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D Sun

Publications and source records attributed to D Sun.

At least 325 records · Page 18Linked to original sources
PubMed1994

Characterization of brain-isolated rat encephalitogenic T cell lines.

In the present study, we have isolated and characterized five myelin basic protein (MBP)-reactive T cell lines directly from the brains of Lewis rats during the early paralytic phase of experimental autoimmune encephalomyelitis (EAE). Each T cell line responded to the dominant encephalitogenic epitope spanning residues 68-88, and did not react against the conserved encephalitogenic epitope [MBP(87-99)] or the nonencephalitogenic MBP epitope [MBP(50-69)]. We determined the T cell receptor (TcR) beta chain usage by polymerase chain reaction, DNA sequencing analysis and by generation of MBP-reactive hybridomas from one of the T cell lines (BT74). The results revealed that brain-infiltrating, MBP-reactive T cells freshly isolated early in the course of the disease exhibit TcR diversity.

Amino Acid Sequence↗
PubMed1994

(+)-CC-1065 as a probe for intrinsic and protein-induced bending of DNA.

(+)-CC-1065 is a biologically potent DNA-reactive antitumor antibiotic produced by Streptomyces zelensis. This antibiotic covalently modifies DNA by alkylation of N-3 of adenine in the minor groove. As a structural consequence of covalent modification of DNA, the helix axis is bent into the minor groove. The drug-induced bending of DNA has similarities to intrinsic A-tract bending and the 3' adenine of A-tracts shows a unique reactivity to alkylation by (+)-CC-1065. Upon covalent modification of A-tracts, the magnitude of bending is increased and the helix is stiffened. Using high-field NMR, hydroxyl-radical footprinting and gel electrophoresis, the molecular basis for the high reactivity of the bonding sequence 5'-AGTTA* (an asterisk indicates the covalent modification site) to (+)-CC-1065 has been shown to involve the inherent conformational flexibility of this sequence. Furthermore, these studies also demonstrate that after alkylation the drug-induced bending is focused over the TT region. By analogy with the junction bend model for A-tracts, a 'truncated junction bend model' is proposed for this structure. Last, the application (+)-CC-1065 entrapped/induced bending of DNA as a probe for the Sp1-induced bending of the 21-base-pair repeat and Mu transposase bending of the att L3 sequence is described.

Antibiotics, Antineoplastic↗
PubMed1994

Repertoire of rat MBP-reactive T cells: DNA sequencing analysis further demonstrates the clonal heterogeneity of rat T cells reactive against encephalitogenic epitopes.

Reports of the expression of very similar TCR structures by disparate rodent encephalitogenic T cells reactive with regions of MBP have aroused much interest for both theoretical and practical reasons. To ascertain the extent to which structural requirements of epitope recognition constrain TCR expression by MBP-reactive T cells, we set out to estimate the size of the overall repertoire of TCR beta-chain V beta-D beta-J beta (VDJ) assemblies in T cells of Lewis rats specific for MBP(68-88) as well as those specific for MBP(87-99). We previously reported that such T cells can express a diversity of V beta genes as revealed by PCR analysis. In this study, we have used direct sequencing of PCR products amplified from encephalitogenic T-cell clones and pauciclonal T-cell lines to demonstrate that VDJ structures of the rat T cells specific for either residues 68 to 88 or 87 to 99 of MBP are highly heterogeneous. Our results showed that (1) no pattern is evident in the utilization of germline J gene segments by individual T-cell clones; from a total of over 100 successfully sequenced clones displaying in-frame rearrangements, all the J beta segments have been demonstrated. (2) Even among the T-cell clones which share the V beta expression, J beta is variable. (3) Due to joining variations between the V beta, D beta, and J beta gene segments, no two of the T-cell clones examined share entire VDJ structures. Our study is the first report of nucleotide and amino acid sequences of TCR beta-chains from rat encephalitogenic T cells expressing V beta genes other than V beta 8.2. It demonstrates that the TCR repertoire of the MBP-reactive as well as encephalitogenic T cells is heterogeneous, even though a certain T-cell subset frequently dominated by the mechanism needs to be clarified.

Amino Acid Sequence↗
PubMed1994

Decrease of heat shock protein 27/28 with heat stress in HTLV-I-transformed cells.

We have previously reported an increase of human T-lymphotropic leukemia/lymphoma virus type I (HTLV-I) replication after heat treatment of MT-2 cells, an HTLV-I-transformed human lymphoid cell line. In this study, we investigated the effect of heat stress on the expression of Hsp27/28 in MT-2 cells. In contrast with previous studies of other cell types, a decrease of Hsp27/28 expression in MT-2 cells and an increase of Hsp70 family proteins in both MT-2 and uninfected lymphoid CEM cells were found following heat treatment at 42 degrees C. Furthermore, heat treatment resulted in an early rapid increase in the phosphorylated form of Hsp27/28 in both MT-2 and CEM cells. The results suggest that early post-translational phosphorylation of HSP27/28 could be a determinant of the ability of MT-2 cells to survive hyperthermia.

Blotting, Northern↗
PubMed1994

Increases in oxygen tension evoke arteriolar constriction by inhibiting endothelial prostaglandin synthesis.

In vivo and in vitro studies concerned with the role of oxygen in the regulation of blood flow have primarily investigated the response of blood vessels to decreases in oxygen tension. In this study, we examined the response of isolated rat cremaster skeletal muscle arterioles to increases in oxygen tensions. First-order arterioles with an average diameter of 90 microns were cannulated and pressurized to 65 mm Hg and studied under constant pressure in a no-flow state. Arterioles were equilibrated in a Krebs bicarbonate-buffered solution (ph 7.4) gassed with 21% O2, 5% CO2, 74% N2. Changes in arteriolar diameters were continuously measured and recorded in response to increases in bath PO2 (20 to 660 mm Hg). Arterioles were studied before and after either the removal of the endothelium or the administration of indomethacin (IND, 10(-5) M), to inhibit prostaglandin synthesis. When the bath PO2 was increased from 20 to 150 mm Hg, arteriolar diameters decreased by 37%; they then decreased an additional 14% when bath PO2 was increased from 150 to 660 mm Hg. Removal of the endothelium or administration of IND completely eliminated the arteriolar constrictions in response to increases in PO2 from 20 to 150 mm Hg, and from 150 to 660 mm Hg. These observations suggest that rat cremaster arterioles constrict to increases in oxygen tension by reduction in the synthesis of endothelium-derived dilator prostaglandins.

Animals↗
PubMed1994

The effect of a free radical scavenger and platelet-activating factor antagonist on FFA accumulation in post-ischemic canine brain.

The effects of the platelet-activating factor antagonist BN 50739 and a free radical scavenger dimethyl sulfoxide on the accumulation of free fatty acids in post-ischemic canine brain are reported. Following 14 min of complete normothermic ischemia and 60 min of reperfusion, the total brain FFAs were approximately 150% higher than in the control group (p < 0.05). Perfusion with the platelet-activating factor antagonist BN50739 in its diluent dimethyl sulfoxide during 60 min of post-ischemic reoxygenation resulted in a 61.8% (p < 0.01) reduction in the total brain free fatty acid accumulation. Palmitic, stearic, oleic, linoleic, and arachidonic acids decreased by 53.8%, 63.5%, 69.0%, 47.4%, and 57.2%, respectively. Although dimethyl sulfoxide alone caused stearic and arachidonic acids to return to the normal concentration range, BN 50739 had a significant influence on recovery of palmitic, oleic, and linoleic acids and was previously shown to provide significant therapeutic protection against damage to brain mitochondria following an ischemic episode. Because free fatty acid accumulation is one of the early phenomena in cerebral ischemia, this study provides evidence to support the hypothesis that both platelet-activating factor and free radicals are involved in initiating cerebral ischemic injury.

Animals↗
PubMed1994

Ischemia-induced changes in cerebral mitochondrial free fatty acids, phospholipids, and respiration in the rat.

Changes in the free fatty acid pool size and fatty acyl chain composition of mitochondrial membrane phospholipids and their relation to disruption of mitochondrial function were examined in rat brains after 30 min of cerebral ischemia (Pulsinelli-Brierley model) and 60 min of normoxic reoxygenation. During ischemia, significant hydrolysis of polyunsaturated molecular species from diacyl phosphatidylcholine, particularly fatty acyl 20:4 (arachidonic acid; 20% decrease) and 22:6 (docosahexaenoic acid; 15% decrease), was observed. Thirty minutes of ischemia caused a 16% loss of 18:2 (linoleic acid) from phosphatidylethanolamine. Recirculation for 60 min did not return the polyunsaturated fatty acid content of phospholipids to normal. Total content of free fatty acids increased during ischemia, particularly 18:2 and 22:6, which exhibited the most dramatic rise. The free fatty acid pool size continued to increase during 60 min of recirculation. The respiratory control ratio decreased significantly during 30 min of ischemia with no apparent recovery following 60 min of reoxygenation. The degree of free radical-mediated lipid peroxidation in mitochondria was significantly increased during ischemia and reperfusion. It was concluded that (a) 30 min of cerebral ischemia caused differential degradation in each of the phospholipid classes and preferential hydrolysis of the polyunsaturated molecular species and (b) 60 min of normoxic reperfusion failed to promote reacylation of the mitochondrial phospholipids and restoration of normal respiration.

Animals↗
PubMed1994

Effect of the platelet-activating factor antagonist BN 50739 and its diluents on mitochondrial respiration and membrane lipids during and following cerebral ischemia.

Recent evidence suggests that platelet-activating factor plays a role in ischemia-induced neural injury. The Pulsinelli-Brierley four-vessel occlusion model was used to study the effect of a synthetic platelet-activating factor antagonist, BN 50739, and its solvents, either dimethyl sulfoxide or hydroxypropyl-beta-cyclodextrin, on cerebral ischemia-reperfusion. Rats were subjected to either 30 min of ischemia or 30 min of ischemia followed by 60 min of recirculation. Changes in the brain mitochondrial free fatty acid pool size, fatty acyl composition of phospholipids, and respiratory function were monitored. When the BN 50739 (2 mg of BN 50739/kg of body weight i.v.) was administered at the onset of recirculation, it significantly reversed the ischemia-induced accumulation of mitochondrial free fatty acids and loss of polyunsaturated fatty acyl chains from phosphatidylcholine and phosphatidylethanolamine while simultaneously improving mitochondrial respiration. Dimethyl sulfoxide alone decreased the mitochondrial level of malonyldialdehyde and total free fatty acid pool size, but there was no improvement in mitochondrial respiration. Hydroxypropyl-beta-cyclodextrin was reported to be pharmacologically inactive and capable of dissolving BN 50739. However, hydroxypropyl-beta-cyclodextrin alone also caused a significant increase in content of cerebral mitochondrial membrane free fatty acids and hydrolysis of phosphatidylcholine in normoxic control animals. The overall effect of BN 50739 on mitochondrial structure and energy metabolism supports the hypothesis that platelet-activating factor may play a key role in ischemia-induced cerebral injury.

Animals↗
PubMed1994

Characteristics and origin of myogenic response in isolated gracilis muscle arterioles.

Responses to changes in intravascular pressure of isolated rat gracilis muscle arterioles were investigated under no-flow conditions. First-, second-, and third- order arterioles were isolated and cannulated. Vascular diameters were measured with an image-shearing device and then recorded. In response to the step increases in perfusion pressure (from 20 to 160 mmHg, by 10- or 20-mmHg steps) arterioles constricted and developed active tone. For example, at 100, 80, and 50 mmHg pressure the steady-state active diameters of 1st-, 2nd-, and 3rd-order arterioles were 76.9 +/- 1.6, 32.3 +/- 1.1 and 22.3 +/- 3.2 microns, respectively. At the same perfusion pressure, by use of a Ca(2+)-free solution (ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid; 1 mM) containing sodium nitroprusside (SNP; 10(-4) M), the passive diameters (PD) of these vessels were 161.8 +/- 3.2, 76.0 +/- 1.7, and 47.6 +/- 2.2 microns. The negative slopes of the pressure-diameter curves indicate that in the physiological pressure range an inverse relationship exists between the arteriolar diameter and intravascular pressure. The maximum constriction expressed as a percent of PD was similar in the various sized arterioles (approximately 60%) but was reached at lower pressures in the smaller vessels. The vasoactive function of endothelium and vascular smooth muscle was assessed by the responses of arterioles to acetylcholine (ACh; 10(-6) M) and SNP (5 x 10(-8) M) before and after removal of the endothelium with air. After removal of the endothelium, dilation to ACh was abolished while dilation to SNP was retained.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1994

Corelease of nitric oxide and prostaglandins mediates flow-dependent dilation of rat gracilis muscle arterioles.

We have studied the mechanisms responsible for the mediation of flow (shear stress)-induced dilation of isolated arterioles of rat gracilis muscle. Active diameter of arterioles at a constant perfusion pressure (PP, 80 mmHg) was approximately 92 microns, while their passive diameter (Ca(2+)-free solution) was approximately 165 microns. At a constant PP the stepwise increase in flow of the perfusion solution (PS, 0-60 microliters/min in 10-microliters/min steps) elicited a gradual increase in diameter up to approximately 140 microns. Flow-induced dilations were eliminated by the removal of the endothelium of arterioles (by air). Dilations were significantly reduced by the cyclooxygenase blocker, indomethacin (Indo, 10(-5) M), by the nitric oxide synthase blocker, N omega-nitro-L-arginine (L-NNA, 10(-4) M), or by the endothelium-derived relaxing factor inhibitor, oxyhemoglobin (Hb, 10(-5) M), as indicated by the significant changes in the slope of the regression lines of the flow-diameter curves. For example, during administration of the inhibitors, dilation to 60 microliters/min perfusate flow was reduced by 41.1, 54.3, and 39.3%, respectively. Combined application of Indo and L-NNA almost completely eliminated flow-induced dilation. Arteriolar dilation maintained calculated wall shear stress close to control values (approximately 30 dyn/cm2 at 60 microliters/min) despite increases in flow, but when the dilation was inhibited by removal of the endothelium or by the combined administration of Indo and L-NNA, wall shear stress was greatly increased as a function of increases in flow of the PS (approximately 125 dyn/cm2).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1994

Short-term daily exercise activity enhances endothelial NO synthesis in skeletal muscle arterioles of rats.

We aimed to test the hypothesis that as a consequence of short-term daily bouts of exercise the control of arteriolar smooth muscle by endothelium is altered. Rats ran on a treadmill once a day, 5 days/wk, for 2-4 wk (with gradually increasing intensity, up to 26 min at 22 m/min at a 1% grade by the beginning of the 3rd wk and up to 38 min at 28 m/min at a 2% grade by the beginning of the 4th wk) while a control group remained sedentary (SED). Cannulated and pressurized arterioles of rat gracilis muscle developed spontaneous myogenic tone, which was slightly enhanced in exercised (EX) compared with SED rat arterioles. At 80 mmHg pressure, the passive (Ca(2+)-free solution) and active diameters of SED and EX rat arterioles were 105.4 +/- 3.8 and 55.1 +/- 2.3 microns and 107.1 +/- 3.4 and 50.2 +/- 2.2 microns, respectively. Dose-dependent dilations to sodium nitroprusside (10(-8)-10(-6) M) and constrictions to norepinephrine (10(-8)-10(-6) M) were not affected in EX arterioles, whereas dilations to adenosine (10(-6)-10(-4) M) were significantly reduced. In contrast, dose-dependent dilations to acetylcholine (ACh; 5 x 10(-9)-10(-7) M) and L-arginine [precursor of nitric oxide (NO); 10(-4)-10(-3) M] were significantly enhanced (by 33-78 and 57-75%, respectively) in arterioles of EX compared with those of SED rats. Responses of arterioles to sodium nitrite were not different in SED and EX groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1994

Ischemia induces translocation of the insulin-responsive glucose transporter GLUT4 to the plasma membrane of cardiac myocytes.

BACKGROUND: Acute myocardial ischemia is accompanied by an increase in glucose uptake and metabolism, which appears to be important in protecting myocardial cells from irreversible ischemic injury. Because insulin augments myocardial glucose uptake by inducing the translocation of glucose transporters from an intracellular compartment to the plasma membrane, we hypothesized that acute ischemia would trigger a similar translocation. METHODS AND RESULTS: We used a subcellular fractionation method to separate intracellular membrane and plasma membranes from control, ischemic, and hypoxic Langendorff-isolated perfused rat hearts and determined the expression of the major myocardial glucose transporter, GLUT4, in these separated membrane fractions. We found that translocation of GLUT4 molecules occurred in ischemic, hypoxic, and insulin-treated hearts and in hearts that underwent ischemia plus insulin treatment. The percentages of GLUT4 molecules present on the plasma membrane in the different conditions were as follows: control, 18.0 +/- 2.8%; ischemia, 41.3 +/- 9.4%; hypoxia, 31.1 +/- 2.9%; insulin, 61.1 +/- 2.6%; and ischemia plus insulin, 66.8 +/- 5.7%. Among the statistically significant differences in these values were the difference between control and ischemia and the difference between ischemia alone and insulin plus ischemia. CONCLUSIONS: Ischemia causes substantial translocation of GLUT4 molecules to the plasma membrane of cardiac myocytes. A combination of insulin plus ischemia stimulates an even greater degree of GLUT4 translocation. GLUT4 translocation is likely to mediate at least part of the increased glucose uptake of ischemic myocardium and may be a mechanism for the cardioprotective effect of insulin during acute myocardial ischemia.

Animals↗
PubMed1994

Dermal fibroblasts activate keratinocyte outgrowth on collagen gels.

The effects of dermal fibroblasts on keratinocyte outgrowth on collagen substrata was studied using an in vitro keratinocyte-collagen gel composite model. Skin fibroblasts were seeded inside collagen gels, which remained attached to the cell culture plastic substratum. Fibroblasts incorporated in collagen gels were either kept viable throughout the study, or were lysed hypotonically with water at different time intervals (2 hours and 5 days). Results show that very little keratinocyte outgrowth occurred on either plain collagen gels or gels that had previously contained viable fibroblasts for 2 hours. A 3- to 4-fold increase in keratinocyte outgrowth occurred on collagen gels that had previously contained viable fibroblasts for 5 days. A striking increase (20-fold) in keratinocyte outgrowth was observed on collagen gels that contain viable fibroblasts. The effect of fibroblast diffusible factors on keratinocyte outgrowth was further studied with a co-culture system using Millicell inserts. It was found that the co-culture of fibroblasts with the composite enhanced keratinocyte outgrowth on collagen gels that had previously contained viable fibroblasts for 5 days. Among all, however, the keratinocyte outgrowth was far better on gels containing viable fibroblasts. Addition of keratinocyte growth factor or its neutralizing antibody did not affect keratinocyte outgrowth. These results suggest that dermal fibroblasts can activate keratinocyte outgrowth on collagen matrices through some diffusible factors other than keratinocyte growth factor, and epithelial-mesenchymal interactions exert some special effects on keratinocyte outgrowth on collagen gels.

Cell Communication↗
PubMed1994

[Analysis on refraction status of eyes with normal vision].

Refractive status of 1,324 eyes with normal vision of the juvenile students in four grades was analysed. It was raised that the meaning of refractive status was different between the medical physiological optics and the physical or geometrical optics. "Emmetropia" did not really mean "the normal eye" in refraction as viewed from normal physiology, and the problem about the physiological refractive status of eyes in the juvenile was discussed preliminarily.

Adolescent↗
PubMed1994

[Comparative study on three serologic tests for detecting antibodies in cases with bancroftian microfilaremia].

A comparative study was conducted for detecting antibody levels of bancroftian microfilaremia cases by using three serologic tests, IFAT, ELISA and dot-ELISA. A total of 102 serum specimens were collected from bancroftian microfilaremia cases. The positive rate was 89.2% (91/102) with IFAT (serum dilution > or = 1:20), 84.3% (86/102) with ELISA (OD value > or = 0.440) and 89.2% (91/102) with dot-ELISA (serum dilution > or = 1:80), respectively (P > 0.05); while in healthy individuals from non-endemic areas the false positive rate was 0(0/30), 1.8(1/55) and 0(0/54), respectively. The results indicated that there were no statistically significant differences among the three serologic tests. There was no correlation found in this study between microfilaria density and the antibody level. It was also proved that the detection rate of the combined use of either 2 or 3 tests was higher than each of the three tests; the positive rates being 94.1%-98.0%.

Animals↗
PubMed1994

A modified technique for bedside placement of nasoduodenal feeding tubes.

A technique for bedside placement of NDT that was used in our ICU and allowed a significant percentage of feeding tubes to be placed in the duodenum without moving the patient from the ICU setting is reported. We believe that this modification for feeding tube placement is effective and safe and represents an improvement of the previous method.

Duodenum↗
PubMed1994

Adenovirus vector-mediated in vivo gene transfer into adult murine retina.

PURPOSE: To determine whether a reporter gene can be introduced into the adult mammalian retina in vivo through means of a recombinant replication-deficient adenovirus. METHODS: A dilution series of purified Ad.CMVlacZ ranging from 10(5) to 10(11) pfu/ml was prepared and microinjected into the subretinal space of adult CD-1 mice. This virus contained the cytomegalovirus (CMV)-promoted Escherichia coli reporter gene, lacZ. LacZ expression was assessed in enucleated eyes from 0 to 95 days after injection by beta-galactosidase (beta-Gal) assay. RESULTS: The efficiency of transfection increased as a function of concentration of recombinant virus injected. Eyes injected with greater than 10(7) pfu of Ad.CMVlacZ demonstrated beta-Gal activity lasting at least 95 days. LacZ expression was apparent only in those cells directly exposed to the adenovirus. LacZ expression was observed in the retinal pigment epithelium (RPE) at high efficiency at 48 hours after exposure. By 2 weeks after injection of > 10(7) pfu, lacZ was also expressed in photoreceptors, but at lower density. CONCLUSIONS: These results demonstrate that high efficiency stable transfer of functional genes can be achieved in vivo in post-mitotic mammalian retina using recombinant adenoviral vectors. Adenovirus vectors appear to be a promising means for delivering therapeutic genes in vivo to the mammalian neural retina and particularly to the RPE.

Adenoviruses, Human↗