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Biomedical subjects

W Shen

Publications and source records attributed to W Shen.

At least 145 records · Page 8Linked to original sources
PubMed1998

[Subxiphoid pericardial window drainage in the management of large pericardial effusions].

OBJECTIVE: To choose a safe, effective, minimum invasive procedure for treatment of patients with a large pericardial effusion and cardiac tamponade. METHODS: Retrospective analysis of 30 cases with large pericardial effusion or cardiac tamponade diagnosed by echocardiography during four years (1993-1997). The subxiphoid pericardial window drainage and pericardial tissue biopsy was performed. RESULTS: The symptoms were improved immediately following the drainage. The drainage volume during operation was 200-2,000 ml, and postoperation was 0-2,000 ml. The drainage tube was kept in position for average of 5.6 days. With the echocardiography follow up, the pericardial effusion disappeared or remained only minimum fluid in 96.7% of the patients. The complications happened in 6 cases. The 30-days mortality was 6.7%. CONCLUSIONS: The subxiphoid pericardial window drainage procedure is the first choice for a safe, effective, minimal invasive and easy to do procedure for the patients with a large pericardial effusions or cardiac tamponade.

Adolescent↗
PubMed1998

[The changes of pancreatic function after cardiopulmonary bypass].

OBJECTIVE: To evaluate the changes of endocrine and exocrine pancreatic function in patients who underwent heart valve replacement under cardiopulmonary bypass (CPB) in order to optimally conside clinical management perioperatively. METHOD: Sixteen patients with heart valve disease were selected. Serum glucose, lactate, insulin, C peptide, amylase and lipase were measured. RESULT: Hyperglycemia and hyperlactacemia were noted after CPB and peaked at 19:00 on the operative day. Their changes were correctly correlated. Serum glucose and lactate returned to the baseline level on the third postoperative day. The average level of serum insulin were normal, but higher on the third postoperative day. However, the level of serum C peptide was higher than the baseline. It doubled the baseline level at 19:00 on the operative day. The average level of serum amylase and lipase was normal, except the higher level of serum lipase on the fourth postoperative day. In our group, 12 patients had normal serum amylase level perioperatively, and 4 increased serum amylase level (25%), among them 2 patients accompanied with hyperlipasimia (16%). There were 8 patients with hyperlipasimia (50%). CONCLUSION: The endocrine and exocrine pancreatic functions were influenced by CPB and did produce pathophysiologic changes.

Adult↗
PubMed1997

Sestamibi scanning is inadequate for directing unilateral neck exploration for first-time parathyroidectomy.

OBJECTIVE: To determine whether technetium Tc 99m sestamibi scanning is accurate enough to allow surgeons to perform unilateral neck exploration for first-time parathyroidectomy in patients with primary hyperparathyroidism. DESIGN: Retrospective review. SETTING: University tertiary care center. PATIENTS: Forty patients with primary hyperparathyroidism who underwent sestamibi scanning before first-time parathyroidectomy, of whom 28 had single adenomas, 9 had multiple adenomas, and 3 had hyperplasia. INTERVENTIONS: All 40 patients underwent bilateral neck exploration with identification of 4 parathyroid glands. MAIN OUTCOME MEASURES: We compared the results of preoperative sestamibi scanning with operative and histologic findings. We then used these data to calculate the projected success rates of parathyroidectomy if unilateral neck explorations had been performed based on the results of sestamibi scanning, instead of bilateral explorations. RESULTS: Sestamibi scanning was correct in 20 (71%) of 28 patients with single adenomas, 4 (44%) of 9 patients with multiple adenomas, and 0 (0%) of 3 patients with hyperplasia. If unilateral neck explorations had been performed on the basis of localization by sestamibi scanning, parathyroidectomy would have failed in 4 (10%) of 40 patients. CONCLUSIONS: Sestamibi scanning, although helpful, is inadequate for directing unilateral neck exploration for first-time parathyroidectomy. Surgeons who perform unilateral neck exploration based on the results of sestamibi scanning will record a higher failure rate and incur higher costs than those who perform bilateral neck exploration for first-time parathyroidectomy.

Adolescent↗
PubMed1997

Mechanism of the hardening process for a hydroxyapatite cement.

The dynamics for the hydraulic process of calcium phosphate cement (CPC) were investigated by X-ray diffraction quantitative analysis. The results show that the hardening process of CPC is initially controlled by the dissolution of reactants in a 4-h period and subsequently by diffusion through the product layer of hydroxyapatite (HAP) around the grains. The compressive strength rises approximately linearly with the increase of the extent of conversion in a 4-h period, and a maximum compressive strength of about 51 MPa, which is superior to those reported by the references, is obtained in 4 h. Then the compressive strength drops a little with an increase in the extent of conversion. The final product of setting reaction is acicular HAP crystal. Crystal seed not only reduces the setting time but also drops the compressive strength. The variation of pH in CPC slurry from 7.5 to 10.5 reveals that the control step of the dissolution process in the hardening process is the dissolution of dicalcium phosphate anhydrous and the presence of crystal seed will reduce the supersaturation to produce HAP.

Biocompatible Materials↗
PubMed1997

Evaluation of the biocompatibility of a nonceramic hydroxyapatite.

In this study, the biocompatibility of calcium phosphate cement (CPC) was systematically investigated, which included systemic injection acute toxicity assay, cell culture cytotoxicity assay, gene mutation assay (Ames test), chromosome aberration assay (micronucleus test), DNA damage assay (unscheduled DNA synthesis test) and implant histological evaluation. The results showed that the CPC had no toxicity and all tests for mutagenicity and potential carcinogenicity of CPC extracts are negative. CPC was implanted into the femurs of rabbits under no-load condition and the histology of specimens revealed that the implant tightly joined with the surrounding bone, only a very slight histological inflammatory reaction occurred. Thus, CPC is a highly biocompatible material and seems to be safe for application in humans.

Animals↗
PubMed1997

Effect of crystal seeding on the hydration of calcium phosphate cement.

In this paper, the effect of crystal seeding on the hydration of calcium phosphate cement (CPC) has been carefully investigated. The setting time of the CPC slurry not containing any crystal seeds was 150 min, while the setting time for the specimen containing 5 wt% low crystallinity hydroxyapatite used as a crystal seed was 7 min. This improvement in the setting time was due to HAP serving as a substrate for heterogeneous nucleation which accelerated nucleation. In addition, the compressive strength of the specimen containing the crystal seeding was deduced and we report values different from those previously reported in the literature. The calorimetric curve indicated that crystal seeding could reduce the induction period. A.c. impedance spectroscopy revealed that at the beginning of hydration, the rate of reaction increased and also that the mean diameter and porosity decreased as the seed content increased. At the end of the hydration reaction the situation was changed with the mean diameter and porosity in the sample without any seeds being a minimum, which indicated that the compressive strength was a maximum. This result could be explained by the dissolution and reprecipitation of small hydration products produced by the high rate of reaction produced by the introduction of the crystal seeds.

Journal Article↗
PubMed1997

Two metabotropic gamma-aminobutyric acid receptors differentially modulate calcium currents in retinal ganglion cells.

Metabotropic gamma-aminobutyric acid (GABA) receptors were studied in amphibian retinal ganglion cells using whole cell current and voltage clamp techniques. The aim was to identify the types of receptor present and their mechanisms of action and modulation. Previous results indicated that ganglion cells possess two ionotropic GABA receptors: GABAAR and GABACR. This study demonstrates that they also possess two types of metabotropic GABAB receptor: one sensitive to baclofen and another to cis-aminocrotonic acid (CACA). The effects of these selective agonists were blocked by GDP-beta-S. Baclofen suppressed an omega-conotoxin-GVIA-sensitive barium current, and this action was reversed by prepulse facilitation, indicative of a direct G-protein pathway. The effect of baclofen was also partially occluded by agents that influence the protein kinase A (PKA) pathway. But the effect of PKA activation was unaffected by prepulse facilitation, indicating PKA acted through a parallel pathway. Calmodulin antagonists reduced the action of baclofen, whereas inhibitors of calmodulin phosphatase enhanced it. Antagonists of internal calcium release, such as heparin and ruthenium red; did not affect the baclofen response. Thus, the baclofen-sensitive receptor may respond to influx of calcium. The CACA-sensitive GABA receptor reduced current through dihydropyridine-sensitive channels. Sodium nitroprusside and 8-bromo-cGMP enhanced the action of CACA, indicating that a nitric oxide system can up-regulate this receptor pathway. CACA-sensitive and baclofen-sensitive GABAB receptors reduced spike activity in ganglion cells. Overall, retinal ganglion cells possess four types of GABA receptor, two ionotropic and two metabotropic. Each has a unique electrogenic profile, providing a wide range of neural integration at the final stage of retinal information processing.

Action Potentials↗
PubMed1997

Expression of the brain creatine kinase gene is low in neuroblastoma cell lines.

The cytoplasmic creatine kinase (CKB) enzyme has a central role in the regeneration of ATP in the brain. We have shown previously that CKB mRNA levels in cultured primary rat brain astrocytes and oligodendrocytes are much higher than in primary neurons. It has been suggested that high CKB expression is essential for the energy-demanding functions of glial cells. Conversely, CKB may be repressed in most neuronal cells; however, CKB protein has previously been detected by immunohistochemistry in several distinct groups of neurons in the adult rodent brain. Presently, little is known of the factors responsible for the high CKB expression in glia and possible repression in neurons. In this report, we investigated if low CKB mRNA was characteristic of some established neuronal cell lines. CKB mRNA was found to be extremely low in mouse C1300 neuroblastomas NS20Y and N1E-115 but 10-fold higher in NG108-15, a hybrid cell composed of a C1300 neuroblastoma and a rat C6 glioma. Since we showed NG108-15 contained only rat CKB mRNA transcribed from the C6 glioma CKB gene, expression of CKB mRNA may be a manifestation of a glial property in NG108-15 cells. However, CKB mRNA expression in NG108-15 appeared not to be fully activated since it was still 5-fold lower than in (parental) C6 glioma and 10-fold lower than in cellular RNA from either total rat brain or cultured primary astrocytes. When neuronal differentiation was increased in NS20Y and N1E-115 by treating cells with prostaglandin E1 and theophylline, the extremely low CKB mRNA level was not significantly changed. In a comparative study, the CKB mRNA levels in NS20Y, N1E-115 and neuronal RT4-B8 and RT4-E5 cells (from the rat RT4 peripheral neurotumor) were at least 50-fold lower than that in C6 glioma and 100-fold lower than in cultured primary astrocytes. These cell lines may provide a system for the identification of factors involved in the possible repression of CKB in many neuronal cells.

Animals↗
PubMed1997

Expression of the brain creatine kinase gene in rat RT4 peripheral neurotumor cell lines and its modulation by cell confluence.

Creatine kinases (CK) catalyze the reversible transfer of a high energy phosphate group between creatine phosphate and ADP to regenerate ATP in cell types where the requirements for ATP are extensive and/or sudden. Previously, we have shown in primary rat brain cell cultures that brain CK (CKB) mRNA levels are highest in astrocytes and oligodendrocytes and much lower in neuronal cells. However, little is known of the factors which regulate CKB expression in the central nervous system and peripheral nervous system. To begin to investigate these factors, we asked in this report (1) if this pattern of CKB expression was also characteristic of some established glial and neuronal cell lines derived from the PNS; (2) whether CKB expression could be rapidly modulated by culture conditions, and (3) if CKB is expressed in cells with characteristics of glial cell progenitors. In subconfluent cells, CKB mRNA and enzyme activity were found to be high in both the rat RT4 peripheral neurotumor stem cell RT4-AC36A and its glial cell derivative RT4-D6. Conversely, CKB mRNA and activity were 5- and 8-fold lower, respectively, in the neuronal derivative RT4-E5 and, more dramatically, CKB was undetectable in neuronal RT4-B8 cells. Maintaining RT4-D6 glial cells at confluence rapidly increased CKB enzyme activity by 7-fold, such that D6 cells contained about 25% of the CKB level in lysates prepared from either whole adult rat brain or primary cultures of rat brain astrocytes. The levels of CKB mRNA and immunoreactive protein were also correspondingly increased in confluent D6 cells. These confluence-mediated increases in CKB appeared to be due to cell-cell contact and not the depletion of serum growth factors or an increase in intracellular cAMP. This study indicates that CKB expression is highest in cells displaying glial properties and can be rapidly modulated by appropriate culture conditions. The results are discussed in relation to the factors which may regulate CKB expression in vivo.

Animals↗
PubMed1997

Ectopic eye development in Drosophila induced by directed dachshund expression.

The dachshund gene encodes a nuclear protein that is required for normal eye development in Drosophila. In the absence of dachshund function, flies develop with severely reduced or no eyes. We show that targeted expression of dachshund is sufficient to direct ectopic retinal development in a variety of tissues, including the adult head, thorax and legs. This result is similar to that observed with the highly conserved Drosophila gene eyeless, which can induce ectopic eye formation on all major appendages. Here, we show that dachshund and eyeless induce the expression of each other and that dachshund is required for ectopic retinal development driven by eyeless misexpression. These results suggest that the control of eye development requires the complex interaction of multiple genes, even at the very highest regulatory levels.

Animals↗
PubMed1997

[Medicine S inhibits class II MHC expression of intragraft renal in rats].

The Purpose of this study was to address the mechanism of medicine S which has anti-rejection effects of renal allografts in rats. Kidney transplantations were performed from SD to Wistar strain (allogeneic) and from Wistar to Wistar (Isograft) using the same modified technigue described by Fabre and kamada. Experimental rats were divided into five groups. Group I (Isograft group) and group II (allograft group) as controls were not treated with medicine. The others were allograft groups which received medicine S, Cyclosporine A, and low-dose Cyclosporine combined with medicine S, respectively. Renal function and resultant morphology changes were assessed 2, 4 weeks after transplantation. All sections of kidney grafts were stained with monoclonal antibody class II MHC (OX6), and then the surface densities of positive staining were quantified by computer image analysis. The level of molecular expression in group II was significantly increased (7.61 +/- 0.57 vs 0.51 +/- 0.2 of group I, P < 0.01). In groups I and IV, the molecule of expression was reduced, compared with the groups II, III and V (P < 0.05). The results suggest that medicine S decreases the level of class II MHC expression and medicines combined with lowe-dose cyclosporine is more effective than cyclosporine alone.

Animals↗
PubMed1997

[Successful 48-72 h cold storage of dog kidneys with HX-1 solution].

HX-1 solution was used in this study to determine its effects on long term kidney preservation. 20 female and male mongrel dogs were randomly divided into control (HC-WCU solution) and experimental (HX-1 solution) groups. Kidneys were flushed with HC-WCU or HX-1 solution and stored at 0.4 degree C for 48 or 72 h. After being preserved, the kidney was implanted in the right groin of the animal and anastomosed to the iliac vessles. This procedure was immediately followed by a contralateral nephrectomy. The experimental findings were: 1. The maximum serum creatinine levels were 642.60 +/- 158.60 mumol/L and 686.20 +/- 154.04 mumol/L respectively in HC-WCU solution subgroups for 48 or 72 h cold storage. But the maximum serum creatinine levels were 448.32 +/- 36.90 mumol/L and 524.60 +/- 109.38 mumol/L respectively in HX-1 solution subgroups. 2. 80% of the kidneys were viable after 48 h storage in HC-WCU kidney solution, but 100% viable when stored in HX-1 solution: 40% of the kidneys were viable after 72 h storage in HC-WCU solution, but 60% viable when stored in HX-1 solution. 3. Histologically the kidney of dogs that died of renal failure was damaged worse in HC-WCU solution group than that in HX-1 solution group. These results suggest that HX-1 solution is superior to HC-WCU solution for preserving kidneys and HX-1 solution may store up the kidney of dogs to 48-72 h.

Animals↗
PubMed1997

Defective endogenous nitric oxide-mediated modulation of cellular respiration in canine skeletal muscle after the development of heart failure.

BACKGROUND: It is well documented that nitric oxide (NO) suppresses the function of a number of mitochondrial enzymes. Our recent studies found that endogenous NO may play an important role in the modulation of tissue oxygen (O2) consumption and cellular respiration both in vitro and in vivo. METHODS: Tissue O2 consumption was measured by a Clark-type O2 electrode at 37 degrees C in freshly isolated skeletal muscle segments from the accessory head of the triceps brachii (90% type I muscle fiber) and extensor carpi radialis (86% type II muscle fiber) from normal dogs and dogs with tachycardia-induced heart failure. RESULTS: S-nitroso-N-acetylpenicillamine (SNAP), carbachol, and bradykinin at doses of 10(-7) to 10(-4) mol/L concentration significantly suppressed tissue O2 consumption both in the absence and presence of 2,4-dinitrophenol (1 mmol/L), a mitochondrial uncoupler. These effects were not significantly different in the accessory head of the triceps brachii (90% type I muscle fiber) and extensor carpi radialis (86% type II muscle fiber). The effects of carbachol and bradykinin but not SNAP were attenuated by NG-nitro-L-arginine (10(-4) mol/L), indicating inhibition of the formation of endogenous NO. The inhibitory effect on tissue O2 consumption in response to carbachol and bradykinin became significantly smaller in skeletal muscle from dogs with pacing-induced heart failure, but the effects of SNAP were unchanged. CONCLUSIONS: Endogenous NO released from microvascular endothelium may play an important physiologic role in the modulation of cellular respiration in skeletal muscle, and the loss of this regulatory function may contribute to peripheral metabolic disorders and poor exercise tolerance during heart failure.

2,4-Dinitrophenol↗
PubMed1997

TGF-beta 3 inhibits the increased gene expressions of pulmonary surfactant proteins induced by dexamethasone in fetal rat lung in vitro.

OBJECTIVE: To determine the effects of transforming growth factor-beta 3 (TGF-beta 3) on expressions of surfactant proteins (SPs). METHODS: Northern blot hybridization and reverse transcriptase polymerase chain reaction (RT-PCR) were employed to determine the SP-A, SP-B and SP-C mRNA levels of cultured lung explants and type II cells from fetal rat lungs. RESULTS: TGF-beta 3 alone did not affect the expressions of SPs either in explants or in type II cells. However, TGF-beta 3 did inhibit the increase of SP-B, SP-C mRNA levels caused by dexamethasone (100 nmol/L), in a dose-dependent manner. Furthermore, TGF-beta 3 had no direct inhibition on the increase of SP-B, SP-C mRNA induced by dexamethasone in type II cells, but had an indirect inhibitory effect mediated by fibroblasts. CONCLUSION: TGF-beta 3 plays an important inhibitory role in the development of pulmonary surfactant proteins. The present study may provide a possible explanation for the unideal effect of glucocorticoids in the prevention of neonatal respiratory distress syndrome.

Animals↗
PubMed1997

Changes in intracellular and extracellular calcium concentration of the myocardial cells during heart failure in children.

OBJECTIVE: To explore the relationship between heart failure and changes in intracellular calcium concentration of the myocardium. METHODS: The intra-and extracellular concentration of ionized calcium and total calcium of myocardium in 11 cases of heart failure was measured using calcium fluorescence indicator Fura-2 and atom absorption spectrophotometry. The activity of the erythrocyte membrane pump was determined with hemolysate chemical method. RESULTS: The concentration of ionized calcium in myocardial cells and the erythrocyte was significantly higher in the patients with heart failure (280.85 +/- 47.8 nmol/L, 1.76 +/- 0.04 F335/F385) than in those without heart failure (121.88 +/- 13.15 nmol/L, 1.47 +/- 0.08 F335/F385). Total calcium in the erythrocyte was also increased markedly in the patients with heart failure, but the activity of the erythrocyte membrane pump was lower than in those without heart failure. The intracellular calcium of the peripheral erythrocyte and the activity of membrane pump returned to normal after the heart failure was cured. CONCLUSION: There is excessive calcium accumulation in the myocardium and erythrocyte and the latter may be cause of the disturbance of myocardial diastolic function during heart failure.

Biological Transport, Active↗