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Biomedical subjects

L Han

Publications and source records attributed to L Han.

At least 73 records · Page 4Linked to original sources
PubMed1998

Application of magnetic field-induced heat shock protein 70 for presurgical cytoprotection.

To develop an alternative to hyperthermia for the induction of hsp70 for presurgical cytoprotection, we investigated the optimal exposure conditions for magnetic field induction of hsp70. Normal human breast cells (HTB124) were exposed to 60-Hz magnetic fields and hsp70 levels were measured following three different exposure conditions: continuous exposure up to 3 h, a single 20-min exposure, and a single 20-min exposure followed by repeated 20-min exposures at different field strengths. In cells exposed continuously for 3 h, hsp70 levels peaked (46%) within 20 min and returned to control levels by 2 h. Following a single 20-min exposure, the return of hsp70 levels to control values extended to more than 3 h. When cells underwent a 20-min exposure followed by repeated 20-min exposures (restimulation) with different field strengths, additional increases in hsp70 levels were induced: 31% at 1 h, 41% at 2 h, and 30% at 3 h.

Breast↗
PubMed1998

Magnetic field activation of protein-DNA binding.

The mechanisms involved in sensing, signaling, and coordinating changes resulting from magnetic field-induced stress show substantial similarities to those of heat shock, e.g., magnetic field-induced heat shock 70 gene (HSP70) expression involves heat shock factor (HSF) activation and heat shock element binding. However, an additional requirement for transactivation of HSP70 expression by magnetic fields is the binding of Myc protein, indicating that additional elements and/or pathways are involved in the induction of HSP70 expression by magnetic fields. To investigate the possible participation of additional genetic elements in magnetic field-induced HSP70 expression, we examined both magnetic field exposure and heat shock on protein-DNA binding of the transcription factors HSF, AP-1, AP-2, and SP-1 in four human cell lines. The binding sites for these transcription factors are present in the HSP70 promoter. AP-1 binding activity, normally not increased by heat shock, was increased by magnetic fields; heat shock induced an increase only in HSF binding. Although intersecting and converging signaling pathways could account for the multiplicity of elements involved in magnetic field-induced HSP70 transcription, direct interaction of magnetic fields with DNA is also a possible mechanism. Because magnetic fields penetrate the cell, they could well react with conducting electrons present in the stacked bases of the DNA.

Binding, Competitive↗
PubMed1998

Myc-mediated transactivation of HSP70 expression following exposure to magnetic fields.

We investigated c-myc protein-binding sites on the HSP70 promoter as modulators of the induction of HSP70 gene expression in response to magnetic field stimulation (8microT at 60Hz) and whether the presence of c-myc protein potentiates transactivation of HSP70 expression. A 320 base pair region in the HSP70 promoter (+1 to -320) was analyzed. This region contains two c-myc-protein binding sites with consensus sequences located at -230 and -160 nucleotide positions (relative to the transcription initiation site) and overlapping with the region reported for the regulation of HSP70 gene expression by c-myc protein. This promoter region is upstream of other regulatory sequences, including the heat shock element (HSE), AP-2, and serum response element (SRE). Transfectants containing both c-myc protein-binding sites, HSP-MYC A and HSP-MYC B, and exposed to magnetic fields showed a 3.0-fold increase in expression of CAT activity as compared with sham-exposed control transfectants. Transfectants containing one c-myc binding site, HSP-MYC A, and exposed to magnetic fields showed a 2.3-fold increase in CAT expression. Transfectants in which both HSP-MYC A and HSP-MYC B binding sites were deleted showed no magnetic field sensitivity; values were virtually identical with sham-exposed controls. If the c-myc expression vector was not co-transfected with the constructs containing myc-binding sites, there was no difference in the expression of CAT activity between magnetically stimulated and sham-exposed controls, although both responded to heat shock. These data suggest that endogenous elevated levels of myc protein contribute to the induction of HSP70 in response to magnetic field stimulation.

Electromagnetic Fields↗
PubMed1998

Effect of PAF receptor antagonists on adrenocortical secretion induced by ACTH in normal and athymic nude mice.

The effect of SM12502 and CV6209, platelet-activating factor (PAF) receptor antagonists on corticosterone (B) secretion induced by ACTH was examined in the perfused adrenals of CD1 ICR (normal) and CD1 ICR nu/nu (athymic) mice. Bilateral adrenals were perfused in situ with an artificial medium equilibrated by 95% O2 + 5% CO2. Continuous infusion of 10 microM SM12502 or CV6209 inhibited the B response to 100 pg/ml ACTH markedly in normal mice but insignificantly in athymic mice. Infusion of PAF did not significantly affect B secretion in either normal or athymic mice. Administration of 0.1 microM of N-methylcarbamyl PAF, a nonmetabolizable PAF agonist, significantly increased B secretion in normal mice, but not in athymic mice. Infusion of SM12502 significantly depressed the B response to 10 microM forskolin or 1 mM dibutyryl cyclicAMP (cAMP) in normal mice, but not in athymic mice. The results indicate that endogenous PAF and its receptor may play a role in the ACTH-initiated signaling pathway at the phase after responsiveness to cAMP and its receptor may have little function in athymic mice.

Adrenal Cortex↗
PubMed1998

Use of silicone oil in the treatment of complicated retinal detachment: results from 1981 to 1994.

PURPOSE: To evaluate the advantages and disadvantages of the retention and removal of silicone oil in the treatment of complicated retinal detachments. METHODS: The records of 344 patients (348 eyes) that underwent vitrectomy and silicone oil injection for complicated retinal detachments were abstracted and analysed. The anatomical and functional results, complications and influencing factors are discussed. The outcome in eyes after removal of the silicone oil was compared with the outcome in a comparable group of eyes in which the silicone oil was retained. RESULTS: The overall retinal reattachment rate was 63% (220/348). The final vision of 5/300 or better was 52% (115/220) in those eyes with totally attached retinas. The silicone oil-related complications included keratopathy (23%) and secondary glaucoma (11%). Comparing removal of silicone oil with retention of silicone oil, we found: (i) there was no statistical difference in the redetachment rate (19 vs 17%); (ii) oil-removed eyes had a better final vision (P < 0.05); and (ii) keratopathy (13 vs 23%), secondary glaucoma (11 vs 25%) and optic nerve atrophy (4 vs 18%) were significantly lower in oil-removed eyes. CONCLUSION: Silicone oil injection is useful in the treatment of complicated retinal detachments. For reducing the incidence of complications, early removal of silicone oil is recommended in those cases in which the retina is attached, all breaks adequately closed and traction relieved.

Adolescent↗
PubMed1998

Characterization of beta-ketoacyl-acyl carrier protein synthase III from Streptomyces glaucescens and its role in initiation of fatty acid biosynthesis.

The Streptomyces glaucescens fabH gene, encoding beta-ketoacyl-acyl carrier protein (beta-ketoacyl-ACP) synthase (KAS) III (FabH), was overexpressed in Escherichia coli, and the resulting gene product was purified to homogeneity by metal chelate chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the purified protein revealed an Mr of 37,000, while gel filtration analysis determined a native Mr of 72,000 +/- 3,000 (mean +/- standard deviation), indicating that the enzyme is homodimeric. The purified recombinant protein demonstrated both KAS activity and acyl coenzyme A (acyl-CoA):ACP transacylase (ACAT) activity in a 1:0.12 ratio. The KAS and ACAT activities were both sensitive to thiolactomycin inhibition. The KAS activity of the protein demonstrated a Km value of 3.66 microM for the malonyl-ACP substrate and an unusual broad specificity for acyl-CoA substrates, with Km values of 2.4 microM for acetyl-CoA, 0.71 microM for butyryl-CoA, and 0.41 microM for isobutyryl-CoA. These data suggest that the S. glaucescens FabH is responsible for initiating both straight- and branched-chain fatty acid biosynthesis in Streptomyces and that the ratio of the various fatty acids produced by this organism will be dictated by the ratios of the various acyl-CoA substrates that can react with FabH. Results from a series of in vivo directed biosynthetic experiments in which the ratio of these acyl-CoA substrates was varied are consistent with this hypothesis. An additional set of in vivo experiments using thiolactomycin provides support for the role of FabH and further suggests that a FabH-independent pathway for straight-chain fatty acid biosynthesis operates in S. glaucescens.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMed1998

The effects of acupuncture, electroneedling and transcutaneous electrical stimulation therapies on peripheral haemodynamic functioning.

For decades, acupuncture and electroneedling treatments have been used, predominately in the Eastern countries, in the management of patients with compromised cardiovascular and digestive functions. Similarly, neuromuscular electrical stimulation is commonly employed in Western countries to modulate pain, augment muscle strength and enhance blood flow in patients with peripheral vascular disease. Many rehabilitation specialists believe that electrical stimulation of acupuncture points with surface electrodes can elicit the same physiological and therapeutic effects as those produced by acupuncture and electroneedling techniques. Electrical stimulation of acupuncture points with surface electrodes is a relatively new and non-invasive treatment with potential clinical application in the management of patients with peripheral vascular disease. Presently, there are controversies in the literature as to the effects of traditional acupuncture, electroneedling and neuromuscular electrical stimulation treatments on peripheral haemodynamic functioning. This paper provides a detailed review of published studies on the above promising therapies. An attempt was made to clarify the pitfalls in the extant literature and delineate the fact from the fiction. Areas for further research were proposed.

Acupuncture Points↗
PubMed1998

Protective effect of anisodamine on reperfusion injury of skeletal muscles in rabbit.

Anisodamine is an alkaloid isolated from a Chinese plant, which was subsequently synthesized. Its chemical structure is similar to atropine. It inhibits cholinergic nerve function, improves microcirculation, and was reported to have a protective effect on reperfusion injury in various organs. We used anisodamine in a rabbit model with ischemia and reperfusion injury of hind limb muscles. We evaluated its effect on skeletal muscle cells, using transmission electron microscopy, and analyzed lipid peroxidation by measuring malondialdehyde and lactate dehydrogenase blood concentrations. We found that malondialdehyde and lactate dehydrogenase concentrations after 1 hour of reperfusion were lower in animals treated with anisodamine than in controls. Damage to membrane structures and myofilaments in muscle cells was less severe after anisodamine treatment. Our findings indicate that anisodamine protects skeletal muscles with ischemia and reperfusion injury.

Animals↗
PubMed1998

An experimental study on rhBMP-2 composite bone substitute for repairing craniomaxillary bone defects.

OBJECTIVE: To measure bone regenerative effects in animal calvarial or mandibular critical-size defects using recombinant human bone morphogenetic protein-2 (rhBMP-2) combined with four selected carriers. MATERIALS AND METHODS: The composite bone grafts were obtained by combining rhBMP-2 with chitin, coral, coral-based porous HA (CHA), and xenogeneic cancellous bone, respectively. These materials were implanted on the calvarial or mandibular defect of rabbits and on the calvarial defect of rats. Each carrier material was also studied as a control group. The animals were examined 2, 4, 8, and 12 weeks after implantation by radiography, histology (under light microscope and scanning electron microscope), immunohistochemistry, and biomechanics. RESULTS: The results showed that the composite graft was absorbed gradually after it was implanted into the defect, during which time new bone was formed within the combined material in the defect site; the amount of new bone increased as time elapsed. At 12 weeks the composite was replaced completely by bone except in the CHA group. In contrast, a large amount of fibrous tissue, and little new bone, formed on the area of the bone defect when the carrier material alone was implanted. CONCLUSIONS: All materials tested seem to be suitable carriers for rhBMP-2, which plays a very important role in new bone formation. These composite bone substitutes may be ideal materials for repairing various bone defects in the craniomaxillofacial region.

Animals↗
PubMed1998

[Protective effect of selenium on human erythrocyte rheology].

OBJECTIVE: To assess the protective effect of selenium on RBC rheology during myocardial ischemia/reperfusion period in patients with VSD or ASD who underwent cardiopulmonary bypass. METHODS: The blood samples were taken from the coronary sinus, and ascorbyl free radical (A.), peroxidants (MDA), antiperoxidative activities (plasma SOD, erythrocyte GSH-Px), the membrane shear elastic module of RBC (mu), molecular rotational correlation times of lipids and proteins of RBC membrane (tau l, tau p) were measured and compared between control and selenium groups. RESULTS: After myocardial reperfusion only for one minute, in both groups A. was significantly increased (The increased percentage in the control group +68%, in the selenium group +66%), but the selenium group had lower MDA and GSH-Px activity. On contrary to the control group with high A. level, A. of the selenium group was dropped about half since reperfusion for 5 minutes and recovered to the pre-ischemia level. After myocardial reperfusion, the control group had specific changes in membrane mu values as well as evidently prologed tau l and tau p. Simultaneously, except tau p at 5 minutes of reperfusion was obviously prolonged, no changes in the membrane mu and tau l were observed in the selenium group during the cardiac ischemia/reperfusion periol. CONCLUSION: Selenium can at least partly protect RBC rheology from free radical damage during the myocardial ischemia/reperfusion period.

Adolescent↗
PubMed1998

[The clinical meaning and determination of the superoxid dismutase activity and malondialehyde content in the serum of the patients suffering from chronic tonsillitis].

The activity of SOD and MDA content in the serum of patients suffering from chronic tonsillitis were determined one day before operation and one week after of operation. It was found that the activity of T-SOD Mn-SOD and CuZn-SOD were decreased in the serum of patients with chronic tonsillitis than that in the normal control group with statistical significance (P < 0.01). T-SOD activity was increased and MDA content was decreased significantly after operation than the time before operation (P < 0.001, P < 0.01). This study indicates that tonsil excision could decrease MDA content and increased SOD activity for the chronic tonsillitis patient.

Adolescent↗
PubMed1998

[Clinical and experimental study on treatment of acute cerebral infarction with Acanthopanax Injection].

OBJECTIVE: To evaluate the effect of Radix Acanthopanacis Senticosi in treating acute cerebral infarction and its mechanism. METHODS: Clinical study using single-blind, control trial, in which 60-80 ml of Acanthopanax Injection (AI) added to 500 ml of 0.9% normal saline was given by intravenous drip once a day for 14 days in the AI group(34 patients), while 500 ml of dextra-40 was given by the same way in the control group(26 patients). In experimental study, rabbit model of acute incomplete cerebral ischemia was made by ligation of bilateral common carotid artery. 10 ml of AI were given once daily intravenously for 7 days to the AI group and 10 ml of normal saline was given to the control group in the same way. Clinical effects (in clinical study) and effect of AI on cerebral oxygen free radicals (OFR), superoxide dismutase (SOD), and serum concentration of ACTH and cortisone were observed (in experimental study). RESULTS: Clinical study showed that the total effective rate of AI group (86%) was higher than that of the control group (50%) while nervous functional deficit score was lower in AI group (9.96 +/- 4.66) than that in the control group (13.56 +/- 1.84) significantly. Experimental study showed that the cerebral level of OFR decreased while SOD increased and serum concentration of ACTH and cortisone decreased after treatment in AI group. CONCLUSIONS: AI was effective in treating acute cerebral infarction, the mechanism is probably by ameliorating peroxidation in brain and improving hypothalamic-pituitary-adrenocortical axis function.

Adrenocorticotropic Hormone↗
PubMed1998

[Effects of whole-body vibration on human tracking performance and visual-motor reaction].

Dual task test (light target tracking and visual-motor reaction of visual oddball mode) and pursuit aiming test were done in 17 male healthy subjects after 30min exposure to whole-body vibrations of 20 Hz 0.15 gz or 20 Hz 0.3 gz. Mean accuracy rate of visual-motor reaction and target stimulus reaction accuracy rate after 0.3 gz vibration were significantly lower than those of control group (P < 0.05), while after 0.15 gz vibration, the changes were not significant. Comparing with control group, the total number of right and wrong pointing, pointing speed in pursuit aiming test were significantly lower (P < 0.05) after vibration. However, light target tracking error, mean reaction time of visual-motor reaction and pointing accuracy rate of pursuit aiming test had no significant change after exposure to any kind of the vibrations. It may be concluded that some kinds of effect on human tracking performance and visual-motor reaction were observed after exposure to whole-body vibration.

Adult↗
PubMed1998

[Effect of noise on human mental rotation performance].

To investigate the effect of moderate level low frequency noise on human mental rotation performance, letter rotation and compass orientation tests were performed in 24 healthy young male subjects during 2 h exposure to 85-95dB (A), it was found that during 120 min exposure to noise of 85dB (A), the mean reaction time increased (P<0.05), performance of reaction time and total performance decreased (P<0.01) significantly as compared with control in letter rotation test, meanwhile, performance of reaction time and total performance at 120 min exposure were significantly higher than that at 30 min (P<0.05). During 120 min exposure to noise of 95dB (A), the mean reaction time increased (P<0.01), the performance of reaction time and total performance decreased (P<0.01) significantly as compared with control in compass orientation test, meanwhile, performance of reaction time at 120 min were significantly higher than that at 30 min(P<0.05). The results show that exposures to 85 dB(A) and 95 dB(A) noise for 2 h have certain effect on the performance of human mental rotation and may affect performance of complex tasks with a higher workload.

Adolescent↗
PubMed1998

Effects of acute moderate hypoxia on human performance of arithmetic.

To observe the effects of acute moderate hypoxia on human performance of arithmetic, the continuous calculation test, addition-subtraction test and mental arithmetic tests were made in 16 health young male subjects during exposure to altitude of 300 m (control), 3600 m, 4400 m and 5000 m by mean of hypobaric cabin simulation. Error rate of the continuous calculation test and reaction time of addition-subtraction test increased significantly and performance decreased significantly (P < 0.05) after exposure to 3600 m for 1 h. Reaction time, total number and performance of all tests decreased significantly (P < 0.05) during exposure to 4400 m. Performance of all tests decreased (P < 0.01) after exposure to 5000 m for 30 min.

Adolescent↗
PubMed1998

[The indication and mode of surgery for the treatment of patients with severe acute pancreatitis].

OBJECTIVE: To study the indication and mode of surgical management in patients with severe acute pancreatitis (SAP). METHOD: 41 patients with SAP were grouped for conservative treatment or surgical. The main procedures of surgical management were pancreatic debridement, peripancreatic and coeliac drainage, combined with peripancreatic instillation and suction alternatively. RESULT: Conservative treatment was adopted in 22 patients (16 patients in grade I, 6 in grade II), among them 19 recovered, and 3 of grade II died. 19 patients underwent surgical treatment including 7 in grade I, 12 in grade II). 15 patients were cured, 4 patients of grade II died. CONCLUSION: Timely operation is necessary for the patients with infection and complications. Surgical intervention is recommended for patients older than 60 years old. Surgery should be less traumatic, simple and prompt. Surgical or conservative treatment are chosen according to the patients' conditions. The cure rate of SAP can be improved.

Adult↗
PubMed1998

[An analysis of treatment of intravitreal lens fragments following phacoemulsification].

OBJECTIVE: To observe and evaluate the outcome of vitrectomy in the treatment of dropped lens fragments. METHOD: Retrospectively the authors reviewed and analyzed 58 cases of dropped lens fragments that were treated with vitrectomy from October 1992 to October 1995 in Royal Victoria Eye and Ear Hospital, Melbourne, Australia and followed for at least 3 months. RESULTS: At the last follow-up, the remained complications were cystoid macular edema in three cases (5.2%), retinal detachment in two cases (3.4%) and hypotony in one case (1.7%). Other complications were all resolved. The final vision was significantly better than that before vitrectomy. There were 38 eyes (65.5%) with final visual acuities of 0.5 or better, and only 6 eyes (6.9%) with < 0.05. CONCLUSION: Once the lens fragments are dropped into the vitreous during phacoemulsification, the ocular anterior segment should be properly managed, if possible intraocular lens is inserted, and then vitrectomy should be performed as soon as possible. Generally, with the above method good therapeutic effects can be obtained.

Aged↗