Biomedical subjects

Y Hua

Publications and source records attributed to Y Hua.

At least 37 records · Page 2Linked to original sources

PubMed2004

Modulation of SMN nuclear foci and cytoplasmic localization by its C-terminus.

The survival of motor neuron ( SMN1) gene product, SMN, is detected both in the cytoplasm and in nuclear gems and cajal bodies. We show here that SMN exon 6 is essential both for formation of its nuclear foci and for its cytoplasmic localization. However, exon 7 inhibits the formation of SMN nuclear foci but promotes SMN cytoplasmic localization. More interestingly, we find that a random C-terminal tag of five or more amino acids downstream of exon 6 is sufficient to inhibit the occurrence of multiple nuclear foci and to promote cytoplasmic localization of SMNDelta7, the primary product of the SMN2 gene. Moreover, SMNDelta7 proteins that bear spinal muscular atrophy mutations in exon 6 either showed defects in nuclear foci formation or enhanced cytoplasmic localization. We conclude that exon 6 and exon 7 synergistically regulate SMN distribution that may require specific exon 6 motifs but is independent of specific sequences in exon 7.

Amino Acid Motifs↗

PubMed2003

A thrombin inhibitor reduces brain edema, glioma mass and neurological deficits in a rat glioma model.

Although thrombin is a critical enzyme in the coagulation cascade, it has become apparent that it has many other effects. Thus, it may induce brain edema formation, angiogenesis and cell proliferation. Because of the importance of these three factors in the extremely poor prognosis of glioma patients, the present study examined the role of thrombin in that disease state. We found that thrombin activity is increased in a rat glioma model and thrombin positive cells were present in the tumor. Anti-thrombin treatment with argatroban reduced brain edema, tumor growth, and tumor-related neurological deficits. Our results suggest that thrombin is a new target for glioma treatment.

Animals↗

PubMed2003

Thrombin exacerbates brain edema in focal cerebral ischemia.

Thrombin contributes to edema formation after intracerebral hemorrhage. Recent studies suggest that thrombin may also play a role in ischemic brain damage. In the present study, adult male Sprague-Dawley rats were anesthetized with pentobarbital. Middle cerebral artery (MCA) was occluded using the suture method. We found that brain thrombin activity was elevated after permanent MCA occlusion as was prothrombin messenger RNA expression. Intracerebral injection of a thrombin inhibitor, hirudin, reduced neurological deficits following cerebral ischemia. In contrast, intracerebral administration of exogenous thrombin (at a dose that is non-toxic to normal brain), markedly exacerbated brain edema after transient focal cerebral ischemia. These results indicate that extravascular thrombin inhibition may be a new therapeutic target for cerebral ischemia.

Animals↗

PubMed2003

Thrombin preconditioning upregulates transferrin and transferrin receptor and reduces brain edema induced by lysed red blood cells.

Pretreatment with a low dose of thrombin reduces brain edema after both hemorrhagic and ischemic stroke. We call this phenomenon thrombin preconditioning (TPC) or thrombin-induced brain tolerance. The present study examines whether TPC can attenuate the brain edema induced by lysed red blood cells (RBCs) to determine whether thrombin production early in an intracerebral hemorrhage (ICH) might alter potentially injurious events associated with clot resolution. It also examines whether TPC might be protective by altering iron handling within the brain, particularly through modulating transferrin (Tf) and transferrin receptor (TfR) levels. Brain edema was measured by wet/dry weight. Western blot analysis and immunohistochemistry were used for Tf and TfR measurements. We found that TPC reduces lysed RBC-induced brain edema and upregulates both Tf and TfR levels in the brain. Thrombin formation after an ICH may be part of a signaling cascade that acts to limit potentially injurious events associated with clot resolution through altering iron-handling proteins.

Animals↗

PubMed2003

Effect of delayed argatroban treatment on intracerebral hemorrhage-induced edema in the rat.

Studies indicate that thrombin plays an important role in intracerebral hemorrhage (ICH) induced edema formation. However, the time window for administration of a thrombin inhibitor to reduce ICH-induced edema is unknown. Nor is it known whether this time window extends beyond the period when a thrombin inhibitor might exacerbate rebleeding. This study examines whether a thrombin inhibitor, argatroban, can reduce edema formation following intracerebral infusion of 100 microl of blood in the rat, the therapeutic time window for argatroban, and whether argatroban promotes rebleeding. Intracerebral injection of argatroban 3 hours after ICH caused a significant reduction in edema measured at 48 hours. The systemic administration of argatroban (0.9 mg/h) starting 6 hours after ICH also significantly reduced edema formation. There was no protection when the onset of argatroban administration was delayed to 24 hours after ICH. Argatroban did not increase collagenase-induced hematoma volume when given into the clot after 3 hours or given systemically at 6 hours. Our data suggest argatroban may be an effective therapy for ICH-induced edema.

Animals↗

PubMed2003

Overexpression of interleukin-1 receptor antagonist reduces brain edema induced by intracerebral hemorrhage and thrombin.

Recent studies indicate that inflammatory reaction occurs around hematoma after intracerebral hemorrhage (ICH). In this study the authors examine the hypothesis that overexpression of IL-1ra in the brain attenuate brain edema formation after ICH. Adenoviruses expressing IL-1ra (Ad.RSVIL-1ra) or LacZ (Ad.RSVLacZ) or saline were injected into the lateral ventricle. On the fifth day after virus injection, 100 microl of autologous blood or 5 U thrombin was infused into the right basal ganglia. Rats with ICH were killed 24 or 72 hours later for measurement of brain water content. Thrombin-treated rats were killed 24 hours later for edema measurements and an assessment of polymorphonuclear leukocyte (PMNL) infiltration by myeloperoxidase (MPO) assay. Compared with control groups, Ad.RSVIL-1ra treated rats had less brain edema formation in the ipsilateral basal ganglia 3 days after ICH (81.5 +/- 0.3% compared with 83.4 +/- 0.4% and 83.3 +/- 0.5% in control animals). Ad.RSVIL-1ra treated rats had also less brain edema following thrombin injection. The reduction of brain edema induced by thrombin was involved in the reduction of PMNL infiltration in basal ganglia, as assessed by MPO assay. Adenovirus-mediated overexpression of IL-1ra attenuated brain edema formation following ICH, perhaps by reduction of thrombin-induced brain inflammation.

Animals↗

PubMed2003

Changes in cerebral oxygenation in children undergoing surgical repair of ventricular septal defects.

There have been few published studies on changes in cerebral oxygenation during paediatric cardiac surgery as measured by conventional near-infrared spectroscopy. We studied changes in cerebral oxygenation in 16 children undergoing surgical repair of ventricular septal defects. Fifteen of the patients showed similar patterns of changes: brain tissue concentrations of oxyhaemoglobin decreased significantly during cardiopulmonary bypass, whereas there was no significant change in brain tissue concentrations of deoxyhaemoglobin. In the remaining patient, who suffered decreased blood flow to the lower body during surgery, the pattern of changes was different to that of the other subjects. This patient suffered postoperative respiratory and renal failure. This study suggests that conventional near-infrared spectroscopy may be useful for clinical monitoring during ventricular septal defect repair.

Analysis of Variance↗

PubMed2002

Experimental intracerebral hemorrhage: effect of lysed erythrocytes on brain edema and blood-brain barrier permeability.

Understanding the mechanism of edema formation following intracerebral hemorrhage (ICH) is important for developing treatment protocols for this condition. This study examines the role of red blood cell (RBC) lysis and hemoglobin in edema formation following ICH. Significant brain edema developed after 24 hours in rats infused with lysed RBCs and this was associated with a 3-fold increase blood brain barrier (BBB) permeability to alpha-aminoisobutyric acid. We have previously shown that intracerebral injection of packed RBCs does not cause edema formation at one day but does at three days. In this study, we found that packed RBCs did not cause significant BBB disruption at one day but produced a 4-fold increase in BBB permeability at three days. These studies show that following ICH the leakage of substances inside the RBC, facilitated by cellular lysis, results in delayed edema. This was confirmed by both experimentally induced lysis and naturally occurring in-vivo lysis.

Animals↗

PubMed2002

Brain edema after intracerebral hemorrhage: the effects of systemic complement depletion.

The complement cascade is activated after experimental intracerebral hemorrhage (ICH) and may play an important, role in edema formation. This study investigated the effects of systemic complement depletion on brain edema formation following ICH. Thirty-six pentobarbital-anesthetized Sprague-Dawley rats were used. Treatment animals were complement-depleted with cobra venom factor (CVF) while controls received an equal volume of saline injection (i.p.). In both treatment and control rats, autologous blood (100-microL) was infused stereotactically into the right basal ganglia. Rats were sacrificed one and three days later for brain water and ion content measurements and immunohistochemical studies. Immunohistochemistry was used to detect complement C3d, C5a, and C9. Western blot analysis was applied for C9 semiquantitation. Perihematomal brain edema was reduced by systemic complement depletion at one and three days. The water content of the cerebellum (a tissue distant from the hematoma site) was unaffected by complement depletion. Immunocytochemistry found complement depletion significantly reduced perihematomal C9 deposition, C3d production, and C5a positive cell accumulation. In conclusion, complement depletion by CVF attenuates brain edema in ICH perhaps by inhibiting the inflammatory response and membrane attack complex (MAC) formation.

Animals↗

PubMed2002

Effect of ischemic preconditioning on edema formation and cerebrovascular injury following focal cerebral ischemia.

Many studies have shown that a brief period of ischemia can protect against a subsequent severe ischemic event and this has been termed ischemic preconditioning (IPC). Most studies have been focused on neuroprotection, with only a little attention on cerebrovascular effects. This study examines the effect of IPC, induced by 15 minutes of middle cerebral artery occlusion (MCAO) in the rat, on brain edema formation and cerebrovascular injury induced by a permanent MCAO induced three days later. Brain edema formation was significantly reduced in IPC treated rats compared to non-IPC treated rats. IPC-treated rats also had reduced blood-brain barrier disruption and reduced cerebrovascular expression of heat shock protein 70, a marker of cell stress. These results indicate that IPC reduces cerebrovascular injury from subsequent permanent focal cerebral ischemia. Understanding the mechanisms involved may provide new therapeutic strategies for stroke.

Animals↗

PubMed2002

Effects of mild and moderate hypothermia on apoptosis in neuronal PC12 cells.

BACKGROUND: There is still a possibility that mild hypothermic therapy may be useful as a neuroprotective tool during the intraoperative period, although the mechanism of cerebral protection by mild hypothermia is not well understood. We hypothesized that mild hypothermia may be protective against cerebral ischaemia by inhibiting post-ischaemia apoptosis. In this study, we used serum-deprived PC12 cells as the neuronal apoptotic model and examined the direct effects of mild and moderate hypothermia. METHODS: Apoptosis was induced by depriving the cell culture medium of serum, which is one of the most representative methods to induce apoptosis, but not necrosis, in PC12 cells. Effects of mild (35 and 33 degrees C) and moderate (31 and 29 degrees C) hypothermia on apoptosis were evaluated. Cytotoxicity (lactate dehydrogenase leakage) and the percentage of apoptotic cells (calculated by flow cytometry with propidium iodide) were evaluated 4 days after induction of apoptosis. As a control, cells without induction of apoptosis were incubated under the same conditions as the apoptosis group. RESULTS: Without induction at 37 degrees C, cytotoxicity and the percentage of apoptotic cells were over 60 and 90%, respectively. At each temperature examined below 35 degrees C, significant decreases in cytotoxicity and the percentage of apoptotic cells were observed. Mean cytotoxicity at 31 and 29 degrees C was 50.2 (SD 4.2)% and 47.9 (4.4)%, respectively. The percentage of apoptotic cells at 31 and 29 degrees C was 42.5 (7.4)% and 36.5 (7.3)%, respectively. In the control group, cytotoxicity and the percentage of apoptotic cells were significantly higher at 29 degrees C than at 37 degrees C. CONCLUSIONS: Mild and moderate hypothermia (29-35 degrees C) inhibited apoptosis, although hypothermia below 30 degrees C may induce apoptosis in intact cells.

Animals↗

PubMed2001

Mechanisms of edema formation after intracerebral hemorrhage: effects of extravasated red blood cells on blood flow and blood-brain barrier integrity.

BACKGROUND AND PURPOSE: Red blood cell (RBC) lysis contributes to brain edema formation after intracerebral hemorrhage (ICH), and RBC hemolysate (oxyhemoglobin) has been implicated to be a spasminogen in subarachnoid hemorrhage. Whether cerebral ischemia contributes to brain edema formation after ICH remains unclear, however. The aims of this study were to test whether extravasation of RBCs induces cerebral ischemia and/or blood-brain barrier disruption in a rat ICH model characterized by perihematomal brain edema. METHODS: In this study, 87 pentobarbital-anesthetized Sprague-Dawley rats were used. In each animal, saline, packed RBCs, or lysed RBCs were injected into the right caudate nucleus. Sham injections served as controls. Regional cerebral blood flow, brain water and ion contents, blood-brain barrier integrity, and plasma volume were measured. RESULTS: Intraparenchymal infusion of lysed RBCs caused severe brain edema by the first day but did not induce ischemic cerebral blood flows. In contrast, blood-brain barrier permeability increased during the first day after infusion of lysed RBCs (a 3-fold increase) and 3 days after infusion of packed RBCs (a 4-fold increase). CONCLUSIONS: These results suggest that ischemia is not present at 24 or 72 hours after hematoma induction by injection of intact or lysed RBCs. RBC constituents that appear after delayed lysis, however, increase blood-brain barrier permeability, which contributes to edema formation.

Animals↗

PubMed2001

Effects and mechanisms of H(2)O(2) on production of dicarboxylic acid.

The system of producing long chain dicarboxylic acid (DCA) by Candida tropicalis is an aerobic and viscous fermentation system. A method to overcome the gas-liquid transport resistance and to increase oxygen supply is by adding hydrogen peroxide (H(2)O(2)) to the fermentation system. Here we report that the H(2)O(2) not only can enhance the oxygen supply but also change the metabolism by inducing cytochrome P450, the key enzyme of a, o-oxidation. When C. tropicalis was cultivated in a 3-L bioreactor using the combination of aeration and H(2)O(2) feeding, DCA production rates increased by about 10% after a short period of decrease at the beginning. Furthermore, the experiments showed that the maximum activities of P450 could be induced at 2 mM H(2)O(2), and the inducible mechanisms are also discussed. Moreover, we suggest that alkane might be oxidized through the "peroxide shunt pathway" when H(2)O(2) is present. By adding H(2)O(2), the DCA yield in a 22-L bioreactor could increase by 25.3% and reach 153.9 g/L.

Aerobiosis↗

PubMed2001

Three SNARE complexes cooperate to mediate membrane fusion.

Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins of the syntaxin, SNAP-25, and VAMP families mediate intracellular membrane fusion through the formation of helical bundles that span opposing membranes. Soluble SNARE domains that lack their integral membrane anchors inhibit membrane fusion by forming nonfunctional complexes with endogenous SNARE proteins. In this study we investigate the dependence of membrane fusion on the concentration of a soluble SNARE coil domain derived from VAMP2. The increase in the inhibition of fusion observed with increasing concentration of inhibitor is best fit to a function that suggests three SNARE complexes cooperate to mediate fusion of a single vesicle. These three complexes likely contribute part of a protein and lipidic fusion pore.

Animals↗

PubMed2001

Abortion history and breast cancer risk: results from the Shanghai Breast Cancer Study.

Studies of the association between induced abortion and breast cancer risk have been inconsistent, perhaps due to underreporting of abortions. Induced abortion is a well-accepted family planning procedure in China, and women who have several induced abortions do not feel stigmatized. The authors used data from a population-based case-control study of breast cancer among women age 25-64 conducted between 1996 and 1998 in urban Shanghai to assess whether a history of and the number of induced abortions were related to breast cancer risk. In-person interviews were completed with 1,459 incident breast cancer cases ascertained through a population-based cancer registry, and 1,556 controls randomly selected from the general population in Shanghai (with respective response rates of 91% and 90%). After adjusting for confounding, there was no relation between ever having had an induced abortion and breast cancer (odds ratio [OR] = 0.9, 95% confidence interval [CI] 0.7-1.2). Women who had 3 or more induced abortions were not at increased risk of premenopausal breast cancer (OR = 0.9, 95% CI 0.6-1.4) or postmenopausal breast cancer (OR = 1.3, 95% CI 0.8-2.3). These results suggest that a history of several induced abortions has little influence on breast cancer risk in Chinese women.

Abortion, Induced↗

PubMed2001

A new focal adhesion protein that interacts with integrin-linked kinase and regulates cell adhesion and spreading.

Integrin-linked kinase (ILK) is a multidomain focal adhesion (FA) protein that functions as an important regulator of integrin-mediated processes. We report here the identification and characterization of a new calponin homology (CH) domain-containing ILK-binding protein (CH-ILKBP). CH-ILKBP is widely expressed and highly conserved among different organisms from nematodes to human. CH-ILKBP interacts with ILK in vitro and in vivo, and the ILK COOH-terminal domain and the CH-ILKBP CH2 domain mediate the interaction. CH-ILKBP, ILK, and PINCH, a FA protein that binds the NH(2)-terminal domain of ILK, form a complex in cells. Using multiple approaches (epitope-tagged CH-ILKBP, monoclonal anti-CH-ILKBP antibodies, and green fluorescent protein-CH-ILKBP), we demonstrate that CH-ILKBP localizes to FAs and associates with the cytoskeleton. Deletion of the ILK-binding CH2 domain abolished the ability of CH-ILKBP to localize to FAs. Furthermore, the CH2 domain alone is sufficient for FA targeting, and a point mutation that inhibits the ILK-binding impaired the FA localization of CH-ILKBP. Thus, the CH2 domain, through its interaction with ILK, mediates the FA localization of CH-ILKBP. Finally, we show that overexpression of the ILK-binding CH2 fragment or the ILK-binding defective point mutant inhibited cell adhesion and spreading. These findings reveal a novel CH-ILKBP-ILK-PINCH complex and provide important evidence for a crucial role of this complex in the regulation of cell adhesion and cytoskeleton organization.

Actinin↗

PubMed2001

Levels of ovine herpesvirus 2 DNA in nasal secretions and blood of sheep: implications for transmission.

A recently developed competitive PCR for ovine herpesvirus 2 (OvHV-2) was used to examine the levels of viral DNA in nasal secretions and peripheral blood leukocytes (PBL) of lambs and adult sheep. Viral DNA first appeared in the PBL of most lambs after about 3 months of age and the levels remained relatively constant thereafter. In most of the lambs (83%, n=12), viral DNA was undetectable by PCR in nasal secretions prior to 5 months of age. A dramatic rise of OvHV-2 DNA levels in the nasal secretions occurred starting at 5-6 months of age, which peaked at approximately 7 months. The highest level recorded in lamb nasal secretions was 7.5x10(8)copies/2microg DNA which were 75,000-100,000-fold higher than the levels in PBL of the same lambs. In adult sheep (n=10), the viral DNA levels in both PBL and nasal secretions were relatively stable over the 13-month period of the study, which included a lambing season. The data strongly suggest that neonatal lambs are not an important source for the transmission of OvHV-2 to clinically susceptible species, and that the nasal cavity is an important portal for shedding of infectious OvHV-2 in sheep. Furthermore, this study failed to identify a seasonal pattern in levels of viral DNA in nasal secretions or PBL of adult sheep that would provide a basis for the traditionally held belief that clinical cases of malignant catarrhal fever are significantly associated with lambing ewes.

Animals↗

PubMed2001

Activation of p44/42 mitogen activated protein kinases in thrombin-induced brain tolerance.

BACKGROUND: Our recent studies have shown that prior intracerebral injection of a low dose of thrombin attenuates the brain edema formation that results from either an intracerebral hematoma, an intracerebral injection of a large dose of thrombin or cerebral ischemia. The aim of the current study is to investigate whether thrombin-induced tolerance (thrombin preconditioning; TPC) is associated with activation of p44/42 mitogen activated protein (MAP) kinases. METHODS: This study contained three parts. In the first, rats received an intracerebral infusion of either saline or one unit thrombin (the TPC dose) into the right caudate nucleus. After 1, 3 and 7 days, the rats will be killed and brains used to detect p44/42 MAP kinases activation using Western blot analysis and immunohistochemistry. In the second and third parts, rats received intracerebral infusions of either vehicle, one unit thrombin (TPC) or one unit thrombin and 5 nmol PD 098059. These rats were either killed to detect kinases activation after 24 h or received a second intracerebral infusion of five-unit thrombin 7 days later with brain edema being assessed after a further 24 h. RESULTS: Western blot analysis demonstrated that p44/42 MAP kinases were activated in the ipsilateral basal ganglia after the intracerebral infusion of thrombin one unit. Cells immunoreactive for activated p44/42 MAP kinases were found in the ipsilateral basal ganglia and ipsilateral cortex. PD 098059, a MAP kinase kinase inhibitor, abolished thrombin-induced activation of p44/42 MAP kinases. TPC suppressed thrombin-induced brain edema while PD 098059 blocked this protective effect. The water contents in the ipsilateral basal ganglia 24 h after infusion of thrombin five units were 82.6+/-0.8%, 79.2+/-0.4% and 81.8+/-1.9% in the control, TPC alone and TPC plus PD 098059 groups, respectively. CONCLUSION: Thrombin can activate p44/42 MAP kinases within the brain and the protective effects of thrombin preconditioning on brain edema formation are related to this activation.

Animals↗