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Biomedical subjects

K Chung

Publications and source records attributed to K Chung.

At least 91 records · Page 5Linked to original sources
PubMed1999

Effect of digital cervical examination on the expression of fetal fibronectin.

OBJECTIVE: To determine whether oncofetal fibronectin (fFN) assays from symptomatic women are influenced by digital examination of the cervix. STUDY DESIGN: Cervicovaginal fFN specimens were obtained from women at 22-34 weeks' gestational age with symptoms of preterm labor immediately prior to a digital examination of the cervix and two hours after. Fetal fibronectin was assayed by a specific enzyme-linked immunoassay. Results were reported as positive (> or = 50 ng/mL) or negative (< 50 ng/mL). Paired initial and repeat fFN results were compared for statistical difference, and the clinical outcomes were used to assess the accuracy of the initial and repeat results. RESULTS: Fifty symptomatic women at an average gestational age of 29.3 +/- 2.0 weeks were enrolled. Eighty-six percent of the repeat fFN results remained unchanged after a digital examination, (P = .26, beta = .2). The predictive value of a negative fFN obtained after a digital examination was 97% for the absence of spontaneous preterm delivery in < 8 or < 15 days. Two of 16 initially positive results became negative after an examination, and one patient delivered two days later. Five of 34 initially negative fFN results became positive after an examination, and 5/5 delivered more than seven days later. CONCLUSION: Digital examination of the cervix has an effect on fFN results. The routine use of fFN after a digital examination is not recommended.

Adult↗
PubMed1998

Cloning and characterization of novel disintegrins from Agkistrodon halys venom.

Snake venom disintegrins act as potent inhibitors of platelet aggregation. In this report, we isolated genes encoding novel members of disintegrins through the screening of Agkistrodon halys venom gland cDNA library. Subsequent characterization of positives revealed the presence of distinct disintegrins named salmosinl, 2, and 3, each containing a characteristic RGD/KGD sequence essential for the binding to integrins. Whereas salmosinl was identical to previously described salmosin purified from A. halys venom, salmosin2 and salmosin3 were predicted to be a novel, 73 amino acid protein with a KGD sequence, and an 80 amino acid protein with an additional 7th disulfide bond, respectively. Taken together, this is the first report describing 3 unique disintegrins, namely, salmosinl with RGD, salmosin2 with KGD and salmosin3 with 7 disulfide bonds are found in a single species of venom. Subsequently, to compare the platelet aggregation inhibitory potential of the recombinant protein with that of natural protein, salmosinl was expressed in E. coli and purified to homogeneity. Recombinant and natural salmosin1 inhibited the binding of alphaIIbbeta3 to fibrinogen with an almost identical IC50 value of 2.2 nM and 4.5 nM respectively. Moreover, recombinant salmosinl displayed an IC50 value approximately 5-fold lower than flavoridin, which was previously described as the most potent venom disintegrin so far. In conclusion, we identified 3 disintegrins with distinct properties through the molecular cloning approach and found that the recombinant salmosinl retained one of the most potent alphaIIbbeta3 antagonist activity.

Agkistrodon↗
PubMed1998

Expression of nerve growth factor in the dorsal root ganglion after peripheral nerve injury.

Nerve growth factor (NGF) is believed to play a critical role in altering the phenotypic and functional properties of dorsal root ganglion (DRG) cells after a pathological insult. The present study examined NGF protein levels and NGF immunoreactivity (NGF-IR) in the DRG at multiple time points following peripheral nerve injury. The NGF protein level in the ipsilateral DRG decreased dramatically at 6 h after the injury, but recovered to an almost normal level at 2 days. In accordance with the NGF level, the proportion of NGF-IR neurons also showed a significant decrease at 6 h after the injury, but recovered to the normal level at 3 days. In addition, NGF-IR can also be found in satellite cells at a time point of 3 days after the injury. These data suggest that there is an increase in synthesis of NGF within the DRG after peripheral nerve injury, which contributes to the recovery of NGF levels. The newly synthesized NGF may play important roles in the reactions of DRG neurons to peripheral nerve injury.

Animals↗
PubMed1998

Comparison of sympathetic sprouting in sensory ganglia in three animal models of neuropathic pain.

Sympathetic postganglionic fibers sprout in the dorsal root ganglion (DRG) after peripheral nerve injury. Therefore, one possible contributing factor of sympathetic dependency of neuropathic pain is the extent of sympathetic sprouting in the DRG after peripheral nerve injury. The present study compared the extent of sympathetic sprouting in the DRG as well as in the injured peripheral nerve in three rat neuropathic pain models: (1) the chronic constriction injury model (CCI); (2) the partial sciatic nerve ligation injury model (PSI); and (3) the segmental spinal nerve ligation injury model (SSI). All three methods of peripheral nerve injury produced behavioral signs of ongoing and evoked pain with some differences in the magnitude of each pain component. The density of sympathetic fibers in the DRG was significantly higher at all examined postoperative times than controls in the SSI model, while it was somewhat higher than controls only at the last examined postoperative time (20 weeks) in the CCI and PSI models. Therefore, data suggest that, although sympathetic changes in the DRG may contribute to neuropathic pain syndromes in the SSI model, other mechanisms seem to be more important in the CCI and PSI models at early times following peripheral nerve injury.

Animals↗
PubMed1998

Expression and characterization of a novel plasminogen activator from Agkistrodon halys venom.

A venom gland cDNA library of Agkistrodon halys was constructed and screened with a probe based on the consensus sequence of venomic serine proteases. Next, we determined the sequences of the entire open reading frames of two selected positives which were found to encode novel serine proteases of 234 and 233 amino acids in length and named as Haly-PA and Haly 2, respectively. Upon protein data base search, Haly-PA showed the highest similarity of 82% to the previously characterized plasminogen activator, TSV-PA (Zhang et al. 1995, J. Biol. Chem. 270, 10246- 10255). Haly 2 displayed a 78% similarity to beta-fibrinogenase (Hung et al. 1994, B. B. R. C., 205, 1707 1715). Haly-PA was successfully expressed using the baculovirus system and secreted into the culture media as a 32 kDa glycoprotein. In the western analysis of snake venom, anti-Haly-PA antibody detected the same size of band indicating that this enzyme is a component of snake venom. Recombinant Haly-PA was purified to homogeneity using the combination of anion exchange and gel filtration column. In the fibrino(geno)lytic assay, recombinant Haly-PA displayed an indirect fibrino(geno)lytic activity depending on the presence of plasminogen and cleaved the plasminogen to generate the active plasimin. These results indicate that Haly-PA is a plasminogen activator and displays fibrino(geno)lytic activity through conversion of plasminogen to plasmin.

Agkistrodon↗
PubMed1998

Glutamate receptors on postganglionic sympathetic axons.

The present study demonstrates that approximately 36% of postganglionic sympathetic axons in gray rami express receptors for the N-methyl-D-aspartate receptor 1 subunit of the N-methyl-D-aspartate receptor and 10% express the glutamate receptor 1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor. If these receptors are active, glutamate released from primary afferent terminals could activate these receptors resulting in the release of noradrenaline and other substances from postganglionic sympathetic neurons. This interaction would constitute a non-synaptic, sensory-sympathetic, peripheral reflex that might be important in local vascular control and in pain states that have a sympathetic component.

Animals↗
PubMed1998

Flexural strength of a provisional resin material with fibre addition.

The effect of fibre addition on the flexural strength of a resin was studied. A provisional material (ALIKE; GC America Inc.) was used as the control and resinous matrix. Silane treated glass fibre was selected for the reinforcing treatment. In order to determine the geometric influence on the strength, ordered fibres (1 w/o) were immersed within a resinous matrix in four different locations. In addition, randomly dispersed fibres, 5 mm in length, were blended at 1 w/o up to 8 w/o with acrylic powder and moulded into rectangular specimens (34 mm x 9 mm x 8 mm) with P:L = 2:1. Ten specimens were prepared for each group. A three-point flexural test was run using a span of 25 mm at a rate of 5 mm/min. The strength values were collected and analysed with ANOVA and Scheffe tests. The strengths of the specimens with orientated fibre addition ranged from 49.4 (s.d. = 5.7) to 64.5 (6.7) MPa and the control was 54.3 (4.0) MPa. In the dispersed groups, the strengths obtained ranged from 55.9 (5.9) to 87.3 (7.9) MPa. The results disclosed that inclusion of orientated fibres horizontally on the tension side of the specimens significantly improved the flexural strength compared with the control (P < 0.05). An optimal strength was obtained in the group of provisional resin containing 5 w/o dispersed fibre. Incorporation of glass fibres significantly improved the flexural strength of the resin and the dispersed method is more efficient than the orientated inclusion method.

Acrylic Resins↗
PubMed1998

The effect of sprue design on the marginal accuracy of titanium castings.

The purpose of this study was to measure the effects of sprue number and position on cast titanium crown margins. Twenty-four complete veneer crown wax patterns were fabricated on a stainless steel die with a 30 degrees bevel finish line. Twelve wax patterns were sprued with one 8-gauge wax sprue and the remaining 12-gauge double sprued. All patterns were invested with a phosphate bonded investment. Castings were made with a titanium casting machine following the manufacturer's instructions and using commercially pure titanium (> 99.5%) ingots. The castings were than carefully cleansed and the margins were examined with indirect impression technique. Data were analysed with an ANOVA and the Student's t-test with confidence level at 95%. The results revealed that the marginal discrepancy for the double sprueing group (32.1 +/- 12.8 microm) has significantly less discrepancy (P < 0.001) than the single sprueing group (49.8 +/- 16.4 microm). There was no statistically significant differences in marginal discrepancy between locations within the sprueing techniques (P > 0.05). An improvement in the degree of casting accuracy of titanium crown was indicated by the double sprue design used in this investigation.

Analysis of Variance↗
PubMed1998

Effects of HCl-pepsin laryngeal instillations on upper airway patency-maintaining mechanisms.

Gastroesophageal reflux has been indicated as an etiopathological factor in disorders of the upper airway. Upper airway collapsing pressure stimulates pressure-responsive laryngeal receptors that reflexly increase the activity of upper airway abductor muscles. We studied, in anesthetized dogs, the effects of repeated laryngeal instillations of HCl-pepsin (HCl-P; pH = 2) on the response of laryngeal afferent endings and the posterior cricoarytenoid muscle (PCA) to negative pressure. The effect of negative pressure on receptor discharge or PCA activity was evaluated by comparing their response to upper airway (UAO) and tracheal occlusions (TO). It is only during UAO, but not during TO, that the larynx is subjected to negative transmural pressure. HCl-P instillation decreased the rate of discharge during UAO of the 10 laryngeal receptors studied from 56.4 +/- 10.9 (SE) to 38.2 +/- 9.2 impulses/s (P < 0.05). With UAO, the peak PCA moving time average, normalized by dividing it by the peak values of esophageal pressure, decreased after six HCl-P trials from 4.29 +/- 0.31 to 2.23 +/- 0.18 (n = 6; P < 0.05). The responses to TO of either receptors or PCA remained unaltered. We conclude that exposure of the laryngeal mucosa to HCl-P solutions, as it may occur with gastroesophageal reflux, impairs the patency-maintaining mechanisms provided by laryngeal sensory feedback. Inflammatory and necrotic alterations of the laryngeal mucosa are likely responsible for these effects.

Animals↗
PubMed1997

Strain differences in adrenergic sensitivity of neuropathic pain behaviors in an experimental rat model.

The aim of this study was to examine and delineate the differences in adrenergic sensitivity of mechanical allodynic behavior among various strains of rats. Neuropathic injury was produced by tight ligation of the L5 and L6 spinal nerves in several strains of rats. The degree of mechanical allodynic behavior was estimated by measuring the mechanical threshold for paw flinching with von Frey filaments. Adrenergic sensitivity of the allodynic behavior was resolved by measuring changes of the mechanical threshold after intraperitoneal injection of phentolamine, an alpha-adrenergic receptor antagonist. Injection of phentolamine caused a significant but small increase in the thresholds for paw flinching in rats of most of the tested strains; however, in Lewis rats, the resulting threshold increase was extensive enough to eliminate allodynic behavior almost completely. It is concluded that there is a difference in adrenergic sensitivity to mechanical allodynic behavior among different strains of neuropathic rats. In particular, rats of the Lewis strain were extremely sensitive to systemic injection of an alpha-adrenergic receptor blocker.

Animals↗
PubMed1997

Sprouting sympathetic fibers form synaptic varicosities in the dorsal root ganglion of the rat with neuropathic injury.

Peripheral nerve injury in a rat model (spinal nerve ligation) of neuropathic pain triggers sprouting of sympathetic fibers in the dorsal root ganglion (DRG). This sympathetic sprouting has been suggested as an important underlying mechanism for pain behaviors. To investigate the possibility of functional interaction between sprouted sympathetic fibers and sensory neurons, the present study examined the fine morphology and structural relationship between sympathetic fibers and the DRG neurons by electron microscopy. Sympathetic postganglionic fibers, as identified by electron microscopic immunostaining for tyrosine hydroxylase (TH), were all unmyelinated fibers and some of them ended as growth cones. In addition, many vesicle-containing axonal enlargements (we will refer these as synaptic varicosities) were found in the interstitial space around DRG neurons, and some were enclosed within the satellite cell capsule which surrounded the DRG soma. The presence of sympathetic synaptic varicosities near or in apposition with either the DRG somata or their processes provides a structural basis for possible interactions between sensory neurons and sympathetic fibers in the DRG of neuropathic rats.

Animals↗
PubMed1997

Appropriate management of atypical ductal hyperplasia diagnosed by stereotactic core needle breast biopsy.

BACKGROUND: Stereotactic core needle breast biopsy (SCNBB) is a minimally invasive technique used to sample nonpalpable mammographic abnormalities. The optimal management of atypical ductal hyperplasia (ADH) diagnosed by SCNBB is unknown. We hypothesized that ADH diagnosed by SCNBB should be evaluated by excisional breast biopsy (EBB) because of the risk of identifying carcinoma in association with ADH that would be missed if a diagnostic sampling technique alone was utilized. METHODS: To test this hypothesis, a prospective diagnostic protocol was created which called for SCNBB instead of EBB for patients with mammographic abnormalities considered suspicious for malignancy. If ADH was noted on histologic evaluation of the cores, patients were advised to undergo an EBB. RESULTS: A review of the initial 900 patients evaluated by SCNBB yielded 39 patients (4.3%) with ADH detected by SCNBB. Thirty-six of these 39 patients agreed to proceed with EBB: 19 patients demonstrated benign findings including atypical ductal hyperplasia, 13 patients demonstrated noninvasive ductal carcinoma, and 4 patients had evidence of invasive carcinoma. CONCLUSIONS: A 47% rate of detecting noninvasive or invasive breast carcinoma supports the hypothesis that ADH detected by a sampling technique, such as SCNBB, should be managed by EBB.

Biopsy, Needle↗
PubMed1997

Cytosolic estrogen receptor concentrations in the lumbosacral spinal cord fluctuate during the estrous cycle.

Estrogen responsive neurons have been anatomically identified with autoradiographic and immunohistochemical techniques and their distribution mapped in the lumbosacral spinal cord of female rats. Such neurons contain estrogen receptors (ERs). The present study was undertaken to: 1) quantify cytosolic estrogen receptor (ER) concentrations in the lumbosacral spinal cord and 2) determine if there is a relationship between cytosolic ER concentrations and fluctuations in serum estradiol (SE2) levels during the estrous cycle. Lumbosacral spinal segments were removed from intact cycling rats during the morning of proestrus, the afternoon of proestrus, and the morning of estrus, metestrus and diestrus. Trunk blood was collected at euthanasia and SE2 levels were determined using radioimmunoassay. Cytosolic ER concentrations were measured using a dextran-charcoal coated tube method. Concentrations of cytosolic ERs were low during estrus and metestrus, increased during diestrus with maximum concentrations during the afternoon of proestrus. These changes in ER concentrations paralleled SE2 levels measured in intact cycling animals; i.e., during estrus SE2 levels were low, but began to rise during metestrus, diestrus, and during the morning of proestrus with a maximum peak increase during the afternoon of proestrus. These data indicate there are fluctuations of cytosolic ER concentrations during the estrous cycle and that these changes coincide with changing SE2 concentrations suggesting that ER content is influenced by SE2.

Animals↗
PubMed1997

Loss of dorsal root ganglion cells concomitant with dorsal root axon sprouting following segmental nerve lesions.

Tight ligation of the fifth and sixth lumbar segmental nerves in the rat provides a model of neuropathic pain. We used this model to assess the changes in primary afferent input to the dorsal horn in neuropathic pain syndromes. Dorsal roots and ganglia were examined for up to 32 weeks following segmental nerve ligation. Stereologic and morphometric techniques revealed a notable decrease in the numbers of dorsal root ganglion cells and unmyelinated dorsal root axons by six weeks post-injury. By 32 weeks following segmental nerve ligations, the numbers of dorsal root ganglion cells have dropped to 50% of pre-ligation levels while the numbers of dorsal root axons have increased to normal levels predominantly due to sprouting of myelinated fibres. These findings indicate that although there is a great loss of dorsal root ganglion cells, there is dramatic sprouting of myelinated fibres and possibly some sprouting of unmyelinated fibres in the dorsal roots. Additionally, a difference in the responses of unmyelinated and myelinated fibres to this peripheral nerve injury is revealed. These changes in dorsal root ganglion cells and their central axons may underlie certain aspects of abnormal pain syndromes because of changes in the types and quantity of input the dorsal horn receives.

Animals↗
PubMed1997

Squamous cell carcinoma of the tonsil--clinical features and treatment results.

Squamous cell carcinoma of the tonsil has a relatively poor prognosis. Aggressive surgery, radiation therapy and combinations of irradiation and surgery have been employed but there exists some controversy about the efficacy of these treatment modalities. The purpose of this paper is to compare the efficacy of treatment between the surgery followed by radiation therapy and the preoperative radiation therapy followed by surgical resection. The medical records of 33 patients treated for squamous cell carcinoma of the tonsil at the Department of Otolaryngology-Head and Neck Surgery, Korea University Hospital between 1989-1993 were reviewed retrospectively. None of the patients were stage I, but stage II, III, and IV were four, five, and 24 patients, respectively. There were 30 males and three females. The most common histopathology was moderately differentiated squamous cell carcinoma (20/33). The 13 patients treated initially with surgery had an overall three-year survival rate of 38.5%, and the rate for the 20 patients treated initially with radiation was 40%. The main pattern of treatment failure was a local recurrence and neck metastases, and pathologic differentiation thought to be an important prognostic factor. Complications are fewer in patients treated initially with surgery (23.1%) than patients initially treated with radiation (50.0%). There is no difference in the efficacy between the two therapeutic groups.

Adult↗
PubMed1996

Sympathetic sprouting in the dorsal root ganglia of the injured peripheral nerve in a rat neuropathic pain model.

The extent of the sprouting of sympathetic postganglionic fibers in the dorsal root ganglion (DRG) and the peripheral nerves was examined in neuropathic rats at different postoperative times. After the L5 and L6 spinal nerves were ligated on one side, three different pain behavior tests (representing mechanical allodynia, cold allodynia, ongoing pain exacerbated by cold stress) were performed at various time intervals. The sympathetic postganglionic fibers were visualized by immunostaining with antibodies to tyrosine hydroxylase (TH). In the neuropathic rats, all three pain behaviors were fully developed within 3 days after the surgery, maintained up to 2 weeks, and then started to decline gradually afterward. At 20 weeks after neuropathic surgery, pain behaviors were reduced significantly compared to the peak response, but were still higher than the presurgery levels. Sympathectomy, performed 4 days after neuropathic surgery, almost completely abolished the signs of mechanical allodynia and ongoing pain behaviors, and it reduced the behaviors of cold allodynia to approximately half. The numerical density of sympathetic fibers in the DRG of an injured segment was significantly higher at 1, 4, and 20 weeks after neuropathic surgery as compared to the normal, suggesting that there is sprouting of sympathetic fibers in the DRG after peripheral nerve injury. Sprouting of sympathetic fibers in the DRG was extensive as early as 2 days after the spinal nerve ligation, and the sprouted fibers were almost completely eliminated after sympathectomy. The data suggest that sympathetic innervation of the DRG may play an important role in the development and maintenance of sympathetically maintained neuropathic pain.

Animals↗
PubMed1996

Polysomies of chromosomes 7 and 17 in head and neck squamous cell carcinomas.

OBJECTIVE: To determine the polysomies (ie, cells with > or = 3 chromosome copies) of chromosomes 7 and 17 in tumor tissue, histologically normal epithelia adjacent to the tumor (tumor-adjacent epithelia), and buccal epithelia distant from the tumor (tumor-distant epithelia) of head and neck squamous cell carcinomas. DESIGN: Nonfluorescent, nonisotopic, in situ hybridization using chromosome-specific centromeric DNA probes for chromosomes 7 and 17 was performed on the formalin-fixed, paraffin-embedded specimens from tumor and tumor-adjacent and tumor-distant epithelia of 19 patients with head and neck squamous cell carcinomas and from buccal epithelia of cancer-free control subjects who smoked and did not smoke cigarettes. MAIN OUTCOME MEASURES: Four hundred nuclei in tumor tissue and 200 nuclei in histologically normal epithelia were scored for hybridized signals in each sample. RESULTS: Buccal epithelia of cancer-free control subjects who smoked and did not smoke cigarettes showed no difference in the polysomies of chromosomes 7 and 17, respectively. The polysomies of chromosomes 7 and 17 in the tumor cells were higher than those in the tumor-adjacent epithelia (P < .001 for both), tumor-distant epithelia (P < .001 for both), and buccal epithelia of cancer-free control subjects who smoked and did not smoke cigarettes (P < .001 for both). The polysomies of chromosomes 7 and 17 in the tumor-adjacent epithelia were higher than those in the tumor-distant epithelia (P < .001 for both) and the control buccal epithelia (P = .002 and P < .001, respectively). The tumor-distant epithelia and the control buccal epithelia for the polysomies of chromosomes 7 and 17 had no differences. CONCLUSIONS: The finding of genotypic abnormalities in the tumor-adjacent epithelia supports the concept of field cancerization. Such genotypic parameters may provide a genetic basis for the development of an early recurrence or second primary tumors after therapeutic treatment of head and neck squamous cell carcinomas.

Aged↗