PubMed Health⌕ Search

Biomedical subjects

Z L Li

Publications and source records attributed to Z L Li.

At least 37 records · Page 2Linked to original sources
PubMed2000

[Prediction and estimation on molar response values of alkanes by using molecular path vector].

A new method based on a novel molecular topological index vector, called the molecular path vector (MPV), of alkane molecules is proposed and employed for estimation and prediction of the molar response values of various alkanes. The novel MPV, p = (P1, P2, P3, P4, P5, P6, P7, P8, P9, P10)', which derived directly from the interaction terms of molecular graph, is used to characterize well molecular structures of all alkanes from one through ten or eleven carbon atoms. It showed that there exists very good correlation between the MPV elements and molar response values on both FID and TCD detectors in classical gas chromatography. Based on the given calibration set with different sample numbers and by using the practical multiple linear regression, the quantitative structure-response relationship (QSRR) equations, for the molar response values (SM) on both FID and TCD, are respectively given as follows: SM(FID) = 15.4004881 + 17.9905995 X1 - 0.1652116 X2 - 0.6974103 X3 - 0.8452390 X4 - 0.2671000 X5 - 1.5657273 X6 + 0.0944440 X7, n = 50, m = 7, r = 0.9976, ST = 26.132, SR = 1.965 1, Ev = 99.72%, RMS = 1.801, F = 1231.71 SM(TCD) = 11.9946996 + 29.1490916 X1 - 4.7451669 X2 - 3.7673385 X3 - 1.4948330 X4 - 1.6278831 X5 - 0.7934611 X6 - 3.0566093 X7, n = 32, m = 7, r = 0.9968, ST = 15.72, SR = 1.4310, Ev = 99.59%, RMS = 1.239, F = 531.227 where the independent descriptor variables, X1-X7, refer to the elements, P1, P2, P3, P4, P5, P6, P7 in the molecular path vector for all samples in both FID and TCD training sets; n, r, ST, SR, Ev, RMS and F are the sample number, regression coefficient, total standard deviation, standard residual deviation, explained variance, rooted mean squared error and F-statistic value, respectively. To test both models by using back-propagation neural network (BPNN) with the topological structure NN(7-4-2) and the cross validation through leave-one-out (LOO) procedure, the correlation coefficient of cross validation is over 0.96. Because there exists a quite good linear relationship between the molar responses and molecular path parameters, BPNN (r = 0.989 and 0.968) does not show its nonlinear advantage over multiple linear regression(MLR) (r = 0.9976 and 0.9968) in both presently examined cases, FID and TCD in the GC technique, for molecular modelling and quantitative prediction.

Alkanes↗
PubMed1999

Stage-specific homeotic vertebral transformations in mouse fetuses induced by maternal hyperthermia during somitogenesis.

To investigate the heat shock effects upon somitogenesis and specification of the vertebral identity, pregnant ICR mice were briefly exposed to 42 degrees C or 43 degrees C at E7.5, E8.5, or E9.5 (noon of the plug day = E0.5). Heat treatment induced embryonic day-specific vertebral transformations whose frequency and severity were dependent on the temperature elevation. Following a heat treatment at E8.5, the vertebral identity of T6 through S1 was shifted anteriorly by one or two segments (posterior transformations). Such shifts were found in more than one-third of the fetuses heat-stressed at 42 degrees C, and in over 90% of those exposed to 43 degrees C. When heated at E7.5, the anterior boundary of vertebral transformations was shifted cranially to cervical levels (C1-C7), and when heated at E9.5, it was shifted caudally to the lower thoracic and lumbar levels (T13-L4). Examination of Hox gene expression domains by in situ hybridization showed that the anterior boundaries of Hoxa-5, Hoxa-7, Hoxc-8, and Hoxc-9 expression domains in the paraxial mesoderm were shifted cranially by one somite segment in embryos heated at E7.5, as compared with the corresponding levels of their expression in control embryos. Such cranial shifts were found for Hoxa-7, Hoxc-8 and Hoxc-9, but not for Hoxa-5, in embryos heated at E8.0. In embryos heated at E8.5, only the expression domains for Hoxc-8 and Hoxc-9 were found to be shifted. The observed stage-specific vertebral transformations and shifts of the Hox gene expression domains were consistent with the temporal colinearity and posterior predominance of Hox gene expression during development. Further histological and cytochemical analyses revealed that heat-induced vertebral transformations may not be a result of induced cell death, but heat-induced transient arrest of cell proliferation and somitogenesis could result in altered expression of Hox genes and subsequently produce vertebral transformations.

Animals↗
PubMed1999

[Effects of basic fibroblast growth factor on repairing injury of intestinal mucosa in acute necrotic pancreatitis].

OBJECTIVE: To observe the effects of basic fibroblast growth factor (bFGF) on repairing injury of intestinal mucosa in acute necrotic pancreatitis (ANP). METHODS: Sixteen dogs of ANP animal model were made by injection of 5% sodium taurocholate (0.5 ml/kg) with 3,000 U/kg trypsin into the pancreatic duct. The mucosa structure, content of protein, DNA and malondiethylaldehyde (MDA) were observed after ANP and treatment with bFGF, and the plasma lipopolysaccharide and endothelin-1 were detected. The organs of dogs were made to bacterial culture. Ileal mucosa was collected for histological and ultrastructural studies. RESULTS: The results showed that after treatment with bFGF, the injury of intestinal mucosa in ANP was abated. The length, height and area of mucosa microvillus, the content of DNA and protein of ileal mucosa were significantly increased, while the plasma endothelin-1 and lipopolysaccharide were reduced. The organ bacterial translocation rate was also decreased in 50%. CONCLUSION: bFGF has good effects on abating injury of intestinal mucosa, protecting gut barrier function, reducing the incidence of lipopolysaccharide and bacterial translocation after ANP.

Animals↗
PubMed1998

Smoking and the development of Warthin's tumour of the parotid gland.

The smoking history was surveyed in 160 consecutive patients with Warthin's tumour of the parotid gland in order to investigate the relationship between smoking and the development of this tumour. Two hundred cases of middle-aged or elderly normal persons and 163 consecutive patients with pleomorphic adenoma in the parotid gland served as controls. The percentage of smoking in patients with Warthin's tumour (96.3%) was much higher than that of middle-aged or elderly normal persons (25.5%) and in patients with pleomorphic adenoma (26.4%). Moreover, the amount of smoking was greater and the smoking history was longer in patients with Warthin's tumour. When the male and female patients were analysed respectively, the same result was shown. This case-control study suggests that smoking may be one of the aetiologic factors associated with the development of Warthin's tumour.

Adenolymphoma↗
PubMed1998

Endoscopic management of huge bezoars.

BACKGROUND AND STUDY AIMS: After the first gastroscopic removal of a bezoar by McKechne in 1972, different endoscopic methods have been reported including a water jet, forceps, snare, and basket. Huge and solid bezoars, however, are still a problem. We report on our experience in fragmenting huge, solid bezoars using a modified needle-knife (bezotome) and a modified mechanical lithotriptor (bezotriptor). PATIENTS AND METHODS: Over a period of 14 months (October 1994 to December 1995), a total of 15 patients (ten male, five female, median age 41 years) with 17 gastric bezoars and one esophageal bezoar, treated endoscopically, were included in the study. A monopolar diathermy knife with a 15 mm needle (bezotome) was used for trichobezoars. For diospyrobezoars we need a bezotriptor. RESULTS: All 18 bezoars, from 4 x 3 x 3 cm to 10 x 8 x 8 cm in size, were successfully fragmented, ten in one session and eight in two sessions. Complete clearance of the upper digestive tract was achieved at the latest three days after the treatment. There were no complications. CONCLUSIONS: Bezotome and bezotriptor are useful endoscopic devices to disintegrate huge, hard bezoars and achieve complete clearance.

Adolescent↗
PubMed1998

Differential north to south gastric cancer-duodenal ulcer gradient in China. China Ulcer Study Group.

There are suggestions that duodenal ulcer protects individuals from gastric cancer and that rice is ulcerogenic while wheat is gastro-protective. We aimed to examine the relationship of gastric cancer, duodenal and gastric ulcers in different geographical regions in China and identified dietary risk factors for duodenal ulcer and gastric cancer. The prevalence of peptic ulcer and gastric cancer among symptomatic patients in eight major cities, four each from the north and the south representing all the six defined regions of China were studied. Endoscopy and case records over a 10 year period were reviewed and cases of confirmed duodenal and gastric ulcer and gastric cancer, together with the total number of endoscopies performed per year, were recorded. Rates were expressed as cases/1000 endoscopies. Results were compared to another epidemiological study on diet and mortality in the same regions in China conducted at the same time. Duodenal ulcer rates were 2.4-fold higher in southern China than northern China, whereas gastric cancer rates were 1.6-fold higher in the north than in the south. Correlation studies showed for the first time an inverse linear relationship between the gastric cancer rates and the duodenal ulcer rates (r=-0.8076, P=0.015), as well as the duodenal ulcer: gastric ulcer ratios (r=-0.9133, P=0.002). Gastric ulcer rates were higher in southern China but did not correlate with the gastric cancer rates (r=0.1455, P=0.731). Duodenal ulcer rates were found to be related to daily rice intake (r=0.8554, P=0.029) and inversely related to daily wheat flour intake (r=-0.8472, P=0.033). Gastric cancer rates were not related to any dietary risk factors tested. We concluded there was an inverse relationship between gastric cancer rates and duodenal ulcer rates. Although duodenal ulceration and gastric cancer are both linked to Helicobacter pylori infection, the findings of this study indicate independent additional aetiological factors for the pathogenesis of these conditions. Dietary factors such as rice or wheat intake may play a role.

Adult↗
PubMed1997

Pure pancreatic juice from patients with chronic pancreatitis has an impaired antibacterial activity.

CONCLUSION: These data show that pure pancreatic juice of AICP patients has a markedly defective antibacterial activity. This finding might be of potential clinical interest in the understanding of the pathophysiology of the disease. BACKGROUND: The aim of the present study was to test the antibacterial activity of pure pancreatic juice in patients with chronic pancreatitis. METHODS: The study group consisted of ten patients with ethanol-induced chronic pancreatitis (AICP) and seven control patients free of pancreatic disease. All subjects had recently undergone a secretin-pancreozymin pancreatic function test. After an overnight fast, through a side-viewing endoscope, selective pancreatic duct cannulation was performed. After secretin stimulation, pure pancreatic juice was obtained. Three fractions of different molecular weights were separated. Samples were incubated with 1-mL suspension of 10(5) Escherichia coli ATCC 25,922, and log10 of colony-forming units were counted. Experiments were repeated by grading pancreatic juice concentration, pH of the medium, and inoculum size. RESULTS: No significant change of pH of pure pancreatic juice appeared between AICP and controls. Starting from 6-h observation, pure pancreatic juice of AICP patients showed a significant bacterial colonization vs controls (p < 0.01). A direct correlation appeared between bacterial colonization and either pH and dilution of pancreatic juice (p < 0.001). Antibacterial activity was independent of inoculum size, enzymatic activation or inhibition, and heat treatment. The fraction with 1000-10,000 molecular weight was the one endowed with antibacterial activity.

Adult↗
PubMed1997

[Environmental pollution, human exposure and its health effect of sodium pentachlorophenate in schistosomiasis prevalent area].

Sodium pentachlorophenate (Na-PCP) has been used in China for years as an molluscacide to kill oncomelania, which is an intermediate host of Schistosome. To evaluate the effects of its long-term successive usage on environment, human exposure and health, studies were carried out in Sichuan, Jiangxi, Jiangsu and Fujian provinces, with a time gap of more than one month between sample collection and last spray of Na-PCP. Results indicated that PCP contents in surface water, soil, sediment, animals and plants were significantly higher in studied areas than in control areas. The daily intake and the content in urine of PCP were also sigificantify higher in studied areas. But, there was no difference on physical and biochemical examinations except that a 22%-28% decrease of blood cholinesterase activity was found in studied areas. The health effect of impurities in Na-PCP, dioxins and furans, was assessed and discussed.

Animals↗
PubMed1997

The role of mitomycin treatment duration and previous intraocular surgery on the success of trabeculectomy surgery.

PURPOSE: This study was performed to determine the effect of duration of mitomycin exposure during trabeculectomy surgery on filtration success in eyes that had and had not been subjected to previous surgery. METHODS: On hundred six eyes of 92 patients were retrospectively reviewed. The effect of previous surgery and exposure duration of mitomycin 0.5 mg/ml on outcomes of trabeculectomy surgery were evaluated. RESULTS: The mean duration of mitomycin exposure was 0.7 +/- 0.02 min (mean +/- SEM) in the eyes that had not been subjected to previous surgery and 1.5 +/- 0.11 min in the eyes that had (p < 0.001). The mean follow-up times were 14 months in both groups. The mean decrease in intraocular pressure was 13.6 +/- 1.25 mm Hg in the group that had not been subjected to previous surgery and 13.9 +/- 1.45 mm Hg in the group that had been subjected to previous surgery. Analysis of variance techniques demonstrated no predictive value of demographics, history of previous surgery, or duration of mitomycin exposure with results of trabeculectomy surgery. Hypotony was the most frequent complication in both the no previous surgery and the previous surgery groups. The incidence of complications was numerically greater in the group that had not been subjected to previous surgery. CONCLUSIONS: The duration of mitomycin exposure and the history of previous surgery did not correlate with postoperative intraocular pressure, medications, or incidence of complications. The exposure duration response curve of mitomycin 0.5 mg/ml in these patients appears to be flat through the time evaluated. Lower concentrations of mitomycin and shorter exposure should be used to maintain efficacy with reduced risk of complications.

Adolescent↗
PubMed1996

Human T-cell lymphotropic virus types I and II infections in patients with leukaemia/lymphoma and in subjects with sexually transmitted diseases in Nigeria.

Serological assays that distinguish antibodies to human T-cell lymphotropic virus types I (HTLV-I) and type II (HTLV-II), and polymerase chain reaction (PCR) tests were used to investigate association of these two human retroviruses with several well-defined clinical conditions in Nigeria. We compared the frequency of HTLV-I and HTLV-II infections among patients with lymphopholiferative disorders (n=65), individuals with various sexually transmitted diseases (n=40), patients with genitals candidiasis (n=25) and apparently healthy individuals (n=60). Serological analysis of blood samples from all four groups showed that 10 of the 190 (5.3%) individuals tested were confirmed positive for the presence of antibodies to HTLV-I(6) or HTLV-II(4). Using the PCR technique, specific HTLV-I or HTLV-II sequences were amplified from the genomic DNA of 4 of 6 HTLV-I seropositive and 3 of the 4 HTLV-II seropositive individuals respectively. However, sequences of both viruses were amplified from the genomic DNAs of the remaining 3 seropositive individuals. Since one of the 5 sets of primer pairs [SK110(II)/SK111(II)], which is used for specific identification of HTLV-II did not amplify the target sequence from the genomic DNAs of any of the 4 HTLV-II confirmed seropositive individuals in this study, it suggested sequence diversity of these viruses in Nigeria. The virus-infected individuals identified in this study were one (1.5%) of the 65 patients with leukaemia/lymphoma (HTLV-I), 6 of 40 (15.0%) individuals (HTLV-I = 1 , HTLV-II = 3, HTLV-I/II = 2) with sexually transmitted diseases (STD), one of 25(4.0%) subjects with genital candidiasis for HTLV-I and 2 of 60 (33.3%) healthy individuals (one for HTLV-I and one for HTLV-I/II). There was a significant difference (P < 0.025) between the prevalence of HTLV-I/II infections among patients with lymphoma/leukaemia and those who attended STD clinic in Ibadan, Nigeria. This study also suggests that while HTLV-I and HTLV-II may be important sexually transmitted viruses, they may not be specific aetiological agents of the common lymphoproliferative disorders in Nigeria.

Adult↗
PubMed1996

Significance of interstitial bone ingrowth under load-bearing conditions: a comparison between solid and porous implant materials.

Interstitial bone ingrowth is extremely important for optimum fixation of implanted materials under load-bearing conditions. In this study, three types of biomaterial test piece were manufactured in solid and open-pore structures, and implanted into dog femoral condyles. Bone formation and remodelling were observed histologically and roentgenologically for 24 weeks thereafter. The study demonstrated that, 24 weeks after implantation, thick fibrous tissue surrounded by corticalized bone formed around both solid smooth-surfaced alumina and titanium implants. On the other hand, however, with an implant made of an artificial osteochondral composite material, thickening of ingrown trabeculae could be observed as early as 4 weeks. Bone ingrowth into the titanium fibre mesh was ambundant and increased with time after implantation. This interstitial bone ingrowth resulted in the complete integration of this implant and the viable host bone. Our findings suggest that interstitial bone ingrowth has great significance, even though new bone formation and remodelling follows Wolff's law after the completion of the bonding between the bone and implanted material under load-bearing conditions. The artificial osteochondral composite material could lead to complete integration of the implant and viable bone, suggesting that it is a promising material for joint replacements. Moreover, the tibial joint surface which bore against the polyvinyl alcohol hydrogel surface of this implant remained intact, which suggests that this composite is a very promising biomaterial for use in joint prostheses.

Animals↗
PubMed1996

[A comparative analysis of biological properties of glucosylrtanterases secreted by Streptococcus sanguis and Streptococcus mutans]

Our study make a comparative analysis of biological properties of glucosyltranterases(GTF) secreted by S.sanguis 34 and S.mutans Ingbritt(c).The results as follows:(1)S.sanguis 34 has more extractions of extracelluar GTF than S.mutans Ingbritt(c) under equal cultured conditions,but S.mutans Inggbritt(c) has more activity of extracelluar GTF than S.sanguis.These differences are identical with the difference of their cariogenicities;(2)GTF of S.sanguis 34 can also synthesize water-soluble glucan,and is a multienzyme complex system as S.mutans. S.sanguis might catalyse sufficient dextran formation to stimulate the primer-dependent activity of the S.mutans GTF enzyme. This might aid the adhesion of this comparatively late colonizer;(3)easier to obstruct high pure GTF of S.sangusi 34 S.mutans.

Journal Article↗
PubMed1996

[Environmental factors in oral cavity effect on growing of Streptococcus sanguis and Streptococcus mutans-effect of Mucin]

Our study use continues culture technique through adding mucin as the limiting element in chemically defined culture,medium in order to observe growing states of S.sanguis 34 and,S.mutants Ingbritt(c).The results as follows:S.sanguis 34 were able to grow as pure culture on mucin;S.mutans was unable to grow as a pure culture on mucin,but attained a significant population size in the presence of S.sanguis.These results indicate a synergetic degradation of mucin by S.sanguis and S.mutans in mixed chemism culture.

Journal Article↗
PubMed1996

[Environmental factors in oral cavity effect on growing of Streptococcus sanguis and Strepococcus mutans-Oxygen of effects]

Oral Streptococcus species belong to facultative aerobes,and are easily inhibited by metabolic products of oxygen.Our study uses continues culture technique through adding oxygen in order to observe growing states of S.sanguis 34 and S.mutans Ingbritt(c) The result is that the resistance to oxygen of S.sanguis 34 is stronger than S.mutans Ingbritt(c).This result is in accordance with the phenomenon that S.sanguis is a pioneer colonizing germ of dental plaque.The lower resistance to oxygen of S.mutans indicates that the growth and cariogenic action of S.mutans are dependent on the internal circumstance of plaque.

Journal Article↗
PubMed1996

Targeting widespread sites of damage in dystrophic muscle: engrafted macrophages as potential shuttles.

Inherited muscle diseases are characterized by widespread muscle damage in the body. This limits the clinical relevance of cell or gene therapy based upon direct injections into muscles. One way to circumvent this obstacle would be to use circulating cells, capable of homing naturally to the sites of lesion, to deliver therapeutic substances. Certain muscular dystrophies present successive cycles of degeneration-regeneration. These sporadic necrotic lesions trigger local inflammations with subsequent infiltration of blood-borne mononuclear cells. We have, therefore, tested the possibility that homing monocytes and macrophages could be appropriate shuttles for delivering a therapeutic agent to disseminated pathogenic sites, their targeting being triggered by the pathogeny itself. First, fluorescently labeled immortalized monocytes were intravenously injected into mice which had previously undergone freeze-damaging of individual muscles. In agreement with our hypothesis, intense labelling was observed in the muscle, specifically in damaged regions. Second, the technique was adapted to meet the needs of chronic diseases with characteristic continuous, widespread degeneration of muscle fibers, by creating a reservoir of genetically engineered monocytes, via bone marrow transplantation. Mdx mice received bone marrow from transgenic mice expressing the lacZ reporter gene, under the control of the vimentin promoter, which is active in monocytes and macrophages. Histological and molecular analyses demonstrated the homing of engineered macrophages at the sites of muscle damage, for periods as long as 2 months. Bone marrow progenitor cells, appropriately engineered to elicit the synthesis, in macrophages, of therapeutically relevant substances, may be of clinical value in various pathologies involving an inflammatory phase.

Animals↗
PubMed1995

Myotube driven myogenic recruitment of cells during in vitro myogenesis.

Muscular dysgenesis (mdg) is a recessive lethal mutation in the mouse which drastically affects skeletal muscle development during embryonic life. Physiologically, the disease is characterized by a complete paralysis resulting from a lack of excitation-contraction coupling. Existing electrophysiological, biochemical, and genetic evidence shows that mdg/mdg mice express a basic alteration of L-type voltage-sensitive Ca2+ channels in skeletal muscle. Studies on mdg/mdg myotubes in primary culture have shown that +/+ fibroblasts or +/+ Schwann cells may fuse with them and correct their functional deficiency by genetic complementation. As the spontaneous formation of heterocaryons is thought to be an exclusive property of myoblasts, we asked whether fibroblasts may have changed their properties before fusion occurred. We used primary cells issued from sciatic nerves dissected from newborn transgenic mice carrying the pHuDes1-nls-LacZ transgene (Des-LacZ cells) as non-muscle cells. These cells were mainly fibroblasts (80%) positive for Thy1.1 and Schwann cells positive for S100. The cultures were negative for myogenic markers (desmin, troponin T), did not form myotubes long-term, and did not display significant activation of the muscle reporter gene (pHuDes1-nls-LacZ). After a few days in coculture with dysgenic or normal myotubes, the muscle reporter gene (beta-galactosidase) was detected both within dysgenic myotubes, correlating with the restoration of normal contractile activity, and normal myotubes. As well as confirming that fusion takes place, this shows that Des-LacZ cells nuclei incorporated into recipient myotubes express their own myogenic genes. Moreover, individual mononucleated Des-LacZ cells expressing beta-galactosidase were observed, indicating that myogenic genes were being expressed before fusion. This suggests a mechanism of myotube driven myogenic recruitment of cells during the in vitro myogenesis. Analysis of the distribution of the induced Des-LacZ cells (positive for beta-galactosidase) in compartmentalized muscle cocultures showed that in the presence of dysgenic myotubes, these cells were equally distributed in both myotube free and enriched areas, whereas in the presence of normal myotubes, the positive cells remained in close vicinity of the myotubes. This difference could be explained by the fact that the dysgenic phenotype might include release of the induction process from its normal controls. Our results are consistent with the idea of a transcellular mechanism triggering myogenic differentiation in non-muscle cells, and that myotubes themselves are able to drive myogenic recruitment of cells during the in vitro myogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗