Search PubMed⌕ Search

Biomedical subjects

T C Lee

Publications and source records attributed to T C Lee.

At least 37 records · Page 2Linked to original sources
PubMed2002

Bone adaptation to load: microdamage as a stimulus for bone remodelling.

Mechanical loading in the proximal radius was increased by ulnar osteotomy (Group O), altered by Steinmann pinning (Group P) or unaltered in sham operated controls (Group C) in skeletally mature female sheep, aged 2-4 years. A series of intravenous fluorochromes were given to label bone formation and fuchsin-stained microdamage assessed at intervals of up to 24 weeks. Microcracks were present in all groups and were found in the original cortex near the periosteal surface. No microcracks were found in the new, fibrolamellar bone laid down at periosteal or endosteal surfaces. Mean microcrack length (49 microm, SD 10 microm) did not differ between groups or overtime. Microcrack numerical and surface densities and resorption cavity density peaked in all groups at 6 weeks, consistent with a regional acceleratory phenomenon (RAP), but the peaks were significantly greater in Group O. The density of refilling or secondary osteons peaked at 10 weeks and the mean time required for the formation of an osteon was 7.51 +/- 0.59 weeks. Fatigue-induced microdamage is normally present in bone and is increased due to repetitive loading of the mechanically overloaded radius. The location and timing of microcracks, resorption cavities and secondary osteons are consistent with the activation-resorption-formation remodelling cycle and suggest that microdamage is a stimulus for bone remodelling.

Analysis of Variance↗
PubMed2002

Three-dimensional reconstruction of Haversian systems in ovine compact bone.

Haversian systems or secondary osteons are an integral component of compact bone. However, as their exact shape is debatable, this study describes a technique to view their morphology in three dimensions. Bone remodeling in adult ovine long bones was labelled at intervals using a series of chelating fluorochromes. A series of longitudinal sections were cut at 25 microm intervals through blocks of the distal radius embedded in methylmethacrylate using a sledge macrotome. The chelating agents were used as markers of bone formation in the study of bone growth and osteon morphology. The two-dimensional image of each section was examined using an epifluorescence microscope. Images were transferred to a PC via a CCD low light colour video camera. Surface reference points were noted on each of the sections and, using computer software, a three-dimensional image of a refilling labelled osteon was reconstructed and its dimensions measured. Haversian systems may have a gentle spiral course along the longitudinal axis of the bone. They intertwine with adjacent osteons and give multiple branches along their course producing a complex pattern of organization. The mean labelled length and diameter of the osteons was 1.4 + 1 mm and 145 + 0.42 microm [Mean + S.D], respectively.

Animals↗
PubMed2001

Preload induces troponin I degradation independently of myocardial ischemia.

BACKGROUND: Although global ischemia induces troponin I (TnI) degradation, regional ischemia does not. We hypothesized that this disparity is related to preload-induced proteolysis, which varies as a function of the amount of myocardium at risk of ischemia. METHODS AND RESULTS: Isolated rat hearts were buffer-perfused at controlled levels of preload. Increasing preload to 25 mm Hg in the absence of ischemia produced pronounced TnI degradation (27 kDa versus 31 kDa bands: 16.4 +/- 3.6% versus 4.7 +/- 1.9% in immediately excised controls, P<0.05). TnI degradation could be blocked by preventing the activation of endogenous calpains with 25 micromol/L calpeptin (4.3 +/- 0.6%). This improved function, with left ventricular systolic pressure increasing from 103 +/- 4 mm Hg to 137 +/- 7 mm Hg (P<0.05). Eliminating elevations in preload after global ischemia-induced stunning also prevented TnI degradation. CONCLUSIONS: Calpain-mediated TnI proteolysis can be dissociated from stunning and arises from elevations in preload rather than ischemia. This raises the possibility that ongoing preload-induced TnI degradation could impair myocardial function long-term.

Animals↗
PubMed2001

Effect of isoflurane versus nicardipine on blood flow of lumbar paraspinal muscles during controlled hypotension for spinal surgery.

STUDY DESIGN: This study compared the effects of isoflurane and nicardipine on regional blood flow of the lumbar paraspinal muscles. OBJECTIVES: The purpose of this study was to determine whether treatment with hypotensive agents result in ischemia of the lumbar paraspinal muscles, thereby facilitating surgical procedures. SUMMARY OF BACKGROUND DATA: Despite the general acceptance of controlled hypotension as effective in reducing blood loss during spinal surgery, the changes of blood flow that occur at the lumbar paraspinal muscles when this technique is applied remain unclear. The use of laser Doppler flowmetry allows changes of muscle blood flow to be easily detected in real time with minimal invasion, thereby allowing differences among distinct pharmacological approaches for induction and maintenance of controlled hypotension to be evaluated. METHODS: The prehypotensive and hypotensive (reduction of mean arterial pressure by 20 mm Hg) blood flow of the lumbar paraspinal muscles were assessed with a laser Doppler flowmeter in 40 patients undergoing lumbar spinal surgery. The first half of the patients (n = 20) received isoflurane, whereas the second half received nicardipine to achieve arterial hypotension. RESULTS: Compared with the prehypotensive state, during the hypotensive state, patients in the isoflurane group exhibited a 17% to 46% (mean, 33.7%) decrease in lumbar paraspinal muscle blood flow, whereas patients in the nicardipine group exhibited a 24% to 177% (mean, 82.5%) increase in lumbar paraspinal muscle blood flow. Statistical analysis showed a significant difference in the changes of flux after induced hypotension between the isoflurane and nicardipine group (P < 0.001). CONCLUSIONS: Depending on the pharmacological treatment used to achieve arterial hypotension in spine surgery, there will be either a reduction in paraspinal muscle blood flow (ischemia) or an enhancement of this blood flow (hyperemia).

Adult↗
PubMed2001

The effect of elastin damage on the mechanics of the aortic valve.

Porcine bioprosthetic heart valves degenerate and fail mechanically through a mechanism that is currently not well understood. It has been suggested that damage to the elastin component of prosthetic valve cusps could be responsible for changes in the mechanical function of the valve that would predispose it to increased damage and ultimate failure. To determine whether damage to elastin can produce the structural and mechanical changes that could initiate the process of bioprosthetic valve degeneration, we developed an elastase treatment protocol that fragments elastin and negates its mechanical contribution to the valve tissue. Valve cusps were mechanically tested before and after digestion to measure the mechanical changes resulting from elastin damage. Elastin damage produced a decrease in radial and circumferential extensibility (from 43 to 18% strain radially and 12 to 7% strain circumferentially), with a slight increase in stiffness (1.3-2.6kN/m for radial and 10.6-11.9kN/m for circumferential directions). Digestions with trypsin, which does not cleave elastin, confirmed that the changes in mechanics of the circumferential samples were likely due to the nonspecific removal of proteoglycans by elastase, while the changes in the radial samples were indeed due to elastin damage. Removing the mechanical contribution of elastin alters the mechanical behavior of the aortic valve cusp, primarily in the radial direction. This finding implies that damage to elastin will distend the cusps, reduce their extensibility, and increase their stiffness. Damage to elastin may therefore contribute to the degeneration and failure of prosthetic valves.

Animals↗
PubMed2001

Non-traumatic cerebrospinal fluid rhinorrhea indirectly caused by remote brain tumor: a case report and review of the literature.

Non-traumatic cerebrospinal fluid rhinorrhea indirectly caused by a remote brain tumor has rarely been reported. Here we describe a case of non-traumatic cerebrospinal fluid rhinorrhea that occurred as the initial symptom of a posterior falx meningioma. In addition, based on the period of occurrence of cerebrospinal fluid rhinorrhea before or after the tumor operation, we introduced a novel classification for these cases into pre-treatment and post-treatment types. The findings of the present case and the results of our literature research suggest that different treatments should be used for patients with these two types of non-traumatic cerebrospinal fluid rhinorrhea resulting from remote brain tumor. After tumor excision, patients of the pre-treatment type may receive conservative management or cerebrospinal fluid shunting, while patients of the post-treatment type need direct repair of the fistula.

Adult↗
PubMed2001

Expression of a bacterial ice nucleation gene in a yeast Saccharomyces cerevisiae and its possible application in food freezing processes.

A 3.6 kb ice nucleation gene (ina) isolated from Erwinia herbicola was placed under control of the galactose-inducible promoter (GAL1) and introduced into Saccharomyces cerevisiae. Yeast transformants showed increased ice nucleation activity over untransformed controls. The freezing temperature of a small volume of water droplets containing yeast cells was increased from approximately -13 degrees C in the untransformed controls to -6 degrees C in ina-expressing (Ina(+)) transformants. Lower temperature growth of Ina(+) yeast at temperatures below 25 degrees C was required for the expression of ice nucleation activity. Shift of temperature to 5-20 degrees C could induce the ice nucleation activity of Ina(+) yeast when grown at 25 degrees C, and maximum ice nucleation activity was achieved after induction at 5 degrees C for approximately 12 h. The effects of Ina(+) yeast on freezing and texturization of several food materials was also demonstrated.

Bacterial Outer Membrane Proteins↗
PubMed2001

Early prediction of aphasia outcome in left basal ganglia hemorrhage.

OBJECTIVES: The independent predictors of aphasia outcome for patients with left basal ganglia hemorrhage were evaluated. PATIENTS AND METHODS: We included 140 patients of 1,036 patients with spontaneous intracerebral hemorrhage admitted to our hospital from January 1993 through December 1997. Aphasia was assessed using the aphasia scale of the Scandinavian stroke scale. Univariate and step-wise logistic regression analyses were performed to assess the relationships between the initial aphasia score, age, gender, blood volume, locations of hematoma and aphasia outcome. RESULTS: Step-wise logistic regression analysis revealed that the following two factors were independently associated with the final aphasia outcome: initial aphasia score (P < 0.0001) and location of hematoma involving the posterior limb of the internal capsule (P = 0.004). CONCLUSIONS: A particularly high likelihood of poor aphasia outcomes of patients with left basal ganglia hemorrhage are predicted in those who have poor initial aphasia score and whose brain computed tomography shows the hematoma involves the posterior limb of the internal capsule.

Aged↗
PubMed2001

Hypertensive caudate hemorrhage prognostic predictor, outcome, and role of external ventricular drainage.

BACKGROUND AND PURPOSE: The purpose of the present study was to analyze the outcome and outcome predictors of caudate hemorrhage and role of external ventricular drainage in acute hydrocephalus. METHODS: Clinical data from 36 consecutive patients with hypertensive caudate hemorrhage was used in the present study. Age, gender, volume of parenchymal hematoma, hematoma in the internal capsule, initial Glasgow Coma Scale (GCS), hydrocephalus, severity of intraventricular hemorrhage, and hemorrhagic dilatation of the fourth ventricle were analyzed for effect on outcome. Effect of external ventricle drainage for hydrocephalus was evaluated by comparing preoperative and postoperative GCS scores. RESULTS: By univariate analyses, poor outcome was associated with a poor initial GCS score (P=0.016), hydrocephalus (P<0.001), intraventricular hemorrhage severity (P<0.01), and hemorrhagic dilatation of the fourth ventricle (P=0.02). By multivariate analysis, stepwise logistic regression revealed that hydrocephalus was the only independent prognostic factor for poor outcome (P<0.001). Postoperative 48-hour GCS score was better than the preoperative score by use of paired-sample t test (P<0.001). CONCLUSIONS: Hydrocephalus is the most important predictor of poor outcome. External ventricular drainage response for hydrocephalus was good in the present study, whereas an early decision should be made regarding preoperative neurological condition.

Basal Ganglia Hemorrhage↗
PubMed2001

Association of blood arsenic levels with increased reactive oxidants and decreased antioxidant capacity in a human population of northeastern Taiwan.

Arsenic is a notorious environmental toxicant known as both a carcinogen and an atherogen in human beings, but the pathogenic mechanisms are not completely understood. In cell culture studies, trivalent arsenic enhanced oxidative stress in a variety of mammalian cells, and this association may be closely associated with the development of arsenic-related diseases. To investigate the effect of arsenic exposure on oxidative stress in humans, we conducted a population study to determine the relationships of blood arsenic to reactive oxidants and antioxidant capacity at the individual level. We recruited 64 study subjects ages 42-75 years from residents of the Lanyang Basin on the northeast coast of Taiwan, where arsenic content in well water varies from 0 to > or = 3,000 microg/L. We used a chemiluminescence method, with lucigenin as an amplifier for measuring superoxide, to measure the plasma level of reactive oxidants. We used the azino-diethyl-benzthiazoline sulphate method to determine the antioxidant capacity level in plasma of each study subject. We determined arsenic concentration in whole blood by hydride formation with an atomic absorption spectrophotometer. The average arsenic concentration in whole blood of study subjects was 9.60 +/- 9.96 microg/L (+/- SD) with a range from 0 to 46.50 microg/L. The level of arsenic concentration in whole blood of study subjects showed a positive association with the level of reactive oxidants in plasma (r = +0.41, p = 0.001) and an inverse relationship with the level of plasma antioxidant capacity (r = -0.30, p = 0.014). However, we found no significant association (p = 0.266) between levels of plasma reactive oxidants and antioxidant capacity. Our results also show that the lower the primary arsenic methylation capability, the lower the level of plasma antioxidant capacity (p = 0.029). These results suggest that ingestion of arsenic-contaminated well water may cause deleterious effects by increasing the level of reactive oxidants and decreasing the level of antioxidant capacity in plasma of individuals. Persistent oxidative stress in peripheral blood may be a mechanism underlying the carcinogenesis and atherosclerosis induced by long-term arsenic exposure.

Adult↗
PubMed2001

Superior rectal artery injury following lumbar disc surgery. Case report.

Traumatic injury of the aorta, inferior vena cava, and iliac vessels due to penetration of the anterior anulus fibrosus and anterior longitudinal ligament is a recognized complication of lumbar disc surgery. The authors report, to the best of their knowledge, the first case of discectomy-related superior rectal artery injury treated by endovascular intervention.

Adult↗
PubMed2001

Atlantoaxial stability in ossiculum terminale. Case report.

The authors describe a patient with ossiculum terminale. Thin-section three-dimensional computerized tomography reconstructions, magnetic resonance images, and radiographs of the cervical spine were obtained to evaluate the atlantoaxial stability and structures of the ossiculum terminale. Bone had formed between the ossicles and the body of the odontoid process, and good atlantoaxial stability was clearly demonstrated.

Adult↗
PubMed2001

The early stages of filamentous phage phiLf infection require the host transcription factor, Clp.

Xanthomonas campestris pv. campestris produces great amounts of an exopolysaccharide (EPS), xanthan gum. Eight eps loci involved in biosynthesis of the EPS were previously located in the chromosome map of strain Xc17. In this study, the eps8 region was cloned, sequenced and found to contain a crp homologue whose deduced amino acid sequence possesses similarity to that of the cyclic AMP receptor protein of bacteria, with the highest identity (97%) being shared with the X. campestris pv. campestris B-1459 clp gene previously shown to be involved in pathogenicity and regulation of the production of xanthan, extracellular enzymes, and pigment (de Crecy-Lagard V., Glaser P., Lejeune P., Sismeiro O., Barber C.E., Daniels M.J., and Danchin A., J. Bacteriol. 172:5877-5883, 1990). Based on sequence identity, pleiotropic effects of the mutation, the ability to complement an Escherichia coli cya crp mutant, and Southern hybridization detecting a single copy in the chromosome, we propose this eps8 gene to be the Xc17 clp. In addition to the previously reported properties, a clp mutant (AU56E) cannot be plaqued with filamentous phage phiLf, although it retains the capability to support phiLf DNA replication and release authentic phage particles upon electroporation of the RF DNA. Infective center assays demonstrated that the frequency of infection is 460- to 7,500-fold lower in AU56E compared to that in the wild-type Xc17. Electron microscopy, which showed no surface appendages other than the monotrichous flagellum, confirmed that AU56E drastically diminishes in the efficiency of phage adsorption. These results suggest Clp to be regulating the biosynthesis of the primary receptor, most likely a type IV pilus. Upstream to clp is a homologue of the E. coli speD gene required for spermidine synthesis. Mutation of the clp flanking regions and transcriptional analyses suggest clp to be monocistronic and the only gene contained at the eps8 locus.

Amino Acid Sequence↗
PubMed2001

Differential telomerase expression and telomere length in primary intracranial tumors.

BACKGROUND: Telomerase activity and telomere length have been shown to be involved in controlling cell proliferation and regulating cell senescence. The authors examined telomerase activity and telomere length in intracranial tumors to determine the clinicopathological behavior of primary intracranial tumors with respect to telomerase expression and alteration of telomere length. METHODS: Telomerase activity was examined in 139 brain tumor samples. Telomere length was examined in 138 of the 139 samples. These tumors included 61 meningiomas, 27 schwannomas, 19 high-grade neuroepithelial tumors, and 32 low-grade neuroepithelial tumors. Telomerase activity was measured with a telomerase polymerase chain reaction, enzyme-linked immunosolvent assay kit. Telomere length was examined by Southern blot analysis for the terminal restriction fragment length. RESULTS: Telomerase activity was detected in 39.2% (20/51) of the neuroepithelial tumors. Detection rates were 47.4% (9/19) for anaplastic astrocytomas and glioblastomas and 34.4% (11/32) for low-grade neuroepithelial tumors. However, detectable telomerase activity was found in 30.8% (4/13) of atypical or malignant meningiomas, but was not detected in any schwannomas. There was a highly significant difference in the telomerase detection rate in neuroepithelial or non-neuroepithelial tumors (p = 0.001). Telomere elongation was found in 11.7% (7/60) of all meningiomas, 46.1% (6/13) of atypical or malignant meningiomas, and 14.8% (4/27) of schwannomas. Elongation of telomere length was detected in 12.6% (11/87) of the cases and 23.5% (12/51) in neuroepithelial tumors. This difference was also significant (p < 0.05). Telomere length was reduced in the majority, (75%, 3/4) of malignant or atypical meningiomas with detectable telomerase activity, but only 45% (9/20) of the neuroepithelial tumors. CONCLUSION: These results indicate that telomerase activation may be a critical step in the pathogenesis of intracranial tumors. Telomere length elongation also indicates a high potential for malignant behavior in these tumors.

Adolescent↗
PubMed2001

Sequence, transcriptional analysis and chromosomal location of the Xanthomonas campestris pv. campestris uvrB gene.

The uvrB gene of Xanthomonas campestris pv. campestris, a Gram-negative plant pathogenic bacterium inhabiting soil and infected plants, was cloned and sequenced. This gene has the capacity to encode a polypeptide of 673 amino acid residues with a calculated molecular mass of 75.9 kDa. Its deduced amino acid sequence shows a high degree of similarity and possesses domain conservation to those of bacterial UvrB. The uvrB mutant, isolated by gene replacement, is extremely sensitive to ultraviolet irradiation. Like the situation in the X. campestris pv. campestris recA gene, no SOS box is present upstream of the uvrB gene. Northern blotting and transcriptional fusion assay with lacZ indicated that X. campestris pv. campestris uvrB is expressed constitutively at high levels and cannot be further induced by UV irradiation. These results suggest a regulatory mechanism different from that for the expression of Escherichia coli uvrB. Using a gene-tagging strategy in conjunction with pulsed-field gel electrophoresis, the uvrB gene was located near 1 o'clock on the X. campestris pv. campestris 17 chromosome (4.8 Mb) map, which is far apart from the lexA-recA-recX cluster near 5 o'clock.

Amino Acid Sequence↗
PubMed2000

Patterns of palmar skin temperature alterations during transthoracic endoscopic T2 sympathectomy for palmar hyperhidrosis.

Transthoracic endoscopic T2 sympathectomy has been widely applied to the treatment of a variety of sympathetically mediated disorders. Palmar hyperhidrosis is probably the most common indication for thoracic sympathectomy, especially in certain subtropical areas. Which sympathetic ganglion is to be ablated and how extensive such ablation is enough to eliminate palm sweating are two important issues. Intraoperative monitoring of palmar skin temperature (PST) is the most frequently used method for assessing the accuracy as well as adequacy of ablation of the target sympathetic ganglia. With continuous monitoring of bilateral PST during the operative course of T2 sympathectomy, it was possible to depict the alterations of bilateral PST in response to specific surgical procedures in a real-time manner. For each case, a PST graph was obtained, which represented the graphical expression of intraoperatively recorded bilateral PST data plotted against time. The PST graphs of 93 consecutive cases were analysed. Three types of PST graphs existed, reflecting different responses of bilateral PST to different surgical procedures during the operation. In Type I PST graph pattern, found in 58 cases, skin incision and intercostal muscle dissection caused dramatic bilateral PST drop; and unilateral T2 sympathectomy induced synchronous bilateral PST elevation. Twenty-four cases demonstrated Type II PST graph pattern, in which unilateral T2 sympathectomy caused only ipsilateral PST elevation, although the PST-depressing effect of skin incision and muscle dissection was as significant as in Type I graph pattern. In the 11 cases who showed Type III PST graph pattern, neither skin incision nor T2 sympathectomy induced any apparent changes of PST on either side, giving rise to two rather flat PST curves on the PST graphs. These findings implicate that reciprocal interactions between bilateral sympathetic activities exist in the majority of cases, and that crossover sympathetic modulation may play a role in the neural control of the sudomotor and vasomotor activities of the palms. This study also provides information regarding how PST would possibly change following specific surgical procedures during transthoracic endoscopic T2 sympathectomy, which may be of importance to those who use intraoperative PST monitoring as a guide in determining whether or not the correct sympathetic ganglia are ablated for adequate sympathetic denervation of the palms.

Adolescent↗
PubMed2000

Arsenite induces p53 accumulation through an ATM-dependent pathway in human fibroblasts.

Arsenic compounds are potent human carcinogens. Accumulated evidence has shown that arsenite-induced cytogenetic alterations are associated with the carcinogenicity of arsenic. Because p53 plays a guarding role in maintaining genome integrity and accuracy of chromosome segregation, the mechanistic effects of arsenite on p53 activation were analyzed. In the present study, arsenite-induced DNA strand breaks were confirmed by alkaline single-cell gel electrophoresis (comet assay) in human fibroblast (HFW) cells. Accompanying the appearance of DNA strand breaks was a significant accumulation of p53 in arsenite-treated HFW cells, as demonstrated by immunoblotting and immunofluorescence techniques. p53 downstream proteins, such as p21 and the human homologue of murine double minute-2, were also significantly induced by arsenite treatment. Cell cycle retardation and G2-M arrest were observed in 5-bromo-2'-deoxyuridine pulse-labeled HFW cells by flow cytometry. Wortmannin, an inhibitor of phosphatidylinositol 3-kinases, inhibited arsenite- or X-ray irradiation-induced p53 accumulation but did not alter UV irradiation- or N-acetyl-Leu-Leu-norleucinal-induced p53 accumulation. p53 phosphorylation on serine 15 was also confirmed by immunoblotting technique in arsenite- and X-ray-treated HFW cells but was not observed in UV- or N-acetyl-Leu-Leu-norleucinal-treated HFW cells. These results suggest the involvement of a phosphatidylinositol 3-kinase-related protein kinase in arsenite-induced p53 accumulation. For confirmation, we demonstrated that arsenite treatment, similar to X-ray irradiation, did not induce p53 accumulation in GM3395 fibroblasts derived from a patient with ataxia telangiectasia. In contrast, UV irradiation did cause p53 accumulation in these cells. Together, these findings infer that arsenite-induced DNA strand breaks may lead to p53 phosphorylation and accumulation through an ataxia telangiectasia mutated-dependent pathway in HFW cells.

Arsenites↗