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Biomedical subjects

L Xu

Publications and source records attributed to L Xu.

At least 595 records · Page 33Linked to original sources
PubMed1996

Reforming China's 50,000 township hospitals--effectiveness, challenges and opportunities.

The 50,000 publicly-owned Rural Township Hospitals (RTHs) in China play an important role in providing both curative and preventive services to China's 800 million rural population. Since the market oriented rural economic reform initiated in the early 1980s, the RTHs' position has been threatened by low efficiency and financial crisis. More than half of the RTH resources have been wasted and about one-third of the RTHs have run into deficit. Reforms have been undertaken, but the problems are still challenging. Several policy options are now being discussed including revolutionary strengthening of the RTHs to attract patients, leaving the RTHs as they are but guaranteeing the funds for prevention services, and strengthening the RTHs having relatively high efficiency. However the discussions have not been translated into national policies. The statistics for 1995 show that the RTHs are taking a turn for the better after a decade of continuous decline in both the number of visits and bed occupancy rates. These changes can be explained by the widespread government concerns with the development of RTHs, the incremental capacity-strengthening of RTHs, and government's efforts to construct a workable Cooperative Medical System (CMS). The authors recommend that the government should play a major and active role in regulating and financing the RTHs and CMS. Demand deflection through promoting CMS and repricing the RTH medical services at relatively low level is important, and government support to strengthen the RTHs is essential for maintaining the deflected demand. Neither of the two conditions can be ignored. Interventions should be made on both supply and demand side.

China↗
PubMed1996

A new wound healing agent--sphingosylphosphorylcholine.

Spingosylphosphorylcholine (lysosphingomyelin or SPC) is an effective and broad spectrum cell growth promoting agent and a candidate for evaluation on wound healing. The effect of SPC on full-thickness excision and incision wounds in genetically healing-impaired diabetic (db/db) mice was evaluated by measurement of wound area, skin strength, and tissue histology. The effect on cell proliferation was measured in vivo by incorporation of bromo-deoxyuridine and in vitro by [3H] thymidine incorporation. SPC increased the rate of wound closure, with a statistically significant improvement in measured wound areas (p < 0.02, compared with vehicle controls). The optimum concentration was 2-3 microM. SPC, alone and in combination with insulin, stimulated DNA synthesis in cells known to participate in wound healing, including microvascular endothelial cells. In vivo, SPC stimulated proliferation of keratinocytes, fibroblasts, endothelial cells, and cells around sebaceous glands and hair follicles at day 2-4 postwound, resulting in a complete re- epithelialization and profound granulation tissue formation in excisional and incisional wound sites of db.db and db/+ mice. Quantitative assessment of wound tissue section morphology indicated that SPC induced up to a 3-fold increase in the numbers of mitotic cells, resulted in smaller cross-sectional scar area, and led to more normalized tissue in the wound sites. SPC had no deleterious effect on wound skin strength. In conclusion, the acceleration of dermal wound healing animal models suggests that SPC could be an interesting candidate for clinical application.

Animals↗
PubMed1996

Role of alpha beta T cells and gamma delta T cells in protective immunity to Actinobacillus actinomycetemcomitans in mutant mice by targeted gene disruption.

The relative roles of alpha beta or gamma delta T cells in protection against Actinobacillus actinomycetemcomitans were analysed by using mutant mice deficient in alpha beta or gamma delta T cell receptor (TCR). The dose of A. actinomycetemcomitans producing lethality for the TCR-alpha deficient mice was 25% of that for control C57BL/6 mice, while that of TCR-delta deficient mice was similar to that of C57BL/6 mice. Reverse transcription (RT)-PCR revealed that gamma delta T cells from the A. actinomycetemcomitans-infected alpha beta TCR deficient mice expressed significant levels of interferon (IFN)-gamma, interleukin (IL)-5 and IL-6 mRNA, whereas alpha beta T cells from A. actinomycetemcomitans-infected gamma delta TCR deficient mice exhibited significant levels of IFN-gamma and IL-2 mRNA. Delayed-type hypersensitivity (DTH) reactions against heat shock protein (HSP) 60 were prominently observed in A. actinomycetemcomitans-infected TCR-delta mutant and C57BL/6 mice, but were absent in TCR-alpha mutant mice, suggesting that the DTH response is exclusively dependent on HSP60-specific alpha beta T cells producing IFN-gamma and IL-2 mRNA. It was found that all the mice used exhibited similar levels of serum IgG and IgM responses against A. actinomycetemcomitans-specific antigens (whole cells and HSP60), suggesting that alpha beta as well as gamma delta T cells participate in the serum immune responses. In addition, the humoral antibody responses displayed in the TCR-alpha deficient mice implies resistance to A. actinomycetemcomitans infection. Thus, the resistance to A. actinomycetemcomitans infection may be ascribed mainly to alpha beta T cells, while gamma delta T cells can partially compensate for the alpha beta T cell defect.

Aggregatibacter actinomycetemcomitans↗
PubMed1996

Diversity of soil actinomycetes in yunnan, china.

Since 1978, about 4,200 soil samples have been collected from 22 selected areas of various vegetational and climatic types throughout the province of Yunnan. Actinomycetes of 29 genera were isolated by the methods employed. The correlations between diversity and climate were grouped into tropical, subtropical plateau, cool temperate mountain, and snowy mountain types. Actinomycete populations of the first two types were more complex than were the other ones. Correlations between actinomycete diversity and vegetation were also attempted. Six types of vegetation were compared. The diversity of actinomycetes was greatest in soil samples of a primeval forest, with an average of 9.0 genera isolated, followed by secondary forest and vegetable farmland samples, with averages of 6.7 and 6.5 genera isolated, respectively. The upper limit for the occurrence of thermophilic actinomycetes is about 3,500 m above sea level in Yunnan. Psychrophilic actinomycetes were isolated at up to the same altitude. In addition, the drier and poorer the soil was and the cooler the climate was, the lower the count of actinomycetes was and the higher the percentage of streptomycetes observed was. The genus Streptomyces appears to be the most important in ecological function. It represents up to 90% of all soil actinomycete diversity in Yunnan and is likely an important characteristic of the soil actinomycete population.

Journal Article↗
PubMed1996

Diversity of aquatic actinomycetes in lakes of the middle plateau, yunnan, china.

A total of 749 sediment and water samples were collected from 12 lakes of the Middle Plateau of Yunnan from 1983 to 1993. The diversity and biological characteristics of the aquatic actinomycetes in these lakes were studied. Sixteen genera of actinomycetes were isolated from these samples. Micromonospores assumed a notable dominance (from 39 to 89%) in the actinomycete populations of these lake sediments. Streptomycetes were the second most abundant organisms. The diversity and counts of actinomycetes varied with the season. Thermophilic actinomycetes have a wide distribution in these lakes, but their counts were smaller. The cell wall compositions of certain Micromonospora and Streptomyces strains from an alkaline lake revealed an unusual combination of glycine and isomers of diaminopimelic acid. It seems that aquatic actinomycetes play a significant role in the decomposition of organic substances, including some toxic compounds such as phenol, in these lakes. It also appears that aquatic actinomycetes are one of the important resources for screening useful enzymes and metabolites.

Journal Article↗
PubMed1996

Learning multiple causes by competition enhanced least mean square error reconstruction.

In this paper we studied a self-organization principle that input should be best reconstructed from a factorial distributed hidden representation, which has been addressed in the literature recently. An auto-encoder network is trained by the Least Mean Square Error Reconstruction (LMSER) while the redundance in the representation is reduced by a proposed anti-Hebbian scheme, in which a penalty term called Receptive Field Overlapping Index (RFOI) is combined into the objective function for enhancing competition among nodes in the network. Our learning scheme provides a way for balancing the cooperation and competition necessary for the self-organization process thus realizes the multiple causes model, which accounts for an observed data by combining assertions from the discovered causes or features in the data. Our experiment results demonstrate again the powerful information processing capability inherent to the popular weighted sum followed by sigmoid squashing. Comparing with previous probability theory based multiple causes models, our scheme is much easier to implement and quite reliable.

Algorithms↗
PubMed1996

ANG II chronically supports renal and lumbar sympathetic activity in sodium-deprived, conscious rats.

The hypothesis that chronic elevations in endogenous angiotensin II (ANG II) increase sympathetic outflow in conscious, normotensive rats was tested by determining if acute blockade of ANG II receptors with losartan (10 mg/kg iv) decreases renal sympathetic nerve activity (RSNA), lumbar sympathetic nerve activity (LSNA), or heart rate (HR) more in rats with higher ANG II levels due to a low sodium (LS) diet compared with a control sodium (CS) or high sodium (HS) diet. In LS rats, losartan decreased (P < 0.05) mean arterial pressure (MAP) in two phases: an immediate decrease of 23 +/- 2 mmHg and a slower fall to 35 +/- 4 mmHg below control 40 min postlosartan. Five minutes after losartan, RSNA (149 +/- 13%), LSNA (143 +/- 5%), and HR (109 +/- 2%) were increased (P < 0.05). Despite further falls in MAP, the elevation in RSNA and HR remained constant, and LSNA decreased toward control (119 +/- 4%). After restoration of MAP to basal levels with methoxamine or phenylephrine infusion, RSNA (46 +/- 8%), LSNA (49 +/- 11%), and HR (76 +/- 2%) were suppressed (P < 0.05). In CS rats, losartan also initially decreased (P < 0.05) MAP by 6 +/- 2 mmHg and increased (P < 0.05) RSNA to 129 +/- 13%. When MAP was returned to control, RSNA was decreased (70 +/- 8%; P < 0.05) but less than in LS rats. In contrast, no changes in MAP, RSNA, LSNA, or HR were observed after losartan in HS rats. In conclusion, endogenous ANG II chronically supports RSNA, LSNA, and HR in conscious, normotensive low and normal sodium intake rats.

Adrenergic alpha-Agonists↗
PubMed1996

Endogenous nitric oxide contributes to strain-related differences in airway responsiveness in rats.

The effects of N(omega-nitro-L-arginine (L-NNA), a nitric oxide synthase inhibitor, on airway responsiveness were studied in the spontaneously hyperresponsive Fischer and the control normoresponsive Lewis rat strains to investigate the role of the endogenous nitric oxide (NO) pathway in strain-related differences in airway responsiveness. Responsiveness to inhaled methacholine was significantly increased in L-NNA-treated Lewis rats but not in Fischer rats. L-NNA increased carbachol-induced tracheal contractions in vitro to a larger extent in Lewis rats compared with Fischer rats. The effect of L-NNA was abolished by removal of the epithelium. Carbachol induced a NO-dependent increase in guanosine 3',5'-cyclic monophosphate levels in tracheal tissues but to a lesser extent in Fischer (2.1-fold increase) than in Lewis (3.7-fold increase) rats. In conclusion, endogenous NO is involved in the regulation of airway responsiveness to cholinergic agonists in rats. A relatively ineffective NO-guanosine 3',5'-cyclic monophosphate regulatory mechanism in Fischer rats contributes, in part, to strain-related differences in airway responsiveness between Fischer and Lewis rats.

Animals↗
PubMed1996

Regulation of cardiac Ca2+ release channel (ryanodine receptor) by Ca2+, H+, Mg2+, and adenine nucleotides under normal and simulated ischemic conditions.

In myocardial ischemia, pHi and [ATP] fall, whereas the free [Ca2+] and [Mg2+] rise. The effects of these changes on cardiac Ca2+ release channel (ryanodine receptor) activity were investigated in [3H]ryanodine binding and single-channel measurements, using isolated membrane and purified channel preparations. In the absence of the two channel ligands Mg2+ and ATP, cardiac Ca2+ release channels were half-maximally activated at pH 7.4 by approximately 4 mumol/L cytosolic Ca2+ and half-maximally inhibited by approximately 9 mmol/L cytosolic Ca2+. Regulation of channel activity by Ca2+ was modulated by Mg2+ and ATP. Single-channel activities were more sensitive to a change of cytosolic pH than SR lumenal pH. Reduction in lumenal and/or cytosolic pH from 7.3 to 6.5 and 6.0 resulted in decreased single-channel activities without a change in single-channel conductance. [3H]Ryanodine binding measurements also indicated that acidosis impairs cardiac Ca2+ release channel activity. Mg2+ and adenine nucleotide concentrations regulated the extent of inhibition and the Ca2+ dependence of binding. In the presence of 5 mmol/L Mg2+ and 5 mmol/L beta, gamma-methyleneadenosine 5'-triphosphate (AMPPCP, a nonhydrolyzable ATP analogue), the free [Ca2+] for half-maximal [3H]ryanodine binding was increased from 1.9 mumol/L at pH 7.3 to 36 mumol/L at pH 6.5 and to 89 mumol/L at pH 6.2. These results suggest that ionic and metabolic changes that might be expected to affect sarcoplasmic reticulum Ca2+ release channel activity in ischemic myocardium include an altered Ca2+ sensitivity of the channel, a fall in pH, and a loss of the high-energy adenine nucleotide pool, leading to an increased inhibition by Mg2+.

Animals↗
PubMed1996

Functional STAT 1 and 3 signaling by the leptin receptor (OB-R); reduced expression of the rat fatty leptin receptor in transfected cells.

The leptin receptor (OB-R) bears homology to members of the class I cytokine receptor family. We demonstrate that leptin binding to OB-R stimulates formation of STAT-1 and STAT-3 complexes, thereby defining transcriptional motifs for genes that are under leptin control. Transfected fa OB-R bound leptin with equal affinity to that of wild type OB-R. fa OB-R abundance was about 7 fold reduced compared to control cells. Surprisingly, the low level of fa OB-R is fully capable of activating the STAT signal transduction pathway. We discuss plausible explanations for the obese phenotype in Zucker fatty rats.

Animals↗
PubMed1996

Decidual prolactin-related protein: heterologous expression and characterization.

As a first step in understanding the role of decidual PRL-related protein (dPRP) during pregnancy, we have generated recombinant dPRP protein. In this report, we present data on the generation, purification, and characterization of recombinant dPRP protein. The dPRP complementary DNA was subcloned into the pMSXND vector, and the vector was transfected into Chinese hamster ovary (CHO) cells by electroporation. After appropriate selection, amplification, and induction procedures, recombinant dPRP was purified from conditioned medium of the CHO-dPRP cells using ultrafiltration, size-exclusion chromatography, and reverse phase HPLC. Recombinant dPRP was found to possess electrophoretic mobility, immunoreactivity, and N-terminal amino acid sequence identical to those of dPRP isolated from decidual tissue. Polyclonal antibodies were generated to the recombinant dPRP and used for Western blot analysis. dPRP is capable of binding heparin, and a significant fraction of synthesized dPRP resides within the decidual extracellular matrix. Recombinant dPRP failed to bind to PRL receptors and showed no stimulatory activity in the PRL-dependent rat Nb2 lymphoma cell proliferation assay. Additional studies have shown that heterologous expression of dPRP in CHO cells significantly increased the ability of CHO cells to form tumors in athymic mice. In conclusion, recombinant dPRP possesses characteristics similar to those of dPRP of decidual origin and is a heparin-binding protein that may facilitate the establishment of pregnancy.

Animals↗
PubMed1996

Effect of antibody specificity on results of selected digoxin immunoassays among various clinical groups.

We examined the specificity of three automated digoxin immunoassays (Abbott TDxFLx Digoxin II assay, Baxter-Dade Stratus II Digoxin assay, and Ciba Corning ACS Digoxin assay) applied without modification to (a) sera from 229 digoxin-free patients in 12 cohorts associated with nonspecific or endogenous digoxin-like immunoreactive factor (DLIF) interference, and (b) drug-free serum supplemented with the major metabolites and analogs of digoxin. We observed three patterns of apparent digoxin results among the DLIF samples: one common to kidney and liver failure patients, where TDx and Stratus assays showed significant positive results; one common to newborns and cord blood, where only the TDx assay had significant interference; and one from cardiac surgery patients, where the Stratus assay alone showed interference. Of the three assays, the ACS had the least interference from DLIF. The assays also behaved differently with respect to cross-reactivity with digoxin metabolites, digitoxin, and digitoxin metabolites. The ACS assay again had the least analog or metabolite cross-reactivity. The three methods agreed well on digoxin-positive specimens, with a mean bias of <0.15 microgram/L digoxin for each and discrepancies (defined as >3 SD between the assay pairs compared) of only 3-5%.

Antibody Specificity↗
PubMed1996

The effects of dermatan sulfate at submicrogram/ml concentrations on in vitro thrombin generation.

Dermatan sulfate is an antithrombotic glycosaminoglycan which has been shown to be effective in preventing deep venous thrombosis in general surgery patients when present at concentrations less than 1 microgram/ml. It has also been found to circulate physiologically in similar concentrations in pregnant women at term and in cord blood. We investigated the ability of dermatan sulfate added to plasma at 0.2, 0.5 and 1.0 microgram/ml to inhibit thrombin generation initiated by low concentrations of recombinant human tissue factor in defibrinated plasma. A dose dependent decrease in thrombin potential was demonstrated at therapeutically relevant concentrations of dermatan sulfate (0.5 and 1.0 microgram/ml) but there was no induction of a lag phase in thrombin generation. We were unable to demonstrate a significant effect on thrombin potential of dermatan sulfate at a concentration similar to that found in pregnancy plasma (0.2 microgram/ml). This indicates that either the dermatan sulfate concentration found in pregnancy plasma is not physiologically relevant or that our experimental system (which lacks platelets and fibrin) does not accurately reflect physiologic conditions. The effect on the thrombin potential was somewhat greater at the lowest concentration of tissue factor and amounted to a maximum inhibition of approximately 50% at 1 microgram/ml dermatan sulfate. A dose dependent increase in formation of thrombin-heparin cofactor II complexes and a decrease in thrombin-antithrombin complex formation with increasing dermatan sulfate concentration were observed at all dermatan sulfate concentrations. Prothrombin consumption was not changed by any dose of dermatan sulfate. We conclude that dermatan sulfate, at the concentrations tested, catalyses inhibition of free thrombin by heparin cofactor II but not efficiently enough to inhibit prothrombinase formation.

Dermatan Sulfate↗
PubMed1996

[Rates of hip fractures in Beijing China].

One-third of the world's hip fractures are said to occur in Asia, but there have been no validated studies of hip fracture rates in China. In 1988-1992 all 76 hospitals in Beijing reported 820 hip fracture admissions coded as ICD-9. Checking against original discharge logs, medical records, X-ray reports, operation notes and operating room logs of a random sample of Beijing hospitals to discover underestimated and misclassified cases. In order to estimate hip fracture treated outside hospitals, we also interviewed a random sample of 2113 women aged 50 and over with a 97% response rate in Beijing. Finally, we also surveyed 27 hospitals in the suburbs of Beijing, but have found that no Beijing residents had been treated for hip fracture outside the city. Based on the 1990 China census, age-standardized rates (per 100,000) of hip fractures in Beijing were 88 for women, 97 for men. From 1988 to 1992, the rates in Beijing increased 35% in women and 33% in men. This is the first validated population-based study on the rates of hip fractures in China that has confirmed the completeness and accuracy of reports of hip fracture cases and has estimated the degree of under-reporting of hospital discharge. Hip fracture rates in Beijing are among the lowest in the world but may rise rapidly.

Aged↗
PubMed1996

[HP8: the partial cDNA clone of a novel member of C/EBP gene family].

OBJECTIVE: To explore the human C/EBP related genes. METHODS: Screening human placenta cDNA library with rat C/EBP cDNA probe. RESULTS: One positive clone, HP8 was obtained. This clone contained 1975 base pairs which include 604 coding base pairs. The matched DNA sequence was not found in the gene database (EMBL 95.6). The 201 amino acids encoded by this gene had the leucine zipper structure and demonstrated the highest homology (97%) with C/EBP throughout the DNA-binding domain and leucine repeat region (C-terminal 60 amino acids). Beyond this region, only low homology was detected in HP8 protein and C/EBP or C/EBP related proteins. Herewith, HP8 was defined as a novel member of C/EBP gene family. Genomic Southern blot analysis confirmed that HP8 was a single copy gene. Northern blot analysis in 14 different fetus tissues showed that high level of HP8 mRNA was expressed in small intestine and skin, middle level in adrenal gland, low level in liver, lung, kidney, thyroid gland and gallbladder. In 3 human adult liver tissues, only one low level HP8 mRNA, whereas of 5 hepatomas and one of their surrounding nontumorous hepatic tissues had, high level HP8 mRNA. CONCLUSION: These results suggested that HP8 gene might be a transactivator related to cell growth. As Northern blot analysis indicated, HP8 gene has about 2.7 Kb full length cDNA.

Adult↗
PubMed1996

[Obstetric quality investigation on urban and rural area in China].

OBJECTIVE: A survey on implementing the proclamation in "National plan of action for the survival, protection and development of children in 1990s" in China (NPA), by reducing the maternal mortality rate (MMR) by half and the infant mortality rate (IMR) by 1/3 by the year 2000 as a proof of improved obstetric quality. METHOD: The maternal and child health (MCH) bureau, ministry of health, have called on a cooperative investigation on obstetric quality in 75 obstetric clinics in 11 provinces, municipalities or autonomous regions, randomly sampled from each of the 6 governmental areas in China. The data were collected and analyzed centrally, together with the yearly reports from the monitored county hospitals. RESULTS: Senior medical professionals associated to 32.68% in provincial and teaching hospitals while only 2.63% in the country hospitals. The former are provided with all necessary equipment while the latter with inadequate and outdated ones. MMR declined year by year, more marked wherever hospital delivery rate was high and when the numbers of antenatal visit were more. However, when antenatal visit began late in pregnancy, MMR rose Zhejiang province and Shanghai ranked first in obstetric quality because of an efficient systematic management of the pregnancies. CONCLUSIONS: Having enough leading professionals in this specialty to train adequate medical ground personnel at grass root level; providing sufficient medical installations; enforcing easily and good quality antenatal care and increasing hospital deliveries carried out under authoritative management are important points to raise the quality of obstetrics.

China↗
PubMed1996

[Study on the level of negative pressure of closed suction drainage of the peritoneal cavity].

An animal experiment and clinical investigations have been done to choose a suitable negative pressure of closed suction drainage of the peritoneal cavity. The results indicated that the efficiency of routine portable bulb suction devices giving 5.6-16 kPa was lower than vacuum bottles made by our hospital giving 58.86-73.15 kPa. This suggested that the level of negative pressure of the portable bulb suction devices can be increased to 58.86 to 73.15 kPa. The best one is 58.86 kPa.

Drainage↗