Biomedical subjects

J Tong

Publications and source records attributed to J Tong.

At least 55 records · Page 3Linked to original sources

PubMed1999

Role of reactive oxygen species in acetylcholine-induced preconditioning in cardiomyocytes.

We examined the ability of ACh to mimic ischemic preconditioning in cardiomyocytes and the role of ATP-sensitive potassium (KATP) channels and mitochondrial reactive oxygen species (ROS) in mediating this effect. Chick embryonic ventricular myocytes were studied in a flow-through chamber while flow rate, pH, PO2, and PCO2 were controlled. Cell viability was quantified with propidium iodide (5 microM), and production of ROS was measured using 2', 7'-dichlorofluorescin diacetate. Data were expressed as means +/- SE. Preconditioning with 10 min of ischemia followed by 10 min of reoxygenation or 10 min of ACh (1 mM) followed by a drug-free period before 1 h of ischemia and 3 h of reoxygenation reduced cell death to the same extent [preconditioning 19 +/- 2% (n = 6, P < 0.05) ACh 21 +/- 5% (n = 6, P < 0.05) vs controls 42 +/- 5% (n = 9)]. Like preconditioning, ACh increased ROS production threefold before ischemia [0.60 +/- 0.16 (n = 7, P < 0.05) vs. controls, 0.16 +/- 0. 03 (n = 6); arbitrary units]. Protection and increased ROS production during ACh preconditioning were abolished with 5-hydroxydecanoate (5-HD, 100 microM), a selective mitochondrial K(ATP) channel antagonist, and the thiol reductant 2-mercaptopropionyl glycine (2-MPG, 1 mM), an antioxidant [cell death: 5-HD+ACh 37 +/- 7% (n = 5), 2-MPG+ACh 47 +/- 6% (n = 6); ROS signals: 5-HD+ACh 0.09 +/- 0.03 (n = 5), 2-MPG+ACh 0.01 +/- 0.04 (n = 4)]. In addition, ACh-induced ROS signaling was blocked by the mitochondrial site III electron transport inhibitor myxothiazol (0.02 +/- 0.07, n = 5). These results demonstrate that activation of mitochondrial K(ATP) channels and increased ROS production from mitochondria are important intracellular signals that participate in ACh-induced preconditioning in cardiomyocytes.

Acetylcholine↗

PubMed1999

Dose-related effect of irradiation on circadian rhythm of cellular messengers in neural and immune system of mouse.

OBJECTIVE: To explore toxic effect of gamma-irradiation on circadian rhythms of cAMP and cGMP in signal pathway between the central nuclei and peripheral lymphocyte. METHODS: 60Co gamma-ray of 0.5 Gy and 5.0 Gy was applied to groups of mice at each circadian timepoint of a day. 24 hours after the irradiation, the pineal and suprachiasmatic nuclei (SCN) were removed, and the T lymphocytes in blood were separated by a step-centrifugal and nylon-filter treatment, for measurements of cAMP and cGMP by using the RIA procedure. The results were expressed as circadian rhythms of the cAMP/cGMP ratio derived from the Cosinor analysis. RESULTS: The daily average cAMP/cGMP ratio in cells of SCN, pineal, serum and lymphocyte changed according to the dose of irradiation at which the mice were exposed. The high dose of 5 Gy increased the ratio, and the low dose of 0.5 Gy decreased the ratio. There was a significant difference of cAMP/cGMP levels between the irradiated and the control groups, as well as between CT00:00 and CT12:00 of a day. In addition, the peak phases of the cAMP/cGMP ratio at the low-dose groups appeared in advance from about 2 to 8 hours, whereas those at the high-dose groups were delayed from about 3 to 6 hours in comparison to that of the normal mice. CONCLUSION: Toxic effect of gamma-irradiation on the cAMP/cGMP circadian rhythm in the central nuclei and peripheral lymphocyte could be characterized by a low-dose hormesis.

Animals↗

PubMed1999

[The biocompatibility of Chinese nitinol alloy intravascular stent].

The aim of this study was to evaluate the biocompatibility of Chinese nitinol alloy intravascular stent. Sixteen Chinese nitinol alloy intravascular stents with 4 mm ID were implanted in the left and right iliac arteries of 8 normal dogs and were observed for one to six months. The results showed that the stents implanted were completely covered by a thin layer of the neointima after one month and the surface of neointima was covered by a monolayer of endothelium-like cells. These suggest that the Chinese nitinol alloy has very good biocompatibility.

Alloys↗

PubMed1999

[Middle ear operation of children and juveniles].

OBJECTIVE: To analyse the results and effective factors of middle ear operation in children and juveniles. METHOD: 105 cases (146 ears) were analyzed retrospectively. 49 ears were followed up over 3 months. RESULT: 120 ear had perfect hearing materials. The difference of average air-bone gap between postoperation (21.86 +/- 13.15) dB HL and preoperation (35.20 +/- 13.87) dB HL was significant (P < 0.01). CONCLUSION: Middle ear operation was a safe, effective operation in children and juveniles, reoperation also was proper option for someone if his first operation didn't success or repeated cases.

Adolescent↗

PubMed1999

[Study on activities of eight kinds of traditional Chinese medicine against urogential Chlamydia trachomatis].

In order to screen the susceptibilities of urogenital chlamydia trachomatis (CT) to 8 kinds of traditional Chinese medicine by microculture technigue of McCoy cell in Vitro. The results showed that 8 kinds of Chinese medicines all had activities against urogenital CT. Their minimal inhibitory concentrations (MIC) were from 0.49 mg/ml to 15.63 mg/ml. The number and the volume of inclusions were reducing gradually, disappeared finally. These traditional Chinese medicines hadn't any action of cytotoxicity to McCoy cell. The result of this study will be useful for the further study.

Animals↗

PubMed1998

Cytochrome c heme lyase activity of yeast mitochondria.

A highly efficient in vitro system was established for measuring by high performance liquid chromatography the formation of holocytochrome c by yeast mitochondria. Holocytochrome c formation required reducing agents, of which dithiothreitol was the most effective. With biosynthetically made, pure Drosophila melanogaster apocytochrome c and Saccharomyces cerevisiae mitochondria, the activity of cytochrome c heme lyase amounted to about 800 fmol min-1 mg-1 mitochondrial protein. The kinetics were typical Michaelis-Menten (Km approximately 1 nM), as were those of mitoplasts with broken outer membranes (Km approximately 3 nM). As tested with mitoplasts, holocytochromes c from a range of species were found to be competitive inhibitors of heme lyase at physiological concentrations, providing a mechanism for controlling this concentration in vivo. Apocytochrome c associated with yeast mitochondria in two phases of Kd approximately 2 x 10(-10) and 10(-8) M, respectively, whereas mitoplasts had lost the high affinity binding. A site-directed mutant of apocytochrome c (lysines 5, 7, and 8 replaced by glutamine, glutamic acid, and asparagine) was found to be converted to holocytochrome c (Km approximately 3.3 nM; maximal activity unchanged), even though the mutations completely eliminated the high affinity binding. Thus, the high affinity binding of apocytochrome c to mitochondria is not directly related to holocytochrome c formation.

Animals↗

PubMed1998

Sustained gene expression in retrovirally transduced, engrafting human hematopoietic stem cells and their lympho-myeloid progeny.

Inefficient retroviral-mediated gene transfer to human hematopoietic stem cells (HSC) and insufficient gene expression in progeny cells derived from transduced HSC are two major problems associated with HSC-based gene therapy. In this study we evaluated the ability of a murine stem cell virus (MSCV)-based retroviral vector carrying the low-affinity human nerve growth factor receptor (NGFR) gene as reporter to maintain gene expression in transduced human hematopoietic cells. CD34(+) cells lacking lineage differentiation markers (CD34(+)Lin-) isolated from human bone marrow and mobilized peripheral blood were transduced using an optimized clinically applicable protocol. Under the conditions used, greater than 75% of the CD34(+) cell population retained the Lin- phenotype after 4 days in culture and at least 30% of these expressed a high level of NGFR (NGFR+) as assessed by fluorescence-activated cell sorter analysis. When these CD34(+)Lin-NGFR+ cells sorted 2 days posttransduction were assayed in vitro in clonogenic and long-term stromal cultures, sustained reporter expression was observed in differentiated erythroid and myeloid cells derived from transduced progenitors, and in differentiated B-lineage cells after 6 weeks. Moreover, when these transduced CD34(+)Lin-NGFR+ cells were used to repopulate human bone grafts implanted in severe combined immunodeficient mice, MSCV-directed NGFR expression could be detected on 37% +/- 6% (n = 5) of the donor-type human cells recovered 9 weeks postinjection. These findings suggest potential utility of the MSCV retroviral vector in the development of effective therapies involving gene-modified HSC.

Animals↗

PubMed1998

Lesion-induced axon sprouting in the deafferented striatum of adult rat.

Synaptic replacement in rat striatum following a unilateral cortical lesion was investigated using electron microscopy and the anterograde tracer, biotinylated dextrin amine (BDA). In the deafferented striatum evidence of axon sprouting and synapse replacement was seen at 20 days after the lesion and most newly-formed axon terminals were labeled with BDA injected previously into the contralateral cortex. In addition, BDA-labeled fibers from the contralateral cortex formed multiple asymmetric axospinous synapses with deafferented striatal neurons, a morphological feature rarely seen in unlesioned rats. These data suggest that in response to a unilateral cortex lesion axons from the contralateral cortex sprout and reinnervated the deafferented striatal neurons and that reinnervation by 'like' afferents maybe crucial for the establishment of functional recovery after the unilateral cortex lesion.

Age Factors↗

PubMed1998

Birth of live mice derived by in vitro fertilization with spermatozoa retrieved up to twenty-four hours after death.

The objective of this study was to determine the viability and fertility of mouse spermatozoa obtained at various postmortem intervals. Male mice were euthanized, and the bodies were kept at approximately 22 degrees C for up to 24 hr. The epididymides were removed and spermatozoa were allowed to swim out into Minimum Essential Medium supplemented with bovine serum albumin. Motility of spermatozoa retrieved within 12 hr postmortem was approximately 60%, whereas motility of those obtained 6 to 12 hr later decreased significantly (P < 0.05). There appeared to be no differences in the percentages of spermatozoa with intact plasma and acrosomal membranes regardless of the time after death. After in vitro fertilization of oocytes with spermatozoa collected immediately after death or at 6, 12, 18, or 24 hr postmortem, the cleavage rates were 81%, 70%, 64%, 34%, and 19%, respectively. Once oocytes were fertilized, more than 65% developed into morulae/blastocysts. Transfer of a total of 166 embryos produced in vitro with postmortem spermatozoa resulted in the birth of 44 live pups (26.5%). Of these 44, 3 live mice were derived by transfer of 11 embryos (27.3%) produced with 24-hr postmortem spermatozoa. Histological examination of the testes and epididymides obtained at various postmortem intervals revealed that degenerative changes of the testes occurred within 6 hr, whereas those of the epididymides were less obvious until 6 hr later. These changes included pyknosis, release of intracellular contents, and disruption of intercellular bridges of the germ cells. This study has demonstrated that spermatozoa recovered from a dead animal as long as 24 hr after death can be used to fertilize oocytes, and that the resulting zygotes can develop into live young.

Acrosome↗

PubMed1998

An analysis of operations for gastroesophageal reflux disease: identifying the important technical elements.

BACKGROUND: Better understanding of the pathogenesis of gastroesophageal reflux disease in recent years has not been accompanied by appreciable advances in the design of antireflux operations. In many cases, operations are still being performed just as they were described 30 years ago. It is important now to go beyond the eponymous procedures traditionally associated with antireflux operations and to identify the technical elements that contribute to effective and durable fundoplications. OBJECTIVES: To compare antireflux operations and identify the important technical elements. DESIGN AND SETTING: Retrospective study in a university-based tertiary care center. PATIENTS: Two hundred one patients had laparoscopic fundoplications for gastroesophageal reflux disease. The first 22 patients underwent Nissen-Rossetti procedures (360 degree wrap; no division of short gastric vessels). Subsequently, 82 patients had a total (360 degree Nissen wrap) fundoplication and 97 patients had a partial (240 degree Guarner wrap) fundoplication (both with the short gastric vessels divided), with the choice between them based on the quality of esophageal peristalsis. The 3 groups of patients were similar in age, duration of symptoms, incidence of hiatal hernia, and incidence of esophagitis. MAIN OUTCOME MEASURES: Resolution of heartburn, incidence of postoperative dysphagia, and stability of the reconstruction. RESULTS: The resolution of heartburn was achieved for 15 patients (68%) who had the Nissen-Rossetti procedure, 73 patients (89%) who had a 360 degrees Nissen wrap, and 88 patients (91%) who had a 240 degree Guarner wrap. Postoperative dysphagia occurred in 3 patients (14%) having the Nissen-Rossetti procedure, 5 patients (6%) having a 360 degree wrap, and 2 patients (2%) having a 240 degree wrap. Herniation or disruption of the wrap occurred postoperatively in 9 patients (4.5%). Review of the videotapes of these 9 operations showed that important technical elements had been omitted in 8. Seven patients required a second operation. CONCLUSION: Laparoscopic antireflux operations control symptoms without producing adverse effects if the following technical elements are included: the hernia is repaired and the hiatus reduced to a normal size, the short gastric vessels are divided, a total or partial wrap is used based on the quality of esophageal peristalsis, and the wrap is anchored in the abdomen.

Digestive System Surgical Procedures↗

PubMed1998

Results of laparoscopic antireflux surgery for dysphagia and gastroesophageal reflux disease.

BACKGROUND: Little attention has been paid to nonobstructive dysphagia (dysphagia in the absence of an esophageal stricture) in patients with gastroesophageal reflux disease (GERD). The objectives of this study were to assess (a) the incidence of nonobstructive dysphagia in patients with GERD; and (b) the effects of laparoscopic fundoplication on nonobstructive dysphagia. METHODS: Esophageal manometry and pH monitoring identified 666 patients with GERD. Two hundred and eight patients (31 %) without esophageal strictures complained of dysphagia in addition to heartburn and regurgitation. Forty-nine (24%) of these patients underwent laparoscopic fundoplication. Esophageal function tests were repeated postoperatively in 12 patients (25%). Main outcome measures were effects of laparoscopic fundoplication on symptoms and esophageal motor function. RESULTS: Dysphagia resolved postoperatively in 44 patients (90%), and improved in 2 patients (4%). Postoperative esophageal manometry showed a significant increase in the length and pressure of the lower esophageal sphincter, without changes in its ability to relax in response to swallowing. CONCLUSIONS: About one third of GERD patients without strictures experienced dysphagia; and dysphagia resolved in about 90% of such patients following a laparoscopic fundoplication.

Deglutition↗

PubMed1998

Measurements of the nonlinearity parameter B/A of contrast agents.

The nonlinearity parameter B/As of two contrast agents (Albunex and Levovist) in a saline solution (Isoton II) were measured. The results show that B/As of both contrast agents were increasing functions of bubble number densities. In general, they are much higher than that of most soft tissues. For Albunex (concentration = 1 microL Albunex: 1 mL Isoton) a B/A of 2000; and for Levovist (concentration = 6.0 mg Levovist powder: 1 mL Isoton), a B/A of 600 was obtained.

Albumins↗

PubMed1998

Experimental study of stability of a contrast agent in an ultrasound field.

Attenuation coefficient and phase velocity measurements and direct optical observations showed that microbubbles of a contrast agent (Albunex) in 5% bovine albumin solution were not stable under ultrasonic irradiation. When the concentration of Albunex was 0.41 microL/mL and a 2.5-MHz phased array transducer of a Hewlett-Packard ultrasound imaging system (Model 77020AC) was used as the ultrasound source (the compression and rarefaction peak pressure amplitudes were, respectively, equal to 2 MPa and 1 MPa, the repetition frequency was 2.64 kHz), the attenuation coefficient at 2.5 MHz dropped from 40 dB/cm to 16 dB/cm after 2 min of continuous insonification. Under a static condition, it was shown by direct optical observations that the microbubbles shrank and aggregated to form clusters or were destroyed under insonification; pressure amplitude was estimated to be 0.5 MPa, frequency = 2.44 MHz, and the pulse repetition frequency was 5 kHz.

Albumins↗

PubMed1998

Apoptosis is a major mode of cell death caused by ischaemia and ischaemia/reperfusion injury to the rat intestinal epithelium.

BACKGROUND AND AIMS: Injuries caused by ischaemia and ischaemia/reperfusion in the small intestine have been widely accepted as resulting in necrosis. The aim of this study was to ascertain whether apoptosis also occurs. METHODS: Intestinal epithelium from rats subjected to ischaemia (15-90 minutes) and ischaemia/reperfusion (15 minutes ischaemia followed by 15-75 minutes of reperfusion) was studied using histological, immunohistochemical, and molecular biological methods as well as FACS. RESULTS: Mucosal injury was induced by both ischaemia and ischaemia/reperfusion. Detachment of epithelial cells from the villous stroma was an early morphological change indicating mucosal injury. More than 80% of the detached cells exhibited characteristic morphological features of apoptosis (condensation of chromatin and nuclear fragmentation). The remainder demonstrated necrotic features. The apoptotic cells eventually underwent spontaneous degeneration with membrane rupture, a process morphologically identical to necrosis. DNA fragmentation was also confirmed by immunohistochemical methods and agarose gel electrophoresis. CONCLUSION: Apoptosis is a major mode of cell death in the destruction of rat small intestinal epithelial cells induced by ischaemia and ischaemia/reperfusion injury. Disruption of epithelial cell-matrix interactions ("anoikis") may play an important part in induction of apoptosis in detached enterocytes.

Animals↗

PubMed1998

[Clinical observation and anatomical analysis of middle turbinate and ethmoidal internal wall moved to external side after microsurgery].

OBJECTIVE: To assess the effect of middle turbinate (MT) and ethmoidal internal wall(EIW) moved externally after microsurgery. METHODS: Twenty-four cases (45 sides) were followed-up endoscopically for (16.3 +/- 9.3) months. Thirteen cases (24 sides) were observed by CT scans. Three cadaver heads were measured for anatomical analysis. RESULTS: Forty-one (91%) of 45 sides obtained better olfactory function after operation. Twenty-two (91%) of 24 sides were found to have better CT changes in sinus ventilation as compared with preoperative CT scans. The gap between the MT and EIW to the orbital wall was (12.0 +/- 1.0) mm, while that between the ethmoidal bulla and processus uncinatus was only (2.3 +/- 0.6) mm as revealed in the autopsy. CONCLUSION: MT and EIW moderately moved suitably to externally had no bad effect on sinus ventilation, and it improved olfaction.

Adolescent↗

PubMed1998

[Studies on the antifertility effect of bis-trichloromethyl sulfone and its reversibility in male rats].

Bis-trichloromethyl sulfone(BTS) given p.o. to male Sprague-Dawley rats at a dose of 10 mg.kg-1.d-1, 6 days a week for 8 weeks(or 30 mg.kg-1.d-1 for 4 weeks), was found to lead to infertility. The density and, in particular, the motility of the spermatozoa in the cauda epididymidis were significantly lower than those of the controls (P < 0.001). The body weight, the sex behavior, the blood testosterone level and the histology of important organs were not significantly different from those of the control rats. Fertility started to recover 4 weeks after cessation of medication and was entirely recovered 2 more weeks later in rats having received BTS for 8 weeks at the dose of 30 mg.kg-1.d-1. In vitro study showed that BTS at a concentration of 0.31 mg.ml-1 would make rat spermatozoa immobile within 20 seconds. These results indicate that BTS has both antifertility effect in male rats and direct inhibitory effect on rat spermatozoa. We conclude that nontoxic doses of BTS can induce reversible infertility in male rats.

Animals↗

PubMed1998

Bone marrow repopulation by human marrow stem cells after long-term expansion culture on a porcine endothelial cell line.

In vitro exposure of murine hematopoietic stem cells (HSCs) to cell cycle-inducing cytokines has been shown to result in a defect in the ability of these cells to engraft. We used a porcine microvascular endothelial cell (PMVEC) line in conjunction with exogenous interleukin (IL)-3, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), and stem cell factor (SCF) to expand human HSCs that express the CD34 and Thy-1 antigens but lack lineage-associated markers (CD34+Thy-1+Lin- cells). Ex vivo expansion of hematopoietic cells was evaluated in comparison to stromal cell-free, cytokine-supplemented cultures. Cells expressing the CD34+Thy-1+Lin- phenotype were detectable in both culture systems for up to 3 weeks. These cells were reisolated from the cultures and their ability to engraft human fetal bones implanted into SCID mice (SCID-hu bone) was tested. HSCs expanded in PMVEC coculture were consistently capable of competitive marrow repopulation with multilineage (CD19+ B lymphoid, CD33+ myeloid, and CD34+ cells) progeny present 8 weeks postengraftment. In contrast, grafts composed of cells expanded in stroma-free cultures did not lead to multilineage SCID-hu bone repopulation. Proliferation analysis revealed that by 1 week of culture more than 80% of the cells in the PMVEC cocultures expressing the primitive CD34+CD38- phenotype had undergone cell division. Fewer than 1% of the cells that proliferated in the absence of stromal cells remained CD34+CD38-. These data suggest that the proliferation of HSCs in the presence of IL-3, IL-6, GM-CSF, and SCF without stromal cell support may result in impairment of engraftment capacity, which may be overcome by coculture with PMVECs.

Animals↗

PubMed1997

Caffeine and halothane sensitivity of intracellular Ca2+ release is altered by 15 calcium release channel (ryanodine receptor) mutations associated with malignant hyperthermia and/or central core disease.

Malignant hyperthermia (MH) and central core disease (CCD) are autosomal dominant disorders of skeletal muscle in which a potentially fatal hypermetabolic crisis can be triggered by commonly used anesthetic agents. To date, 17 mutations in the human RYR1 gene encoding the Ca2+ release channel of skeletal muscle sarcoplasmic reticulum (the ryanodine receptor) have been associated with MH and/or CCD. Although many of these mutations have been linked to MH and/or CCD, with high lod (log of the odds favoring linkage versus nonlinkage) scores, others have been found in single, small families. Independent biochemical evidence for a causal role for these mutations in MH is available for only two mutants. Mutations corresponding to the human MH mutations were made in a full-length rabbit RYR1 cDNA, and wild type and mutant cDNAs were transfected into HEK-293 cells. After about 48 h, intact cells were loaded with the fluorescent Ca2+ indicator, fura-2, and intracellular Ca2+ release, induced by caffeine or halothane, was measured by photometry. Ca2+ release in cells expressing MH or CCD mutant ryanodine receptors was invariably significantly more sensitive to low concentrations of caffeine and halothane than Ca2+ release in cells expressing wild type receptors or receptors mutated in other regions of the molecule. Linear regression analysis showed that there is a strong correlation (r = 0.95, p < 0.001) between caffeine sensitivity of different RYR1 mutants measured by the cellular Ca2+ photometry assay and by the clinical in vitro caffeine halothane contracture test (IVCT). The correlation was weaker, however, for halothane (r = 0.49, p > 0.05). Abnormal sensitivity in the Ca2+ photometry assay provides supporting evidence for a causal role in MH for each of 15 single amino acid mutations in the ryanodine receptor. The study demonstrates the usefulness of the cellular Ca2+ photometry assay in the assessment of the sensitivity to caffeine and halothane of specific ryanodine receptor mutants.

Animals↗