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Biomedical subjects

P Han

Publications and source records attributed to P Han.

At least 37 records · Page 2Linked to original sources
PubMed2000

Virtual endoscopy of the nasal cavity in comparison with fiberoptic endoscopy.

PURPOSE: To apply virtual-endoscopic mode to display the nasal cavity and to evaluate clinical application of virtual endoscopy in comparison with nasal fiberoptic endoscopy. MATERIALS AND METHODS: Eleven patients were examined by virtual endoscopy after axial spiral computed tomography (CT) scanning was performed. In addition, 9 out of these 11 patients underwent fiberoptic endoscopy. Spiral CT scanning was performed with 1-mm collimation, 0.5- to 1-mm increment, 25-250 mA s, and pitch 1-2. Virtual endoscopy was performed by Explorer software package. RESULTS: Virtual endoscopy could clearly demonstrate anatomic structures in the nasal cavity, septal deviation, stenosis and obstruction of the middle meatus, turbinate hyperplasia, and pathological masses larger than 3 mm in diameter. However, "false adhesions" may appear in virtual endoscopy. The main limitation of virtual endoscopy was the inability to evaluate mucosa and its surface. CONCLUSION: Virtual endoscopy of the nasal cavity is a new and noninvasive method. It can demonstrate normal and pathological structures in the nasal cavity. Its ability to visualize is comparable with fiberoptic endoscopy except for evaluating mucosal surface and secretions. In the future, this method will probably be a basic instrument of computer-assisted surgery in the midfacial region.

Adult↗
PubMed2000

Effect of factor VIII concentrate on antigen-presenting cell (APC)/T-cell interactions in vitro: relevance to inhibitor formation and tolerance induction.

Inhibitor formation in patients with haemophilia receiving factor VIII (FVIII) concentrate is a common problem requiring tolerance induction therapy. Immune tolerance is dependent on defective T cell/antigen-presenting cell (APC) interactions and inhibitor antibody formation is associated with effective T-cell/B-cell interaction. We studied the expression of the cell-surface molecules involved with these interactions using multiparameter flow cytometry and a whole blood stimulation assay-phytohaemaglutinin (PHA) to activate T cells and Escherichia coli lipopolysaccharide (LPS) to activate monocytes and B cells. Up-regulation of T-cell co-stimulatory receptors CD11a, CD40 ligand (CD40L) and CTLA4 were inhibited in a dose-dependent manner by plasma-derived (pd)FVIII, but CD28 was unchanged. Up-regulation of monocyte and B-cell co-stimulatory ligands CD4O, B7-1 (CD80) and B7-2 (CD86) were also inhibited in a dose-dependent manner by pdFVIII, but LFA-3 (CD58) was unchanged. The combined inhibitory effect of prednisolone, an immunosuppressive agent used in several tolerance induction protocols, with pdFVIII on co-stimulatory molecules, was additive. There was no significant alteration in T-cell/APC adhesion or co-stimulatory molecules noted in the presence of recombinant (rh)FVIII concentrate. The inhibitory effect of pdFVIII on molecules involved in interaction between T cells and APCs may result in immune tolerance in recipients of pdFVIII concentrate. The inhibitory effect of pdFVIII on CD40/CD40L up-regulation may result in defective antibody formation. We now provide evidence that the use of pdFVIII, through interfering with APC/T-cell interactions, may be more appropriate than rhFVIII for tolerance induction.

Antigen-Presenting Cells↗
PubMed2000

Surface and intracellular interleukin-2 receptor expression on various resting and activated populations involved in cell-mediated immunity in human peripheral blood.

The kinetics of assembly of the high-affinity interleukin-2 receptor (IL-2R)alpha/beta/gamma were investigated by studying intracellular and surface expression of IL-2Ralpha, beta and gamma by T cells, monocytes and natural killer (NK) cells. IL-2Ralpha and IL-2Rgamma were expressed by small numbers of resting T cells. These numbers increased following stimulation, to maximal expression at 48 h and 72 h, respectively. This observation was consistent with de novo synthesis of the receptor protein in response to the stimulus. The proportion of T cells producing IL-2Rbeta was smaller and up-regulated later than the proportion of cells producing IL-2Ralpha or IL-2Rgamma. IL-2Rbeta may therefore slow the assembly of the high-affinity IL-2R on T cells. A small number of resting NK cells expressed IL-2Ralpha, both on the cell surface and intracellularly, but this increased over 72 h on stimulated NK cells. IL-2Rbeta was constitutively expressed, both on the cell surface and intracellularly, by monocytes and NK cells. An increased proportion of NK cells and monocytes produced IL-2Rbeta, 24 h and 4 h post-stimulation, respectively. Maximal or plateau expression occurred at 72 h and 24 h post-stimulation, for NK cells and monocytes, respectively. The early up-regulation of intracellular IL-2Rbeta for monocytes may facilitate the up-regulation of surface IL-2Rbeta, and early assembly of the high-affinity IL-2R, accelerating monocyte activation and function. High constitutive intracellular IL-2Rgamma expression (> 80%) in all types of leucocyte investigated, decreased over the 72 h following stimulation with a concurrent increase in surface expression. IL-2Rgamma was expressed by increased proportions of T cells, monocytes and NK cells, 4 h following stimulation. The intracellular storage of IL-2Rgamma may accelerate translocation to the cell surface after stimulation. The early translocation of IL-2Rgamma may reflect its usage as a signal transduction molecule by other cytokine receptors - IL-4, IL-7, IL-9 and IL-15. This study delineated the potential expression of the high-affinity IL-2Ralpha/beta/gamma on various stimulated leucocytes. The differential kinetics of assembly of the high-affinity IL-2Ralpha/beta/gamma on different leucocyte subsets suggests that IL-2 may regulate the inflammatory cellular responses in a sequential manner, paralleling the timed expression of IL-2Ralpha/beta/gamma on the monocytes, NK cells and T cells.

Adult↗
PubMed2000

Coil occlusion of the parent artery for treatment of symptomatic peripheral intracranial aneurysms.

BACKGROUND AND PURPOSE: Peripheral intracranial aneurysms can be difficult to treat with traditional surgical or embolization techniques that spare the parent vessel. We report the results of our use of coil occlusion of the parent vessel for the treatment of nine peripheral intracranial aneurysms. METHODS: During approximately a 4-year period, nine patients (six men and three women, 27 to 68 years old; average age, 42 years) presented to our institution with peripheral intracranial aneurysms. The aneurysms were located on branches of the right posterior inferior cerebellar artery (n = 2), the right superior cerebellar artery (n = 1), the right anterior inferior cerebellar artery (n = 1), the right posterior cerebral artery (n = 3), the left middle cerebral artery (n = 1), and the left anterior cerebral artery (n = 1). Parent vessel occlusion was performed using microcoils after test injection with amobarbital (Amytal) in eight of the nine cases (one patient was comatose and could not be tested before occlusion). RESULTS: Angiography immediately after the procedure showed aneurysmal occlusion in every patient. Follow-up arteriography, performed in six patients 2 to 12 months after treatment, documented continued aneurysmal occlusion in every case. Three patients exhibited mild, nondisabling neurologic deficits after coil placement; the rest had no new deficits, although one patient was severely disabled from the initial hemorrhage and one patient died of an unrelated cause. CONCLUSION: Our results lend support to the use of parent vessel occlusion for peripheral aneurysms that are difficult to treat surgically or that are not amenable to intra-aneurysmal coil placement.

Adult↗
PubMed2000

[3D finite element analysis of stress distributions in supporting tissues of clasp-type partial dentures of transferring occlusion force].

OBJECTIVE: To provide a theoretical basis for clinical application of the clasp-type partial denture of transferring occlusion force, the stress distributions in its supporting tissue were analyzed. METHODS: The 3D finite element model was made, and the features of stress distributions in the supporting tissues of the clasp-type partial dentures which had different rest recess angles were discussed. RESULTS: The medial stress component was significantly larger than the distal one in the supporting tissue around main abutment root. When the rest recess angles were equal or greater to 60 degrees, the stress values were greatly reduced in the supporting tissue around the roots of the three abutments. When the rest recess angle reached 75 degrees, the stress values in the supporting tissue around the main abutment root wore decreased by 30% than the angle 0 degree and by 52% than the angle 45 degrees, the stress values in the supporting tissue around the root of second abutment (adjacent to the main abutment) were wholly increased by 44% than the angle 0 degree and reduced by 23% than the angle 45 degrees, the stress values in supporting tissue around the root of third abutment (outside of the second abutment) were wholly increased by 53% than the angle 0 degree and decreased by 31% than the angle 45 degrees, the stress values in the medial root of the main abutment were reduced by 73%. CONCLUSION: The clasp-type partial denture can resolve part of the occlusion force into two components the medial and distal components, and the occlusion force is distributed to several abutments, at the same time the conversed force components can be canceled by each other. So the whole stress values are greatly reduced and the stress around abutment root is greatly decreased. As a result the damage to the abutment will be eliminated. A design with centralized multi abutments and multi fixed bodies are used in this denture, which are more fixed and stable and have no obvious sinkage in the plate base. Therefore, the mastication function can be satisfactorily recovered, and the reasonable rest recess angle for the clasp-type partial denture of transferring occlusion force is about 75 degrees.

Bite Force↗
PubMed1999

The calcium/calmodulin-dependent phosphodiesterase PDE1C down-regulates glucose-induced insulin secretion.

To understand the role cAMP phosphodiesterases (PDEs) play in the regulation of insulin secretion, we analyzed cyclic nucleotide PDEs of a pancreatic beta-cell line and used family and isozyme-specific PDE inhibitors to identify the PDEs that counteract glucose-stimulated insulin secretion. We demonstrate the presence of soluble PDE1C, PDE4A and 4D, a cGMP-specific PDE, and of particulate PDE3, activities in betaTC3 insulinoma cells. Selective inhibition of PDE1C, but not of PDE4, augmented glucose-stimulated insulin secretion in a dose-dependent fashion thus demonstrating that PDE1C is the major PDE counteracting glucose-dependent insulin secretion from betaTC3 cells. In pancreatic islets, inhibition of both PDE1C and PDE3 augmented glucose-dependent insulin secretion. The PDE1C of betaTC3 cells is a novel isozyme possessing a K(m) of 0.47 microM for cAMP and 0.25 microM for cGMP. The PDE1C isozyme of betaTC3 cells is sensitive to 8-methoxymethyl isobutylmethylxanthine and zaprinast (IC(50) = 7.5 and 4.5 microM, respectively) and resistant to vinpocetine (IC(50) > 100 microM). Increased responsiveness of PDE1C activity to calcium/calmodulin is evident upon exposure of cells to glucose. Enhanced cAMP degradation by PDE1C, due to increases in its responsiveness to calcium/calmodulin and in intracellular calcium, constitutes a glucose-dependent feedback mechanism for the control of insulin secretion.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Optimal storage conditions for preserving granulocyte viability as monitored by Annexin V binding in whole blood.

It is important in the laboratory to develop techniques to preserve leucocyte viability in blood specimens for subsequent flow cytometric analysis. This article describes a new simple whole blood lysis method using Annexin V FITC staining which can be used to define both early and late apoptosis of granulocytes in heterogeneous cell populations, without the need for additional stains or to purify the cells (which may result in loss of the cells of interest). The differential Annexin V binding assay was in good agreement with the light microscopy reference method and showed excellent correlation with 7-aminoactinomycin D (7-AAD) staining. It was not affected by problems of morphological interpretation and artifactal changes of granulocyte deformability noted using light microscopy, or the technical difficulties encountered due to red cell contamination using the 7-AAD method. Using this new differential Annexin V staining method, we determined the optimum conditions that maintain granulocyte viability for subsequent flow cytometric analysis and are now employed in our laboratory. These conditions were lithium heparin (Hep) anticoagulated whole blood specimens kept at 4 degrees C with the addition of nutrient medium. Specimens that are anticoagulated with acid citrate dextrose (ACD) or ethyl-diacetyl-tetraacetic acid (EDTA) should also be treated similarly to preserve granulocyte viability and to overcome problems associated with identification of cell populations by flow cytometry.

Adult↗
PubMed1999

A mini binary vector series for plant transformation.

A streamlined mini binary vector was constructed that is less than 1/2 the size of the pBIN19 backbone (3.5 kb). This was accomplished by eliminating over 5 kb of non-T-DNA sequences from the pBIN19 vector. The vector still retains all the essential elements required for a binary vector. These include a RK2 replication origin, the nptIII gene conferring kanamycin resistance in bacteria, both the right and left T-DNA borders, and a multiple cloning site (MCS) in between the T-DNA borders to facilitate cloning. Due to the reduced size, more unique restriction sites are available in the MCS, thus allowing more versatile cloning. Since the traF region was not included, it is not possible to mobilize this binary vector into Agrobacterium by triparental mating. This problem can be easily resolved by direct transformation. The mini binary vector has been demonstrated to successfully transform Arabidopsis plants. Based on this mini binary vector, a series of binary vectors were constructed for plant transformation.

Agrobacterium tumefaciens↗
PubMed1999

Functional lymphocyte immunophenotypes observed in thalassaemia and haemophilia patients receiving current blood product preparations.

Immune abnormalities have been reported in recipients of cellular and plasma blood products. To document the effect of current transfusion practices, we performed ex vivo lymphocyte immunophenotypic studies on patients with thalassaemia major who had received multiple (leucocyte-depleted) transfusions and patients with haemophilia A and B who had received heat viral-inactivated factor concentrates. Patients with thalassaemia major showed a significant lymphocytosis, with mainly B-cell changes consistent with ongoing B-cell stimulation associated with chronic exposure to red cell antigens. Reduced T-cell IL-2Ralpha expression would be consistent with inhibition by desferrioxamine chelation therapy. In contrast, patients with haemophilia showed predominantly T-cell changes. Patients with haemophilia A showed significantly elevated activated CD8+ cytotoxic T lymphocytes whereas those with haemophilia B showed an increase in CD8+CD11adim and CD4+CD45RA+ suppressor T cells. Several of the immune abnormalities found may be due to the presence of cytokines not removed by leucocyte filtration or destroyed by factor concentrate production (e.g. TGF-beta) causing a T-helper-2-like response. The extensive lymphocyte characterization in this study has not previously been performed and has enabled a closer examination of the functional lymphocyte immunophenotypes seen in patients treated according to current transfusion practices.

Adolescent↗
PubMed1999

Effect of factor VIII concentrate on leucocyte cytokine production: characterization of TGF-beta as an immunomodulatory component in plasma-derived factor VIII concentrate.

Clinical and subclinical immunological abnormalities have been reported in HIV-seronegative haemophiliacs. The mechanisms by which these abnormalities arise remain unclear. As cytokines are important biological response modifiers, the effect of a FVIII concentrate on production of a range of cytokines, by a variety of cells, was investigated. A whole blood technique was used and the in vitro modulation of cytokine synthesis by an intermediate-purity plasma-derived factor VIII (pdFVIII) concentrate was analysed using multiparameter flow cytometry. In cell cultures exposed to pdFVIII, T cells showed reduced production of TNF-alpha, IL-2 and IFN-gamma; monocytes showed reduced production of TNF-alpha, IL-1alpha, IL-1beta, IL-6, IL-8 and IL-12 but an increase in IL-10 synthesis; IFN-gamma synthesis by NK cells was reduced. All changes in cytokine synthesis and the reduction in cell surface expression of CD69, a signal transduction molecule contributing to both cytokine and cytokine receptor synthesis, were in a dose-dependent manner in cultures exposed to FVIII concentrate. These changes were characteristic of TGF-beta. Addition of anti-TGF-beta to FVIII reduced these changes in T-cell cytokine production, suggesting TGF-beta may be an important immunomodulatory agent in the pdFVIII concentrate. The Th2 cytokine bias shown in the presence of pdFVIII concentrate, in vitro, may explain the increase in rates of certain types of infections reported in these patients, which require Th1 cytokine production for an effective response.

Antigens, CD↗
PubMed1999

Intracellular cytokine production and cytokine receptor interaction of cord mononuclear cells: relevance to cord blood transplantation.

A 'cytokine storm' consisting of IL-1, IL-2, IL-12, IFNgamma and TNFalpha is considered important in the development of graft-versus-host disease (GvHD). These cytokines activate effector cells or damage host tissues. Cord blood transplantation has been associated with a low incidence of GvHD. We hypothesized that the low incidence of GvHD relates to the cord mononuclear cells being poor producers of pro-inflammatory cytokines. The cytokine profile (IL-1alpha/beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IFNgamma and TNFalpha) of cord blood cells induced by immune stimuli was determined in heparinized whole blood. Compared to adult, cord blood CD3+ and NK cells produced less IFNgamma, less cord blood CD3+ cells and monocytes produced TNFalpha and less monocytes produced IL-1alpha/beta. Although more cord T cells produced IL-2 compared to adult T cells at 4 h, adult T cells produced more at 24 h. Cord blood had similar proportions of monocytes to adult producing IL-6, IL-10 and IL-12. Both adult and cord mononuclear cells constitutively expressed receptors for IFNgamma and TNFalpha but not IL-12. In contrast to the adult cells, cord CD3+ and NK cells did not express IL-12 receptor but did up-regulate IL-10 receptor after mitogenic stimulation. The findings of this study indicate that the cord blood cytokine-receptor network is biased towards anti-inflammatory activity compared to adult and helps to explain the decreased incidence of GVHD in cord blood transplantation.

Adult↗
PubMed1999

Methyl-prednisolone up-regulates monocyte interleukin-10 production in stimulated whole blood.

Glucocorticosteroids (GCS) have been used successfully in the treatment of inflammatory conditions such as asthma and acute graft-vs-host disease, but their mode of action remains unclear. There have been numerous reports of the in-vitro suppression of cytokine production by GCS based on quantitation of cytokines by ELISA on bulk supernatants from isolated cell culture systems. We report the use of a whole-blood intracellular cytokine assay which is more representative of an in-vivo environment. We examined the effects of GCS, prednisolone and dexamethasone, on cytokine production by individual cells (monocytes, T lymphocytes and natural killer or NK cells) in heterogenous cell populations. Cells in whole blood were activated with various stimuli: phorbol ester and calcium ionophore for T cells, Escherichia coli lipopolysaccharide (LPS) for monocytes, and phytohaemagglutinin (PHA) plus interleukin (IL)-12 for NK cells. Brefeldin A was used as an intracellular transport inhibitor to enhance the detection of intracellular cytokine production. The effects of various concentrations (10-5, 10-7, 10-9 and 10-11 m) of GCS on cytokine production were studied using multiparameter flow cytometry. After surface staining with fluorescently-conjugated monoclonal antibodies (MoAbs) to identify cell type, cells were fixed and permeabilised. Intracellular cytokines interferon (IFN)-gamma, IL-10, IL-1alpha and beta, IL-2, tumour necrosis factor (TNF)-alpha, and IL-12 were stained with their respective conjugated MoAbs. The GCS both caused a dose-dependent modulation of cytokine production by T cells, monocytes and NK cells. After 4 h, a decrease in the MFI (amount of cytokine produced per cell) was noted for all cell types. After 24 h a decrease in both MFI and the percentage of cells producing cytokine was observed for all cell types. The exception was monocyte production of IL-10 which was enhanced at low concentrations of GCS (10-9 and 10-11 m). Our findings thus suggest that one anti-inflammatory mechanism of GCS action may be through inhibition of the release of pro-inflammatory cytokines IL-1alpha and beta, IL-2, IFN-gamma and TNF-alpha, and up-regulation of the anti-inflammatory cytokine IL-10.

Adult↗
PubMed1999

Intraocular pressure lowering by S-allylmercaptocysteine in rabbits.

The purpose of this study was to examine the actions of a garlic-derived compound, S-allylmercaptocysteine (SAMC) on intraocular pressure (IOP) and to determine the possible involvement of sulfhydryl reactivity, sympathetic neuronal activity and atrial natriuretic peptide (ANP) in the IOP response. Topical, unilateral application of SAMC (20, 100, 200 microg) elicited dose-dependent decreases in IOP. The magnitude of the IOP-lowering effect induced by SAMC was between four to six mmHg. The ocular hypotensive responses were unilateral, peaked at one to three hours and lasted from two to four hours. The IOP-lowering effect by SAMC (100 microg) was enhanced modestly by topical, bilateral pretreatment with a reducing agent, tris(2-carboxyethyl) phosphine (100 microg) which itself produced no change in IOP. No alteration of pupil diameter was observed following topical application of either SAMC or tris(2-carboxyethyl) phosphine. Thus, alteration of sulfhydryl reactivity does not seem to be a major mechanism of action for SAMC. SAMC caused no change of basal and electrically stimulated norepinephrine release in rabbit iris-ciliary bodies, ruling out a prejunctional effect on sympathetic nerve activity. However, SAMC increased the ANP levels in aqueous humor by five-fold. It is concluded that the ocular hypotensive response induced by SAMC in rabbits could involve the elevation of ANP levels in aqueous humor.

Administration, Topical↗
PubMed1998

Surface activation markers of T lymphocytes: role in the detection of infection in neonates.

Diagnosis of perinatal infection in the newborn is difficult; there may be few clinical signs and current tests are slow or non-specific. Detection of organisms, antigen or specific antibody to common pathogens often requires repeat samples and does not give immediate results. Haematological parameters, although relied upon frequently to diagnose infection in the neonate prior to a positive bacterial isolation, are unreliable and insensitive. Indicators such as an increase in neutrophil band cell counts are highly variable between morphologists. Infection induces the expression of a number of T lymphocyte surface markers, including CD45RA/CD45RO and CD45RO. The use of changed expression of surface markers as a laboratory test for detection of infection in neonates was evaluated. We used multiparameter flow cytometry to detect expression of early (CD45RA/CD45RO) and late (CD45RO) activation markers. In the respective groups of 50 full term (including 25 normal vaginal deliveries and 25 caesarean deliveries) and 30 premature, i.e. < 36 weeks gestation (born by either normal vaginal delivery or caesarean delivery) the CD45RA isoform was brightly expressed on newborn 'naive' CD4+ T cells, whereas the CD45RO isoform (including both 'bright' and 'dim' populations) was present on < 19% of CD4+ T cells from these newborn infants. In a group of 37 infants, tested to evaluate possible effects of non-infective parameters such as respiratory distress and iso-immunization, no significant changes in surface marker expression were found and specificity of the test was confirmed. In 14 neonates with documented sepsis, up-regulation of dual staining CD45RA/CD45RO isoforms on CD4+ T cells was detected early in the infection. In addition, we found that CD45RO expression persisted for several weeks after bacterial infection, and up to several months in viral infection. In conclusion, detection of T cell activation by flow cytometry for the early diagnosis of neonatal infection is an easy test to carry out on small volumes of blood, is inexpensive, and may be a specific indicator of infection.

Bacterial Infections↗
PubMed1998

Repair of cyclobutane pyrimidine dimers in unstimulated human mononuclear cells is deficient at very low fluences of ultraviolet B and is not enhanced by addition of deoxyribonucleosides.

Unstimulated human T lymphocytes are exquisitely sensitive to UVB irradiation. This hypersensitivity appears to relate to low deoxyribonucleotide pool sizes. They have also been reported to be defective in global excision of cyclobutane pyrimidine dimers, but such experiments may have been carried out at supralethal doses, where unrepaired excision breaks persist indefinitely. We use a T4 endonuclease Comet assay to show that removal of cyclobutane pyrimidine dimers is defective in the unstimulated mononuclear cell fraction (mainly T lymphocytes) even at sublethal fluences from an FS20 broad spectrum UVB lamp. Moreover, removal is not enhanced by addition of deoxyribonucleosides to the medium. Cells which are failing to remove cyclobutane pyrimidine dimers readily form fresh incision breaks in response to a second UVB fluence, indicating that they retain repair capacity and suggesting that removal of types of damage other than cyclobutane pyrimidine dimers is effective.

Adult↗