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Biomedical subjects

Z Yuan

Publications and source records attributed to Z Yuan.

At least 163 records · Page 9Linked to original sources
PubMed1995

[The role of tumor necrosis factor in acute pancreatitis and associated multiple organ failure].

In 32 patients with acute pancreatitis (AEP = 15, ANP = 17), tumor necrosis factor (TNF) activity, oxygen-derived free radicals (OFR) and endotoxin contents were determined by L929 cell bioassay, Tetrabarbituric acid fluorometry and Limulus test respectively. The results showed that TNF and OFR elevated in patients with AP at the admission (P < 0.05 vs normal). The change of TNF and OFR responded to the clinical symptoms. TNF correlated to early multiple organ failure (MOF). In patients with late MOF, TNF and OFR were both the important factors. By measuring endotoxin, we found that endotoxemiae were not so important in early phase of the disease as in late phase, in which they made TNF and OFR released profusely.

Acute Disease↗
PubMed1995

Study of cellulose acetate membrane-based glucose biosensors.

A new immobilization procedure was designed to covalently immobilize enzymes onto a cellulose acetate membrane that was simple and easy to handle. The resultant enzyme membrane was very stable, with high specific activity. A glucose oxidase membrane was prepared by using this method, which was combined either with an oxygen electrode or with a hydrogen peroxide electrode to construct a glucose biosensor. The response characteristics of both biosensors were compared.

Biosensing Techniques↗
PubMed1994

Inactivation of a cytosolic phospholipase A2 by thiol-modifying reagents: cysteine residues as potential targets of phospholipase A2.

The cytosolic phospholipase A2 (cPLA2) from the human monocytic cell line U937 contains nine cysteine residues and is subject to oxidation. Iodoacetamide and 5,5'-dithiobis(2-nitrobenzoic acid) were used to explore the susceptibility of cysteine residues to thiol modification agents as outlined in Schemes 2 and 3. In the absence of thiol reducing agents such as DTT, cPLA2 takes up only 2.8 equiv of [1-14C]iodoacetamide at pH 8.03/37 degrees C. With DTT present, cPLA2 is in its fully reduced form, and 4-5 equiv of acetamide are taken up without altering enzyme activity to give IA-cPLA2. A single equivalent of DTNB suffices to inactivate IA-cPLA2, giving a TNB-labeled enzyme, with the loss of activity correlating with release of an equivalent of 5-thio-2-nitrobenzoate. The TNB-labeled enzyme is quite stable up to 33 degrees C; enzyme activity is recoverable with DTT, even after this disulfide-enzyme adduct is incubated with iodoacetamide at pH 9.5, conditions that inactivate the free enzyme. At pH 9.5/37 degrees C, a single equivalent of 14C-labeled iodoacetamide is incorporated by IA-cPLA2 concomitant with complete loss of enzyme activity. Amino acid analysis of the 14C-labeled enzyme indicates that only cysteine residues are labeled. Lys-C digestion of labeled enzyme with 2 M guanidine at pH 8.0 yields a 40-mer peptide. Amino acid sequencing establishes that the label resides primarily in Cys324, although Cys331 is also labeled. These results identify a region of the enzyme that is susceptible to labeling by group modification reagents and may represent a suitable target for small molecule inhibitors.

Amino Acid Sequence↗
PubMed1994

Cloning of four cyclins from maize indicates that higher plants have three structurally distinct groups of mitotic cyclins.

While a large number of cyclins have been described in animals and yeasts, very limited information is available regarding cyclins in plants. We describe here the isolation of cDNA clones encoding four putative mitotic cyclins from maize. All four cyclins were able to induce maturation of Xenopus oocytes, demonstrating that they can act as mitotic cyclins in this system. Northern analysis showed that all four cyclins were expressed only in actively dividing tissues and organs, with a stronger correlation between expression and mitotic activity than is observed with cdc2. The deduced protein sequences suggest that the four maize cyclins belong to the cyclin A and B families identified from animal and yeast studies but that they cannot be described easily as either A-type or B-type cyclins. However, comparison with previously cloned plant cyclins shows that cyclins in higher plants form three distinct structural groups that have been conserved in both monocotyledonous and dicotyledonous species and that cyclins from all three groups are present within a single plant species.

Amino Acid Sequence↗
PubMed1994

Lumbar spine surgery and mortality among Medicare beneficiaries, 1986.

OBJECTIVES: The purpose of this study was to compare lumbar spine surgical procedures by age, gender, and number of comorbidities with respect to mortality in patients 65 years of age and older in the United States. METHODS: A 100% sample of the 1986 Medicare inpatient Health Care Financing Administration claims files databases involving lumbar spine surgical procedures was analyzed. RESULTS: Lumbar spine surgery in 34,418 patients (median age = 71 years) was associated with a significant increase in in-hospital and 1-year cumulative mortality only beyond 80 years of age. When adjusted for age, in-hospital and 1-year cumulative mortality with both decompression and excision procedures were significantly higher in men than in women. When adjusted for both age and gender, mortality increased significantly as the number of comorbidities increased. CONCLUSIONS: With lumbar spine surgery in elderly patients, mortality did not significantly increase until 80 years of age and was consistently associated with decompression and excision, with male gender, and with an increase in number of comorbidities.

Age Factors↗
PubMed1994

Lymph flow and lymphatic drainage of inflammatory cells from the peritoneal cavity in a casein-peritonitis model in sheep.

The purpose of this study was to characterize the cellular responses in the peritoneal cavity and draining lymph in a sterile peritonitis model in conscious sheep. Lymph was collected from lymphatics that drained the peritoneal space (caudal mediastinal and thoracic ducts) as well as from lymph vessels that drained peripheral tissues (prescapular). Casein was used as the inflammatory agent. Dialysis solution (Dianeal 4.25%) containing 1g% casein and 25 microCi 125I-human serum albumin was infused into the peritoneal cavity in 50 ml/kg volumes. Peritoneal volumes increased from a mean infused volume of 1572 +/- 51 ml to a maximum of 2119 +/- 77 ml at 3 hours. Over 6 hours, the number of macrophages and lymphocytes in the peritoneal cavity remained relatively constant but the number of neutrophils increased from 9.9 +/- 4.2 x 10(7) to 9.2 +/- 1.9 x 10(9) total cells. Caudal lymph which drains directly from the peritoneal cavity through diaphragmatic stomata, demonstrated a 5 fold increase in flow rate over 6 hours following the Dianeal-casein infusion. Thoracic duct and prescapular flows declined approximately 70% and 50% respectively in the same time period. the concentration of lymphocytes and the lymphocyte outputs (product of volume and concentration) declined in all lymph compartments. No elevations in neutrophil numbers in the thoracic and prescapular lymph compartments were observed but neutrophil output in the caudal lymph increased steadily from 3.1 +/- 1.5 x 10(6) to 4.6 +/- 1.3 x 10(7)/hr at the 6 hour mark. We conclude that the major route of removal of inflammatory cells and fluid from the peritoneal cavity is through diaphragmatic lymphatics.

Animals↗
PubMed1994

Anatomy and clinical use of posterior interosseous island forearm flap.

Posterior interosseous island flap of the forearm is still not widely known. It deserves more attention as a useful means of reconstruction on the dorsal side of the hand up to the PIP joints of the fingers. The technique is relatively easy, and the anatomy is quite consistent, as described. Tactile sensation can be re-established, and infection cavities can be filled up. Two cases are illustrated as examples.

Adolescent↗
PubMed1993

Alcohol-related hospitalizations of elderly people. Prevalence and geographic variation in the United States.

OBJECTIVE: To determine the prevalence, geographic variation, and charges to Medicare of alcohol-related hospitalizations among elderly people in the United States. DESIGN: A cross-sectional prevalence study using 1989 hospital claims data from the Health Care Financing Administration (HCFA). Rates were determined using (1) hospital claims records from the HCFA's Medicare Provider Analysis and Review Record (MEDPAR) database for all Medicare Part A beneficiaries aged 65 years and older; (2) county population estimates for 1985 from the Bureau of the Census; and (3) per capita consumption of alcohol by state in 1989 as estimated by the US Department of Health and Human Services. SETTING: Data include all hospital inpatient Medicare Part A beneficiaries aged 65 years and older in the United States in 1989. RESULTS: The prevalence of alcohol-related hospitalizations among people aged 65 years and older nationally in 1989 was 54.7 per 10,000 population for men and 14.8 per 10,000 for women. Comparison with hospital records showed that MEDPAR data had a sensitivity of 77% to detect alcohol-related hospitalizations. There was considerable geographic variation; prevalence ranged from 18.9 per 10,000 in Arkansas to 77.0 per 10,000 in Alaska. A strong correlation existed between alcohol-related hospitalizations and per capita consumption of alcohol by state (Spearman correlation coefficient, .64; P < .0001). In 1989, the hospital-associated charges to Medicare for all admissions where the primary diagnosis was alcohol related (N = 33,039) totaled $233,543,500. Median charge per hospital stay was $4514. CONCLUSIONS: Alcohol-related hospitalizations among elderly people are common; rates were similar to those for myocardial infarction as detected by the same method. The charges to Medicare for this preventable problem are considerable. Ecological analysis suggests that per capita consumption in the total US population predicts alcohol-related hospitalizations in the elderly population.

Aged↗
PubMed1993

[Narrow angle type of chronic simple glaucoma: a report of 9 cases].

Nine patients (16 eyes) with narrow angle type of chronic simple glaucoma were evaluated. Besides the general definition, narrow angle type of chronic simple glaucoma is a special type of primary open angle glaucoma which has a narrow and open angle on goniogscopy, no obvious difference on angle configuration at low or high IOP. Laser peripheral iridectomy may be a method of differential diagnosis in this type of glaucoma and may be relatively effective in preventing further attacks of acute angle closure glaucoma which is due to the lens continues to enlarge with age and causes pupillary block. The medical treatment is the first choice to deal with this type of glaucoma, while it can not be controlled, the filtering operations should be used in time.

Diagnosis, Differential↗
PubMed1993

Extended Kalman filter (EKF) application in vitamin C two-step fermentation process.

Based on kinetic model study of vitamin C two-step fermentation, the extended Kalman filter (EKF) theory is conducted for studying the process which is disturbed by white noise to some extent caused by the model, the fermentation system and operation fluctuation. EKF shows that calculated results from estimated process parameters agree with the experimental results considerably better than model prediction without using estimated parameters. Parameter analysis gives a better understanding of the kinetics and provides a basis for state estimation and state prediction.

Ascorbic Acid↗
PubMed1992

Electron transfer from nucleobase electron adducts to 5-bromouracil. Is guanine an ultimate sink for the electron in irradiated DNA?

Electron transfer to 5-bromouracil (5-BrU) from nucleobase (N) electron adducts (and their protonated forms) has been studied by product analysis and pulse radiolysis. When an electron is transferred to 5-BrU, the ensuing 5-BrU radical anion rapidly loses a bromide ion; the uracilyl radical thus formed reacts with added t-butanol, yielding uracil. From the uracil yields measured as the function of [N]/[5-BrU] after gamma-radiolysis of Ar-saturated solutions it is concluded that thymine and adenine electron adducts and their heteroatomprotonated forms transfer electrons quantitatively to 5-BrU. Like the electron adduct of adenine, those of cytosine and guanine are rapidly protonated by water. The (protonated) electron adduct of guanine does not transfer an electron to 5-BrU, and in the case of the (protonated) cytosine electron adduct only partial electron transfer is observed. The results can be modelled if the protonated electron adduct (protonated at N(3) or at the amino group) of cytosine, CH., which can transfer its electron to 5-BrU (k approximately 2 x 10(7) dm3 mol-1 s-1) is transformed in a slow tautomerization reaction (k approximately 2.5 x +/- 10(3) s-1) into another form C'H. (possibly protonated at C(6) or C(5)) which does not transfer an electron to 5-BrU. There is also electron transfer from the electron adduct of thymine to cytosine and guanine which serve as electron sinks. The rate constant of electron transfer from the thymine electron adduct to cytosine is about 250 times greater than that of the reverse reaction. The heteroatom-protonated electron-adduct of thymidine transfers an electron to 5-BrU more slowly (k = 2.3 x 10(7) dm3 mol-1 s-1) than the electron-adduct itself (k = 7.2 x 10(8) dm3 mol-1 s-1). Phosphate buffer-induced protonation of the electron-adduct of thymine at carbon (C(6)) prevents electron transfer to 5-BrU. Such phosphate catalysis is also observed as an intramolecular process (k approximately 2 x 10(4) s-1) with thymidine-5'-phosphate but not with the 3'-phosphate. Phosphate-induced protonation at carbon also reduces transfer efficiency for the electron adducts of dinucleoside phosphates such as dTpdT and dTpdA. The data raise the question whether in DNA the guanine moiety may act as the ultimate sink of the electron in competition with other processes such as protonation at C(6) of the thymine electron adduct.

Adenine↗
PubMed1992

Studies on kinetic model of vitamin C two-step fermentation process.

This paper aims at analyzing the bioconversion process from L-sorbose to 2-Keto-L-gulonic acid with the aid of the growth factor assumption. Fermentation mechanism is discussed after making necessary simplifications. A model is established for this second step fermentation process. Nonlinear optimization together with Runge-Kutta method, are used to obtain model parameters. Results of computer simulation agree with experimental data to show the reliability of the kinetic model.

Ascorbic Acid↗
PubMed1992

[DNA probe for identification of sibling species of Anopheles sinensis and Anopheles anthropophagus].

Genomic DNA libraries of Anopheles sinensis and Anopheles anthropophagus were constructed. The positive clones suitable for discrimination sibling species of An. sinensis and An. anthropophagus were screened and a clone from An. sinensis DNA library was selected and the insert DNA was used as a DNA probe to test dot blot of genomic DNA from An. sinensis and An. anthropophagus. The results showed that the DNA probe hybridized with all stages of An. sinensis DNA, but had very weak hybridization signal with An. anthropophagus DNA. The probe was very sensitive and could detect as little as 7.5ng An. sinensis which represents approximately one-150th part of the total DNA from single mosquito. The results demonstrated that the DNA probe reported here could be used to distinguish species of An.sinensis from An. anthropophagus.

Animals↗
PubMed1990

The role of fructose 2,6-bisphosphate in glycolytic oscillations in extracts and cells of Saccharomyces cerevisiae.

Fructose 2,6-bisphosphate is physiologically one of the most potent activators of yeast 6-phosphofructo-1-kinase. The glycolytic oscillation observed in cell-free cytoplasmic extracts of the yeast Saccharomyces cerevisiae responds to the addition of fructose 2,6-bisphosphate in micromolar concentrations by showing a pronounced decrease of both the amplitude and the period. The oscillations can be suppressed completely by 10 microM and above of this activator but recovers almost fully (95%) to the unperturbed state after 3 h. Fructose 2,6-bisphosphate shifts the phases of the oscillations by a maximal +/- 60 degrees. Oscillations in concentration of endogenous fructose 2,6-bisphosphate in the extract were also observed. Fructose 2,6-bisphosphate alters the dynamic properties of 6-phosphofructo-1-kinase which are vital for its role as the 'oscillophore'. However, the minute amount (approximately 0.3 microM) of endogenous fructose 2,6-bisphosphate and the phase relationship of its oscillations compared with other metabolites indicate that this activator is not an essential component of the oscillatory mechanism. Further support for this conclusion is the observation of sustained oscillations in both the extracts and a population of intact cells of a mutant strain (YFA) of S. cerevisiae with no detectable fructose 2,6-bisphosphate (less than 5 nM).

Adenosine Monophosphate↗
PubMed1990

[Bioelectric potentials of bone in experimental fracture healing].

A specific electric potential gradient exists on the surface of long bone and the electric gradient changes after fracture. The electric potentials at the fracture site were measured and it was shown to change most actively during the early healing phase, and thereafter reached the normal level gradually. When soft tissue was damaged, certain potential changes occurred. But this change was different from that in the fracture site, indicating that the tissue has "biological window" effect of electrization.

Animals↗
PubMed1990

[Establishment of standard strains of serotypes (groups) of Streptococcus pneumoniae in China].

Streptococcus pneumoniae is an important human pathogen which is responsible for life-threatening infections such as pneumonia, bacteremia and meningitis as well as for less severe but highly prevalent diseases such as otitis media and sinusitis. The number of serogroups (types) of Streptococcus pneumoniae found in the world is total 46 groups or 83 types according to typing system of Statens Serum Institute, Copenhagen, Denmark. The standard strains established in our lab of 42 groups or 67 types distributed in 17 different regions in China. The significance of this study is that two of the new serotypes (10C, 16A) are first reported in the literature in which the microbes were the agents causing pneumococcal infections. Our standard strains also include some serotypes on rare occasions such as 19C and 22A and 33C which have been found only in Asia. Our findings not only increase the total number of known types of pneumococci from 83 to 85, but also indicate that China has made progress in the field of pneumococcal research. It is the first time to report establishing a series of standard strains of pneumococci involving many serotypes (groups) in China. The work is necessary as a preliminary for pneumococcal disease prevention and treatment. The standard strains listed here with providing the resource of strain and scientific basis for developing vaccine and biological products.

China↗