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Biomedical subjects

T Kang

Publications and source records attributed to T Kang.

At least 37 records · Page 2Linked to original sources
PubMed1997

Evaluating the merits of option-3 methods in relative attachment level measurement in a healthy population.

Attachment loss is the principal clinical indicator for periodontal disease progression. However, the attachment measurement can be inaccurate due to outliers. A remedial scheme, the option-3 scheme, has been suggested in the literature. This scheme involves first measuring the relative attachment twice at any given site. A third measurement is required if there is a large disagreement between the first two probings. When the third measurement is taken, there are several possible ways to make the final assessment of the true attachment level. Among them are the average of the 3 measurements, the average of the closest 2, and the median of the 3. This report evaluates the merits of the option-3 scheme by comparing it with other schemes to reduce measurements variance and outliers. Since true attachment levels are unknown, we chose to check accuracy through measurement consistency between visits in healthy subjects using the fact that such subjects should have little real change in attachment levels. 12 healthy subjects participated in the study. They visited the clinic 4 times in 4 months. Two types of the Florida stent probe were used by 2 calibrated examiners. It was found that option-3 schemes were more accurate than a single probing or duplicate probings in estimating the relative attachment level. The 3 final assessment schemes performed almost equally well from a practical standpoint, but the median was the best among them in a statistical sense.

Adult↗
PubMed1997

Melatonin attenuates photic disruption of circadian rhythms in Siberian hamsters.

Body temperature (Tb) was recorded via a biotelemetry system from 28 adult male Siberian hamsters maintained in a light-dark (LD) cycle of 16 h light/day for several months. After Tb was recorded for 3 wk, the LD cycle was phase delayed by extending the light phase by 5 h for 1 day; animals remained on a 16:8 LD cycle for the remainder of the experiment. Hamsters were injected daily with melatonin or vehicle solution for several weeks, beginning either 2 mo after (experiment 1) or on the day of (experiment 2) the phase shift; injections occurred within 30 min of dark onset. In experiment 1, 75% of animals free ran with circadian periods >24 h, beginning on the day of the phase shift, and never reentrained to the LD cycle; no hamsters unambiguously entrained to daily injections. In contrast, 78% of animals in experiment 2 entrained to melatonin injections, and 71% of those animals subsequently reentrained to the photocycle when the injection regimen ended. No vehicle-treated animals entrained to the injection schedule. Melatonin had no effect on daily mean Tb and Tb rhythm amplitude in either experiment; however, melatonin doubled the duration of a hyperthermic response that occurred after each injection. Thus melatonin can prevent loss of entrainment induced by a phase shift of the LD cycle but cannot restore entrainment to free-running animals. Failure to reentrain in the presence of two appropriately coordinated entraining agents also suggests that a phase shift of the photocycle can diminish the sensitivity of the circadian system to both photic and nonphotic input.

Animals↗
PubMed1997

[Dynamic study of anti-NS5 and ALT in post-transfusion hepatitis C].

In order to study the character and dynamic changes of HCV NS5 antigen in post-transfusion hepatitis C, EIA was established with fusion protein, and different groups of population were investigated. The results showed the positive rate of whole blood donor, normal people, chronic hepatitis C patients and post transfusion hepatitis C patients is 0.0%, 1.66%, 50.7% and 70.5%, respectively. Serial blood samples of 25 cases of acute or chronic post-transfusion hepatitis C were detected, and the results indicated that the antibody of NS5 appeared relatively late, and the serum conversion time was 182.9 +/- 168.5 days. The anti-NS5 positive rate in 1, 3, 6, 12 and 24 months after HCV infection was 28%, 40%, 52%, 68% and 76%, respectively. The positive rate of anti-NS5 in sera with HCV RNA was 61.9%. Analysis on the appearance of antibody to the different antibody region of the gene, ALT and HCV RNA showed the dynamic changes of anti-NS5 were corresponding to the serum ALT in some cases, indicating antibody of NS5 appear later and may reflect the disease activity to some extent. The dynamic changes of anti-NS5 are of four kinds: transient positive, intermittent positive, persistent positive and persistent negative in during the two years period.

Alanine Transaminase↗
PubMed1996

Selective ligand-induced intracellular calcium changes in a population of rat isolated gastric endocrine cells.

BACKGROUND & AIMS: Peripheral regulation of acid secretion depends mainly on stimulation or inhibition of the three major gastric endocrine cells (enterochromaffin-like, gastrin, and somatostatin). The aim of this paper was to define physiological responses of enterochromaffin-like, gastrin, and somatostatin cells in a mixed endocrine cell population by measuring ligand-selective changes of intracellular calcium ([Ca2+]i) in individual cells. METHODS: Endocrine cells were enriched from a rat gastric cell suspension by elutriation, a density-gradient fractionation, and a 48-hour short-term culture. [Ca2+]i responses of individual cells to various ligands such as gastrin/carboxy-terminal cholecystokinin octapeptide and selective cholecystokinin antagonists, carbachol, and gastrin-releasing peptide were monitored using video imaging in a perfusion chamber. Characteristic [Ca2+]i changes distinguished the three cell types, confirmed by immunostaining. RESULTS: All enterochromaffin-like cells respond to cholecystokinin-B receptor stimulation, but only a few respond to carbachol. Gastrin cells respond to both gastrin-releasing peptide and carbachol but not to cholecystokinin-receptor agonists. Somatostatin cells have both stimulatory cholecystokinin-A and cholecystokinin-B receptors and inhibitory muscarinic receptors. All cells have inhibitory somatostatin receptors. CONCLUSIONS: Calcium-signaling responses of gastric endocrine cells are distinctive. This allows individual cell types in a mixed population to be characterized and permits an analysis of the hormones and transmitters that act directly on a specific cell type.

Animals↗
PubMed1996

Comparison of biaxial mechanical properties of excised endocardium and epicardium.

A complete understanding of cardiac mechanics requires knowledge of the mechanical properties of each of the tissues that comprise the heart, Data and constitutive relations are available for the nonlinear multiaxial behavior of epicardium and noncontracting myocardium, but there have been no comparable results for endocardium. In this paper, we present biaxial mechanical data for endocardium and epicardium excised from the same bovine hearts. The data reveal that these two membranes behave differently; endocardium exhibits a greater stiffness in the low-strain range. Moreover, quantification of endocardial behavior requires a seven-parameter, polynomial-exponential pseudostrain-energy function w, whereas epicardium can be described by a four-parameter exponential w. Comparison of our current findings with previous results on canine epicardium reveals further that canine and bovine epicardium behave similarly, although the latter is more extensible. Thus there appear to be marked species differences.

Animals↗
PubMed1996

The need to account for residual strains and composite nature of heart wall in mechanical analyses.

We studied 19 excised, passive rabbit left ventricular walls to delineate the forms of the strain-energy functions (W) for myocardium and epicardium, to quantify residual strains across the wall, and to investigate whether the mechanical behavior of the intact wall can be predicted by accounting for the above properties. The unloaded dimensions and the stress-strain responses to equibiaxial and uniaxial loadings were obtained first for the intact wall and then individually for the epicardium and myocardium. Results show that the previously proposed W for canine myocardium and epicardium are suitable. The unloaded intact wall has residual strains: the epicardium is stretched and the myocardium shrunk from their respective isolated, unloaded states. The predicted mechanical responses of the intact wall to biaxial loadings were inaccurate when the residual strains were not taken into account. Accounting for these, however, yielded reasonable predictions. Thus information on the unloaded reference state and properties of each portion is needed to accurately predict the behavior of the intact wall.

Animals↗
PubMed1996

Siberian hamsters free run or become arrhythmic after a phase delay of the photocycle.

Body temperature (Tb) and locomotor activity were recorded telemetrically from male Siberian hamsters (Phodopus sungorus sungorus) that were 3 or 12 mo of age and maintained in a light-dark (LD) cycle of 16 h light/day for 2-4 mo. After 3 wk of Tb recording, the LD cycle was phase delayed by extending the light phase by 5 h for 1 day; animals remained on a 16:8-h LD cycle for the remainder of the experiment. Tb and activity rhythms of all animals were stably entrained to the LD cycle before the phase shift. After the phase shift, > or = 80% of the animals in each age group failed to reentrain and expressed free-running Tb rhythms with stable periods that ranged from 24.33 to 26.33 h; one hamster in each age group reentrained within several days. Tb became arrhythmic in 10% of all animals immediately after, and in 28% of free running animals several weeks after, the phase shift. Changes in tau and phase of activity rhythms closely paralleled Tb rhythms in individual hamsters. Daily mean Tb was unchanged, but Tb rhythm amplitude decreased by 25-50% in individual animals after the phase shift. We believe this to be the first report of neurologically intact animals failing to reentrain to a phase shift of the LD cycle. These phenomena are not readily explained by current knowledge of circadian systems and suggest that the entrainment process in Siberian hamsters differs markedly from that in other rodent species.

Animals↗
PubMed1996

Transient permeabilization of airway epithelium by mucosal water.

We describe a simple hyposmotic shock procedure whereby the apical membrane of airway epithelium can be made transiently leaky to proteins and other macromolecules. Bovine or human tracheal epithelial cells were grown as confluent polarized cell sheets on porous inserts. While physiological saline was maintained on the basolateral surface, the mucosal surface was exposed to water. This led to marked increases in the uptake of [14C]mannitol across both apical and basolateral membranes. On restoring saline to the mucosal surface, the [14C]mannitol permeability returned to preexposure levels with a half-life of approximately 5 min. Mucosal water also increased efflux of lactate dehydrogenase and the uptakes of fluorescent albumin and dextran (2,000 kDa). Water-induced increases in mannitol permeability were similar at 4 and 37 degrees C, suggesting that pinocytosis was not the mechanism. Detailed time courses of the uptake of dextran and the loss of lactate dehydrogenase and 36Cl showed that the bulk of the permeability increase occurred during the first 2- to 4-min exposure to water. Transepithelial resistance was reversibly decreased by exposure to water, but short-circuit current responses to transport blockers and secretagogues remained qualitatively normal. The hyposmotic shock procedure also successfully permeabilized apical membranes of primary cultures of nasal epithelial cells from a patient with cystic fibrosis (CF) and of JME/CF 15 cells, a cell line derived from CF bronchial epithelium. This simple and efficient procedure may prove useful in studies on the cell and molecular biology of airway and other epithelia.

Animals↗
PubMed1996

[Commodity identification of semen Plantaginis and herba Plantaginis].

The Semen Plantaginis from 29 provinces and regions and the Herba Plantaginis from 18 provinces and regions in our country were identified, and the main commodities of these two crude drugs are described in this paper. The identification may serve as a scientific basis for expanding new drug resources.

Drug Contamination↗
PubMed1995

Heat-induced changes in the mechanical behavior of passive coronary arteries.

We performed in vitro pressure-diameter and axial force-length experiments on nondiseased, passive bovine coronary arteries subjected to bath temperatures from 21 to 80 degrees C for 90 s to 4 hr. Over the strain ranges studied, we found that: (a) vessel behavior remained the same over 20 min of testing at 21 to 55 degrees C, (b) vessels stiffened multiaxially after 5 min of exposure to 60 degrees C and continued to stiffen over 20 min of testing, (c) dramatic multiaxial vessel stiffening and shrinkage occurred after 90 s of exposure to 70 and 80 degrees C, and (d) heat-induced changes at 70 degrees C depended on the intraluminal pressure during heating. Thus, passive bovine coronary arteries exhibit a complex thermomechanical behavior that depends on the temperature, duration of thermal exposure, and the mechanical loads applied during heating.

Analysis of Variance↗
PubMed1993

Wild type GAL4 binds cooperatively to the GAL1-10 UASG in vitro.

Transcription of the genes required for utilization of galactose in Saccharomyces cerevisiae is controlled primarily by the transcriptional activator protein GAL4. The upstream activating sequences for galactose (UASG) of most GAL genes have multiple sites to which GAL4 can bind. In this report we compare the binding properties of wild type GAL4 and derivatives of GAL4 bearing the N-terminal DNA-binding domain to multiple DNA-binding sites in vitro. To produce wild type GAL4, we constructed a recombinant baculovirus for expression in insect cells. Recombinant wild type GAL4 was found to bind efficiently to an oligonucleotide containing a near-consensus 17-mer GAL4 DNA-binding site in electrophoretic mobility shift assays. Footprinting experiments revealed that wild type GAL4 binds cooperatively to the four GAL4 DNA-binding sites of the GAL1-10 UASG; however, in contrast an N-terminal fragment of GAL4 containing only the DNA-binding/dimerization domains binds to each of these sites with slightly different affinity. With increasing concentrations of GAL4(1-147), the four sites become filled in the following order: site II, site IV, site I, and site III. In experiments with wild type GAL4, these four sites become fully occupied at approximately the same concentration of protein. In footprints of wild type GAL4 on the USAG, enhancements and protections of DNase I-sensitive cleavages are detectable between sites III and IV, indicative of formation of a loop between these distantly spaced sites. Binding of wild type GAL4 to a strong near-consensus binding site assists binding to an adjacent mutant site in both electrophoretic mobility shift and footprinting assays. GAL4(1-147) and GAL4(1-147) fused to portions of GAL4's activating region II were incapable of cooperative DNA binding in our assays. We conclude from these observations that wild type GAL4 has a cooperative DNA-binding function that is distinct from the DNA binding and dimerization or transcriptional activation functions, and likely plays and important role in precise regulation of GAL gene transcription.

Animals↗
PubMed1993

Computer-aided vascular experimentation: a new electromechanical test system.

We present a new computer-controlled, electromechanical system for performing simultaneous extension, inflation, and torsion experiments on cylindrical segments of natural and artificial blood vessels. Specimens are tested while immersed in a temperature-controlled, oxygenated, physiologic solution. Deformations are measured within a central region of the specimen using noncontacting video methods. The associated axial loads, luminal pressures, and torques are measured with standard transducers. Data are collected and stored on-line, and are used in the feedback control of experimental protocols, which are prescribed using custom interactive software. Finally, we present illustrative data obtained from canine aortas and common carotid arteries.

Animals↗
PubMed1992

Regulation of purine nucleotide synthesis in human B lymphoblasts with both hypoxanthine-guanine phosphoribosyltransferase deficiency and phosphoribosylpyrophosphate synthetase superactivity.

Human B lymphoblast lines severely deficient in hypoxanthine-guanine phosphoribosyltransferase (HGPRT) were selected for resistance to 6-thioguanine from cloned normal and phosphoribosylpyrophosphate (PP-Rib-P) synthetase-superactive cell lines and were compared with their respective parental cell lines with regard to growth and PP-Rib-P and purine nucleotide metabolism. During blockade of purine synthesis de novo with 6-methylthioinosine or aminopterin, inhibition of growth of all HGPRT-deficient cell lines was refractory to addition of Ade at concentrations which restored substantial growth to parental cell lines. Ade-resistant inhibition of growth of parental lines by 6-methylthioinosine, however, occurred during Ado deaminase inhibition. Insufficient generation of IMP (and ultimately guanylates) to support growth of lymphoblasts lacking HGPRT activity and blocked in purine synthesis de novo best explained these findings, implying that a major route of interconversion of AMP to IMP involves the reaction sequence: AMP----Ado----Ino----Hyp----IMP. PP-Rib-P generation and purine nucleoside triphosphate pools were unchanged by introduction of HGPRT deficiency into normal lymphoblast lines, in agreement with the view that accelerated purine synthesis de novo in this deficiency results from increased availability of PP-Rib-P for the pathway. Cell lines with dual enzyme defects did not differ from PP-Rib-P synthetase-superactive parental lines in rates of PP-Rib-P and purine synthesis despite 5-6-fold increases in PP-Rib-P concentrations, excretion of nearly 50% of newly synthesized purines, and diminished GTP concentrations. Fixed rates of purine synthesis de novo in PP-Rib-P synthetase-superactive cells appeared to reflect saturation of the rate-limiting amidophosphoribosyltransferase reaction for PP-Rib-P. In combination with accelerated purine excretion, increased channeling of newly formed purines into adenylates, and impaired conversion of AMP to IMP, fixed rates of purine synthesis de novo may condition cell lines with defects in HGPRT and PP-Rib-P synthetase to depletion of GTP with consequent growth retardation.

Aminopterin↗