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Biomedical subjects

L W Chen

Publications and source records attributed to L W Chen.

At least 55 records · Page 3Linked to original sources
PubMed1998

Mesencephalic dopaminergic neurons expressing neuromedin K receptor (NK3): a double immunocytochemical study in the rat.

By using a double immunocytochemical method we examined the distribution of dopaminergic neurons expressing neuromedin K receptor (NKR; NK3) in the rat brain. The distribution of NKR-like immunoreactive (-LI) neurons completely overlapped that of tyrosine hydroxylase (TH)-LI neurons in the retrorubral field (A8), substantia nigra (A9), ventral tegmental area and nucleus raphe linealis (A10). Completely or partially overlapping distributions of NKR- and TH-LI neurons were found in certain regions of the hypothalamus (A11-A15) and olfactory bulb (A16). Neurons showing both NKR- and TH-like immunoreactivities, however, were only found in A8-A10: All of the NKR-LI neurons displayed TH-like immunoreactivity, and about 71-86% of the TH-LI neurons expressed NKR-like immunoreactivity. The present results provided morphological evidence for physiological modulation of dopaminergic neurons by tachykinins through NKR in A8-A10.

Animals↗
PubMed1998

Specific inhibition of iNOS decreases the intestinal mucosal peroxynitrite level and improves the barrier function after thermal injury.

Failure of GI tract mucosa to act as a barrier against bacterial translocation (BT) has been proposed as a potential source of sepsis and subsequent multiple organ failure post thermal injury. Nitric oxide (NO) is an inorganic radical produced by NO synthase (NOS) from L-arginine. Gut mucosal constitutive NOS (cNOS) provides protection for itself. In contrast to cNOS, inducible NOS (iNOS) releases far greater amounts of NO, promotes oxidative reactions and is responsible for tissue injury. Peroxynitrite formed by the rapid reaction between superoxide and NO, is a toxic substance that contributes to tissue injury in a number of biological systems. This study was designed to investigate the effect of iNOS specific inhibitor S-methylisothiourea (SMT) on the postburn intestinal mucosal barrier function and the possible mechanism of SMT's action. Female SPF Sprague Dawley rats underwent 35% total body surface area (TBSA) or sham burn. Either SMT or the same volume of saline was given (5 mg/kg, i.p. q 12 h) for 2 days to assess the effect of iNOS inhibition. On postburn day 2, the intestinal mucosal cNOS and iNOS activity were assayed by using Griess' reagent, the mesenteric lymph node (MLN), spleen and liver were collected and cultured for BT assay and the cellular localization of nitrotyrosine, a marker for peroxynitrite activity, was examined by immunostaining. After thermal injury in rats, administration of SMT for 2 days decreased the intestinal mucosal iNOS activity/ tNOS activity ratio and the BT incidence. Nitrotyrosine immunostaining of the intestinal mucosa showed a decrease in the SMT-treated group. These findings suggest that SMT, a specific inhibitor for iNOS improves the barrier function after burn by suppression of the intestinal mucosal iNOS activity. The decrease in NO production resulted in decreased formation of peroxynitrite and subsequently decreased damage of mucosal tissue.

Animals↗
PubMed1998

Use of health services by Chinese elderly in Beijing.

OBJECTIVES: This article provides an inquiry into use of health services by the elderly. METHODS: The authors operationalize models of use with a survey of 350 elderly Chinese. Because the survey involves native Chinese, the empirical test can isolate functional social support as well as "structural" social supports (marriage, living with children). RESULTS: The principal findings comport with prior work: the strongest determinants of the use of health services by the elderly are those that relate to need. In addition, structural social support impacts use but demonstrates complex patterns. CONCLUSIONS: The availability of family support increases physician visits while diminishing the probability of a hospital stay. Increased Western physician use ties to increased use of Chinese physicians and increased hospitalization. Functional social support plays a role as well. Finally, income effects did not play a large role in determining the use of health services among this population.

Activities of Daily Living↗
PubMed1997

Loss of expression of the p16 gene is frequent in malignant skin tumors.

Expression of the p16 gene from 30 malignant skin tumors has been surveyed by immunohistochemical assay. Gene point mutations were detected by DNA direct sequencing and the mRNA level of gene expression was measured by RT-PCR. A silent point mutation of the p16 gene was found in only one patient. However, loss of expression of the p16 gene was noticed in 23 of 29 samples (79.3%). Correlation between loss of expression of the p16 gene and metastasis is significant (p = 0.0036). These findings suggest that loss of expression of the p16 gene may play a critical role in tumor progression of malignant skin tumors.

Adenocarcinoma↗
PubMed1997

Renal function of substance P in rats chronically exposed to hypoxia.

BACKGROUND: We studied the renal action of substance P (SP) in rats chronically exposed to hypoxia (high altitude, HA), compared to control rats kept at sea level (SL). METHODS: Hypoxia was induced by placing female Wistar rats (182-225 g) in an altitude chamber (5500 m) 15 h.d-1 for 4 weeks. RESULTS: Intrarenal arterial infusion of substance P (60 ng.kg-1. h-1) increased the excretion of urine, sodium in both groups of rats, however, the excretion of kallikrein (KK) and the glomerular filtration rate (GFR) were not significantly altered. After aprotinin (10,000 kiu.kg-1. min-1) treatment, kallikrein was depleted, and substance P lost its diuretic action. Spantide, an SP antagonist (6000 ng.kg-1. h-1, I.V.) decreased urine, and urinary excretion of sodium and potassium in SL rats, but not in HA rats. Acute renal denervated diuresis in SL rats was not modified after Spantide administration. Finally, it was found that both SP and SP antagonist did not significantly change the renal parameters in either group of rats after chronic renal denervation. CONCLUSION: We made the following conclusions: a) endogenous renal action of SP was suggested in SL but not in HA rats; b) the renal action of SP might be through KK release, although urinary KK did not increase after SP administration; and c) SP action is renal nerve dependent in both groups of rats.

Altitude Sickness↗
PubMed1997

Neurokinin B receptor (NK3)-positive neurons expressing c-fos after chemical noxious stimulation on the peritoneum: a double staining study in the nucleus tractus solitarius of the rat.

Neurokinin B receptor (NKR; NK3)-like immunoreactivity (LI) was densely distributed in the nucleus tractus solitarius (NST) of the rat. Approximately 32% of the neurons with NKR-LI in the NST expressed c-fos protein after chemical irritation on the peritoneum with acetic acid. The present results suggest that neurons containing NKR in the NST may be involved in the integration of noxious afferent information from the peritoneum in the rat.

Acetic Acid↗
PubMed1996

Effect of forms of collagen linked to polyurethane on endothelial cell growth.

Collagen has been widely coated or grafted onto polymer surfaces to improve the biocompatibility of materials. To better support the growth of endothelial cells on polyurethane (PU), collagen was grafted to the carboxyl group enriched PU through 1,2-bis(2,3-epoxypropoxy)ethane linking. Our results demonstrated that collagen in various conditions may result in different forms being grafted to the PU substrate, which subsequently affected the growth of endothelial cells. Collagen predialyzed against physiological phosphate buffered saline (PBS) could be reconstituted into native type fibrils with a bigger diameter at 37 degrees C than could collagen neutralized by titration with NaOH. At low temperature, titrated collagen formed floss-like fibrils packed in a ball with cobblestone-like morphology. The amount of collagen grafted was related to the condition of the collagen used, which in consequence affected the diameter of the collagen fibril formed and the growth of endothelial cells. In conclusion, reconstituted collagen fibrils formed from collagen in PBS at 37 degrees C grafted in the highest amounts to an epoxy-PU substrate and that optimally supported the growth of endothelial cells. Such prepared materials may be potentially good vascular bioprosthetic materials and may provide a wide range of biological applications.

Animals↗
PubMed1996

Evaluation of asymmetric poly(vinyl alcohol) membranes for use in artificial islets.

Islets of Langerhans surrounded by a semipermeable membrane to prevent the host immunosystem is a potential way to treat type I diabetes mellitus. In this study, a series of poly (vinyl alcohol) membranes were formed by adding polyethylene glycols to create pores in the skin layer. The permeability study showed the skin layer structure had an influence on the diffusion of low molecular weight glucose, vitamin B12 and insulin. The mass transfer coefficient was improved from 1.04 x 10(-4) to 2.16 x 10(-4) cm/ sec for glucose, from 2.84 x 10(-5) to 8.36 x 10(-5) cm/sec for vitamin B12 and from 1.45 x 10(-6) to 4.15 x 10(-6) cm/sec for insulin, whereas the passage of immunoglobulin G was completely prevented, indicating that these membranes could be effective in protecting islets from immunorejection. Thus such a membrane is an alternative potential material for artificial islets. In addition, we examined the insulin secretory response of islets separated by a poly(vinyl alcohol) membrane. We found that the insulin-secretion rate is relatively rapid compared to the permeation rate of insulin; thus, the process of the artificial islets is insulin-diffusion-controlled.

Biocompatible Materials↗
PubMed1996

Renal kallikrein in chronic hypoxic rats.

1. We have studied the role of kallikrein (KK) in the maintenance of renal function in chronic hypoxic rats (high altitude; HA), compared with control rats kept at sea level (SL). Hypoxia was induced by placing female Wistar rats (198-290 g) in an altitude chamber (5500 m) 15 h/day for 4 weeks. Experiments were also conducted to study the interaction of KK with renal nerve activity and endothelin (ET), two parameters previously shown to be altered in this model. 2. It was found that renal cortex tissue KK activity (TKA) was not significantly different in 10 SL and 10 HA rats. However, the urinary KK activity (UKA) was reduced nearly to half (from 35.2 +/- 4.6 to 18.5 +/- 1.7 pkat/min) in HA rats after 4 weeks of chronic hypoxia. 3. Acute renal denervated diuresis was accompanied by a significant increase in UKA (from 9 +/- 2 to 14 +/- 2 pkat/min in HA and denervated HA rats, respectively; P < 0.05) in HA rats. Intrarenal arterial pretreatment of aprotinin reduced the denervated diuresis. 4. Endothelin (600 ng/kg per h) reduced urine flow, sodium and potassium excretion in the ipsilateral kidney in another 10 SL and 10 HA rats. The extent of the drop of these parameters was significantly less in HA rats. Urinary KK activity was correlated significantly with the measured renal functional parameters (r ranging from 0.472 to 0.612) in SL rats, but was insignificant in HA rats (r ranging from 0.032 to 0.192). 5. We have demonstrated that chronic exposure to hypoxia decreases urinary KK excretion and that KK is involved in acute renal denervated diuresis generated in these animals. The present study suggests that KK plays a partial role in the maintenance of renal function in chronic hypoxic rats.

Analysis of Variance↗
PubMed1996

A child of suspected malignant hyperthermia during general anesthesia for dental surgery.

Malignant hyperthermia is clinically an uncommon disorder characterized by acute hypercatabolic reactions in muscles in response to the triggering effects of certain drugs mainly used during anesthesia or to physical or emotional stress. We present a pediatric patient with multiple caries who was suspected to contract malignant hyperthermia while underwent the operative procedure of comprehensive restoration. Sinus tachycardia, hyperthermia, hypercapnia, metabolic acidosis, hyperkalemia and hypercalcemia developed unexpectedly during the operation. Fortunately, the patient survived the episode with early recognition and prompt management.

Anesthesia, General↗
PubMed1995

Functional analysis of EA-D of Epstein-Barr virus.

Different mutations were generated in the diffused-form early antigen (EA-D) of Epstein-Barr virus (EBV) for study of the effects of these mutations in DNA binding, stimulating the activity of EBV-specific DNA polymerase (EBV-DP), and binding to monoclonal antibody R3. Results revealed that the N-terminal 303 amino acids were essential for DNA binding and were sufficient for the enhancement of the activity of EBV-specific DNA polymerase. Deletion study also showed that the region recognized by the R3 monoclonal antibody was located between aa 315 and aa 377. Our results failed to demonstrate the binding between EA-D and EBV-DP, using the proteins synthesized in vitro, suggesting that direct contact between the two proteins is not required for the EBV-DP activity in vitro. We have generated fusion between EA-D and DNA-binding domain of yeast GAL4 protein; however, this fusion protein was not able to transactivate the promoter containing UAS sequence in P3HR1 cells.

Antigens, Viral↗
PubMed1995

Catecholaminergic neurons in the nucleus tractus solitarii which send their axons to the midbrain periaqueductal gray express Fos protein after noxious stimulation of the stomach: a triple labeling study in the rat.

In rats which were injected with horseradish peroxidase (HRP) into the midbrain periaqueductal gray (PAG) and then administered with formaldehyde into the stomach, Fos-like immunoreactivity was found in tyrosine hydroxylase-like immunoreactive neurons in the nucleus tractus solitarii (NTS) which were retrogradely labeled with HRP. The results indicate that catecholaminergic NTS neurons may mediate nociceptive visceral information to the PAG.

Animals↗
PubMed1995

Selenate fortification improves selenium status of term infants fed soy formula.

Thirty-three healthy term infants were fed either soy formula (SF, 0.028 mumol Se/L; n = 17) or soy formula with added selenate (SF+Se, 0.17 mumol Se/L; n = 16) from birth (+4 d) to 16 wk. Selenium intakes of infants fed SF+Se were similar to the recommended dietary allowance and significantly greater than those of SF-fed infants. The SF group had significantly lower plasma, erythrocyte, and urine selenium, and lower plasma and erythrocyte glutathione peroxidase (GPx) activities at 16 wk compared to those of infants fed SF+Se. A decrease in plasma selenium was observed in SF-fed infants, whereas no differences in plasma selenium were found in infants fed SF+Se. These results indicate that selenate added to soy formula is highly available and effective at maintaining infant plasma and erythrocyte selenium concentrations and GPx activities that are greater than those of infants fed soy formula not fortified with selenium.

Double-Blind Method↗
PubMed1995

Measurement of wall deformation and flow limitation in a mechanical trachea.

A mechanical model of the human trachea is investigated experimentally. A modified version of an earlier model, it consists of a square sectioned rigid tube in which part of one wall is removed, and replaced by a prestretched flat latex membrane. Air is drawn from atmosphere through an inlet into the rigid upstream tube; it then flows through the flexible section and finally through a rigid section into a plenum chamber where suction is applied. As the membrane collapses in response to flow, the transmural pressure and deflection are measured at the mid-point. These values are used in conjunction with a finite deformation membrane wall theory to determine the elastic constant in a nonlinear material constitutive equation. This equation is used to predict the tube law. Results show that the flow limits at the long wave speed predicted by this law. Thus it behaves as a conventional collapsible tube while having the advantage of a rational wall model.

Airway Resistance↗
PubMed1995

[The thermoregulatory threshold during surgery with propofol-nitrous oxide anaesthesia].

BACKGROUND: Thermoregulatory responses are thought to be drastically suppressed by general anesthesia. In previous studies, it was shown that halothane, isoflurane and fentanyl-N2O combination decrease the threshold of vasoconstriction in general anesthesia. Propofol is a recently introduced intravenous anesthetic. The thermoregulatory threshold of its administration during surgery has not been quantified. MATERIALS: Fourteen unpremedicated ASA class I patients were anesthetized with N2O (67%) and propofol (2 mg/kg in bolus followed by 6 mg/kg/h infusion) during elective surgery of free flap. Patients were randomly assigned either to receive additional warming (n = 5) or standard (n = 9) management. Significant vasoconstriction was prospectively defined as the temperature gradient between forearm surface and finger-tip surface is > or = 4 degrees C, and the thermoregulatory threshold was defined as the esophageal temperature (core temperature) at a point where the skin temperature gradient between two tested zones exceeds 4 degrees C. RESULTS: Vasoconstriction did not occur in patients who received additional warming and they remained in nearly normothermia. The average minimum core temperature was 36.3 +/- 0.4 degrees C. In patients who underwent standard management the core temperature ranged from 32.8 to 34.6 degrees C (33.6 +/- 0.7 degrees C), signifying significant vasoconstriction. CONCLUSIONS: General anesthesia with propofol/N2O during surgery drastically inhibits thermoregulatory vasoconstriction. This effect should also be noted during long-term use of propofol (e.g. ICU-sedation).

Adult↗
PubMed1995

Effects of aprotinin on renal function in chronic hypoxic rats.

The effect of aprotinin, a nonspecific kallikrein inhibitor on renal function was studied in chronic hypoxic rats (high altitude, HA), comparing to control rats kept at sea level (SL). Hypoxia was induced by placing female Wistar rats (195-230 g) in an altitude chamber (5,500 m) 15 hr per day for 4 weeks. Intrarenal arterial administration of aprotinin (300 kiu/kg/min), reduced the urinary kallikrein activity (UKA) in 9 SL and 10 HA anesthetized rats. Aprotinin did not significantly alter the urinary excretion of urine, sodium and potassium in SL rats, however, those parameters increased after aprotinin administration in HA rats. These data support the hypothesis that kallikrein participates in the regulation of renal function in chronic hypoxic rats.

Altitude↗