Biomedical subjects

Zhen-Du Zhang

Publications and source records attributed to Zhen-Du Zhang.

10 recordsLinked to original sources

PubMed2006

Voltage-dependent calcium channels of dog basilar artery.

Electrophysiological and molecular characteristics of voltage-dependent calcium (Ca(2+)) channels were studied using whole-cell patch clamp, polymerase chain reaction and Western blotting in smooth muscle cells freshly isolated from dog basilar artery. Inward currents evoked by depolarizing steps from a holding potential of -50 or -90 mV in 10 mm barium consisted of low- (LVA) and high-voltage activated (HVA) components. LVA current comprised more than half of total current in 24 (12%) of 203 cells and less than 10% of total current in 52 (26%) cells. The remaining cells (127 cells, 62%) had LVA currents between one tenth and one half of total current. LVA current was rapidly inactivating, slowly deactivating, inhibited by high doses of nimodipine and mibefradil (> 0.3 microM), not affected by omega-agatoxin GVIA (gamma100 nM), omega-conotoxin IVA (1 microM) or SNX-482 (200 nM) and probably carried by T-type Ca(2+) channels based on the presence of messenger ribonucleic acid (mRNA) and protein for Ca(v3.1) and Ca(v3.3) alpha(1) subunits of these channels. LVA currents exhibited window current with a maximum of 13% of the LVA current at -37.4 mV. HVA current was slowly inactivating and rapidly deactivating. It was inhibited by nimodipine (IC(50) = 0.018 microM), mibefradil (IC(50) = 0.39 microM) and omega-conotoxin IV (1 microM). Smooth muscle cells also contained mRNA and protein for L- (Ca(v1.2) and Ca(v1.3)), N- (Ca(v2.2)) and T-type (Ca(v3.1) and Ca(v3.3)) alpha(1) Ca(2+) channel subunits. Confocal microscopy showed Ca(v1.2) and Ca(v1.3) (L-type), Ca(v2.2) (N-type) and Ca(v3.1) and Ca(v3.3) (T-type) protein in smooth muscle cells. Relaxation of intact arteries under isometric tension in vitro to nimodipine (1 microM) and mibefradil (1 microM) but not to omega-agatoxin GVIA (100 nM), omega-conotoxin IVA (1 microM) or SNX-482 (1 microM) confirmed the functional significance of L- and T-type voltage-dependent Ca(2+) channel subtypes but not N-type. These results show that dog basilar artery smooth muscle cells express functional voltage-dependent Ca(2+) channels of multiple types.

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PubMed2006

A novel device for in vitro isometric tension recordings of cylindrical artery segments.

There are few instruments specifically designed to measure circumferential force generated by ring segments of arteries in vitro. Typical limitations of some existing machines include poor isometry, large organ bath volume or difficult sample mounting. The authors designed, built and tested a device for isometric tension recording of force developed by rings of arteries in vitro. It is suitable for assessment of arteries from 0.3 to 3 mm in diameter and allows measurements of forces in the range 0-20 g on eight rings simultaneously. The organ baths are independently regulated in temperature, stirred, disposable and have a minimum useable volume of only 1.2 mL.

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PubMed2006

Calcium sensitivity of vasospastic basilar artery after experimental subarachnoid hemorrhage.

Arteries that develop vasospasm after subarachnoid hemorrhage (SAH) may have altered contractility and compliance. Whether these changes are due to alterations in the smooth muscle cells or the arterial wall extracellular matrix is unknown. This study elucidated the location of such changes and determined the calcium sensitivity of vasospastic arteries. Dogs were placed under general anesthesia and underwent creation of SAH using the double-hemorrhage model. Vasospasm was assessed by angiography performed before and 4, 7, or 21 days after SAH. Basilar arteries were excised from SAH or control dogs (n = 8-52 arterial rings from 2-9 dogs per measurement) and studied under isometric tension in vitro before and after permeabilization of smooth muscle with alpha-toxin. Endothelium was removed from all arteries. Vasospastic arteries demonstrated significantly reduced contractility to KCl with a shift in the EC(50) toward reduced sensitivity to KCl 4 and 7 days after SAH (P < 0.05, ANOVA). There was reduced compliance that persisted after permeabilization (P < 0.05, ANOVA). Calcium sensitivity was decreased during vasospasm 4 and 7 days after SAH, as assessed in permeabilized arteries and in those contracted with BAY K 8644 in the presence of different concentrations of extracellular calcium (P < 0.05, ANOVA). Depolymerization of actin with cytochalasin D abolished contractions to KCl but failed to alter arterial compliance. In conclusion, it is shown for the first time that calcium sensitivity is decreased during vasospasm after SAH in dogs, suggesting that other mechanisms are involved in maintaining the contraction. Reduced compliance seems to be due to an alteration in the arterial wall extracellullar matrix rather than the smooth muscle cells themselves because it cannot be alleviated by depolymerization of smooth muscle actin.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed2006

Expression and function of inwardly rectifying potassium channels after experimental subarachnoid hemorrhage.

Cerebral vasospasm after subarachnoid hemorrhage (SAH) is because of smooth muscle contraction, although the mechanism of this contraction remains unresolved. Membrane potential controls the contractile state of arterial myocytes by gating voltage-sensitive calcium channels and is in turn primarily controlled by K(+) ion conductance through several classes of K(+) channels. We characterized the role of inwardly rectifying K(+) (K(IR)) channels in vasospasm. Vasospasm was created in dogs using the double-hemorrhage model of SAH. Electrophysiological, real-time quantitative reverse-transcriptase polymerase chain reaction, Western blotting, immunohistochemistry, and isometric tension techniques were used to characterize the expression and function of K(IR) channels in normal and vasospastic basilar artery 7 days after SAH. Subarachnoid hemorrhage resulted in severe vasospasm of the basilar artery (mean of 61% +/- 5% reduction in diameter). Membrane potential of pressurized vasospastic basilar arteries was significantly depolarized compared with control arteries (-46 +/- 1.4 mV versus -29.8 +/- 1.8 mV, respectively, P < 0.01). In whole-cell patch clamp of enzymatically isolated basilar artery myocytes, average K(IR) conductance was 1.6 +/- 0.5 pS/pF in control cells and 9.2 +/- 2.2 pS/pF in SAH cells (P = 0.007). Blocking K(IR) channels with BaCl(2) (0.1 mmol/L) resulted in significantly greater membrane depolarization in vasospastic compared with normal myocytes. Expression of K(IR) 2.1 messenger ribonucleic acid (mRNA) was increased after SAH. Western blotting and immunohistochemistry also showed increased expression of K(IR) protein in vasospastic smooth muscle. Blockage of K(IR) channels in arteries under isometric tension produced a greater contraction in SAH than in control arteries. These results document increased expression of K(IR) 2.1 mRNA and protein during vasospasm after experimental SAH and suggest that this increase is a functionally significant adaptive response acting to reduce vasospasm.

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PubMed2006

Contribution of the remodeling response to cerebral vasospasm.

The authors review the remodeling response of blood vessels that occurs after various injuries to arteries. The role of this response in vasospasm after subarachnoid hemorrhage (SAH) is reviewed. There is some evidence that cerebral arteries remodel after SAH in that they are less compliant and contractile than normal. Evidence for other features, such as alteration of smooth muscle phenotype, proliferation of cells and synthesis of extracellular matrix, is conflicting and requires a further study. A remodeling response probably contributes to vasospasm but the magnitude of its importance, in relation to smooth muscle contraction, which also occurs, also needs to be further defined.

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PubMed2005

Reversal of cerebral vasospasm by sphenopalatine ganglion stimulation in a dog model of subarachnoid hemorrhage.

BACKGROUND: Sphenopalatine ganglion stimulation dilates the ipsilateral arteries of the normal dog anterior circle of Willis. This experiment tested whether similar stimulation would reverse cerebral vasospasm. METHODS: Six dogs underwent baseline angiography followed by creation of subarachnoid hemorrhage (SAH) by injection of autologous blood into the cisterna magna. Two days later, subarachnoid blood injection was repeated. Seven days later, angiography was repeated and the left sphenopalatine ganglion was exposed microsurgically. Angiography was repeated 15 minutes after exposure of the ganglion. The ganglion was then stimulated electrically 3 times and angiography repeated during, and 15 and 30 minutes after stimulation. The protocol was repeated again. Adequacy of stimulation was confirmed by the presence of immediate ipsilateral nasal mucus production. RESULTS: Subarachnoid hemorrhage was associated with significant vasospasm of both middle cerebral arteries (11% +/- 4% and 18% +/- 7%, P < .05, paired t tests). Exposure of the ganglion and sham stimulation produced no substantial changes in arterial diameters compared with the diameter before stimulation and after ganglion exposure (n = 2-6 per measurement, paired t tests). Ganglion stimulation produced significant dilatation of the ipsilateral extracranial and intracranial internal carotid, middle cerebral, and anterior cerebral arteries compared with the contralateral arteries (13% +/- 6% to 32% +/- 14%, P < .05, paired t tests). CONCLUSIONS: The mild to moderate vasospasm that results from SAH in dogs was reversed by sphenopalatine ganglion stimulation. Since this method carries a potential for human application, additional studies are warranted to determine the effects on more severe vasospasm.

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PubMed2004

Flt3-ligand, IL-4, GM-CSF, and adherence-mediated isolation of murine lung dendritic cells: assessment of isolation technique on phenotype and function.

Lung dendritic cells (DCs) are difficult to study due to their limited quantities and the complexities required for isolation. Although many procedures have been used to overcome this challenge, the effects of isolation techniques on lung DCs have not been reported. The current study shows that freshly isolated DCs (CD11c+) have limited ability to induce proliferation in allogeneic T cells, and are immature as indicated by low cell surface expression of costimulatory molecules compared with liver or splenic DCs. DCs isolated after overnight culture or from mice treated with Flt3L are phenotypically mature and potent stimulators of allogeneic T cells. DCs could not be propagated from lung mononuclear cells in response to IL-4 and GM-CSF. Contrary to data reported for nonpulmonary DCs, expression of CCR6 was decreased on mature lung DCs, and only a subset of mature DCs expressed higher levels of CCR7. Absence of CD8alpha expression indicates that freshly isolated DCs are myeloid-type, whereas mature DCs induced by overnight culture are both "lymphoid" (CD8alpha+) and "myeloid" (CD8alpha-). DCs from mice genetically deficient in CD8alpha expression were strong simulators of allogeneic T cells which was consistent with data showing that CD8alpha- DCs from CD8alpha-sufficient mice are better APCs compared with CD8alpha+ DCs from the same mice. These data show that freshly isolated lung DCs are phenotypically and functionally distinct, and that the isolation technique alters the biology of these cells. Therefore, lung DC phenotype and function must be interpreted relative to the technique used for isolation.

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PubMed2004

Magnesium and experimental vasospasm.

OBJECT: Interest has developed in the use of magnesium (Mg++) as a neuroprotectant and antivasospastic agent. Magnesium may increase cerebral blood flow (CBF) and reduce the contraction of cerebral arteries caused by various stimuli. In this study the authors tested the hypothesis that a continuous intravenous infusion of Mg++ reduces cerebral vasospasm after experimental subarachnoid hemorrhage (SAH). METHODS: A dose-finding study was conducted in five monkeys (Macaca fascicularis) to determine what doses of intravenous MgSO4 elevate the cerebrospinal fluid (CSF) concentrations of Mg++ to vasoactive levels and to determine what effects these doses have on the diameters of cerebral arteries, as shown angiographically. After a standard dose of MgSO4 had been selected it was then administered in a randomized, controlled, blinded study to 10 monkeys (five animals/group) with SAH, beginning on Day 0 and continuing for 7 days, at which time angiography was repeated. A 0.086-g/kg bolus of MgSO4 followed by an infusion of 0.028 g/kg/day MgSO4 significantly elevated serum and CSF levels of Mg++ (five monkeys). Magnesium sulfate significantly elevated the serum level of total Mg++ from a control value of 0.83 +/- 0.04 mmol/L to 2.42 +/- 1.01 mmol/L on Day 7 and raised the CSF level from 1.3 +/- 0.04 mmol/L to 1.76 +/- 0.14 mmol/L. There was no angiographic evidence of any effect of MgSO4 on normal cerebral arteries. After SAH, the vasospasm in the middle cerebral artery was not significantly reduced (46 +/- 8% in the MgSO4-treated group compared with 35 +/- 6% in the placebo [vehicle]-treated group, p > 0.05, unpaired t-test). CONCLUSIONS: Magnesium sulfate did not significantly reduce cerebral vasospasm after SAH in the doses tested. An investigation of SAH is warranted mainly to test whether a benefit can be achieved by neuroprotection or by augmentation of CBF by dilation of small vessels and/or collateral pathways.

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PubMed2002

Up-regulation of parathyroid hormone receptor in cerebral arteries after subarachnoid hemorrhage in monkeys.

OBJECTIVE: Complementary deoxyribonucleic acid array analysis was used to determine whether vasospasm after subarachnoid hemorrhage (SAH) is associated with changes in gene expression. METHODS: Right SAHs were created in three monkeys, and the right and left middle cerebral arteries were collected 3, 7, or 14 days after SAH. Vasospasm was assessed by angiography performed on Day 0 and at tissue harvest. A complementary deoxyribonucleic acid array containing 5184 genes was used to screen for changes in gene expression by comparing the right and left middle cerebral arteries. RESULTS: There was significant expression (greater than fivefold expression of messenger ribonucleic acid compared with internal standard control) of 537 genes (10%) in the middle cerebral arteries. One hundred sixty-four genes (31%) did not change significantly, and 373 (69%) were differentially expressed at 3, 7, or 14 days after SAH. These 373 genes changed from 1.2- to 7-fold as compared with control arteries. The most common pattern was a progressive increase with increased time after SAH. The functions of differentially expressed genes included the regulation of gene expression, cell proliferation, inflammation, membrane proteins and receptors, kinases, and phosphatases. There was a marked increase in parathyroid hormone and parathyroid hormone receptor with time after SAH. Immunoblotting demonstrated a significant increase in parathyroid hormone receptor protein. CONCLUSION: The up-regulation of these proteins involved in vascular relaxation suggests that they may play a role in vasospasm. The progressive increase in messenger ribonucleic acids involved in the functions noted suggests that the pathogenesis of cerebral vasospasm involves cell proliferation, inflammation, and possibly smooth muscle phenotype change.

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PubMed2002

Intracisternal sodium nitroprusside fails to prevent vasospasm in nonhuman primates.

OBJECTIVE: Hemoglobin contributes to vasospasm after subarachnoid hemorrhage. One mechanism may involve binding of nitric oxide, destruction of nitric oxide, or both. Support for this mechanism would be evidence that nitric oxide donors prevent vasospasm. This study attempted to provide such evidence. METHODS: A randomized, blinded study was conducted in which 13 monkeys underwent cerebral angiography and creation of a right subarachnoid hemorrhage. Subcutaneous osmotic pumps were implanted to deliver sodium nitroprusside (n = 7) or vehicle (n = 6) via catheters into the right basal cisterns. Seven days later, angiography was repeated, and the animals were humanely killed. Levels of cyclic nucleotides, hemoglobins, and thiocyanate were measured. RESULTS: Significant vasospasm of the right middle cerebral artery was present in animals treated with sodium nitroprusside (35 +/- 22% reduction in diameter, P < 0.05, paired t test) and placebo (28 +/- 20% reduction, P < 0.05, not significantly different from nitroprusside group by unpaired t test). Adequate delivery of sodium nitroprusside was supported by the finding of a significant increase in cyclic guanosine monophosphate levels in the cerebral arteries of treated animals compared with placebo (P < 0.05, unpaired t test). Thiocyanate was not present in significantly increased amounts in animals treated with nitroprusside, although this group did display elevated concentrations of nitrosyl hemoglobin (measured by electron paramagnetic resonance spectroscopy) and cyanomethemoglobin (measured by spectrophotometry) in the cerebrospinal fluid on Day 7. CONCLUSION: The lack of effect of sodium nitroprusside was not the result of inadequate drug delivery because cyclic guanosine monophosphate levels were significantly increased in vasospastic arteries. Vasospasm may not have been prevented because of a toxic effect of sodium nitroprusside metabolites, involvement of smooth muscle relaxation or contraction processes downstream of cyclic guanosine monophosphate, or both.

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