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Biomedical subjects

Jun Pan

Publications and source records attributed to Jun Pan.

29 records · Page 2Linked to original sources
PubMed2005

Effects of hyperbaric oxygen on skin blood flow and tissue morphology following sciatic nerve constriction.

BACKGROUND: Constriction of the sciatic nerve by loose ligation produces an inflammatory neuropathic injury. This represents an animal model for peripheral mononeuropathy. Oxygen-derived free radicals are suspected to play an important role in the pathogenesis of ischemia/reperfusion injury, leading to neurogenic inflammation. Hyperbaric oxygen (HBO) has been used anecdotally to treat clinically similar conditions in humans, but specific effects on the animal model have not been well studied. OBJECTIVE: This study in a rat model examined the effects of hyperbaric oxygen on skin blood flow and tissue morphology by light and electron microscopy following sciatic nerve constriction. DESIGN: A scientific investigation in a rat model. METHODS: In this study, the neuropathic injury was established by loose ligation of the rat sciatic nerve. The animals were divided into three groups, sham (S, n=8), ligation but no treatment (LN, n=8) and ligation and treatment with hyperbaric oxygen (LT, n=8). The treatment group (n=8) received hyperbaric oxygen treatment immediately following the injury and daily for four additional days at the same time interval. One hundred percent O2 at 3 atmospheres absolute pressure (66 feet sea water) was administered for two hours. The hindpaws of the rats were observed by light microscopy, electron microscopy, laser Doppler flowmetry (LDF), and clinically for the presence of edema. RESULTS: Untreated animals demonstrated marked tissue edema following sciatic constriction, whereas animals that received hyperbaric oxygen had minimal to no edema. The sham group demonstrated normal histology. The group not treated with hyperbaric oxygen demonstrated swollen mitochondria (2-3 times), with loss of cellular integrity, multiple vacuole formation in both nerve and muscle tissue, widened sarcomeres in muscle, and degenerative changes in the nerve myelin sheaths. The group treated with hyperbaric oxygen demonstrated preservation of cellular structure including mitochondrial integrity, no vacuole formation, and maintenance of normal, easily identifiable nerve structure. The sham group had no change of skin blood flow. Skin blood flow of LT group was decreased immediately after ligation (p<0.05) and recovered to baseline level before ligation on Day 5 after four hyperbaric oxygen treatments. Skin blood flow of LN group was decreased immediately after ligation (p <0.01) and did not recover (p <0.01). CONCLUSION: This study evaluated tissue changes after nerve injury caused by loose ligation of the sciatic nerve in rats. Hyperbaric oxygen treatment following sciatic nerve injury reduced tissue edema, improved skin blood flow, and preserved muscle and neuronal ultrastructural integrity.

Journal Article↗
PubMed2004

Norepinephrine transporter function and desipramine: residual drug effects versus short-term regulation.

Previous research has shown that exposure of norepinephrine transporter (NET)-expressing cells to desipramine (DMI) downregulates the norepinephrine transporter, although changes in the several transporter parameters do not demonstrate the same time course. Exposures to desipramine for <1 day reduces only radioligand binding and uptake capacity while transporter-immunoreactivity is unaffected. Recent demonstration of persistent drug retention in cells following desipramine exposures raises the possibility that previous reported changes in the norepinephrine transporter may be partly accountable by residual drug. In this study, potential effects of residual desipramine on norepinephrine transporter binding and uptake were re-evaluated following exposures of PC12 cells to desipramine using different methods to remove residual drug. Using a method that minimizes residual drug, exposure of intact PC12 cells to desipramine for 4h had no effect on uptake capacity or [(3)H]nisoxetine binding to the norepinephrine transporter, while exposures for > or =16 h reduced uptake capacity. Desipramine-induced reductions in binding to the transporter required >24 h or greater periods of desipramine exposure. This study confirms that uptake capacity of the norepinephrine transporter is reduced earlier than changes in radioligand binding, but with a different time course than originally shown. Special pre-incubation procedures are required to abolish effects of residual transporter inhibitor when studying inhibitor-induced transporter regulation.

Adaptation, Physiological↗
PubMed2004

The effect of step-wise increased stretching on rat calvarial osteoblast collagen production.

Mechanical forces regulate the function of bone cells. In this paper, the effects of cyclic stretching on osteoblasts derived from rat calvaria were studied at a magnitude occurring in physiological loaded bone tissue. A four-point bending apparatus was used to apply cyclic stretching on osteoblasts. Stretching at 500 microepsilon for 2-24 h resulted in an increase in matrix synthesis(P<0.01). In contrast, the cyclic stretching at 1000 and 1500 microepsilon for 2-24 h inhibited osteoblast collagen production (P<0.01). We also described our new loading method to increase strain magnitude step-by-step. The strain magnitude increased by 500 microepsilon increments from 500 to 1500 microepsilon every 2 or 12 h, respectively. Results showed that osteoblasts could absorb large amount of proline for collagen synthesis when stretched at 500 microepsilon. However, not all the absorbed proline was used to synthesize collagen. Some of it was stored in cells. When the suitable signal (500 microepsilon) was changed to an inhibiting signal (1000 microepsilon), cells responded to it accordingly and released proline to medium. These results demonstrate that the response of osteoblasts is dependent on the magnitude of the strain applied and cells can adjust their bio-chemical response to adapt to the changing environmental stimulation.

Animals↗
PubMed2003

Elevated concentrations of CRF in the locus coeruleus of depressed subjects.

Research evidence that corticotropin-releasing factor (CRF) plays a role in the pathophysiology of major depressive disorder (MDD) has accumulated over the past 20 years. The elevation of lumbar cerebrospinal fluid (CSF) concentrations of CRF decreased responsiveness of pituitary CRF receptors to challenge with synthetic CRF, and increased levels of serum cortisol in MDD subjects support the hypothesis that CRF is chronically hypersecreted in at least the endocrine circuits of the hypothalamic-pituitary-adrenal (HPA) axis and may also involve other CRF brain circuits mediating emotional responses and/or arousal. One such circuit includes the excitatory CRF input to the locus coeruleus (LC), the major source of norepinephrine in the brain. Furthermore, there are now reports of decreased levels of CRF in lumbar CSF from MDD patients after symptom relief from chronic treatment with antidepressant drugs or electroconvulsive therapy. Whether this normalization reflects therapeutic effects on both endocrine- and limbic-associated CRF circuits has not yet been effectively addressed. In this brief report, we describe increased concentrations of CRF-like immunoreactivity in micropunches of post-mortem LC from subjects with MDD symptoms as established by retrospective psychiatric diagnosis compared to nondepressed subjects matched for age and sex.

Adult↗
PubMed2003

Atomic force microscopy of actin.

Atomic force microscope (AFM) is a powerful and novel tool to investigate the surface and submembranous structures of living cells under physiological conditions at high resolution, and has force measure at nano-Newton level. AFM can image and manipulate samples (single macromolecule, cells, and so on) at very high, sometimes atomic resolution by scanning a fine tip over the surface of interest and detecting physical interactions between the tip and sample. Actin is one of the most important proteins, involved extensively in various cell physiological activities and functions in eukaryotes. The present paper clarified the crucial significance and the enormous applicable prospects of AFM in modern biological sciences by reviewing the usage of AFM in actin study, which can be taken as a good example for expounding almost all functions that AFM owns, and can be utilized in life sciences exploration.

Actins↗
PubMed2003

Spectrophotometry on measuring the size of liposomes.

AIM: To establish a spectrophotometric method for measurement of the sizes of liposomes for evaluating physical stability of liposomes. METHODS: The sterically stabilized liposomes (SLs) were prepared by ethanol injection method and extrusion method. The mean cumulant diameters (D) of the vesicles were determined by electron microscopy and dynamic light scattering. On the basis of Rayleigh-Gans-Debye theory, the absorbance at 436 nm per unit lipid concentration (A436 nm/Cp) was measured as a function of vesicle diameter. RESULTS: log(A436 nm/Cp) was closely related to logD (r2 > or = 0.93, n = 5). CONCLUSION: The absorbance of liposomes reflect their relative sizes and can be used to evaluate physical stability of liposomes.

Liposomes↗
PubMed2003

[Clinical feature and surgical treatment of recurrent craniopharyngiomas].

OBJECTIVE: To explore the clinical feature and surgical treatment of recurrent craniopharyngiomas. METHODS: The imaging features, intraoperative course, and postoperative outcomes of 83 patients with craniopharyngiomas were retrospectively analyzed. RESULTS: Of the 81 patients that survived, 19 experienced recurrence of the craniopharyngioma 6 to 62 months after the completion of the initial treatment, with recurrence rates of patients with total, subtotal and partial removal being 5.3%, 52.9%, and 100% respectively. Five of the 24 patients aged 6 years or older, who had an incomplete surgical removal, received radiation therapy, and only 1 of them experienced tumor recurrence (20%) whereas as many as 15 of the 19 patients (78.9%) did who did not received it. CONCLUSION: Surgery resection should be the primary therapeutic option for patients with recurrent craniopharyngioma and radiation therapy should also be considered but only as adjuvant therapy.

Adolescent↗
PubMed2002

Significance of radiological identification of the pituitary stalk in surgical removal of craniopharyngiomas.

OBJECTIVE: To explore the radiological characteristics of craniopharyngiomas and particularly, to discuss the radiological manifestations of the pituitary stalk and their significance in safe resection of craniopharyngiomas. METHODS: Retrospective analyses of the data obtained in preoperative radiological evaluation and intraoperative observation were conducted in 63 cases of craniopharyngiomas that were surgically removed. RESULTS: In 6 cases (9.5%) the pituitary stalk was identified in preoperative radiological examination, and in 17 cases (27%) the position and course of pituitary stalk could be presumed according to the displacement of the third ventricle floor, which were confirmed in all cases during the operation. While in the other 33 (52.5%) cases, the pituitary stalk was only located during the operation. Massive calcification in the central position of the tumor stood in the way of achieving complete tumor removal, and the irregular peripheral enhancement in the superoposterior part of the tumor indicated tumor invasion of the hypothalamus. CONCLUSION: Preoperative identification of the pituitary stalk and tumor calcification, together with a clear understanding of the position of the posterior part of the tumor in association with the hypothalamus is crucial to safe and complete surgical removal of craniopharyngiomas.

Adolescent↗
PubMed2002

[Expression of proliferating cell nuclear antigen in craniopharyngioma and tumor recurrence].

OBJECTIVE: To investigate proliferating cell nuclear antigen labeling indices (PCNA-LI) in craniopharyngiomas in association with tumor recurrence. METHODS: Immunohistochemistry was employed to examine the expression of PCNA in 43 craniopharyngioma samples of different pathological types, and the relationship between PCNA-LI and tumor recurrence was evaluated. RESULTS: PCNA-LI was much higher in adamantinous tumors than in squamous papillary tumors that did not give rise to postoperative recurrence. Although PCNA-LI was higher in the recurrent lesions than in the primary tumor in adamantinoma group, the difference was not statistically significant. CONCLUSIONS: Craniopharyngioma cells with different pathological features may possess varied proliferating potentials, and active proliferation is the main factor for postoperative recurrence of adamantinoma.

Adolescent↗
PubMed2002

Preparation and degradation characteristic study of bone repair composite of DL-polylactic acid/hydroxyapatite/decalcifying bone matrix.

OBJECTIVE: To explore the preparative method and study the degradation characteristics of bone repair composite of DL-polylactic acid (PDLLA)/hydroxyapatite(HA)/decalcifying bone matrix (DBM) in vitro. METHODS: An emulsion blend method was developed to prepare the composite of PDLLA/HA/DBM in weight ratio of PDLLA:HA:DBM = 1.5-2:1-1.5:1. The dynamic changes of weight, biomechanical property and pH value of PDLLA/HA/DBM and PDLLA in phosphate buffered saline (PBS, pH 7.4) were studied respectively through degradation tests in vitro. RESULTS: Without being heated, PDLLA, HA and DBM could be synthesized with the emulsion blend method as bone composite of PDLLA/HA/DBM, which had both osteoconductive and osteoinductive effects. The diameter of the aperture was 100-400 microm and the gap rate was 71.3%. During degradation, the pH value of PDLLA solution decreased lightly within 2 weeks, but decreased obviously at the end of 4 weeks and the value was 4.0. While the pH value of PDLLA/HA/DBM kept quite steady and was 6.4 at the end of 12 weeks. The weight of PDLLA changed little within 4 weeks, then changed obviously and was 50% of its initial weight at the end of 12 weeks. While the weight of PDLLA/HA/DBM changed little within 5 weeks, then changed obviously and was 60% of the initial weight at the end of 12 weeks. The initial biomechanical strength of PDLLA was 1.33 MPa, decreased little within 3 weeks, then changed obviously and kept at 0.11 MPa at the end of 12 weeks. The initial biomechanical strength of PDLLA/HA/DBM was 1.7 MPa, decreased little within 4 weeks, then changed obviously and kept at 0.21 MPa at the end of 12 weeks. CONCLUSIONS: The emulsion blend method is a new method to prepare bone repair materials. As a new bone repair material, PDLLA/HA/DBM is more suitable for regeneration and cell implantation, and the environment during its degradation is advantageous to the growth of bone cells.

Biocompatible Materials↗