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Biomedical subjects

S Li

Publications and source records attributed to S Li.

At least 973 records · Page 54Linked to original sources

[Time resolved photoluminescence of PPV derivatives/C60 combination system].

We report the integrated and picosecond time-resolved photoluminescence (TRPL) measurement from two kinds of combination films: Poly(2-methoxy-5-(4-butenyloxy)phenylene vinylene) (MB-PPV)/C60 and Poly (2-methoxy-5-(4'-bromo-butoxy) phenylene vinylene) (MBB-PPV)/C60. Comparing with the pure MBB-PPV film, PL weakening and quenching of MBB-PPV were observed in the multilayer and mixed MBB-PPV/C60 films respectively. From TRPL spectra, the change of PL decay lifetime could be clearly seen, those could be attributed to the excitation transfer (ET) process between the excited MBB-PPV molecule and C60 molecule. Further measurements indicate that there is no noticeable dependence of the ET process on the temperature in the combination films.

English Abstract↗

[The thin film and absorption spectra of CsCu2I3].

This paper introduces a method of manufacturing CsCu2I3 thin films through hot evaporation. According to the absorption spectra at low temperature, the excitonic coefficient of CsCu2I3 was calculated. The spectral analysis shows that the localization of electron and exciton excitations in the twofold Chain created by CuI4(3-) causes the complicated character of the optical spectra of CsCu2I3.

English Abstract↗

[Application of charge transfer reaction in the determination of aminosalicylate sodium].

A spectrophotometric method for the determination of aminosalicylate sodium has been developed based on the charge transfer reaction. The Beer's law is obeyed in the range of 40-160 microg/mL of aminosalicylate sodium. The apparent molar absorptivity of the complex at 660nm is 1.17 X 10(3)L x mol(-1). The average standard deviation of ten determination is 0.67%. The composition of aminosalicylate sodium 2, 6-Dichloroquinone chlorimide complex is 1:1. The proposed method has been applied to the determination of aminosalicylate sodium tablets with satisfactory results.

Absorption↗

Mutagenesis of the mouse delta opioid receptor converts (-)-buprenorphine from a partial agonist to an antagonist.

An aspartic acid at residue 95 (Asp95) in the delta receptor has previously been shown to be critical for the binding affinity of selective delta agonists. To gain a better understanding of the functional consequence of agonist action at the delta receptor, the Asp95 residue was mutated to an asparagine (D95N) and opioids were tested for binding and functional activation of the wild-type and mutant delta receptors. Selective agonists such as [D-Ser2,D-Leu5]enkephalin-Thr6 (DSLET) and [D-Ala2,D-Leu5]enkephalin (DADLE) had greatly reduced affinity for the D95N mutant receptor but still inhibited cAMP accumulation, which indicated that the mutant receptor was still functionally coupled to adenylyl cyclase. Antagonist binding was not affected by the Asp95 mutation. Similarly, the partial agonist buprenorphine bound with equally high affinity to the D95N mutant and the wild-type delta receptor, which indicated that Asp95 is not essential for the binding affinity of this opioid. Buprenorphine did not affect cAMP accumulation in HEK 293 cells expressing the D95N mutant, and it blocked the ability of DSLET and bremazocine to inhibit cAMP accumulation via the D95N mutant, which indicated that buprenorphine acts as an antagonist at the D95N mutant. These findings confirm the essential role of Asp95 in the activation of the delta receptor by agonists and reveal a molecular basis of the unique property of buprenorphine.

Analgesics, Opioid↗

Inactivation and conformational changes of yeast invertase during unfolding in urea and guanidinium chloride solutions.

Yeast invertase exists in two different forms. The cytoplasmic enzyme is non-glycosylated, whereas the external invertase contains approximately 50% carbohydrate of the high mannose type. In this paper, the inactivation and the conformational changes of the yeast external invertase are analyzed for unfolding in urea and guanidinium chloride. The results show that much lower concentrations of denaturants are required to bring about inactivation than are required to produce significant conformational changes of the yeast external invertase. The results suggest that the active sites of the external invertase containing carbohydrate residues may display more conformational flexibility than the enzyme molecules as a whole.

Glycoside Hydrolases↗

Fentanyl and its analogs desensitize the cloned mu opioid receptor.

Fentanyl, and its structural analogs lofentanil and sufentanil, are potent analgesics used clinically in the management of pain. However, the high analgesic potency of these compounds is limited by the development of tolerance after chronic use. To investigate whether their tolerance development may be related to mu receptor desensitization, the cloned mouse mu receptor as well as mutant forms of the receptor were stably expressed in HEK 293 cells and tested for their response to continuous opioid treatment. Fentanyl and its analogs potently bound to the mu receptor and effectively inhibited cAMP accumulation. Three-hour pretreatment of mu receptors with fentanyl and its analogs desensitized the mu receptor by uncoupling it from adenylyl cyclase. The fentanyl analogs caused a slight internalization of the mu receptor as accessed by antibody binding to the epitope-tagged mu receptor. Truncation of the mu receptor by removal of its carboxyl terminus at Glu341 did not affect the ability of the fentanyl analogs to bind to and activate the mu receptor nor did it prevent the fentanyl analogs from desensitizing the receptor. In a previous study we showed that morphine did not desensitize the cloned mu receptor even though it is a potent and effective agonist at the mu receptor. Mutagenesis studies revealed that morphine interacts differently with the mu receptor to activate it than do the fentanyl analogs which may explain its lack of desensitization of the mu receptor. These results indicate that desensitization of the mu receptor may be a molecular basis for the development of tolerance to fentanyl and its analogs.

Analgesics, Opioid↗

Role of polyethylene oxidation and consolidation defects in cup performance.

Quality factors such as particle consolidation and oxidation have been claimed to impair the performance of ultrahigh molecular weight polyethylene implants, but no definite data estimate their real effect. To assess the influence of these quality determinants in wear, wear rate, and time in service at a single, well proven design, the percentage area of polyethylene sections occupied by nonconsolidated polyethylene particles, the presence of a white band, and the amount of polyethylene oxidation (through density curves) were evaluated in 92 retrieved Charnley acetabular components with available clinical data. The average percentage area of nonconsolidated polyethylene particles in cup sections was 3.1%. There were 11 cups showing a subsurface white band. The authors observed an average density in the deep polyethylene of 0.9420 g/cc after an average in vivo use of 9.8 years (range, 0.08-20.3 years). Banded cups showed significantly higher subsurface densities. When studying the relationship among clinical and material factors with performance variables, wear measurements (obtained through radiographic methods and direct measurements of polyethylene thickness in the collected implants) correlated with age at implantation, activity, and time in service. Weight was a determinant of the wear rate. None of the studied polyethylene quality factors showed a definite association with wear performance or time to failure in this series. Implant survivorship was not significantly impaired in the 22.225-mm Charnley low friction replacement by a subsurface white band or by a higher area occupied by nonconsolidated particles. Fewer nonconsolidated particles were not associated with longer survivorship. This design proved tolerance to polyethylene quality variations, in the signaled ranges, without a significant effect in the system performance.

Arthroplasty, Replacement, Hip↗

Associations of demographic and health-related characteristics with prostate cancer screening in Washington State.

This report describes associations of demographic and health-related characteristics with use of prostate cancer screening. Data are from a random-digit dial survey of Washington State residents. Analyses are restricted to men ages 40-79 years (n = 332) and examine both digital rectal examination (DRE) and blood tests for prostate-specific antigen (PSA) in the previous 2 years. Results are adjusted to be representative of the state's population. In 1996, 53.6% of men received either DRE, PSA, or both. Among those screened, 42% received DRE alone, 15% PSA alone, and 43% both PSA and DRE, and the percentages of men receiving PSA increased markedly with age (30%, ages 40-49 years; 58%, ages 50-59 years; and 77%, ages 60-79 years). After control for other demographic characteristics, the relative odds for any prostate cancer screening were 5.5 for ages 60-79 versus 40-49 years, 2.4 for 16+ versus < or = 12 years of education, and 4.0 for 2+ versus no physician visits in the previous 2 years (all P < 0.05). Characteristics generally associated with good health, including regular exercise and low fat and high fruit and vegetable intakes, were also significantly associated with prostate cancer screening. In conclusion, in 1996, approximately one-half of the men in Washington State over age 40 years had received prostate cancer screening in the previous 2 years. Few men were screened with PSA alone, and the use of PSA as part of prostate cancer screening increased markedly with age. Because PSA screening increases detection of prostate cancer, epidemiological studies of health behavior and cancer risk must carefully control for screening history to avoid detection bias.

Adult↗

A partial conditioning strategy for achieving mixed chimerism in the rat: tacrolimus and anti-lymphocyte serum substantially reduce the minimum radiation dose for engraftment.

Development of partial conditioning strategies to achieve reliable engraftment of allogeneic bone marrow with minimum recipient morbidity could extend the therapeutic application of bone marrow transplantation (BMT) to enzyme deficiency states, hemoglobinopathies, autoimmune diseases, and the induction of tolerance for solid organ and cellular allografts. In this study we describe a nonmyeloablative rat BMT model and examine the effect of clinically available immunosuppressants on the minimum amount of total body irradiation (TBI) required for allogeneic engraftment. Donor ACI marrow was depleted of T cells using immunomagnetic beads and transplanted to major histocompatibility complex- and minor antigen-mismatched Wistar Furth (WF) rats (ACI --> WF) conditioned with varying doses of TBI. Recipients conditioned with TBI alone required myeloablation with 1000 cGy for reliable allogeneic marrow engraftment. Administration to WF recipients of a single dose of anti-lymphocyte serum (ALS) 5 days prior to BMT together with a limited course of tacrolimus (1 mg/kg/day) resulted in engraftment of ACI bone marrow at only 500 cGy TBI. ACI --> WF recipients were stable mixed chimeras (mean donor chimerism 49% at 330 days post-BMT). Chimerism was multilineage. All recipient animals were free of graft-versus-host disease. These results suggest that a nonmyeloablative conditioning strategy based on low-dose TBI and a limited course of tacrolimus plus ALS can produce long-term mixed multilineage chimerism.

Animals↗

Mixed allogeneic chimerism prevents obstructive airway disease in a rat heterotopic tracheal transplant model.

BACKGROUND: Mixed bone marrow chimerism reliably produces donor-specific transplantation tolerance for a variety of solid organ and cellular grafts. We used a rat heterotopic tracheal transplant model for chronic rejection to investigate whether mixed chimerism could successfully prevent obstructive airway disease. METHODS: Mixed allogeneic chimeras were prepared by reconstituting lethally irradiated Wistar-Furth (WF) recipients with a mixture of 5 x 10(6) T-cell-depleted syngeneic (WF) and 100 x 10(6) T-cell-depleted allogeneic (ACI) bone marrow cells (ACI + WF --> WF). Mixed chimerism was present in all animals 28 days after bone marrow transplantation. Donor-specific, syngeneic, or major histocompatibility complex (MHC)-disparate allogeneic tracheas were implanted in recipient's omentum and removed for histologic analysis 30 to 150 days after transplantation. RESULTS: At 30 days after implantation, median luminal obstruction grades (0=none, 4=complete) of syngeneic and allogeneic tracheas were 0 and 4, respectively. Donor-specific (ACI) tracheas implanted in chimeric (ACI + WF --> WF) recipients were remarkably free of obstruction (median luminal obstruction grade=0 at 150 days) and had excellent preservation of respiratory epithelium. Third-party F344 tracheas implanted in chimeric recipients developed progressive luminal obstruction (grade 2 at 30 days, grade 3 at 90 days). CONCLUSIONS: Mixed allogeneic chimerism induces donor-specific tolerance and prevents development of the characteristic fibroproliferative obstructive lesion of bronchiolitis obliterans in a rat heterotopic tracheal transplant model. Excellent preservation of tracheal structure and morphology was achieved across major and minor histocompatibility barriers.

Airway Obstruction↗

An improved, inexpensive method for the large-scale purification of human nerve growth factor.

Human nerve growth factor (hNGF) was purified to near homogeneity on a large scale from human term placenta with an improved and inexpensive method. The purification procedure included tissue homogenization, ultrafiltration and single CM-cellulose column chromatography. The purified hNGF was a 14.4-kDa protein with an isoelectric point of approximately 9.3. The specific activity of the purified hNGF was approximately 38000 units/mg, and the activity was completely inhibited by the monoclonal antibody against recombinant hNGF (rhNGF). Western-blot analysis showed that the purified hNGF could interact with the monoclonal antibody against rhNGF.

China↗

Sarcoidosis with nasal obstruction and septal perforation.

Although sarcoidosis is predominantly a pulmonary disorder, it often produces disease in the head and neck. For this reason, otolaryngologists should be comfortable in evaluating and treating the disease. The diagnosis of sarcoidosis often can be made with a biopsy of conjunctival or oral mucosa, even when disease manifestations are not apparent in those parts of the body. In a case of sarcoidosis involving the nose, a 54-year-old black man had a proliferation of small lumps on the tip of his nose. For many years, he had had daily epistaxis, anosmia and severe difficulty breathing through this nose. The bridge of his nose was deformed, and he had a large anterior septal perforation. Physical examination revealed palpable bilateral cervical lymphadenopathy. Laboratory test results were, for the most part, normal; however, fine-needle aspiration of one of the cervical lymph nodes showed multiple epithelioid granulomas with interspersed lymphocyte, and an incisional biopsy of the nasal tissue was highly suggestive of sarcoidosis. Unenhanced computed tomography also revealed widespread nasal inflammation and an abnormal soft tissue mass anterior to the maxilla consistent with chronic osteomyelitis. The patient's condition dramatically improved following treatment with oral prednisone; however, he considered undergoing reconstructive surgery for the noticeable nasal septal deformity.

Biopsy, Needle↗

[Evaluation of therapy for dilated cardiomyopathy with heart failure by iodine-123 metaiodobenzylguanidine imaging: comparison with heart rate variability power spectral analysis].

The relationship between the myocardial uptake of iodine-123 metaiodobenzylguanidine (123I-MIBG) and heart rate variability parameters has not been determined. This study determined the relationship between the change in myocardial uptake of 123I-MIBG and improvement in left ventricular function after treatment, to determine the usefulness of 123I-MIBG imaging to assess the effect of therapy on heart failure due to dilated cardiomyopathy (DCM). 123I-MIBG imaging and power spectral analysis of heart rate variability were performed before and after treatment in 17 patients with heart failure due to DCM. The following parameters were compared before and after treatment: New York Heart Association (NYHA) functional class, radiographic cardiothoracic ratio (CTR), blood pressure, echocardiographic data [left ventricular end-systolic (LVDs) and end-diastolic (LVDd) diameters, left ventricular ejection fraction (LVEF)], plasma concentrations of norepinephrine and epinephrine, heart rate variability power spectral analysis data [mean low frequency (MLF) and high frequency power (MHF)] and the myocardium to mediastinum activity ratio (MYO/M) obtained in early and late images, and washout rate calculated by anterior planar imaging of 123I-MIBG. The NYHA functional class, LVEF, LVDs, CTR, MLF and MHF improved after treatment. Early MYO/M and late MYO/M improved after treatment. The rate of increase in late MYO/M was positively correlated with the rate of improvement of LVEF after treatment. Furthermore, the late MYO/M was negatively correlated with MLF. Washout rate revealed no correlation with hemodynamic parameters. These findings suggest that late MYO/M is more useful than washout rate to assess the effect of treatment on heart failure due to DCM. Furthermore, the 123I-MIBG imaging and heart rate variability parameters are useful to assess the autonomic tone in DCM with heart failure.

3-Iodobenzylguanidine↗

Elevated rates of severe neural tube defects in a high-prevalence area in northern China.

In the northern provinces of China, the birth prevalence rate of neural tube defects (NTDs) is among the highest in the world-at about 6 per 1,000 births in rural areas. A unique population-based birth defects surveillance system in which photographs are taken of infants with selected external birth defects was implemented in two provinces in northern China and two provinces in southern China where NTD rates approximate those in the United States. In the period from March 1992 through December 1993, 660 infants with NTDs were identified by the surveillance project from a birth cohort of 251,567. We compared data from the two surveillance areas in China with data from a low-prevalence area in the United States to determine if the pattern of NTD types differs. Based on birth prevalence rates of NTDs from the Metropolitan Atlanta Congenital Defects Program, the observed to expected ratios for two types of NTDs are markedly increased at 80.8 for craniorachischisis and 25.0 for iniencephaly. Rates of these two NTDs in the southern provinces are increased to a lesser degree with observed to expected ratios of 7.1 for craniorachischisis and 2.7 for iniencephaly. The pattern of NTDs in northern China shows an increase in types that are rare in low-prevalence areas such as metropolitan Atlanta. Increased awareness of varying patterns of NTDs in different populations may have important implications for identifying etiologic and pathogenetic mechanisms of NTDs.

China↗

Fluid shear stress activation of focal adhesion kinase. Linking to mitogen-activated protein kinases.

Shear stress, the tangential component of hemodynamic forces, activates the extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) signal transduction pathways in cultured vascular endothelial cells to induce the transcriptional activation of many immediate early genes. It appears that integrins, protein-tyrosine kinases, and the structural integrity of actin are important factors involved in these shear stress-induced responses. The underlying molecular events were investigated by the application of a shear stress of 12 dyn/cm2 on bovine aortic endothelial cells (BAEC). We found that such a shear stress increased the tyrosine phosphorylation and the kinase activity of focal adhesion kinase (FAK) and its association with growth factor receptor binding protein 2 (Grb2) in a rapid and transient manner, suggesting that FAK may be linked to these mitogen-activated protein kinase signaling pathways through a Grb2. Son of sevenless (Sos) complex. FAK(F397Y), which encodes a dominant negative mutant of FAK, attenuated the shear stress-induced kinase activity of Myc epitope-tagged ERK2 and hemagglutinin epitope-tagged JNK1. DeltamSos1, encoding a dominant negative mutant of Sos in which the guanine nucleotide exchange domain has been deleted, also attenuated shear stress activation of Myc-ERK2 and hemagglutinin-JNK1. Pretreating the confluent BAEC monolayers with a blocking type anti-vitronectin receptor monoclonal antibody had similar inhibitory effects in these shear stress-activated ERKs and JNKs. Confocal microscopic observation further demonstrated that FAK tended to cluster with vitronectin receptor near the abluminal side of the sheared BAEC. These results demonstrate that FAK signaling is critical in the shear stress-induced dual activation of ERK and JNK.

Actins↗

Recruitment of IRAK to the interleukin 1 receptor complex requires interleukin 1 receptor accessory protein.

The proinflammatory cytokine interleukin 1 (IL-1) activates the transcription of many genes encoding acute phase and proinflammatory proteins, a function mediated primarily by the transcription factor NF-kappaB. An early IL-1 signaling event is the recruitment of the Ser/Thr kinase IRAK to the type I IL-1 receptor (IL-1RI). Here we describe the function of a previously identified IL-1 receptor subunit designated IL-1 receptor accessory protein (IL-1RAcP). IL-1 treatment of cells induces the formation of a complex containing both IL-1RI and IL-1RAcP. IRAK is recruited to this complex through its association with IL-1RAcP. Overexpression of an IL-1RAcP mutant lacking its intracellular domain, the IRAK-binding domain, prevented the recruitment of IRAK to the receptor complex and blocked IL-1-induced NF-kappaB activation.

Animals↗

Effect of significant two-vessel versus one-vessel coronary artery stenosis on myocardial contrast defects observed with intermittent harmonic imaging after intravenous contrast injection during dobutamine stress echocardiography.

OBJECTIVES: We sought to determine the effect of multivessel as opposed to single-vessel coronary artery stenosis on myocardial contrast defects observed with intermittent harmonic imaging and intravenous perfluorocarbon-exposed sonicated dextrose albumin contrast injection. BACKGROUND: Intermittent harmonic imaging has permitted the detection of myocardial perfusion abnormalities with an intravenous ultrasound contrast agent. The effect of multivessel disease on inducibility of these perfusion abnormalities is unknown. METHODS: In 10 dogs, intravenous injections of contrast agent were given at rest and during dobutamine stress echocardiography when a single coronary artery stenosis was present (> or = 50% diameter by quantitative angiography) and again when a second stenosis (range 44% to 92% diameter) was present in the vessel supplying the adjacent perfusion bed. The peak myocardial contrast was visually and quantitatively assessed in the mid and lateral regions of the perfusion bed of the first stenosis (original stenosis zone) in the presence of one- and two-vessel stenosis. RESULTS: Peak myocardial contrast defects in both the mid and lateral segments of the original stenosis zone during dobutamine stress echocardiography was significantly lower when two-vessel stenosis was present (p = 0.015), especially in the lateral segment. The spatial extent of the perfusion defect in the original stenosis zone risk area increased significantly when two-vessel stenosis was present, and correlated closely with actual risk area (r = 0.99). Previous total occlusion followed by reperfusion of the vessel supplying the original stenosis zone significantly increased the amount of collateral activity between perfusion beds. CONCLUSIONS: Collateral flow limits the spatial extent of inducible ischemia within the risk area of single-vessel stenosis. Restoring blood flow to one perfusion bed reduces the extent of a perfusion abnormality that can be induced in an adjacent stenosed bed.

Animals↗

The effect of peripherin/rds haploinsufficiency on rod and cone photoreceptors.

Haploinsufficiency because of a null mutation in the gene encoding peripherin/rds has been thought to be the primary defect associated with the photoreceptor degeneration seen in the retinal degeneration slow (rds) mouse. We have compared the effects of this haploinsufficiency on rod and cone photoreceptors by measuring the levels of rod- and cone-specific gene expression, by determining the relative rates of rod and cone degeneration, and by electroretinography. These analyses were performed at ages before and after the onset of degeneration of the photoreceptor cells. The data were consistent in demonstrating that measures for cone photoreceptors are relatively spared in comparison to comparable measures for rod photoreceptors. Blue cones were retained in higher number than red/green cones for the first 3 months of the degeneration. Our results indicate that the haploinsufficiency present in rds/+ mice has a greater impact on the rod than on the cone photoreceptor, a finding that likely reflects the tight regulation of peripherin/rds and the need for two functional alleles to assemble the structure of the rod outer segment and/or differences between the ultrastructure of the rod and cone outer segments.

Animals↗