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Biomedical subjects

D Feng

Publications and source records attributed to D Feng.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Clinical applications of the anterolateral skin flap and the fascial flap in the lower leg].

OBJECTIVE: To introduce the applied anatomy, operative method and clinical application of the anterolateral skin flap and fascial flap of the lower leg. METHODS: Anatomic dissection was performed on 14 adult cadavers' legs and one amputated lower limb. The origin, course and distribution of cutaneous branches of the superficial peroneal vessels were traced. Four types of anterolateral flaps were designed in the lower leg including the island skin flap, the island fascial flap, the rectangular flap, and the cross-leg flap. Since 1988, twenty-six cases of leg defects(21 patients), chronic osteomyelitis of the tibia(3 cases) and defects on the back of the opposite heel and ankle(2 cases) were treated with the operative methods. RESULTS: All the flaps survived. Primary healing occurred in 23 and secondary in 3 cases. Twenty cases were followed-up for 4 months to 5 years. The flaps were growing well, the tibia fracture healed 3 months after the treatment and the chronic osteomyelitis of tibia had no recurrence. CONCLUSION: This flap is a useful method for repairing various defects in the leg and adjacent regions. It is simple, safe and reliable in manipulation and has minimal influence to the donor site.

Adolescent↗
PubMed1999

[Association of polymorphisms of apolipoprotein B gene with cholesterol gallstone disease].

OBJECTIVE: To investigate the association between the apolipoprotein B (apoB) gene polymorphic sites Ins/Del and Xbal, and cholesterol gallstone disease. METHODS: The two polymorphic sites of apoB gene were examed in 101 cholesterol gallstone patients and 50 controls by polymerase chain reaction and restriction fragment length polymorphism methods. RESULTS: For Xbal polymorphic site, the frequency of the rare allele X+ and the distribution of X+X- genotype were significantly higher in the patient group than in the control group (P < 0.05). For Ins/Del polymorphic site, no significant difference was found in allele frequency and genotype distribution between the patient group and the control group. CONCLUSIONS: Xba1 polymorphism of apoB gene may be associated with cholesterol gallstone disease. The association, however, is not present for Ins/De1 polymorphism of apoB gene with cholesterol gallstone disease.

Adult↗
PubMed1999

[Changes on positive rate and distribution of Helicobacter pylori during progression of gastric cancer].

We observed changes on the positive rate and the distribution of helicobacter pylori (HP) in 7 case during early stage of gastric cancer and in 42 cases during middle-late stage of gastric cancer. The results showed that 1. the positive rate during early stage of gastric cancer was 57.1%, the positive rate during middle-rate stage of gastric cancer was 23.8%, 2. HP was not found within the gastric cancer lesions, 3. for HP positive cases, HP distribution during early stage of gastric cancer was more sparse than during middle-late stage of gastric cancer. These results suggested that HP can hardly live within the gastric cancer tissue, so the progression of gastric cancer is probably independent of HP. It may be a question that HP eradication can prevent later development of gastric cancer.

Adenocarcinoma↗
PubMed1999

[Regulation of p53 and bcl-2 proteins to apoptosis and cell proliferation in liver cirrhosis and hepatocellular carcinoma].

In situ apoptosis labelling was used for detecting apoptotic cells, and immunohistochemistry for p53, bcl-2 proteins and proliferation cell nuclear antigen(PCNA) in hepatocellular carcinoma(HCC) and liver cirrhosis tissues. The results were that in HCC, the number of apoptotic cells was higher, the density of proliferation cells lower, and expressions of p53 and bcl-2 protein were stronger than that in liver cirrhosis, and they were related to differentiation degree of HCC. The data indicate that overexpression of bcl-2 and mutant p53 proteins, which causes imbalance between cell proliferation and apoptosis, may bring about genesis and development of HCC by selecting proliferation of cells.

Adult↗
PubMed1999

[Observation of apoptosis and proliferation in nasopharyngeal carcinoma].

In order to observe the apoptosis and proliferation of cells in nasopharyngeal carcinoma(NPC) and pericarcinomatous tissue(PCT), 49 cases of NPC and partly PCT were detected by in situ end-labelling (ISEL) technique and proliferating cell nuclear antigen(PCNA) immunohistochemical staining. The results showed that: 1. Massive distribution of ISEL positive cells was frequently exhibited in vesicular nucleus cell carcinoma(VNCC) of NPC, in which no apoptotic pattern character was found. 2. The positive rate and the staining intensity index(SII) of ISEL signals in NPC were higher than that in PCT(P < 0.05); the positive correlation between ISEL SII and PCNA SII was found in NPC(r = 0.341, P < 0.05), whereas the positive rate and the SII of ISEL signals were significantly lower than that of PCNA (P < 0.01). 3. The ISEL SII and the PCNA SII in VNCC were obviously higher than that in poorly differentiated squamous cell carcinoma(PDSCC) (P < 0.01, P < 0.05). Patients with VNCC had a high five-year survival rate. The results suggest that there is a relationship between cellular proliferation and cellular apoptosis in NPC.

Apoptosis↗
PubMed1999

[Apoptosis of CD4(+) T cells during experimental autoimmune neuritis in Wistar rats].

The present study describes apoptosis of T cells in the sciatic nerve in Wistar rats with experimental autoimmune neuritis(EAN). Morphological characterizations of apoptosis were found at the 18th day from onset, peaked at the 22nd day by immunocytochemical analysis. In situ end labeling(ISEL) techniques confirmed the presence of DNA fragmentation in CD4(+) T cells. It is suggested that apoptosis is an important clearance mechanism of infiltrated T cells in the peripheral nervous system(PNS) in EAN.

Animals↗
PubMed1998

Neutrophils emigrate from venules by a transendothelial cell pathway in response to FMLP.

Circulating leukocytes are thought to extravasate from venules through open interendothelial junctions. To test this paradigm, we injected N-formyl-methionyl-leucyl-phenylalanine (FMLP) intradermally in guinea pigs, harvesting tissue at 5-60 min. At FMLP-injected sites, venular endothelium developed increased surface wrinkling and variation in thickness. Marginating neutrophils formed contacts with endothelial cells and with other neutrophils, sometimes forming chains of linked leukocytes. Adherent neutrophils projected cytoplasmic processes into the underlying endothelium, especially at points of endothelial thinning. To determine the pathway by which neutrophils transmigrated endothelium, we prepared 27 sets of serial electron microscopic sections. Eleven of these encompassed in their entirety openings through which individual neutrophils traversed venular endothelium; in 10 of the 11 sets, neutrophils followed an entirely transendothelial cell course unrelated to interendothelial junctions, findings that were confirmed by computer-assisted three-dimensional reconstructions. Having crossed endothelium, neutrophils often paused before crossing the basal lamina and underlying pericytes that they also commonly traversed by a transcellular pathway. Thus, in response to FMLP, neutrophils emigrated from cutaneous venules by a transcellular route through both endothelial cells and pericytes. It remains to be determined whether these results can be extended to other inflammatory cells or stimuli or to other vascular beds.

Animals↗
PubMed1998

New method for the analysis of multiple positron emission tomography dynamic datasets: an example applied to the estimation of the cerebral metabolic rate of oxygen.

Positron emission tomography (PET) provides the ability to extract useful quantitative information not available through other radiological techniques. In certain studies, the physiological parameters of interest cannot be determined from the data obtained from a single PET experiment alone. In this case, multiple experiments are required. At present, the methods used to analyse measurements acquired from multiple experiments often involve considering them separately during the modelling procedures. These methods of analysis may cause errors to be propagated through successive modelling procedures and do not fully utilise the information content provided by the PET measurements. A new method is presented, based on linear least squares for the analysis of PET dynamic data acquired from multiple experiments. This method simultaneously considers the complete set of measurements obtained and provides reliable parameter estimates. The efficient use of the information content provided by multiple experiments is considered and the propagation of errors is discussed. To facilitate our discussion, we apply this new method to the estimation of the cerebral metabolic rate of oxygen and the parameters of the oxygen utilisation model as a practical example. The results demonstrate a significant improvement in the reliability and estimation accuracy of the estimates for this new method. Furthermore, this method reduced the likelihood of errors being propagated. Therefore, the proposed method is suitable for the analysis of multiple PET dynamic datasets.

Brain↗
PubMed1998

Estimation of myocardial glucose utilisation with PET using the left ventricular time-activity curve as a non-invasive input function.

The validation study is described of a new modelling method that has been developed, using tracer kinetic modelling with positron emission tomography (PET) to achieve non-invasive measurement of myocardial metabolic rate of glucose (MMRGlc). Eight data sets obtained from dynamic cardiac PET 2-[18F]fluoro-2-deoxy-D-glucose (FDG) studies on human subjects are employed, and the estimation of MMRGlc using both the new and traditional methods is compared. The results from all eight human FDG studies are consistent with those from previous computer simulations. With the new method, the estimated mean of K (a parameter directly proportional to MMRGlc) increases by about 8%, and that of k 4 (the rate constant of FDG dephosphorylation) decreases by about 48%. The approach should be more suitable for use in dynamic cardiac PET studies when non-invasive means are used to obtain the plasma time-activity curve from left-ventricle PET images.

Computational Biology↗
PubMed1998

Generalized linear least squares algorithm for non-uniformly sampled biomedical system identification with possible repeated eigenvalues.

The recently developed generalized linear least squares (GLLS) algorithm has been found very useful in non-uniformly sampled biomedical signal processing and parameter estimation. However, the current version of the algorithm cannot deal with signals and systems containing repeated eigenvalues. In this paper, we extend the algorithm, so that it can be used for non-uniformly sampled signals and systems with/without repeated eigenvalues. The related theory and detailed derivation of the algorithm are given. A case study is presented, which demonstrates that the extended algorithm can provide more choices for system identification and is able to select the most suitable model for the system from the non-uniformly sampled noisy signal.

Algorithms↗
PubMed1998

Noninvasive quantification of the cerebral metabolic rate for glucose using positron emission tomography, 18F-fluoro-2-deoxyglucose, the Patlak method, and an image-derived input function.

The authors developed and tested a method for the noninvasive quantification of the cerebral metabolic rate for glucose (CMRglc) using positron emission tomography (PET), 18F-fluoro-2-deoxyglucose, the Patlak method, and an image-derived input function. Dynamic PET data acquired 12 to 48 seconds after rapid tracer injection were summed to identify carotid artery regions of interest (ROIs). The input function then was generated from the carotid artery ROIs. To correct spillover, the early summed image was superimposed over the last PET frame, a tissue ROI was drawn around the carotid arteries, and a tissue time activity curve (TAC) was generated. Three venous samples were drawn from the tracer injection site at a later time and used for the spillover and partial volume correction by non-negative least squares method. Twenty-six patient data sets were studied. It was found that the image-derived input function was comparable in shape and magnitude to the one obtained by arterial blood sampling. Moreover, no significant difference was found between CMRglc estimated by the Patlak method using either the arterial blood sampling data or the image-derived input function.

Brain↗
PubMed1998

Generalized linear least squares method for fast generation of myocardial blood flow parametric images with N-13 ammonia PET.

In this paper, we developed and tested strategies for estimating myocardial blood flow (MBF) and generating MBF parametric images using positron emission tomography (PET), N-13 ammonia, and the generalized linear least square (GLLS) method. GLLS was generalized to the general linear compartment model, modified for the correction of spillover, validated using simulated N-13 ammonia data, and examined using PET data from several patient studies. In comparison to the standard model-fitting procedure, the GLLS method provided similar accuracy and superior computational speed.

Aged↗
PubMed1998

Optimized acquisition time and image sampling for dynamic SPECT of Tl-201.

With the recent development in scatter and attenuation correction algorithms, dynamic single photon emission computerized tomography (SPECT) can potentially yield physiological parameters, with tracers exhibiting suitable kinetics such as thallium-201 (Tl-201). A systematic way is proposed to investigate the minimum data acquisition times and sampling requirements for estimating physiological parameters with quantitative dynamic SPECT. Two different sampling schemes were investigated with Monte Carlo simulations: 1) Continuous data collection for total study duration ranging from 30-240 min. 2) Continuous data collection for first 10-45 min followed by a delayed study at approximately 3 h. Tissue time activity curves with realistic noise were generated from a mean plasma time activity curve and rate constants (K1 - k4) derived from Tl-201 kinetic studies in 16 dogs. Full dynamic sampling schedules (DynSS) were compared to optimum sampling schedules (OSS). We found that OSS can reliably estimate the blood flow related K1 and Vd comparable to DynSS. A 30-min continuous collection was sufficient if only K1 was of interest. A split session schedule of a 30-min dynamic followed by a static study at 3 h allowed reliable estimation of both K1 and Vd avoiding the need for a prolonged (>60-min) continuous dynamic acquisition. The methodology developed should also be applicable to optimizing sampling schedules for other SPECT tracers.

Animals↗
PubMed1998

Dynamic imaging and tracer kinetic modeling for emission tomography using rotating detectors.

When performing dynamic studies using emission tomography the tracer distribution changes during acquisition of a single set of projections. This is particularly true for some positron emission tomography (PET) systems which, like single photon emission computed tomography (SPECT), acquire data over a limited angle at any time, with full projections obtained by rotation of the detectors. In this paper, an approach is proposed for processing data from these systems, applicable to either PET or SPECT. A method of interpolation, based on overlapped parabolas, is used to obtain an estimate of the total counts in each pixel of the projections for each required frame-interval, which is the total time to acquire a single complete set of projections necessary for reconstruction. The resultant projections are reconstructed using traditional filtered backprojection (FBP) and tracer kinetic parameters are estimated using a method which relies on counts integrated over the frame-interval rather than instantaneous values. Simulated data were used to illustrate the technique's capabilities with noise levels typical of those encountered in either PET or SPECT. Dynamic datasets were constructed, based on kinetic parameters for fluoro-deoxy-glucose (FDG) and use of either a full ring detector or rotating detector acquisition. For the rotating detector, use of the interpolation scheme provided reconstructed dynamic images with reduced artefacts compared to unprocessed data or use of linear interpolation. Estimates for the metabolic rate of glucose had similar bias to those obtained from a full ring detector.

Algorithms↗
PubMed1998

Platelets exit venules by a transcellular pathway at sites of F-met peptide-induced acute inflammation in guinea pigs.

Platelets maintain the integrity of vascular endothelium, but also appear outside of blood vessels in pathological states such as acute inflammation. However, it is widely believed that platelets extravasate from blood vessels only as the result of endothelial injury and that, on contacting extravascular collagen, they undergo a morphologically defined activation sequence and release their granule contents. We here report that platelets may cross intact venular endothelium without exhibiting this release reaction or injury. Platelets became adherent to the luminal surface of venular endothelium within approximately 15 min of intradermal injection of 10(-5) M N-formyl-methionyl-leucyl-phenylalanine in guinea pig flank skin. Individual intact platelets were noted in large endothelial cell cytoplasmic vacuoles from which they subsequently migrated abluminally. They then crossed the vascular basal lamina and entered the dermis without exhibiting evidence of a release reaction. Serial electron-microscopic sections confirmed that the cytoplasmic vacuoles within which platelets crossed endothelial cells were independent of interendothelial cell junctions which remained normally closed. Platelets extended pseudopods and gave other evidence of cell motility. These findings require a paradigm shift in our thinking about platelet movement and functions.

Animals↗
PubMed1998

[Genotype distribution of hepatitis C virus in hepatocellular carcinoma tissue in Hunan province].

Genotypes of hepatitis C virus(HCV) were detected by PCR using type-specific primer in 50 patients' hepatocellular carcinoma(HCC) tissue. The results showed that in the 50 HCC specimens, 30(60%) and 3(6%) were infected with the HCV type II and III, 5(10%) and 8(16%) with type II + III and type II + IV, 2(4%) with type II + I + III in combination, respectively. 2 cases were negative for HCV. These data suggest that HCV type II may be a predominant genotype related to hepatocarcinogenesis in Hunan Province, some cases of HCC may result from coinfection of HCV type II and other genotypes, and only few HCC be separately caused by infection of HCV type III.

Adult↗
PubMed1998

[Study on relationship between apoptosis and proliferation of cells in liver cirrhosis and hepatocellular carcinoma].

Apoptosis and nuclear antigen of proliferating cells were detected by labelling technique of in situ terminal deoxynucleotide transferase and immunohistochemical method in liver cirrhosis and hepatocellular carcinoma(HCC). The density of apoptotic cells in HCC was significantly lower than that in cirrhosis, and the density of proliferating cells was much higher in HCC than that in cirrhosis. Apoptotic cells mainly distributed in the peripseudolobular region of cirrhosis and formed an apoptosis zone. But they scattered within the cancer tissue. The results suggest that the formation of apoptosis zone in cirrhosis may be related to the change of liver blood stream. Selective proliferation of cells may exist during carcinogenesis of liver cirrhosis.

Adult↗