Biomedical subjects

G R Liu

Publications and source records attributed to G R Liu.

12 recordsLinked to original sources

PubMed2007

Prediction of recovery from a post-traumatic coma state by diffusion-weighted imaging (DWI) in patients with diffuse axonal injury.

INTRODUCTION: To determine whether diffusion-weighted magnetic resonance (MR) imaging findings combined with initial clinical factors indicate the depth of shearing lesions in the brain structure and therefore relate to coma duration in diffuse axonal injury (DAI). METHODS: A total of 74 adult patients (48 male and 26 female) with DAI were examined with conventional MR imaging and diffusion-weighted MR imaging between 2 hours and 20 days after injury. Apparent diffusion coefficient (ADC) maps were obtained and the mean ADC values of each region of interest (ROI) were measured using MRI console software. The involvement of the brainstem, deep gray matter, and corpus callosum was determined for each sequence separately as well as for the combination of all sequences. The correlations between MR imaging findings indicating the presence of apparent brain injury combined with initial clinical factors were determined. RESULTS: Clinical characteristics, such as initial score on the Glasgow coma scale (GCS), age and number of all lesions, and ADC scores were predictive of the duration of coma. CONCLUSION: It was possible to predict post-traumatic coma duration in DAI from cerebral MR imaging findings combined with clinical prognostic factors in the acute to subacute stage after head injury. Age, ADC scores, GCS score and number of lesions were highly significant in predicting coma duration. The technique presented here might provide a tool for in vivo detection of DAI to allow the prediction of the coma duration during the early stages in patients with traumatic brain injury.

Accidents, Traffic↗

PubMed2005

Relationships between the folding rate constant and the topological parameters of small two-state proteins based on general random walk model.

In this paper, we propose an analytically tractable model of protein folding based on one-dimensional general random walk. A second-order differential equation for the mean folding time of a single protein is constructed which can be used to derive the observed relationship between the folding rate constant and the number of native contacts. The parameters appearing in the model can be determined by fitting the theoretical prediction to the experimental result. In addition, taking into account the fact that the number of native contacts is almost proportional to the relative contact order, we can also explain the observed relationship between the folding rate constant and the relative contact order.

Animals↗

PubMed2005

Early diffusion weighted imaging and expression of heat shock protein 70 in newborn pigs with hypoxic ischaemic encephalopathy.

OBJECTIVE: To establish a cerebral hypoxia ischaemic model in piglets and to explore the early diffusion weighted imaging (DWI) as well as the expression of heat shock protein 70 (HSP70) with hypoxic ischaemic encephalopathy (HIE). METHODS: Twenty four 3 day old piglets were permanently ligated common carotid arteries bilaterally and ventilated with 3% oxygen for 30 minutes, and their brains were examined at three hours, six hours, and 24 hours after hypoxic ischaemia with T2 weighted images and diffusion weighted images. Apparent diffusion coefficient (ADC) values were measured and HSP70 expression was detected in the central and peripheral regions of lesions. RESULTS: Abnormal signal intensity was detected on DWI and ADC maps in three hypoxic ischaemic groups. ADC values in the central lesions rapidly decreased, whereas ADC values in the peripheral regions reduced prominently at 24 hours after hypoxic ischaemia. There were significant differences (p<0.01) between ADC values of the central regions and the peripheral regions of lesions. The number of HSP70 positive cells was low at three hours, raised at the highest peak at six hours, and then rapidly decreased. There was statistical difference between HSP70 positive cells in the central regions and those in peripheral regions (p<0.01). CONCLUSION: DWI may identify more early lesions, and improve conspicuity in the acute setting. ADC values can be used as an objective measure for hypoxic ischaemic injury. Tissue reversibility can be further reflected according to the information of ADC values and HSP70 immunohistochemical staining.

Animals↗

PubMed2004

Protein designability analysis in sequence principal component space using 2D lattice model.

The number of proteins that fold into a certain structure differs drastically. The designability of a protein structure, which is defined as the number of sequences that have that structure as their unique lowest energy state, is studied in this paper using a simplified lattice model. The two-letter (HP) code and the pair-contact energy model are employed in the formulation of the relationship between the protein sequences and the compact structures. Due to the correlations between different dimensions, principal component analysis (PCA) is carried out to remove these correlations and develop reliable approximations of probability density functions of the protein sequences and the compact structures. An estimation of designability is derived using these probability density functions. Good correlation between estimated designabilities and those obtained through enumerative calculations is successfully achieved.

Algorithms↗

PubMed2004

Finite element analysis of four thread-form configurations in a stepped screw implant.

The purpose of this study was to determine the optimal thread form configuration for an experimental stepped screw implant. Two-dimensional finite element analysis was applied to model the experimental stepped screw implant in a standard cross-section of the posterior human mandible digitized from a CT-generated patient data set. Four different thread form configurations: v-thread (V), thin-thread (T), and two square-thread forms of 0.24 mm (S1) and 0.36 mm (S2) thread width were compared under oblique load in normal cortical bone condition. The support-type constraint position changed from middle to the base of the bone segment. In middle support-type constraint position only the thin-thread (T) model demonstrated significantly different stress distribution from the other three models, however, in base support-type constraint position T and S1 models demonstrated significantly different stress distribution from the other two models. The results implies that v-thread (V) or large square-thread (S2) are optimal thread form for the experimental stepped screw implant. While, minimal support constraints allow clearer differentiation of the stress picture between the different stepped screw types at the trabecular bone-implant interface.

Bone Screws↗

PubMed2004

Finite element analysis of an osseointegrated stepped screw dental implant.

An osseointegrated stepped screw dental implant was evaluated using 2-dimensional finite element analysis (FEA). The implant was modeled in a cross section of the posterior human mandible digitized from a computed tomography (CT) generated patient data set. A 15-mm regular platform (RP) Branemark implant with equivalent length and neck diameter was used as a control. The study was performed under a number of clinically relevant parameters: loading at the top of the transmucosal abutment in vertical, horizontal, and 45 degrees oblique 3 orientations. Elastic moduli of the mandible varied from a normal cortical bone level (13.4 GPa) to a trabecular bone level (1.37 GPa). The study indicated that an oblique load and elastic moduli of the cortical bone are important parameters to the implant design optimization. Compared with the cylindrical screw implant, the maximum von Mises stress of the stepped screw implant model was 17.9% lower in the trabecular bone-implant area. The study also showed that the stepped screw implant is suitable for the cortical bone modulus from 10 to 13.4 GPa, which is not necessarily as strict as the Branemark implant, for which a minimum 13.4 GPa cortical bone modulus is recommended.

Biomechanical Phenomena↗

PubMed2003

Shape identification of underwater objects using backscattered frequency signals.

The inverse problems in the area of the acoustic scattering often concern the determination of the size, shape, and orientation of an object using the scattered field data. This paper presents a method to retrieve the shape information of an underwater object using illuminated lengths, which can be obtained from the ramp response signatures of the object. An ellipsoidal object submerged in water is considered. Both the low and high backscattered frequency data have been employed to calculate the illuminated lengths. The calculated results show that the illuminated lengths will be more accurate, if only the high-frequency-range data are employed. For ellipsoidal objects, any three illuminated lengths that are not of a same plane can in theory fully determine the shape of the ellipsoid. As the calculated illuminated lengths contain numerical errors, the calculated results of the three semiaxes of the ellipsoid will deteriorate and become unreliable, especially when the three incident directions of the illuminated lengths become close. The reason is that the condition number of the coefficient matrix becomes big in such situations, which leads to an increase of the relative error upper limit in the calculated results. To avoid such errors in close incident wave cases, it is found that the use of more than three incident waves works very well in the shape identification of an underwater object.

Journal Article↗

PubMed2001

Application of finite element analysis in implant dentistry: a review of the literature.

Finite element analysis (FEA) has been used extensively to predict the biomechanical performance of various dental implant designs as well as the effect of clinical factors on implant success. By understanding the basic theory, method, application, and limitations of FEA in implant dentistry, the clinician will be better equipped to interpret results of FEA studies and extrapolate these results to clinical situations. This article reviews the current status of FEA applications in implant dentistry and discusses findings from FEA studies in relation to the bone-implant interface, the implant-prosthesis connection, and multiple-implant prostheses.

Biomechanical Phenomena↗

PubMed1997

An investigation of adolescent health from China.

In a senior high school in the Weicheng District of Weifang City, we studied the health of a total 445 students. The age of the first emission was 15.22 +/- 2.24 years, and the age of menarche was 13.56 +/- 2.26 years. Because 47.9% of boys and 63.8% of girls did not have previous knowledge about puberty, 39.9% of boys and 52.2% of girls felt puzzled and disgusted with the onset of puberty. About 18% of boys and about 2% of girls reported masturbation. The average frequency of masturbation was 3.5 times a month in the boys and two times monthly in girls. Adolescents acquired sexual knowledge and information predominantly from magazines (25.8% of boys and 28.0% of girls). About 64% of boys and 44% of girls wanted to be given educational programs on sex. About 43% of boys and 1% of girls smoked cigarettes and 83.5% of boys and 54.9% of girls drank alcohol. The survey suggested that it is essential to teach the senior high school students about the psychosocial and behavioral characteristics of adolescence and promote research on adolescent medicine.

Adolescent↗

PubMed1994

[Lipid metabolism and pregnancy induced hypertension].

Lipid metabolism was studied in 30 healthy non-pregnant women, 35 normal pregnant women and 34 patients with pregnancy induced hypertension (PIH). Total cholesterol (TC), triglycerides (TG), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), LDL-C/HDL-C ratio, and athero-sclerosis index (AI) were determined. In comparison with the non-pregnant status, lipid levels did not increased during normal mid-trimester pregnancy, but significantly increased at late trimester of normal pregnancy (P < 0.05). There was no significant difference in lipid levels between normal late pregnancy and PIH of mild and moderate degree, but TG and AI were significantly higher in cases with severe PIH. It showed that: lipid profiles in severe PIH was characterized by type IV hyperlipidemia; high lipid levels during normal late pregnancy might be a physiological phenomenon which presents a risk factor for PIH; marked increase of TG and AI in severe PIH may result in a rise of lipid peroxide (LPO).

Adult↗

PubMed1993

[Experimental method and clinical significance of hidden rheumatoid factors].

Hidden rheumatoid factor (HRF) was detected in rheumatoid arthritis (RA) serum with ELISA after separation and dissociation of immune complex (IC). It was found that 60% of the patients with active RA has positive latex fixation test, whereas 96% of them has been demonstrated to have IgM hidden rheumatoid factor (HIgMRF) and 70% of them IgG hidden rheumatoid factor (HIgGRF). When the disease was controlled, HIgMRF and HIgGRF was found in 24% and 12% respectively. The difference was significant with P < 0.01. Our results show that the presence of HRF in RA patients is related with the activity of the disease, but not with duration of disease, sex and age.

Adult↗

PubMed1993

[Cytotoxicity of human lymphokine-activated killer cells against mitotic phase tumor cells].

To improve LAK/IL-2 efficiency in tumor immunotherapy, the cytotoxicity of human LAK cells against mitotic phase of human lung adenocarcinomas Anip 973 cells was studied in vitro. Anip 973 cells were synchronized by the specific mitotic phase antitumor drug vincristine (VCR). The differences in morphology between mitotic tumor cells and normal tumor cells were observed by light microscopy and transmission electronmicroscopy. The cytotoxicity of human LAK cells against mitotic phase Anip973 cells was significantly increased in standard 4-hour 51Cr release assay. In scanning and transmission electronmicroscopies, LAK cells were in close contact with target cells in the form of interdigitate of microvilli and protrusions structure. The form of death of mitotic phase tumor cells was lytic necrosis and apoptosis.

Adenocarcinoma↗