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Biomedical subjects

X Di

Publications and source records attributed to X Di.

32 records · Page 2Linked to original sources
PubMed1998

[Measurement of interfragmentary micromovement induced by mechanical vibration with accelerometers in vitro].

The interfragmentary micromovement induced by mechanical vibration was measured in vitro in seven preserved adult cadaveric femurs by using accelerometers. Accuracy analysis of this method indicated that it can detect relative interfragmentary micromovement as small as 0.1 mm or below under certain range of frequency. Also, the results have shown that the mechanical vibration can induce interfragmentary micromovement under intramedullary nailing, but it can not do so under plate fixation.

Adult↗
PubMed1997

Effects of mild hypothermia on cerebral blood flow-independent changes in cortical extracellular levels of amino acids following contusion trauma in the rat.

The mechanism of hypothermic cerebroprotection after traumatic brain injury (TBI) is unknown. The present study was conducted to investigate the effects of mild hypothermia on the changes in cortical extracellular amino acids and cerebral blood flow (CBF) caused by cerebral contusion created in the rat parietal cortex by a weight-drop method. CBF in both normothermia (37 degrees C) and hypothermia (32 degrees C) groups, which was monitored using the hydrogen clearance technique, decreased significantly after contusion, but never fell below the threshold for ischemia. Cortical levels of glutamate, aspartate, glycine and taurine, which were measured by intracerebral microdialysis, were significantly increased after contusion in each group. However, these increases were greater in the hypothermic than in the normothermic rats. Normal plasma amino acid levels were high, and autoradiography following intravenous injection of 14C-labeled glutamate revealed marked extravasation of [14C]glutamate at the site of cortical impact. These results suggest that the post-traumatic increase in extracellular amino acids occurs independently of CBF reduction, and that extravasation of amino acids from the vascular compartment partly contributes to this increase. Hypothermic cerebroprotection in TBI is thus likely to occur through a mechanism other than reduction in interstitial excitatory amino acids. In TBI, it is postulated that the postsynaptic effects of hypothermia may be more important than the presynaptic effects, when CBF is kept above the ischemic threshold.

Amino Acids↗
PubMed1997

Effect of CP101,606, a novel NR2B subunit antagonist of the N-methyl-D-aspartate receptor, on the volume of ischemic brain damage off cytotoxic brain edema after middle cerebral artery occlusion in the feline brain.

BACKGROUND AND PURPOSE: The purpose of this study was to test the hypothesis that the neuroprotective compound CP101,606 will ameliorate the increase in lactate, retard the development of cytotoxic edema, and decrease the infarct volume after ischemic stroke. METHODS: Seventeen adult cats were allocated to control (n = 7) and CP101,606-treated groups (n = 10). Transorbital middle cerebral artery occlusion was performed under anesthesia. Extracellular fluid lactate by microdialysis as well as infarct volume measurement by triphenyltetrazolium chloride (TTC)-stained section, with and without neuroprotective agents, was used to determine the value of these potential "surrogate markers" of ischemic damage. RESULTS: The control group showed an increased dialysate lactate (15.5% increase) at 30 minutes and a peak (332.0% increase) in dialysate lactate at 1 hour after middle cerebral artery occlusion compared with the drug-treated group. Significant differences between control and drug-treated groups were seen in the rate of fall of the apparent diffusion coefficient at both 1 and 5 hours. A close correlation was seen between the 1- and 5-hour apparent diffusion coefficient maps and the TTC-stained sections. There was a significantly smaller lesion in the CP101,606-treated group (62.9% reduction in infarct size compared with the control group; P < .001). CONCLUSIONS: CP101,606 ranks very highly among the current neuroprotection candidates for clinical trials, and its excellent safety record in both animals and phase II studies in conscious, moderate head injury patients suggests that it will be highly effective in human occlusive stroke.

Animals↗
PubMed1997

[cDNA cloning of human stem cell factor and its high level expression in E. coli].

The total RNA of HepG2 cell was extracted as the template by ultrocentrifuge method. The full length cDNA (0.8 kb) encoding the human stem cell factor (hSCF) was amplified by RT-PCR method. The cDNA encoding mature hSCF (0.5 kb) was sequenced and was recombined into the expression vector (PBV-220). The expression level of rhSCF in E. coli DH5 alpha was about 15% of the total protein.

Amino Acid Sequence↗
PubMed1997

Proliferative potentials of glioma cells and vascular components determined with monoclonal antibody MIB-1.

Proliferative activity in 78 glioma specimens was assessed immunohistochemically by determining proliferating index of tumor cells (PTC-PI) and endothelial cells (PEC-PI) using the MIB-1 monoclonal antibody. The PTC-PI of anaplastic astrocytoma (9.0 +/- 5.8: mean + standard deviation) was significantly higher than that of astrocytoma (1.2 +/- 0.4, < 0.01), and lower than that of glioblastoma multiforme (12.0 +/- 5.6, < 0.05). We then compared PTC-PI values with the prognosis of patients with malignant glioma (both glioblastoma and anaplastic astrocytoma). Kaplan-Meier survival rate analysis demonstrated higher survival rates in patients with less than 8.0% of PTC-PI at 5 and 10 years (p < 0.05). These results suggested PTC-PI provides useful information which may allow better assessment of the biological behaviour and clinical prognosis of glioma, in addition to histological grading. While the average PEC-PI value (3.3) was lower than that of PTC-PI (7.0), there was a significantly close relationship between them (p < 0.01), fostering the developments novel therapies directed towards suppression of microvascular regeneration.

Antibodies, Monoclonal↗
PubMed1997

Proliferative potentials of glioma cells and vascular components determined with monoclonal antibody MIB-1.

Proliferative activity in 78 glioma specimens was assessed immunohistochemically by determining proliferating index of tumor cells (PTC-PI) and endothelial cells (PEC-PI) using the MIB-1 monoclonal antibody. The PTC-PI of anaplastic astrocytoma (9.0 +/- 5.8: mean +/- standard deviation) was significantly higher than that of astrocytoma (1.2 +/- 0.4, < 0.01), and lower than that of glioblastoma multiforme (12.0 +/- 5.6, < 0.05). We then compared PTC-PI values, patients' age and extent of tumor resection with the prognosis of patients with malignant glioma (both glioblastoma and anaplastic astrocytoma). Kaplan-Meier survival rate analysis demonstrated higher survival rates in patients with less than 8.0% of PTC-PI at 5 and 10 years (p < 0.05). The mean age of patients who survived more than a year was lower than that of patients who died within a year (53.0 y.o., vs. 59.7 y.o., p < 0.01). Total or subtotal resection of the tumor was more often performed in the former than latter patients (51% vs. 21%, p < 0.01). These results suggested PTC-PI provides useful information which may allow better assessment of the biological behavior and clinical prognosis of glioma, in addition to histological grading, patients' age and extent of tumor resection. While the average PEC-PI value (3.3) was lower than that of PTC-PI (7.0), there was a significantly close relationship between PTC- and PEC values (p < 0.01), providing an impetus to develop novel therapies directed toward suppression of microvascular regeneration.

Adult↗
PubMed1996

Voltage-dependent Na+/K+ ion channel blockade fails to ameliorate behavioral deficits after traumatic brain injury in the rat.

Traumatic brain injury (TBI) induces massive, transient ion flux, after impact. This may be via agonist gated channels, such as the muscarinic, cholinergic or NMDA receptor, or via voltage-dependent channels. Pharmacological blockade of the former, is neuroprotective in most TBI models, but the role of voltage-dependent Na+/K+ channels has not been tested. We have therefore tested the hypothesis that intraventricular tetrodotoxin (TTX) (20 microliters, 5 mM) induced blockade of post-TBI ion flux will prevent cytotoxic cell swelling, Na+ and K+ flux, and behavioral deficit. Microdialysis demonstrated blockade of [K+]d flux in the TTX group compared to controls. Behavioral evaluation of motor (days 1-5) and memory function (days 11-15) after TBI revealed no beneficial effect in the TTX group compared to controls. Thus, although evidence of reduced ionic flux was demonstrated in the TTX group, memory and behavior were unaffected, suggesting that agonist-operated channel-mediated ion flux is more important after TBI.

Animals↗
PubMed1996

Effect of the novel high-affinity glycine-site N-methyl-D-aspartate antagonist ACEA-1021 on 125I-MK-801 binding after subdural hematoma in the rat: an in vivo autoradiographic study.

Acute subdural hematoma (SDH) complicates 20% of severe human head injuries and causes death or severe disability in 60% of these cases, due to brain swelling and high intracranial pressure. Although the mechanisms for these phenomena are unknown, previous studies have implicated excitatory amino acid-mediated mechanisms in both humans and animal models. The authors therefore performed in vivo autoradiography using 125I-MK-801, a high-affinity noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, as a tracer to evaluate NMDA ion channel activation spatially and temporally as a factor causing cytotoxic swelling. Acute SDH was induced in 16 anesthetized rats using 0.4 ml autologous venous blood. Fifty microcuries of 125I-MK-801 was injected via an aortic arch cannula 30 minutes after onset of SDH. The effect of a new putatively neuroprotective drug, ACEA-1021, a glycine-specific binding site NMDA antagonist, on 125I-MK-801 binding was tested on five animals "Nonspecific" 125I-MK-801 binding in the rat brain was assessed by pretreatment with "cold" (nonradiolabeled) MK-801 in five more animals. Four hours later the animals were sacrificed and brain sections were apposed to radiation-detecting high-sensitivity photographic film with precalibrated plastic standards for 4 weeks. A striking and highly significant 1.7- to 4.8-fold increase in 125I-MK-801 binding was seen in the penumbra of viable tissue surrounding the ischemic zone beneath the acute SDH, when compared to contralateral hemisphere binding (p < 0.001). The MK-801 pretreatment markedly reduced 125I-MK-801 uptake in this penumbral zone (4.73 +/- 0.36 nCi/mg control vs. 2.85 +/- 0.08 nCi/mg cold MK-801; p < 0.0001), indicating that the increased binding in the penumbra of the lesion was due to NMDA ion channel activation. Pretreatment with ACEA-1021 reduced 125I-MK-801 uptake by 28% (3.41 +/- 0.26 nCi/mg vs. 4.73 +/- 0.36 nCi/mg; p < 0.05), indicating that this agent prevents opening of the NMDA ion channel and, thus, exposure of its receptor for MK-801 binding. These studies show intense foci of penumbral NMDA receptor-mediated ion channel activation after onset of SDH, which is markedly reduced by an NMDA antagonist. Such agents are thus likely to reduce cell swelling after SDH occurs.

Animals↗
PubMed1996

[The cloning and expression of salmon calcitonin gene in Escherichia coli].

The DNA fragment encoding salmon calcitonin was separated from the salmon DNA with PCR method. It was recombined into the fusion expression vector (pGEX-2T) which included a Glutathion-S-Transferase (GST) gene and was transformed into E. coli JM109 and then expression was induced with IPTG. The fusion protein (GST-sCT) accounted for 38%-40% of the total cellular protein and was purified from the soluble expression products by glutathion sepharose 4B affinity chromatography. The purity of GST-sCT is about 80% and it showed a positive immunological reaction in calcitonin enzyme immunoassay.

Amino Acid Sequence↗
PubMed1996

[Increased promoter activity of human delta-globin gene with point mutation of C-T at site-64].

With PCR point mutation technique, the CCAAC box in the promoter region of delta-globin gene was changed into CCAAT which is required in the normal transcription of beta-globin gene at the corresponding site. The normal and mutant segments of the delta-globin promoter region obtained with each segment of about 300 bp (-280/+54 bp), a fragment sufficient for the requirement of its normal promoter function, were separately cloned into pUC19/Hinc II. After sequencing, it showed that the CCAAC box had been successfully changed into CCAAT without other mutations. The two segments were released by Nco I and BamH I, and were cloned into the corresponding site of plasmid pMG3 which has the firefly luciferase as its reporter gene. The positive clones were selected by Dot Blot and were comfirmed with restriction mapping. Then the two recombinant plasmids were transfected into HeLa cell line respectively and the promoter activities of the two fragments were identified by comparing the light intensity generated by the cell extracts when added with luciferase assay substrate. The results demonstrated that the luminescence of the mutant group is on average five times higher than that of the normal group, which indicate that the C-T mutation of the CCAAC box of delta-globin promoter region could increase its promoter activity. Our results have confirmed the hypothesis that the sequence of CCAAC box of human delta-globin gene is one of the main reasons which accounts for its low expression level. The author is now studying the specific DNA binding protein of the upstream promoter region of human delta-globin gene.

Globins↗
PubMed1995

Brain oxygen, CO2, pH, and temperature monitoring: evaluation in the feline brain.

Currently, no ideal method exists for monitoring the injured brain. Recently, a single, compact, fiberoptic sensor has become available for measuring oxygen, CO2, pH and temperature in blood. We have adapted this instrument for continuous use in brain tissue to measure oxygen tension, carbon dioxide tension (pCO2), pH, and temperature. To evaluate this new technique, we produced hypercapnia, hypocapnia, intracranial pressure increase, and hypoxemia in seven normal cats. In an additional six animals, sensors were placed within a zone of focal brain ischemia induced by occluding the left middle cerebral artery. The sensor readings were compared with cerebral blood flow measurements, intracranial pressure, and brain histological findings. An in vitro experiment was also performed using human blood to test the accuracy of the sensor over a wide range of pCO2 and oxygen tension values. After careful precalibration and rigid cranium fixation, stable measurements could be obtained throughout the 6- to 8-hour experiments. In normal animals, brain oxygen was 42 +/- 9 mm Hg, brain CO2 was 59 +/- 14 mm Hg, brain pH was 7.0 +/- 0.2, and brain temperature was 36.7 +/- 0.7 degrees C. Hypocapnia and hypoxemia produced a significant decline in tissue oxygen (< or = 30 +/- 3 mm Hg; P < 0.001), whereas hypercapnia caused by hypoventilation and intracranial pressure increase produced a significant increase in tissue CO2 (> or = 74 +/- 4 mm Hg; P < 0.001). Focal ischemia produced a rapid 42% decline in brain oxygen (25 +/- 7 mm Hg) and a 25% increase in tissue pCO2 (71 +/- 23 mm Hg). Brain oxygen further decreased to 19 +/- 6 mm Hg toward the end of the experiment, 4 hours later. After middle cerebral artery occlusion, the regional cerebral blood flow decreased to 10 +/- 5 ml per 100 g per minute, within the 1st hour, from a baseline value of 65 +/- 15 ml per 100 g per minute. It then gradually increased to 15 +/- 5 ml per 100 g per minute by the end of the 4-hour experiment. Brain pH was closely and inversely related to brain CO2. The brain temperature in the focally ischemic tissue decreased from 36.7 +/- 0.7 to 35.5 +/- 1.6 degrees C by the end of the experiment. The in vitro experiment demonstrated good linear correlation between the sensor readings and the blood gas analysis. Continuous monitoring of oxygen, CO2, pH, and temperature in damaged or at-risk brain tissue using a single sensor is now feasible and will, thus, allow improved continuous monitoring of neurosurgical patients who are at risk of significant secondary brain damage.

Acid-Base Equilibrium↗
PubMed1991

X-ray powder pattern analysis of cytoplasmic polyhedrosis virus inclusion bodies.

Cytoplasmic polyhedrosis virus is an insect reovirus which is occluded in crystalline inclusion bodies that form in the mid-gut of certain insects. Inclusion bodies of cytoplasmic polyhedrosis virus from Bombyx mori were isolated and purified. These crystalline bodies, about 1-3 microns in linear size, were compacted in a capillary tube while immersed in buffer. X-ray diffraction photographs showed powder rings, extending to 8.2 A resolution, which could be indexed with a cell measuring a = b = 49.9 +/- 0.4 A, c = 41.5 +/- 0.4 A, alpha = beta = gamma = 90 degrees. The polyhedrin protein, which is the major component of the inclusion body, has a molecular weight of about 30,000 daltons and, hence, there are probably two molecules in the unit cell. Thus, the unit cell is monoclinic or possibly triclinic. A Patterson derived from the measured powder pattern intensities, assuming monoclinic symmetry, could be interpreted in terms of a molecule with two larger globes. Such a structure is roughly consistent with the breakdown of the polyhedrin into two larger fragments of molecular weight 17,000 and 14,000 when raising the pH to near 10. Under these conditions the inclusion bodies disintegrate, releasing virus and catalyzing the proteolysis of the polyhedrin.

Electron Probe Microanalysis↗
PubMed1986

Diagnostic pattern for neuroses in China, Japan, and the United States.

To investigate the diagnostic patterns for neuroses in China, Japan, and the United States, the authors showed videotapes and brief written case histories of six Chinese patients to psychiatrists and psychiatrists-in-training in Beijing, Tokyo, and Honolulu. In cases with a well-distinguished clinical picture the diagnoses were congruent in the three countries. Diagnostic disagreement occurred in cases with symptoms of decline in mental function, which were overwhelmingly diagnosed as neurasthenia by the Chinese clinicians, and cases with situational stress, which were diagnosed as adjustment reaction by the Americans. This illustrates that different professional concepts and classification systems are used in different countries.

Adjustment Disorders↗