Biomedical subjects

Lei Liu

Publications and source records attributed to Lei Liu.

178 records · Page 10Linked to original sources

PubMed2002

CT value analysis and clinical significance before and after percutaneous lumbar discectomy.

OBJECTIVE: To provide theoretical basis for effect and mechanism of percutaneous lumbar discectomy in clinic. METHODS: A total of 180 patients with lumbar intervertebral disc herniation were evaluated by CT on the fifth day before and after operation. Meanwhile, CT value was measured in the determined level and region. RESULTS: After operation, CT value of the central and posterior determined point of herniated intervertebral disc was lower significantly than that before operation (P<0.01), but CT value of the anterior determined point was different insignificantly. The excellent and good results of the patients together were 83% postoperatively. CONCLUSIONS: The curative effect of percutaneous lumbar discectomy is achieved through reduction of lumbar intradiscal pressure.

Adult↗

PubMed2002

[Effects of external counterpulsation on the pulsatility of blood pressure and blood flow in dogs].

Pulsatile blood flow plays an important role in maintaining normal vascular endothelial function. Quantitative measurement of pulsatility of artery blood pressure and blood flow in dogs and effects of enhanced external counterpulsation (EECP) on the pulsatility were taken in this study. Common carotid artery blood pressure and blood flow were measured in 6 beagle dogs that had suffered from an acute myocardial infarction 6 weeks before. A 6F tip transducer catheter was inserted into the right common carotid artery to measure blood pressure, and blood flow was measured in the left common carotid artery by an electromagnetic blood flow probe under anesthesia before and during EECP. Blood pulse pressure, pulsatility index (ratio of peak pressure to end diastolic pressure) and standard deviation of blood pressure were calculated to evaluate the pulsatility of arterial blood pressure. Blood pulse flow, pulsatility index (ratio of peak flow to trough flow) and standard deviation of blood flow were calculated to evaluate the pulsatility of blood flow. Mean vascular resistance (MVR) was calculated as MVR = mean blood pressure/mean blood flow. Blood pulse pressure, pulsatility index and standard deviation of blood pressure were elevated from 30 +/- 9 mmHg, 1.26 +/- 0.05 and 8.7 +/- 2.5 mmHg to 43 +/- 8 mmHg (P < 0.05), 1.54 +/- 0.13 and 12.4 +/- 2.0 mmHg (P < 0.05) before and during EECP, respectively. Blood pulse flow, pulsatility index and standard deviation of blood flow were elevated from 317 +/- 48 ml/min, 2.85 +/- 0.21 and 96 +/- 21 ml/min to 447 +/- 88 ml/min, 4.56 +/- 0.90 and 131 +/- 39 ml/min before and during EECP (P < 0.05). MVR was decreased from 578 +/- 72 before EECP to 476 +/- 85 Wood units during EECP(P < 0.05). These data demonstrate that EECP gives an elevation of pulsatility to blood pressure and blood flow, thus it may lead to the decrease of vascular resistance.

Animals↗

PubMed2002

The influence of the intervertebral disc on stress distribution of the thoracolumbar vertebrae under destructive load.

OBJECTIVE: To compare the influence of normal and degenerative discs on stress distribution of the thoracolumbar vertebrae under destructive load, explore the biomechanical background and clinical meaning and provide theoretical basis for clinical diagnosis and treatment. METHODS: A mechanical model of thoracolumbar motion segment of normal and degenerative discs was built with a three dimensional finite element method and three stresses of vertical compression, compressive flexion and distractive flexion were comparatively analyzed. RESULTS: With vertical compression and compressive flexion loads, the thoracolumbar motion segment of the normal disc showed that the central part of the upper and lower end-plates of the vertebrae and the central part of the trabecular bone adjacent to the end-plate were loaded with the most intensive stresses, meanwhile, the postero-lateral part of the annulus fibrosus was concentrated with stresses. Degenerative disc showed that the stress distribution of the trabecular bone was relatively averaged, the stresses of the central part adjacent to the end-plate were low, while at the same time, the stresses of the peripheral part were elevated relatively. With distraction flexion load, the stresses of the cortex bone, trabecular bone, end-plate and annulus fibrosus of the thoracolumbar vertebrae of degenerative discs were low, meanwhile, the stresses of the posterior structure of the vertebral body were relatively elevated compared with that of normal discs. CONCLUSIONS: There is difference in influence between normal and degenerative discs on the stress distribution of the thoracolumbar vertebrae with destructive load. The transferring way of load is changed after disc degeneration.

Elasticity↗

PubMed2002

The study of biocompatibility of super high molecular weight poly D,L-lactic acid implant.

OBJECTIVE: To evaluate the biocompatibility of the super high molecular weight poly D,L-lactic acid (SHMW-PDLLA) implant. METHODS: The SHMW-PDLLA plates were implanted into the SD-rats between the masseter and ramus of the mandible. The blood specimens were gained at 3, 6, 9, 12 months after the operation. The proteins, electrolyte, enzyme and other indices were tested by use of Beckman automatic biochemical analysis device. The soft tissue specimens around the SHMW-PDLLA plates were gained at 3, 6, 9, 12 months after the operation and the tissue reaction was observed with the pathological and haematological methods. RESULTS: There were not any abnormal findings in the blood after the SHMW-PDLLA plates implanted in the body of SD-rats. The implanted SHMW-PDLLA plates were degraded gradually in 6 to 12 months after the operation. There was not any abnormal tissue reaction found to the soft tissue around the SHMW-PDLLA plates by histological and pathological observations. CONCLUSIONS: The SHMW-PDLLA implant has a good biocompatibility to SD-rats.

Animals↗

PubMed2002

[The changes of IL-1 and NO levels in the testes of rats with experimental varicocele].

OBJECTIVES: To evaluate the effects of varicocele (VC) on IL-1 and NO levels in testes of rats with VC. METHODS: Male adult Wistar rats were divided into two groups randomly, VC group (n = 30) and pseudo-operation group (n = 20), and the levels of IL-1 and NO in the testes were determined and compared. RESULTS: The levels of IL-1 and No of left tests in VC group were higher than those in pseudo-operation group, respectively(P < 0.01). While the levels of IL-1 and NO of right testes between two groups were not significantly different (P > 0.05). More over, the level of IL-1 correlated significantly with that of NO(r = 0.572, P < 0.01). CONCLUSIONS: The results revealed that the changes of IL-1 and NO levels in the testes of rats with VC might be the reason which caused testes damage, disturbance of spermatogenesis and even infertility.

Animals↗

PubMed2002

[Effects of external counterpulsation on the pulsatility of blood pressure in human subjects].

Pulsatile blood flow plays an important role in maintaining normal vascular endothelial function. Quantitative measurement of pulsatility of human arterial blood pressure and the influence of enhanced external counterpulsation (EECP) on the pulsatility were investigated in this study. Eight healthy young male volunteers aged 22 to 35 were included. A 4F tip transducer catheter was inserted under local anaesthesia into the radial artery up to the aortic arch. Intraarterial blood pressure was recorded before and during EECP. Blood pulse pressure, pulsatility index (ratio of peak pressure to end diastolic pressure) and standard deviation of blood pressure in 5 cardiac cycle was calculated to evaluate the pulsatility of arterial blood pressure. The results showed that blood pulse pressure, pulsatility index and standard deviation of blood pressure were elevated from 47 +/- 5 mmHg, 1.64 +/- 0.11 and 13.6 +/- 1.5 mmHg to 77 +/- 3 mmHg, 2.46 +/- 0.25 and 19.3 +/- 2.2 mmHg before and during EECP respectively (P < 0.05). Decreasing of systolic pressure and increasing of diastolic pressure during counterpulsation were also observed. EECP gives an elevation of pulsatility to human blood pressure.

Adult↗

PubMed2002

[A clinical study on immediate implantation of particulate hydroxylapatite artificial bone after teeth extraction].

OBJECTIVE: The aim of this study is to investigate the effect and complication of immediate implantation of particulate hydroxylapatite artificial bone after teeth extraction. METHODS: Particulate hydroxylapatite artificial bone was implanted into 65 extraction sockets after teeth extraction. All patients were followed up until 3 months after the operation. They are examined with clinical examination and X-ray examination to observe the effect and complication of the implantation operation. RESULTS: The wound healed well in all cases without any complication. Compared to the alveolar ridge before teeth extraction, and the height of the alveolar ridge after teeth extraction didn't decrease. CONCLUSION: Implantation of particulate hydroxylapatite artificial bone after teeth extraction could maintain the height of the alveolar ridge and reduce the complication of teeth extraction. It would be helpful for the following prosthetic restoration. The immediate implantation of artificial bone is therefore needed further study.

Adult↗

PubMed2002

[Experimental research on degradation and biocompatibility of super-high-molecular-weight poly-DL-lactic acid].

OBJECTIVE: The super-high-molecular-weight poly-DL-lactic acid (PDLLA), with the molecular weight of 900 kD, is a newly emerging biomaterial and potentially used in the therapy of bone fracture because of its excellent mechanical property. However the biocompatibility of this material has not been reported so far, therefore this experiment was designed to examine whether the super-high-molecular-weight PDLLA was harmful to creatures, when it was implanted in the body of animals for a long period. METHODS: The material was prepared in small cuboids, with the size of 1.0 mm x 1.5 mm x 2.0 mm, and these blocks were implanted into the masseteric space of SD rats and, the activity of the SD-rats was monitored continuously. The animals were sacrificed in the 3rd, 6th, 9th, 12th months after the operation and, the specimens were taken out from the animals. The examination included anatomical, pathological and haematological methods. The data were analyzed with SPSS 8.0. RESULTS: The wound healed well after the operation. Super-high-molecular-weight PDLLA degraded 6 months after the implantation. In the 3rd month after the operation, a thin fiber membrane around the materials was formed. In the 6th month, the membrane was much thinner than that in the 3rd month and completely disappeared in the 9th month. The pathological examination showed that slightly inflammatory reaction appeared in the tissue around these blocks in the 3rd month, but the inflammatory reactions were gradually remitted in the following 6th, 9th and 12th months. Further, the haematological examination did not show any abnormity during the 12-month observation period. CONCLUSION: The super-high-molecular-weight PDLLA can be degrade when it is implanted into the body of creatures, which proves its good biocompatibility.

Animals↗

PubMed2000

Comparison of stress distribution of thoracolumbar vertebrae under forces with CT value.

OBJECTIVE: To provide a new method to estimate t he effectiveness of thoracolumbar vertebral finite element model. METHODS: A mechanical model of human thoracolumbar vertebrae mo tion segment was made using three-dimensional finite element method and the str ess distribution of vertically compressed thoracolumbar vertebrae was analyzed, meanwhile, 20 patients with burst fracture of thoracolumbar vertebrae were t ested by CT to calculated average CT value at ascertained different points of th oracolumbar vertebrae. The calculated results and effective stress at the same p osition were analyzed with straight line correlation. RESULTS: The stress level of different position of thoracolumba r vertebrae under vertical compressive force was positively correlated with the correlative CT value, and the regressive style, Y=214.028+45.268X, r=0.7386, P<0.05 (n=8) showed a statistical significance. CONCLUSIONS: To study mechanism of thoracolumbar vertebrae in juries under different forces has clinical significance.

Journal Article↗

PubMed2000

Experimental study on early division of cross-finger pedicle flap and its clinical application.

OBJECTIVE: To observe the revascularization and the opportunity of cross-finger flap. METHODS: An animal model was developed to permit daily monit oring of neovascularization of the flap with autoradiography, tissue transparent technique, gross observation and histological examination. RESULTS: The revascularization of the flap was chiefly raised f rom the surrounding tissues. The pedicles of 334 cross-finger flaps of the pati ents were successfully divided from 1 to 5 d after operations, averagely 3. 3 d. All of the cases showed satisfatory results according to a follow-up sur vey of 3 to 72 mon. The results further proved that the revascularization of the cross-finger flaps had accomplished within 3 d. CONCLUSIONS: It suggests that the division of a cross-finger f lap can be carried out between the 3rd and 5th day after operation with a high d egree of safety.

Journal Article↗

PubMedDate not supplied

The nonpolar resonance effects and the non-Hammett behaviors.

In the study we tried to unify the observed non-Hammett behaviors in various fields by proposing the nonpolar resonance effect. This effect was shown to be important not only for carbon radicals but also for some closed-shell systems. Therefore, the odd electron or spin is not the essential cause of the effect. The real origin of the non-Hammett effect should be the HOMO(reaction-center)-LUMO(acceptor) and LUMO(reaction-center)-HOMO(donor) interactions. This means that the nonpolar resonance effect is a universal effect. However, we found that the nonpolar resonance effect could not be well exhibited in many systems because of the serious competition from the polar Hammett effect. Finally, we showed that our proposal of the nonpolar resonance effect was valuable from a practical point of view, because using it we could perform much better correlation studies on some "tough" problems such as radical and multiple bond stabilities, UV and IR spectra, and molecular structures.

Journal Article↗

PubMedDate not supplied

Assessment of experimental bond dissociation energies using composite ab initio methods and evaluation of the performances of density functional methods in the calculation of bond dissociation energies.

Composite ab initio CBS-Q and G3 methods were used to calculate the bond dissociation energies (BDEs) of over 200 compounds listed in CRC Handbook of Chemistry and Physics (2002 ed.). It was found that these two methods agree with each other excellently in the calculation of BDEs, and they can predict BDEs within 10 kJ/mol of the experimental values. Using these two methods, it was found that among the examined compounds 161 experimental BDEs are valid because the standard deviation between the experimental and theoretical values for them is only 8.6 kJ/mol. Nevertheless, 40 BDEs listed in the Handbook may be highly inaccurate as the experimental and theoretical values for them differ by over 20 kJ/mol. Furthermore, 11 BDEs listed in the Handbook may be seriously flawed as the experimental and theoretical values for them differ by over 40 kJ/mol. Using the 161 cautiously validated experimental BDEs, we then assessed the performances of the standard density functional (DFT) methods including B3LYP, B3P86, B3PW91, and BH&HLYP in the calculation of BDEs. It was found that the BH&HLYP method performed poorly for the BDE calculations. B3LYP, B3P86, and B3PW91, however, performed reasonably well for the calculation of BDEs with standard deviations of about 12.1-18.0 kJ/mol. Nonetheless, all the DFT methods underestimated the BDEs by 4-17 kJ/mol in average. Sometimes, the underestimation by the DFT methods could be as high as 40-60 kJ/mol. Therefore, the DFT methods were more reliable for relative BDE calculations than for absolute BDE calculations. Finally, it was observed that the basis set effects on the BDEs calculated by the DFT methods were usually small except for the heteroatom-hydrogen BDEs.

Journal Article↗

PubMedDate not supplied

Hammett equation and generalized Pauling's electronegativity equation.

Substituent interaction energy (SIE) was defined as the energy change of the isodesmic reaction X-spacer-Y + H-spacer-H --> X-spacer-H + H-spacer-Y. It was found that this SIE followed a simple equation, SIE(X,Y) = -ksigma(X)sigma(Y), where k was a constant dependent on the system and sigma was a certain scale of electronic substituent constant. It was demonstrated that the equation was applicable to disubstituted bicyclo[2.2.2]octanes, benzenes, ethylenes, butadienes, and hexatrienes. It was also demonstrated that Hammett's equation was a derivative form of the above equation. Furthermore, it was found that when spacer = nil the above equation was mathematically the same as Pauling's electronegativity equation. Thus it was shown that Hammett's equation was a derivative form of the generalized Pauling's electronegativity equation and that a generalized Pauling's electronegativity equation could be utilized for diverse X-spacer-Y systems. In addition, the total electronic substituent effects were successfully separated into field/inductive and resonance effects in the equation SIE(X,Y) = -k(1)F(X)F(Y) - k(2)R(X)R(Y) - k(3)(F(X)R(Y) + R(X)F(Y)). The existence of the cross term (i.e., F(X)R(Y) and R(X)F(Y)) suggested that the field/inductive effect was not orthogonal to the resonance effect because the field/inductive effect from one substituent interacted with the resonance effect from the other. Further studies on multi-substituted systems suggested that the electronic substituent effects should be pairwise and additive. Hence, the SIE in a multi-substituted system could be described using the equation SIE(X1, X2, ..., Xn) = Sigma(n-1)(i=1)Sigma(n)(j=i+1)k(ij)sigma(X)isigma(X)j.

Journal Article↗

PubMedDate not supplied

The longitudinal chronic kidney disease study: a prospective cohort study of predialysis renal failure.

Chronic kidney disease (CKD) is a significant public health problem: every year the number of Americans living with CKD and requiring renal replacement therapy increases. In addition, individuals with CKD have substantially increased morbidity and mortality compared to the general population. The Longitudinal Chronic Kidney Dialysis (LCKD) Study is a multicenter, prospective, observational study of patients with moderate to severe CKD that was designed to better describe the course of the disease and the determinants of patient outcomes. Patients with moderate to severe CKD (glomerular filtration rate [GFR] < 60 ml/min/m2) from four academic nephrology clinics were enrolled between 2000 and 2002. Special cardiac and vascular testing has recently commenced as phase II of this study. Areas that have been or are currently being studied include anemia management, health-related quality of life (HRQOL), medication use, and markers of cardiovascular disease. This article describes the LCKD Study in the context of current knowledge of CKD.

Anemia↗

PubMedDate not supplied

Molecular and cellular characterization during chondrogenic differentiation of adipose tissue-derived stromal cells in vitro and cartilage formation in vivo.

Human adipose tissue is a viable source of mesenchymal stem cells (MSCs) with wide differentiation potential for musculoskeletal tissue engineering research. The stem cell population, termed processed lipoaspirate (PLA) cells, can be isolated from human lipoaspirates and expanded in vitro easily. This study was to determine molecular and cellular characterization of PLA cells during chondrogenic differentiation in vitro and cartilage formation in vivo. When cultured in vitro with chondrogenic medium as monolayers in high density, they could be induced toward the chondrogenic lineages. To determine their ability of cartilage formation in vivo, the induced cells in alginate gel were implanted in nude mice subcutaneously for up to 20 weeks. Histological and immunohistochemical analysis of the induced cells and retrieved specimens from nude mice at various intervals showed obviously cartilaginous phenotype with positive staining of specific extracellular matrix (ECM). Correlatively, results of RT-PCR and Western Blot confirmed the expression of characteristic molecules during chondrogenic differentiation namely collagen type II, SOX9, cartilage oligomeric protein (COMP) and the cartilage-specific proteoglycan aggrecan. Meanwhile, there was low level synthesis of collagen type X and decreasing production of collagen type I during induction in vitro and formation of cartilaginous tissue in vivo. These cells induced to form engineered cartilage can maintain the stable phenotype and indicate no sign of hypertrophy in 20 weeks in vivo, however, when they cultured as monolayers, they showed prehypertrophic alteration in late stage about 10 weeks after induction. Therefore, it is suggested that human adipose tissue may represent a novel plentiful source of multipotential stem cells capable of undergoing chondrogenesis and forming engineered cartilage.

Adipose Tissue↗

PubMedDate not supplied

Erianin induces a JNK/SAPK-dependent metabolic inhibition in human umbilical vein endothelial cells.

BACKGROUND: Erianin is a natural product derived from Dendrobium chrysotoxum, with promising antitumor activity. MATERIALS AND METHODS: To evaluate the metabolic effect of erianin, a cytosensor assay for acidification rate, MTT assay, measurement of lactate, glucose and ATP were performed in human umbilical vein endothelial cells (HUVECs) exposed to 1-100 nM erianin. JNK/SAPK activity was detected by Western blot. RESULTS: Twelve- or 24- hour incubation with erianin induced a dose-dependent metabolic inhibition, as indicated by reduced acidification rate and cell viability, with an endothelium-selectivity. Erianin caused decreases in lactate production, glucose consumption and intracellular ATP level. Pretreatment with the JNK/SAPK inhibitor SP600125 significantly abolished these inhibitory responses, and especially restored the erianin-induced decreases in ATP and the erianin-induced phosphorylation of JNK/SAPK with dose- and time- dependence. CONCLUSION: Erianin inhibited endothelial metabolism in a JNK/SAPK-dependent manner. This mechanism may be involved in the potential antitumnor and antiangiogenic actions of erianin.

Adenosine Triphosphate↗