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Biomedical subjects

K Zhang

Publications and source records attributed to K Zhang.

At least 325 records · Page 18Linked to original sources
PubMed1996

[Determination of copper and cadmium in water by continuous flow analysis].

A continuous flow analysis system for the preconcentration of Cu2+ and/or Cd2+ in water was developed. Trace copper or cadmium in water could be concentrated on activated carbon particles packed in micro column at pH > or = 9.0. The adsorbed analyte was eluted with 0.5 ml 2.5% nitric acid and determined by flame atomic absorption spectrometry. A sample size of 10-25 ml sufficed for the determination of copper2+ or cadmium at a level as low as microgram/L. The relative standard deviation of 6 parallel determinations was 4.3% for copper and 11% for cadmium. The proposed method was applied to the determination of copper and cadmium in natural water with a recovery of 84.4%-118%.

Cadmium↗
PubMed1996

Cataract extraction by phacoemulsification in situ and elliptical intraocular lens implantation.

OBJECTIVE: To investigate the technique of phacoemulsification in situ for cataract extraction and elliptical intraocular lens (IOL) implantation. METHODS: 60 eyes of 57 cases with cataract were included and the hardness of nucleus was grade-1-2 in 25 eyes, grade-3 in 27 eyes and grade-4 in 8 eyes. Tunnel incision was made and in situ phacoemulsification with elliptical (5 mm x 6 mm) IOL implantation was performed on all the cases. RESULTS: Phaco-spent-time was 45 seconds to 3 minutes 45 seconds (average 1 minute 52 seconds). Phacoemulsification in 53 eyes (88.3%) was successful in situ Visual acuities of 0.5 or better and 1.0 or better at postoperative one week were obtained in 75.0% and 56.7%, and at 1-12 month follow-up in 85.0% and 71.7% respectively. CONCLUSION: The technique of phacoemulsification in situ and elliptical IOL implantation is worthy to be spread due to minimum postoperative astigmatism and fast restoration of visual acuity.

Adult↗
PubMed1996

[Comparisons of three simple nutritional assessments applied to patients with oral and maxillofacial malignancies].

Combined subjective and objective nutritional assessment (SNA), concise nutritional assessment (CNA), general nutritional status score (GNS), and subjective global assessment of nutritional status (SGA) were applied to assess the nutritional status of 127 patients with oral and maxillofacial malignancies. On this base SNA was used as a standard nutritional assessment to compare the validities of CNA, GNS, and SGA. The results showed: 1) the total agreement rate of CNA (88.2%) was higher than that of GNS (78.0%) and SGA (78.7%); 2) the false positive rate (9.9%) and false negative rate (15.2%) of CNA was lower than that of GNS (17.3%, 30.4%) and SGA (14.8%, 32.6%); 3) the diagnosis index of CNA (74.9%) was significantly (P < 0.05) higher than that of GNS (52.3%) and SGA (52.6%); and 4) the nutritional parameters of CNA were measured by instruments with little man-made errors. These results indicate that CNA can be regarded as the best nutritional assessment for the patients in oral and maxillofacial surgery.

Facial Neoplasms↗
PubMed1995

Structure of binary and ternary complexes of zinc and cobalt carboxypeptidase A as determined by X-ray absorption fine structure.

Carboxypeptidase A, ZnCPD, is typical of a wide range of exo- and endo-metalloproteases that have three protein ligands and a water molecule bound to a catalytic zinc atom and a glutamate residue in the active site that likely acts in conjunction with the Zn-bound water to bring about catalysis. Such enzymes generally have bell-shaped pH-activity profiles (EH2 in equilibrium with EH in equilibrium with E) where the concentration of the catalytic species EH is regulated by pKEH2 and pKEH. The present X-ray absorption fine structure, XAFS, study has determined the structure and pH behavior of the binary and ternary product complexes in order to examine the role of the Zn-bound water in catalysis. Increasing the pH from 7 to 10 of the ZnCPD.L-Phe complex results in the same type of progressive spectral changes in the near-edge XAFS spectrum as is seen for ZnCPD, but the changes are complete by more than 1 pH value below that observed for ZnCPD. The results are in agreement with kinetic studies that show E binds the protonated form of L-Phe more tightly than EH, thus in effect decreasing the value of pKEH. The XAFS results show the average interatomic distance. R. for the zinc ligands of the EH.L-Phe complex decreases by 0.02 A upon formation of the E.L-Phe complex, essentially identical to that obtained for the EH and E forms of the native enzyme. Addition of azide to ZnCPD.L-Phe at pH 7 markedly changes the zinc coordination sphere from 4 N/O atoms at 2.021 +/- O.06 A and 1.4 +/- 0.5 N/O atoms at 2.54 +/- 0.5 A to 3.9 N/O atoms at 1.995 +/- 0.006 A. The decrease in R of about 0.03 A in both the Zn- and CoCPD.L-Phe.N3-complexes is likely due to the ligand exchange from a neutral water to an anion. The XAFS spectra of the ternary complex is pH independent from 7 to 9, in agreement with the ionization of the water being the source of the spectral changes in the free enzyme and its binary L-Phe complex. The enzyme.azide.L-Phe complex is likely bound in a manner analogous to that expected for a post-transition state in a biproduct complex for peptide hydrolysis--that is, the carboxylate anion of the peptide bound to the Zn and the protonated form of L-Phe H-bonded to the catalytic Glu-270 carboxylate. The XAFS results on the "spectroscopically silent" ZnCPD are compared to nuclear magnetic resonance and electron absorption studies on CoCPD.

Animals↗
PubMed1995

IL-4 plus CD40 monoclonal antibody induces human B cells gamma subclass-specific isotype switch: switching to gamma 1, gamma 3, and gamma 4, but not gamma 2.

Stimulation with IL-4 plus CD40 mAb is known to induce production of IgE and IgG4. In this study, we determined the IgG subclass specificity of IL-4 plus CD40 mAb stimulation for human purified B cells. We determined true in vitro switching by the generation of switch circular DNA (S gamma/S mu) representing primary S mu/S gamma events and production of gamma subclass-specific germ-line transcripts by a combination of reverse transcription-PCR and restriction endonuclease digestion. We simultaneously measured changes in the levels of IgG subclass proteins produced. Forty-two clones of circular switch DNA were identified and sequenced. The IgG subclass of S gamma fragment in the S gamma/S mu chimeric PCR products was determined by analyzing key S gamma nucleotides. The switch-deleted clones were found to consist of S gamma 1/S mu, S gamma 3/S mu, and S gamma 4/S mu chimeric switch sequences, showing that such switching had occurred. No S gamma 2/S mu chimeric switch sequences were found. While a consensus sequence was not identified at the S gamma/S mu breakpoints, four contiguous guanines (GGGG) were noticeably present in the S gamma region near the breakpoint. The induction of gamma 1, gamma 3, and gamma 4 switch circles in human purified B cells was accompanied by enhanced production of IgG1, IgG3, and IgG4 but not IgG2. Similarly, stimulation with IL-4 alone induced gamma 1, gamma 3, and gamma 4 but not gamma 2 germ-line transcripts. These results demonstrate that IL-4 plus CD40 mAb induces Ig isotype switch from mu to gamma 1, gamma 3, and gamma 4 but not to gamma 2.

Antibodies, Monoclonal↗
PubMed1995

Differential regulation of alternative 3' splicing of epsilon messenger RNA variants.

Alternative 3' splicing of the one active human epsilon heavy chain gene results in variants of epsilon mRNA encoding distinct IgE proteins. The same relative amounts of these epsilon mRNA variants were produced by non-atopic donor B cells when driven in a variety of T-dependent or T-independent systems. The most abundant variants were those for classic secreted epsilon a novel secreted form (CH4-M2"). In contrast, cells from subjects with high levels of serum IgE secondary to parasitic infection or atopy spontaneously produced higher relative levels of the CH4-M2' epsilon mRNA variant, lower relative amounts of both the membrane and CH4-M2" secreted variants, and very low levels of the CH4'-CH5 variant. The existence of and corresponding changes in levels of the CH4-M2'-encoded secreted protein were demonstrated. IL-10 induced this same differential expression of epsilon splice variants in vitro when used to costimulate IL-4 plus CD40-driven B cells and could differentially enhance the production of CH4-M2' protein by established IgE-secreting cell lines. Inhibition of IgE by cross-linking the low affinity IgE receptor (CD23) decreased the levels of epsilon mRNA and resulted in a distinct pattern of epsilon mRNA characterized by a dramatic decrease in CH4-M2' splice variant. IL-6, IL-2, or IFN-gamma did not change the epsilon mRNA pattern. Overall, the absolute and relative amounts of the different epsilon mRNA splice variants produced appear to be controlled in a differentiation-related fashion.

Adult↗
PubMed1995

Expression of the leukocyte-associated sialoglycoprotein CD43 by a colon carcinoma cell line.

The colon adenocarcinoma cell line COLO 205 secretes L-CanAg, a mucin-like glycoprotein carrying the carcinoma-associated sialyl-Lewis a carbohydrate epitope. In an attempt to identify its apoprotein, an NH2-terminal peptide sequence was obtained from purified L-CanAg. In all interpretable positions, this sequence showed 100% identity to the NH2-terminal of human CD43 (leukosialin, sialophorin), a plasma membrane-bound sialoglycoprotein hitherto only identified in leukocytes and other hematopoietic cells. An antiserum against deglycosylated L-CanAg and an anti-CD43 antiserum both immunoprecipitated a 61-kDa band, interpreted as the CD43 precursor, from COLO 205 cells as well as from the known CD43-expressing cell line HL-60. Results from immunoprecipitations following pulse-chase experiments and tunicamycin treatments were in agreement with earlier studies on the CD43 precursor. RNA blot analysis confirmed the expression of CD43 by the COLO 205 cell line, whereas three other colon carcinoma cell lines were negative. The glycosylation-dependent monoclonal antibody Leu-22, which recognizes leukocyte CD43, failed to bind L-CanAg, probably due to its much more extensive glycosylation. We conclude that L-CanAg is the secreted extracellular domain of a novel glycoform of CD43 and that CD43, if expressed in other carcinoma cells, may have escaped notice in studies relying on glycosylation-dependent monoclonal antibodies against leukocyte CD43.

Adenocarcinoma↗
PubMed1995

Water on the sun.

High-resolution infrared spectra of sunspot umbrae have been recorded with the 1-meter Fourier transform spectrometer on Kitt Peak. The spectra contain a very large number of water absorption features originating on the sun. These lines have been assigned to the pure rotation and the vibration-rotation transitions of hot water by comparison with high-temperature laboratory emission spectra.

Solar System↗
PubMed1995

Studies on the structure and function of glycosylated and nonglycosylated neu differentiation factors. Similarities and differences of the alpha and beta isoforms.

Comparative analyses of both glycosylated and nonglycosylated neu differentiation factor (NDF) isoforms revealed significant similarities and differences of their overall structures and functions. Biophysical analyses confirmed that all NDF isoforms are monomeric, but have an extended ellipsoidal shape in solution. All full-length NDFs are similar in secondary and tertiary structures and they contain no alpha-helix but are abundant in beta-strand structures. A small NDF fragment containing only the epidermal growth factor domain is also rich in beta-strand structures, but exhibits tertiary structure different from the long NDF forms. Monoclonal antibodies that selectively recognize epidermal growth factor domains of human NDF-alpha and -beta can specifically bind the respective NDF-alpha and -beta isoforms independent of NDF origins. Western blot analysis and quantitative binding assays further identify that an NDF preparation produced naturally from Rat1-EJ cells contains both alpha and beta isoforms in a 3 to 2 ratio. In receptor-binding competition experiments, human and rat NDF-beta isoforms have higher affinity than NDF-alpha isoforms. NDF-beta isoforms can dramatically enhance the stimulation of DNA synthesis for transfected NIH3T3 cells that overexpress HER-3 and HER-4 receptors, while NDF-alpha isoforms can only stimulate proliferation of HER-4-transfected cells with lower activity. Taken together, NDF-alpha and -beta isoforms share similar gross protein conformations but are biologically distinct.

3T3 Cells↗
PubMed1995

Secondary deletional recombination of rearranged switch region in Ig isotype-switched B cells. A mechanism for isotype stabilization.

Analysis of the Ig switch (S) region structure from many stable isotype-switched B cells reveals that the majority of the ultimate switch recombination sites are located at the 5' end, or even upstream of the 5' end of the Smu region. These findings strongly contrast with results from switch circle analysis which reveal that the primary switch recombination sites are preferentially distributed in the middle or at the 3' end of the Smu region. Secondary deletion within recombined chimeric S regions has been proposed as a mechanism to account for the different results. We directly tested whether secondary deletion of rearranged chimeric S regions indeed occurs in human cells. Circular DNAs representing secondary deletion events in gamma switched cells were isolated and characterized by using a specially designed PCR-based approach. Nucleotide sequence analysis revealed that all clones had the S gamma 1-Smu-S gamma 1 structure. Thus, these cloned fragments resulted from secondary deletion/recombination events within a chimeric Smu-S gamma 1 switch region, i.e., rearrangement between its 5' Smu and 3' S gamma 1. Analysis of the Smu region from stimulated B cells also revealed that some Smu regions undergo an internal deletion/rearrangement between the 5' and 3' ends. These results definitively demonstrate that secondary deletion/recombination of chimeric S regions of isotype-switched B cells occurs. Such secondary deletion/recombination events potentially can be responsible for isotype stabilization of switched B cells, as the active Ig gene may have an insufficient amount of retained chimeric switch sequence to serve as a substrate for further S-S recombination.

B-Lymphocytes↗
PubMed1995

A role for C-C chemokines in fibrotic lung disease.

Pulmonary fibrosis is the end point of a chronic inflammatory process characterized by leukocyte recruitment and activation, fibroblast proliferation, and increased extracellular matrix production. Previous studies of models of pulmonary fibrosis have investigated the role of cytokines in the evolution of the fibrotic response. The involvement of tumor necrosis factor and interleukin-1 in bleomycin-induced lung injury, a model of idiopathic pulmonary fibrosis, has been well established, suggesting that cytokines mediate the initiation and maintenance of chronic inflammatory lesions. However, the aforementioned cytokines alone cannot account for the recruitment and activation of specific leukocyte populations found in the bleomycin model. Recently, a family of novel proinflammatory cytokines (chemokines) was cloned and characterized, yielding many putative mediators of leukocyte functions. Macrophage inflammatory protein-1 alpha (MIP-1 alpha) and monocyte chemoattractant protein-1 (MCP-1) belong to the C-C chemotactic cytokine family, a group of low-molecular-weight peptides. These molecules modulate chemotaxis, proliferation, and cytokine expression in leukocyte subsets. Our group has investigated the roles of MCP-1 and MIP-1 alpha in the bleomycin model. Both MCP-1 and MIP-1 alpha are expressed in a time-dependent manner after bleomycin challenge, and passive immunization of these animals with either anti-MIP-1 alpha or anti-MCP-1 antibodies attenuated leukocyte accumulation. In addition, we have identified specific cell types expressing MCP-1 or MIP-1 alpha by in situ hybridization and immunohistochemical localization, respectively. Furthermore, our results indicate that MIP-1 alpha expression is mediated by alveolar macrophage-derived tumor necrosis factor, identifying an important cytokine pathway in the initiation of pulmonary fibrosis. Finally, anti-MIP-1 alpha therapy attenuated fibrosis, providing direct evidence for its involvement in fibrotic pathology. Our work has clearly established that the C-C chemokines MCP-1 and MIP-1 alpha are expressed and contribute to the initiation and maintenance of the bleomycin-induced pulmonary lesion.

Bleomycin↗
PubMed1995

A method for predicting common structures of homologous RNAs.

We have developed a procedure, composed of a set of computer programs, for predicting common RNA structures of homologous sequences. Given a set of homologous RNAs, these programs perform a multiple sequence alignment, generate a list of possible helical stems that are thermodynamically favored in RNA folding from a selected individual sequence, establish a conserved stem list by inspecting the equivalent base pairings and/or conserved helical stems from the derived alignment of homologous RNAs, and build common RNA secondary structures with the maximum scores (i.e., compensatory base changes and number of base pairs, etc.). The approach is a combination of phylogenetic and thermodynamic methods and has been applied to the prediction of common folding structures of the 5' untranslated regions in a number of positive RNA viruses.

Algorithms↗
PubMed1995

Enhanced human IgE production results from exposure to the aromatic hydrocarbons from diesel exhaust: direct effects on B-cell IgE production.

Epidemiologic and experimental studies suggest that air pollution, and particularly diesel exhaust particles (DEPs) may play a role in the increasing prevalence and severity of airway allergic disease. We show that the extract of polyaromatic hydrocarbons (PAHs) from DEPs (PAH-DEP) enhances human IgE production from purified B cells. Interleukin-4 plus CD40 monoclonal antibody-stimulated IgE production was enhanced 20% to 360% by the addition of PAH-DEP over a period of 10 to 14 days. This effect was increased when PAH-DEP was added 2 to 5 days after cultures were initiated. PAH-DEP itself did not induce IgE production or synergize with interleukin-4 alone to induce IgE from purified B cells, suggesting that it was enhancing ongoing IgE production rather than inducing germline transcription or isotype switching. The prototype nonmetabolized aromatic hydrocarbon 2,3,7,8 tetracholorodibenzo-p-dioxin, which functions solely through activation of the cytosolic aromatic hydrocarbon receptor complex, also increased IgE production. Additionally, the pattern of mRNAs coding for distinct isoforms of the epsilon chain was altered by PAH-DEP, and B-cell expression of the low-affinity IgE receptor was upregulated by PAH-DEP. Enhanced IgE production in the human airway, resulting from exposure to PAH-DEP, may be an important factor in the increase in airway allergic disease.

Adult↗
PubMed1995

Omega-3 fatty acids attenuate glomerular capillary hydraulic pressure in rats with renal ablation.

To clarify the emerging role of omega-3 fatty acids (FAs) in the regulation of the renal microcirculation, we recently performed micropuncture studies in normal rats maintained on diets enriched with omega-3 FAs. Although those studies suggested that omega-3 FAs alter the renal microcirculation in normal rats, it was not apparent whether this dietary maneuver could modulate intrarenal hemodynamics in the setting of renal disease. Therefore, the present renal micropuncture studies were performed in nephrectomized rats maintained on control diets or diets enriched with omega-3 FAs. Omega-3 FAs abrogated glomerular capillary (56.2 +/- 0.8 vs. 63.9 +/- 2.0 mm Hg) and transcapillary hydraulic pressure (40.9 +/- 1.4 vs. 50.6 +/- 1.3 mm Hg) compared to untreated rats. This effect was attributable to (1) a reduction in mean arterial pressure (138 +/- 3 vs. 163 +/- 2 mm Hg) and (2) a decrease in efferent arteriolar resistance (0.43 +/- 0.06 vs 0.98 +/- 0.19 dyn x seconds x cm-5 x 10(10)). Sclerosis index and albuminuria were also lessened by this dietary maneuver. To further characterize the mechanism of altered renal arteriolar resistance, we then explored the effects of omega-3 FAs on renal prostaglandin synthesis and angiotensin II-stimulated phospholipid turnover. A significant decrease in the urinary excretion of the renal vasoconstrictor, TXA2 (12.8 +/- 2.3 vs. 35.1 +/- 14.0 ng/24 hr), was induced by treatment with omega-3 FAs. Moreover, angiotensin II-stimulated phospholipid turnover was attenuated in intact glomeruli pretreated with omega-3 FAs. We conclude that omega-3 FAs exert favorable effects on experimental renal injury by eliciting a salutary effect on the renal microcirculation of rats subjected to subtotal renal ablation. Moreover, the similarities between these findings and those obtained with sustained inhibition of angiotensin II converting-enzyme suggest that these compounds act through parallel pathways of inhibition.

Albuminuria↗
PubMed1995

Increased types I and III collagen and transforming growth factor-beta 1 mRNA and protein in hypertrophic burn scar.

Hypertrophic scar is the result of abnormal healing that often follows thermal injury. Hypertrophic scar is characterized by excessive dermal fibrosis and scarring. Five cases of human hypertrophic scar were compared with normal skin using in situ hybridization to localize mRNAs for procollagen types I and III and transforming growth factor-beta 1. Expression of type I procollagen and TGF-beta 1 were also examined with immunohistochemistry. The results demonstrated a significant increase in the expression of mRNA for types I and III procollagen and type I procollagen protein by fibroblasts in hypertrophic scar compared with normal skin. In all cases of hypertrophic scar, significant numbers of cells expressed TGF-beta 1 mRNA or peptide. Neither TGF-beta 1 mRNA nor protein was detected in control tissues. These results suggest a profound increase in production and expression of types I and III collagen mRNA by the fibroblasts in hypertrophic scar. This may result from increased TGF-beta 1 production, through paracrine and autocrine pathways, as have been described for this fibrogenic cytokine.

Base Sequence↗
PubMed1995

[Preconcentration of trace chromium in natural water with activated carbon and its determination by colorimetry].

The adsorption and desorption behavior of chromium was studied. Trace chromium in water could be adsorbed on activated carbon at pH 9-10, then eluted with 0.5% sulfuric acid and determined by colorimetry. The content of chromium could be concentrated by 100 times. For sample, the coefficient of variation of 8 parallel determinations was 7.7%. The proposed method has been applied to the determination of trace chromium in natural waters with the recovery of 71.4%-90.0%, and with the detection limit of 0.04 microgram/L.

Carbon↗