the magnocellular corticopetal neurons of the nucleus basalis of Meynert. Although previous studies have shown that this region is richly innervated by GABAergic fibers, little is known with respect to the relative densities of GABAergic to non-GABAergic axon terminals in this region. To address this issue, we have developed a specific rabbit antiserum to GABA and used a postembedding immunocytochemical reaction to analyse the distribution of GABA-like immunoreactive axon terminals in the rat ventral striatum, ventral pallidum and substantia innominata. Of all axon terminals that form identifiable synapses within single ultrathin sections taken from these regions, 11.6% in the ventral striatum, 85.5% in the ventral pallidum and 64.8% in the substantia innominata were GABAergic. Differences were also found in the distribution patterns of these terminals with respect to the size of their synaptic target dendrites. These findings are consistent with previous findings that a majority of inputs to the ventral striatum are excitatory, and that a majority of inputs to the ventral pallidum are inhibitory. Our results provide a first approximation of the anatomical substrate for the physiology and pharmacology of GABA actions in the ventral forebrain region. These results also show that GABA may play an important role in the substantia innominata, where both the cholinergic and the non-cholinergic magnocellular corticopetal neurons reside within a neuropil innervated by many different non-cholinergic fibers.

Animals↗
PubMed1995

Feasibility of electrophoresis of a subcellular-sized particle in polymer solutions, using automated horizontal gel apparatus.

Electrophoresis in polymer solutions of a fluorescently labeled polystyrene carboxylate particle of 46.5 nm radius was carried out in a horizontal gel electrophoresis apparatus with intermittent scanning of the migration path. Polymers of the order of 10(6) (dextran, polyvinylpyrrolidone, polyacrylamide and polyethyleneglycol) and 10(5) (hydroxyethylcellulose, polyethyleneglycol) M(r) were used. In each application, bands formed, became symmetric and narrowed with increasing polymer concentration. The decrease in dispersion coefficients, D', with polymer concentration was sharpest with the polymers of M(r) 10(6); but significant differences in the effectiveness of polymers within that group also exist which are not accounted for. Provided that the demonstrated feasibility of banding in concentrated polymer solutions will allow for separations similar to those achieved at low polymer concentrations in CZE, the method promises to overcome the inherent shortcomings of capillary electrophoresis in polymer solutions with regard to inaccessibility of bands for immunological and affinity detection as well as to preparative scale and preparative instrumental complexity.

Automation↗
PubMed1994

Synaptic relationships of enkephalinergic and cholinergic neurons in the nucleus accumbens of the rat.

Leucine5-enkephalin- and choline acetyltransferase-containing, presumably cholinergic, neurons revealed by dual label immunocytochemistry were found in the shell and core of the rat nucleus accumbens. The perikarya, dendrites and boutons of cholinergic neurons were labeled with the diaminobenzidine precipitate, whereas those of the enkephalinergic neurons were labeled with silver-intensified colloidal gold. Ultrastructural examination revealed that both the enkephalinergic and the cholinergic boutons generally formed symmetric synapses with unlabeled dendrites and, occasionally, with unlabeled dendritic spines. Enkephalin-immunoreactive terminals which were much larger than cholinergic boutons, seldom apposed or formed synapses with cholinergic structures in the nucleus. In the core, cholinergic terminals were frequently found apposed to enkephalin-immunoreactive dendrites and perikarya and were often seen in synaptic contact with enkephalinergic dendrites, whereas in the shell, cholinergic boutons seldom apposed or contacted enkephalinergic targets. These findings show that enkephalinergic and cholinergic neurons differ in their synaptic arrangements within the nucleus accumbens and provide further evidence for differentially organized intrinsic connections of shell and core territories.

Animals↗
PubMed1994

Relationship of calbindin D-28k with afferent neurons to the rostral ventrolateral medulla in the rat.

The phenylethanolamine-N-methyltransferase (PNMT)-containing neurons in the rostral ventrolateral medulla (RVLM) (the C1 adrenergic group) have been implicated in the generation of the tonic sympathetic nerve activity. Using a double-labeling immunohistofluorescence technique, we found that 34.6 +/- 11.4% (mean +/- S.D.) of PNMT immunoreactive neurons in the RVLM were immunoreactive for Calbindin D-28k (CaBP), a Vitamin D-dependent calcium binding protein. Since CaBP is probably involved in regulating intracellular calcium concentrations in cells that are metabolically or electrically very active, our results suggest that at least some C1 adrenergic neurons (those containing calbindin) may have calcium mediated high metabolic or electrophysiologic activity that is associated with generating tonic nerve function. The RVLM has wide connections with many different nuclei in the brain which are known to contain clusters of neurons that express immunoreactivity to CaBP. In order to determine whether CaBP could be used as a molecular marker for projection neurons to the RVLM or to identify a subpopulation of projection neurons containing CaBP, we sought to determine the relationships between CaBP and the neurons that project to RVLM. Following injections of the retrograde tracer FluoroGold (FG) into the rat RVLM, sections containing retrogradely labeled neurons in (1) the nucleus tractus solitarii (NTS), (2) the contralateral RVLM, (3) the area postrema, (4) the mesencephalic central gray (mCG), (5) the lateral hypothalamus (LH), (6) the substantia innominata (SI), and (7) the paraventricular hypothalamic nucleus (PV) were tested for CaBP immunoreactivity. Although many retrogradely labeled neurons were found amidst many CaBP immunoreactive neurons in each of these nuclei, only a subpopulation of the retrogradely labeled neurons expressed CaBP immunoreactivity. The NTS demonstrated the higher proportion of double-labeled cells (mean 31.5 +/- 4.3%), whereas the lower proportion corresponded to the contralateral RVLM (mean 9.6 +/- 3.2%). On the other hand, both the retrogradely labeled neurons and the CaBP immunoreactive neurons in each of these nuclei were often found in regions containing a great number of adrenergic axons (i.e. immunoreactive for PNMT). Our results suggest that: (1) Two types of adrenergic RVLM neurons could be found, those containing CaBP and those lacking this calcium binding protein. (2) CaBP is not a common marker for the afferent neurons to the RVLM, but rather is found in selective subsets of them. (3) Both the non-CaBP projection neurons and the CaBP immunoreactive neurons in these nuclei may be innervated by adrenergic fibers.

Animals↗
PubMed1993

Topography of cholinergic afferents from the nucleus basalis of Meynert to representational areas of sensorimotor cortices in the rat.

We investigated (1) the topography of projection neurons in the nucleus basalis of Meynert (NBM) with efferents to restricted regions of the primary somatosensory (SI), the second somatosensory (SII), and the primary motor (MI) cortices in the rat; (2) the percentage of these NBM projection neurons that were cholinergic; and (3) the collateralization, if any, of single NBM neurons to different subdivisions within SI, to homotopic areas of SI and SII, and to homotopic areas of SI and MI. Retrograde single- and double-labeling techniques were used to study NBM projections to electrophysiologically identified subdivisions of SI and to homotopic representational areas of SI and SII, and of SI and MI. Choline acetyltransferase immunocytochemistry was done to identify cholinergic NBM neurons. Of the retrogradely labeled NBM neurons that projected to selective subdivisions of SI, SII, and MI, 89%, 87%, and 88%, respectively, were cholinergic. We found a rostral-to-caudal progression of retrogradely labeled NBM neurons following a medial-to-lateral sequence of injections into subdivisions of SI. Overlapping groups of single-labeled NBM neurons were observed after injections of different tracers into adjacent subdivisions within SI or homotopic areas of SI and SII, and of SI and MI. We conclude that NBM innervation to SI, SII, and MI is mostly cholinergic in the rat, that each cortical area receives cholinergic afferents from neurons widely distributed within the NBM, and that each NBM neuron projects to a restricted cortical area without significant collateralization to adjacent subdivisions within SI or to homotopic areas of SI and SII, or SI and MI.

Acetylcholine↗
PubMed1993

Immunoperoxidase labeling of the anterograde tracer fluoro-ruby (tetramethylrhodamine-dextran amine conjugate).

Fluoro-Ruby (tetramethylrhodamine-dextran amine conjugate) has been shown recently to be an effective anterograde tracer readily visible in brain sections with fluorescence microscopy. We show in this study that further microscopic analysis of Fluoro-Ruby-labeled elements is feasible with a conventional immunoperoxidase reaction using an antiserum raised against tetramethylrhodamine.

Animals↗
PubMed1992

Ventral pallido-striatal pathway in the rat brain: a light and electron microscopic study.

Most theories of basal ganglia functions have been based on a model circuit in which the flow of information follows a one-way loop proceeding from the cerebral cortex to the striatum, the pallidum/nigra, the thalamus, and then returns to the cortex. However, this model neglects data from several studies that show a direct feedback projection from the pallidum to the striatum. In this study, we have examined this feedback connection in the ventral striopallidal system to determine the morphology and chemical properties of ventral pallido-striatal projection neurons and to determine the morphology of ventral pallidal efferents in the ventral striatum. Fluoro Gold was injected into the ventral striatum to retrogradely label ventral pallidal projection neurons. Substance P immunoreactivity was used as a pallidal marker to delineate the ventral pallidum. The results show that most neurons retrogradely labeled by Fluoro Gold lie in the ventral pallidum. Additional double-labeling experiments show that none of these Fluoro Gold-labeled cells are cholinergic neurons; however, some are immunoreactive for parvalbumin, a calcium-binding protein found in many pallidal neurons. Electron microscopy revealed that the somata and dendrites of these labeled ventral pallidal projection neurons form many synapses with unlabeled terminals. Injection of Phaseolus vulgaris-leucoagglutinin into the ventral pallidum anterogradely labeled many fibers in the ventral striatum. Electron microscopy revealed that these labeled axons form both symmetric and asymmetric synapses with ventral striatal neurons. We have thus confirmed that there is a significant direct projection from the ventral pallidum to the ventral striatum. Whether this projection forms a part of either monosynaptic or polysynaptic feedback loops remains to be clarified. Nevertheless, this pallidostriatal projection must be integrated into the theories on basal ganglia functions.

Animals↗
PubMed1992

Interneurons in the rat striatum: relationships between parvalbumin neurons and cholinergic neurons.

A pre-embedding double-labeling immunocytochemical method was used to examine the synaptic relationships between cholinergic neurons and the parvalbumin immunoreactive (PV+) neurons. The PV+ neurons were labeled by silver-intensified colloidal gold particles, and the cholinergic neurons by immunoperoxidase reaction products. Cholinergic and PV+ axon terminals form synapses with both the somata and dendrites of PV+ neurons, as well as unlabeled medium-sized somata with round un-indented nuclei, a typical characteristic of the medium spiny projection neurons. These observations suggest that the PV+ and the cholinergic neurons have converging influences on both the projection neurons and the PV+ interneurons in the striatum.

Acetylcholine↗
PubMed1992

[Laparoscopic cholecystectomy: experience of VGH-Kaohsiung].

One hundred consecutive patients underwent laparoscopic cholecystectomy from May 1991 to February 1992 at Veterans General Hospital--Kaohsiung. Ninety-seven of them presented on an elective basis, including eight patients undergoing endoscopic sphincterotomy with extraction of common bile duct stone before laparoscopic cholecystectomy. The remaining 3 patients were operated during acute cholecystitis episode. Two patients with biliary injuries during laparoscopic cholecystectomy were converted to laparotomy, with a conversion rate of 2%. Intraoperative cystic cholangiogram was done selectively in 7 patients. Major complications occurred in 3 patients, including two biliary injuries and one residual CBD stone. Minor complications of wound infection were found in 7 patients. The overall morbidity rate was 10%. No operative mortality was found. Mean operation time was 112 minutes and mean blood loss was 90 ml. The mean hospital stay (3.1 days) and the mean time of returning to normal activity (14.7 days) were longer than those of Western series, but were shorter than those of open cholecystectomy. Laparoscopic cholecystectomy is a safe and effective procedure that can be performed with minimal risk. However, the importance of accurate preoperative screening and surgical experience should be emphasized for this new procedure. In patients with gall stone plus CBD stone, combined endoscopic sphincterotomy with extraction of CBD stone and laparoscopic cholecystectomy may offer a new therapeutic approach but the long term effect of endoscopic sphincterotomy needs further evaluation.

Adult↗
PubMed1991

Relationship of calbindin D-28k and cholinergic neurons in the nucleus basalis of Meynert of the monkey and the rat.

Double-labeling immunocytochemistry reactions were carried out in the monkey and the rat nucleus basalis of Meynert (NBM) to determine the extent of overlap between cholinergic neurons and neurons immunoreactive for calbindin-D-28k (CaBP), a Vitamin D-dependent calcium binding protein. The results indicate that most, but not all, NBM cholinergic neurons in the monkey are immunoreactive for CaBP. On the other hand, none of the rat NBM cholinergic neurons are immunoreactive for CaBP.

Animals↗