Biomedical subjects

K Chen

Publications and source records attributed to K Chen.

At least 307 records · Page 17Linked to original sources

PubMed1997

bFGF ameliorates focal ischemic injury by blood flow-independent mechanisms in eNOS mutant mice.

Genetically engineered mice deficient in the expression of type III nitric oxide synthase (NOS) [endothelial NOS (eNOS)] were used to decipher the importance of nitric oxide (NO)-dependent augmentation of regional cerebral blood flow (rCBF) to infarct volume reduction following basic fibroblast growth factor (bFGF) infusion during acute middle cerebral artery (MCA) occlusion. We have shown previously that intravenously administered bFGF reduces infarct volume following MCA occlusion in rats and that bFGF dilates cerebral pial arterioles by NO-dependent mechanisms. Halothane-anesthetized eNOS knockout and wild-type mice were subjected to permanent MCA occlusion by intraluminal filament for 24 h. bFGF (100 microg x kg(-1) x h(-1)) was infused intravenously for 2 h, beginning 15 min after the onset of occlusion. Infarct volume was reduced from 119 +/- 8 to 93 +/- 4 mm3 (22% reduction, P < 0.05) or from 102 +/- 9 to 77 +/- 6 mm3 (24% reduction, P < 0.05) in eNOS knockout or wild-type mice, respectively (means +/- SE; n = 10 per group), and neurological deficits were also significantly reduced. Although bFGF infusion caused a 27% increase in rCBF and a 17% reduction in vascular resistance in the infarct margin of wild-type animals as measured by laser Doppler flowmetry, bFGF did not enhance rCBF in the infarct margin of eNOS mutant mice. These data indicate that intravenous bFGF reduces infarct volume following focal ischemia by mechanisms that are largely blood flow independent.

Animals↗

PubMed1997

Use of positron emission tomography for presurgical localization of eloquent brain areas in children with seizures.

Successful surgical management of a neoplastic or nonneoplastic seizure focus in close proximity to or within eloquent brain areas relies on precise delineation of the relationship between the lesion and functional brain areas. The aim of this series was to validate the usefulness and test the efficacy of noninvasive presurgical PET mapping of eloquent brain areas to predict surgical morbidity and outcome in children with seizures. To identify eloquent brain areas in 15 children (6 female and 9 male; mean age 11 years) with epileptogenic lesions PET images of regional cerebral blood flow were performed following the administration of [(15)O]water during motor, visual, articulation, and receptive language tasks. These images with coregistered magnetic resonance (MR) images were then used to delineate the anatomic relationship of a seizure focus to eloquent brain areas. Additional PET images using [18F]fluoro-2-deoxy-D-glucose (FDG) and [11C]methionine (CMET) were acquired to help localize the seizure focus, as well as characterize the lesion. Patient surgical management decisions were based on PET mapping in combination with coregistered MR images, PET-FDG findings, and the anatomic characteristics of the lesion. At follow-up 1-26 months after surgery, all patients that underwent temporal lobectomy (9 patients) and extratemporal resection (4 patients) for a neoplastic or nonneoplastic seizure focus are seizure-free with minimal postoperative morbidity. Of prime importance, no child sustained a postoperative speech or language deficit. PET imaging was also well tolerated without procedural complications. Based on PET mapping, a nonoperative approach was used for 2 children and a biopsy only was used in one child. When cortical injury involved prenatally determined eloquent cortex, PET demonstrated reorganization of language areas to new adjacent areas or even to the contralateral hemisphere. Integration of anatomical and functional data enhanced the surgical safety, defined optimal surgical approach, delineated the seizure focus from eloquent brain areas, facilitated maximum resection and optimized the timing of surgery, thereby minimizing surgical morbidity while maximizing surgical goals. PET measurements of FDG and CMET uptake were also helpful in localizing the seizure focus and grading the tumors. PET used for brain mapping in children provides the surgeon with strategic preoperative information not readily attainable with traditional invasive Wada testing or intraoperative cortical stimulation. PET mapping may also improve the outcome of extratemporal resections by allowing aggressive seizure focus resection. In addition, serial brain maps may optimize timing for surgical intervention by demonstrating reorganization of eloquent cortex often seen in younger children after cortical injury. Our results suggest that noninvasive presurgical brain mapping has the potential to reduce risk and improve neurologic outcome.

Adolescent↗

PubMed1997

Neuroanatomical correlates of externally and internally generated human emotion.

OBJECTIVE: Positron emission tomography was used to investigate the neural substrates of normal human emotional and their dependence on the types of emotional stimulus. METHOD: Twelve healthy female subjects underwent 12 measurements of regional brain activity following the intravenous bolus administration of [15O]H2O as they alternated between emotion-generating and control film and recall tasks. Automated image analysis techniques were used to characterize and compare the increases in regional brain activity associated with the emotional response to complex visual (film) and cognitive (recall) stimuli. RESULTS: Film- and recall-generated emotion were each associated with significantly increased activity in the vicinity of the medial prefrontal cortex and thalamus, suggesting that these regions participate in aspects of emotion that do not depend on the nature of the emotional stimulus. Film-generated emotion was associated with significantly greater increases in activity bilaterally in the occipitotemporparietal cortex, lateral cerebellum, hypothalamus, and a region that includes the anterior temporal cortex, amygdala, and hippocampal formation, suggesting that these regions participate in the emotional response to certain exteroceptive sensory stimuli. Recall-generated sadness was associated with significantly greater increases in activity in the vicinity of the anterior insular cortex, suggesting that this region participates in the emotional response to potentially distressing cognitive or interoceptive sensory stimuli. CONCLUSIONS: While this study should be considered preliminary, it identified brain regions that participate in externally and internally generated human emotion.

Adult↗

PubMed1997

Positron emission tomography in children with neurofibromatosis-1.

Neurofibromatosis-1 is an autosomal dominant genetic disorder commonly associated with neuropsychological complications. Focal areas of high signal intensity on magnetic resonance imaging (MRI) scans occur commonly but have shown inconsistent correlation with neuropsychological problems. Positron emission tomography (PET) scans utilizing [18F]fluoro-2-deoxy-D-glucose and MRI studies were performed on 10 children with neurofibromatosis-1 and multiple focal areas of high signal intensity to evaluate the regional cerebral metabolic rate for glucose of these lesions and other central nervous system structures. Co-registered PET and MRI studies confirmed reduced glucose metabolism of large focal areas of high signal intensity. Visual inspection and semiquantitative analysis of PET images demonstrated thalamic hypometabolism and varying degrees of cortical inhomogeneity in all cases of neurofibromatosis-1 compared to normal controls. Although a primary defect of the thalamus or cerebral cortex has not been defined, the metabolic abnormalities of this study suggest a potential relationship between these structures and the neuropsychological dysfunctions noted in neurofibromatosis-1.

Adolescent↗

PubMed1997

[The effect of endurance training and exhaustive exercise on metallothionein in rats].

To understand physiological role of metallothionein (MT) during exercise, MT levels in liver, brain, heart, lung, blood vessel, skeletal muscle and serum were observed in rats. The results showed that the levels of MT were decreased by 13-34% in lung, liver, heart and skeletal muscle of rats trained by swimming for 10 weeks and were increased by 21%-75% in skeletal muscle, heart, brain, lung and liver of rats after exhaustive swimming respectively, compared with normal control rats. (P < 0.05 and P < 0.01). But the levels of MT in blood vessel and serum were not changed in two groups of rats by swimming for 10 weeks and acute exhaustive swimming (P > 0.05). It is suggested that the different changes of MT levels under physical training and acute exhaustive exercise may be of importance in protection against oxygen free radicals.

Animals↗

PubMed1997

[Clinical study of effect of yizhi capsule on senile vascular dementia].

OBJECTIVE: To assess the efficacy of Yizhi capsule (YZC) in treating senile dementia. METHODS: Sixty-one vascular dementia (VaD) patients were randomly divided into YZC and control groups. There were 32 cases in YZC group, 4 capsules each time three times a day. In control group, there were 29 cases, 2 mg of hydergine were given each time three times a day, single-blind method was used and the treatment course was two months. RESULTS: YZC could remarkably increase mini-mental state examination (MMSE) and Hamilton Depression Scale (HDS) marks of VaD patients. YZC had the effect of improving balance and gait ability of VaD patients. YZC could improve the abnormal blood velocity (BV), as well as improve cerebral blood flow, brain electrical activity monitoring (BEAM) and hemorheological indexes especially for the abnormal case. No side-effect or toxic-effect was observed in the administration period. CONCLUSION: YZC had certain effect on senile VaD, and it was safe in application.

Aged↗

PubMed1997

[En bloc vein resection in the treatment of pancreatic tumors adherent to the superior mesenteric-portal vein confluence].

Contraindication is often considered to pancreaticoduodenectomy for patients with malignant tumors of the pancreatic head. From 1989 through 1995, 15 patients with tumors of the pancreatic head adherent to the superior mesenteric-portal vein confluence (SMPV) underwent pancreaticoduodenectomy with en bloc resection of SMPV. There was no perioperative mortality. Follow-up data showed a mean survival of 17.1 months among 7 deaths, which was significantly longer than an average of 3.8 months among previous 17 patients who abandoned radical resection (P < 0.001). We consider that pancreaticoduodenectomy with en bloc resection of SMPV is feasible in some cases.

Aged↗

PubMed1997

[Inherent mdr-1 gene expression in fresh tumor tissue specimens from several high-incidence malignancies].

OBJECTIVE: To ascertain frequency of inherent mdr-1 gene expression in several common neoplasms. METHODS: One hundred fifty one surgically resected tumor specimens confirmed pathologically to be malignant from preoperatively untreated cancer patients were studied. Expression of mdr-1 gene was examined by RT-PCR. RESULTS: The frequency of primary mdr-1 gene expression was 33.3% for cancer of the stomach and gastric cardia (17/51), 37% for cancer of the esophagus (17/46), 31.3% for cancer of the colon and rectum (5/16), 13.2% for cancer of the breast (2/15), 40.0% for cancer of the thyroid (4/10), 55.0% for cancer of the lung (5/9) and 0% for cancer of the uterine cervix (0/4). CONCLUSION: Primary mdr-1 gene expression is relatively of frequent occurrence as detected by RT-PCR technique.

Adenocarcinoma↗

PubMed1997

[The application of artificial neural network based on ambiguous function to heart sound classification].

In this study the artificial neural network was applied to heart sound classification. The network input data are ambiguous function, hence the crossterm problem of Wigner distribution is avoided. The simulation result shows that this is an effective technique. A suboptimal network model was proposed by many times of training and checking. The main factors related to network property were also discussed.

Aerospace Medicine↗

PubMed1997

[Effect of sodium iron chlorophyllin (SIC) on CFU-E and CFU-GM yields of normal and anemic animal models].

OBJECTIVE: To observe the effect of sodium iron chlorophyllin (SIC) on hematopoiesis and its therapeutic efficacy in anemic mice. METHODS: The effects of SIC on CFU-E and CFU-GM yields of normal and anemic animal models were studied. RESULTS AND CONCLUSIONS: (1) SIC significantly enhanced the CFU-E and CFU-GM yields of mouse bone marrow. (2) SIC also increased the percentage of reticulocyte in mouse. (3) In hemolytic anemia mice induced by i.p. N-acetphenylhydrazine, SIC markedly prevented the decrease of RBC and Hb. (4) In hemorrhagic anemia rats induced by bleedletting, SIC accelerated the normalization of RBC, Hb and elevated the serum iron level and transferrin saturation.

Anemia↗

PubMed1997

[Correlation between the serum levels of interleukin-2 and soluble interleukin-2 receptor and the response to immunosuppressive therapy in severe aplastic anemia patients].

OBJECTIVE: To explore factors influencing the effectiveness of immunosuppressive therapy in severe aplastic anemia (SAA). METHODS: The serum levels of interleukin-2 (IL-2) and soluble IL-2 receptor (sIL-2R) of 22 SAA patients and 15 normal controls were measured by immunoenzyme assay. RESULTS: Comparing with the normal controls, 40.9% and 63.6% of the SAA patients had higher serum levels of IL-2 (>840ng/L) and of sIL 2R (>320 x 10(3) U/L), respectively. Those who had higher IL-2 levels and higher sIL-2R levels got better responses to cyclosporin A(CsA) and CsA plus antilymphocyte globulin (ALG). CONCLUSION: The serum levels of IL-2 and sIL-2R were correlated with the responsiveness to immunosuppressive therapy in SAA patients and might be useful for directing treatment.

Adolescent↗

PubMed1997

Compartment model for measuring myocardial oxygen consumption using [1-11C]acetate.

UNLABELLED: Although [1-11C]acetate has been validated as a PET tracer for myocardial oxygen consumption (MVO2) in animals and humans, mono- and biexponential fitting of the tissue time-activity curve yields only estimates of MVO2. This study attempts to develop and validate a simple tracer kinetic model in vivo for estimation of regional MVO2. METHODS: Twenty-seven experiments were performed in 12 anesthetized dogs with [1-11C]acetate and serial PET images under different MBF and MVO2 (baseline, ischemia, xylazine, dobutamine and dipyridamole). Estimates of MVO2 were obtained from dynamic [1-11C]acetate PET and model fitting. MBF was measured by radiolabeled microspheres, and MVO2 was calculated by the Fick method using arterial and coronary blood samples. RESULTS: The proposed model fitted equally well for all study conditions with a multiple correlation coefficient of 0.985 +/- 0.026. Estimated MVO2 correlated linearly with measured MVO2 (y = 0.033 + 0.690x, r = 0.92, s.e. of estimates = 0.020). CONCLUSION: This study indicates that MVO2 can be assessed with PET and [1-11C]acetate over a wide range with a simple tracer kinetic model.

Acetates↗

PubMed1997

Non-linear large deformation FE analysis of orthodontic springs.

Large deformation non-linear finite element models of T, V, L and B (Baldwin) orthodontic springs were developed and experimentally validated. Spring stiffnesses and moment/force ratios were computed. Compared to the T loop, under horizontal activation, the V loop was half as stiff, the L loop was equal, and the B spring was 10% as stiff. The moment/force ratio was 30% higher in the V configuration, while the B spring was less by 95%. The asymmetric L loop exerted a moment/force ratio that was 30% on the one side, but 180% in the opposite direction on the other side. With vertical activation, also compared to the T spring, the horizontal stiffnesses were 500% (V), 150% (L), and 30% (B). The concomitant vertical stiffnesses were 100%, 50% and 25%. The vertically activated moment/force ratios were nearly equal in the four springs. Experiments validated these FEM calculations.

Algorithms↗

PubMed1997

[Metallothionein involvement in the delayed protection after ischemic or anoxic preconditioning in myocardium or cultured cardiomyocytes].

OBJECTIVE: To study whether metallothionein (MT) is an OH scavenger and plays a protective role in cardiac ischemic/reperfusion injury. MT involves in the delayed protection 24 hr after preconditioning (PC). METHODS: MT contents in myocardium or cultured cardiomyocytes are assayed at the 0 hr, 12 hr, and 24 hr after PC on the model of rabbit heart in situ or that of the cultured cardiomyocytes. The myocardial infarct size, LDH release, cell viability, and the content of cellular MDA were measured with or without the intervention of PD098059, the inhibitor of mitogen-activated protein kinase in the models before PC and different time intervals after PC. RESULTS: The MT contents were increased significantly at 2 hr (1406.2 +/- 112.2 vs 129.9 +/- 10.4 pmol/mg Pr., P < 0.01, in cardiomyocytes) and 24 hr (1032.7 +/- 199.1 vs 129.9 +/- 10.4 pmol/mg Pr., P < 0.01, in cardiomyocytes; 62.1 +/- 12.6 vs 27.2 +/- 3.7 pmol/mg Pr., P < 0.01, in myocardium) after PC compared with those in normal group. The infarct sizes (13.2 +/- 3.6% vs 32.3 +/- 5.7%, P < 0.05) and the rise of LDH release in plasma (1944 +/- 256 vs 2826 +/- 239 IU/L, P < 0.05) were greatly decreased in preconditioned myocardium after a long time ischemia-reperfusion than those in the unpreconditioned. Compared with the cardiomyocytes unconditioned, the number of viable cell (71.0 +/- 1.6 vs 48.2 +/- 2.2%, P < 0.01) was greatly increased, the cellular MDA contents (33.5 +/- 12.8 vs 103.5 +/- 15.0 nmol/mg Pr., P < 0.01) and the LDH release (850.0 +/- 139.1 vs 1552.0 +/- 102.6 IU/L, P < 0.01) were dramatically decreased in preconditioned ones. All the delayed protection at 24 hr after PC were completely disappeared with the inhibition of MT's production with PD098059 (P > 0.05). CONCLUSION: The myocardium or cardiomyocytes at 24 hr after PC are offered more capacity to tolerate the I/R damage, and MT involves in the delayed protection.

Animals↗

PubMed1997

[A study on the reliability of data provided by patients' family surrogates].

In epidemiological investigations, the validity and reliability of data under different ways of collection might not be consistent. In order to evaluate the consistency of data collected from cases themselves or from their surrogates (for example, the spouse) through answering the same questionnaire, at personal interview, was carried out among 50 cases of lung cancer and their surrogates respectively. Other than the item starting age of smoking by a paired-t test, the results showed that between the two groups of quantitative data sources, the overall consistent rate was 84.1% and the differences were not significant (P < 0.05). When Kappa consistency test was used to the count variables, an average consistent rate of 87.8% was noticed, but P values were less than 0.001 for all items. Results from this study were quite similar to those with have been published abroad and suggested that it is credible to collect data from surrogates when dead cases were selected as research subjects.

Aged↗

PubMed1997

[Evaluation of effectiveness of comprehensive control for diarrhea diseases in rural areas of east Fujian and analysis of its cost-benefit].

An intervention trial with comprehensive prevention and control for diarrhea diseases was carried out in the rural areas of East Fujian, China during 1991 to 1993, focusing on improvement of drinking water, health education, and supervision and direction to villagers to improve their environmental and family health. Results showed the intervention could reduce the incidence of diarrhea diseases by 55.1 percent in average. Economic benefit analysis of the effectiveness of the intervention showed ratios of cost to benefit were 1:5.6, 1:4.9 and 1:6.5 in 1991, 1992 and 1993, respectively, and net benefit amounted to 13,674,000 Chinese yuan. It suggests that effectiveness of this comprehensive control was significant and cost-effective.

China↗

PubMed1997

[Effects of hypoxia/reoxygenation on mitogen-activated protein kinase activity in cultured neonatal rabbit cardiac myocytes].

Cardiomyocytes subjected to brief episode of hypoxia possess a resistance to serious damaging effect exerted by a subsequent long-time hypoxia on these cells, which is called hypoxic preconditioning (PC). The pathway of intracellular signal transduction during hypoxia PC has not yet been validated. On a model of hypoxia/reoxygenation (H/R) of cultured neonatal rabbit cardiomyocytes, the present study is taken to investigate the changes of mitogen-activated protein kinase (MAPK) and ribosomal S6 kinase (S6K) activity. It was found that intracellular total MAPK and nuclear MAPK, after a 15-min period of reoxygenation preceded by a single 60-min period of hypoxia, were increased by 95% and 230%, respectively. Intracellular S6K activity increased by 142% at 30 min of H/R vs the control group (P < 0.01). Phosphatase 1 (PPase 1) inhibitor (ocadaic acid, OA 1 mumol/L) augmented the increase of MAPK and S6K activity induced by H/R. However, tyrosine kinase (Tyr K) inhibitor (genistein), protein kinase C (PKC) inhibitor (H7) and preincubation of cardiomyocytes with PKC activator PMA all reduced MAPK activation by H/R. Protein kinase A (PKA) inhibitor (H89), Ca2+/Calmodulin-dependent protein kinase (PKM) inhibitor (W7) or PPase 2a inhibitor (OA 10 nmol/L) had no significant effect on MAPK and S6K activity. The above results suggested that activation of MAPK and S6K activity during hypoxia/reoxygenation there might require participation of PKC, Tyr K and PPase 1, while PKA, PKM and PPase 2a were not involved.

Animals↗

PubMed1996

Association between flow cytometric S-phase fraction and apoptotic rate in breast cancer.

Tumor heterogeneity may adversely affect the flow cytometric measurement of S-phase fraction (SPF) in breast cancer specimens, and 10-20% of breast cancer specimens are not evaluable by flow cytometry due to technical factors such as debris, high coefficients of variation, poor specimen quality, or small sample size. Therefore, we performed this study on 207 specimens of breast cancer in order to determine if the apoptotic rate (AR) could serve as a useful adjunct to flow cytometric SPF measurements in breast cancers. The average AR in each specimen was determined by microscopic examination of tumor tissue that was specifically stained for apoptotic bodies by a commercially available TUNEL (Tdt-mediated dUTP digoxigenin nick end labelling) assay kit. The mean AR (4.5 +/- 3.0, n = 37) in the high SPF (> 10%) group was significantly (P < 0.01) higher than the mean AR (1.3 +/- 1.2, n = 72) in the low SPF (< 6%) group. Although the distributions of AR values in the two groups had substantial overlap, AR values greater than 5.5 per high power field (h.p.f.) were not observed in the low SPF cases but were present in 13 out of 37 cases with a high SPF. Simple linear regression analyses relating SPF to the mean AR in 57 DNA diploid cases and 41 DNA aneuploid cases yielded a minimal correlation (r2 = 0.21) between the two parameters only in the DNA aneuploid group. We conclude that an elevated AR has an association with high SPF in breast cancers, but the association is too weak to permit the general use of AR as a predictor of SPF. Our study also identified a subset of breast cancers with both a high SPF (> 10%) and a high AR (> 5.5/h.p.f.) that may warrant further investigation to determine its clinical significance.

Apoptosis↗