YAG laser-induced reperfusion of photothrombotic middle cerebral artery occlusion in rats]

The laser-driven photochemical occlusion of middle cerebral artery(MCA) is much easier, and less traumatic than standard electrocautery or even clip methods, while the infarct size is fairly reproducible. This study aimed to establish the system for YAG laser-induced reperfusion of photothrombotic MCA occlusion. Male spontaneously hypertensive rats(5-7 months old, 350-450 g) were anesthetized with halothane, endotracheally intubated, and mechanically ventilated. The photosensitizing dye rose bengal(20 mg/kg body weight) was administered intravenously over 90 sec starting simultaneously with 3 min of krypton laser irradiation(568 nm, 20 mW). The irradiated middle cerebral artery was completely occluded by an intraluminal thrombus. A YAG laser operating at 355 nm(16 mW, 15 Hz) was focused with a cylindrical lens and positioned with a mirror onto the occluded distal MCA. This YAG laser irradiation for approximately 3 min caused reperfusion of the thrombosed distal MCA. We demonstrated a novel method of reperfusion in the photothrombotic MCA occlusion model. This reperfusion model should facilitate study of the therapeutic window for reversibility in thrombotic stroke.     

Renal and carotid vascular resistance assessed with Doppler sonography

PURPOSE: Resistance index (RI) is widely used for the evaluation of circulatory resistance and atherosclerosis with Doppler sonography, but differences in RI among vascular beds have not been fully elucidated. The present study was designed to evaluate the relationship between renal and carotid artery RI and to compare their relative risk factors for an increase in RI. METHODS: One hundred eighty-five inpatients who underwent sonographic assessment of the renal and carotid arteries were enrolled in the study. RESULTS: Multivariate analyses revealed that age, pulse pressure (PP), and serum glucose level were positively correlated, whereas diastolic blood pressure (DBP) and creatinine clearance were negatively correlated with the RI of the interlobar arteries. Sex (male) and PP correlated positively, whereas DBP correlated negatively with the RI of the common carotid artery (CCA). The RI of the interlobar arteries was positively associated with that of the CCA, even after adjustment for major cardiovascular risk factors. CONCLUSIONS: These findings suggest that RI of the renal and carotid arteries increase in parallel to a certain extent. On the other hand, risk factors for the increase of RI of the carotid and renal arteries differed in part, suggesting that specific control of respective risk factors may also be needed to prevent vascular damage in each vascular bed.     

NAD(P)H oxidase p22phox C242T polymorphism and ischemic stroke in Japan: the Fukuoka Stroke Registry and the Hisayama study

The C242T polymorphism of p22 ^phox , a component of NAD(P)H oxidase, may have an impact on cardiovascular diseases; however, the association between this polymorphism and brain infarction is not fully understood. Here, we investigate the relationship between the C242T polymorphism and brain infarction in Japan. We recruited 1055 patients with brain infarction and 1055 control subjects. A chi-squared test revealed that the T-allele frequency was lower in patients with cardioembolic infarction (5.6%) than in control subjects (11.0%, P  < 0.001); however, allele frequencies in patients with lacunar and atherothrombotic infarction (11.2%) were not significantly different from those in control subjects (11.0%). A multivariate-adjusted conditional logistic regression analysis also revealed no association between CT + TT genotype, and lacunar and atherothrombotic infarction (odds ratio = 0.97, 95% confidence interval: 0.72–1.32). To investigate the functional effects of the C242T polymorphism, we examined superoxide production in COS-7 cells cotransfected with Nox4 and p22 ^phox of each genotype. The superoxide-producing activity in those cells expressing p22 ^phox with the T allele was not significantly different from that in cells expressing p22 ^phox with the C allele. The present results suggest that the p22 ^phox C242T polymorphism may have a protective effect against cardioembolic infarction, but is not related to lacunar and atherothrombotic infarction in Japan.     

Elevated cerebrospinal fluid lactate levels and the pathomechanism of calcification in Fahr''s disease

In this study, we report the case of a 68-year-old man complaining of involuntary movement of his left shoulder and lower jaw plus dyspnea. On cranial computed tomography and magnetic resonance imaging, marked and symmetrical calcification at the basal ganglia and dentate nuclei was documented. An elevated cerebrospinal fluid (CSF) lactate level was confirmed by spinal tap examination and magnetic resonance spectroscopy. The raised CSF lactate level, clinical characteristics such as diabetes, bilateral hearing loss and symmetrical cerebral calcification strongly suggested some kinds of mitochondrial disease. However, gene analysis of peripheral blood leukocytes revealed no typical or known mutations. Under the diagnosis of Fahr's disease, we treated him with haloperidol, which completely abolished his symptoms. In Ellsworth-Howard test, he showed markedly decreased phosphaturic response to parathyroid hormone with same pattern as type 2 pseudohypoparathyroidism. This abnormal response in our patient, probably due to respiratory alkalosis reflecting chronic hyperventilation, might in part explain similar mechanism of ectopic calcification underlying these two diseases.     

Gene therapy as a novel pharmaceutical intervention for stroke

Cerebrovascular disease is the leading cause of death and disability in Japan and most Western countries. Gene transfer techniques may be applicable to the treatment of serious types of stroke, since several experimental studies have revealed the usefulness of gene therapy in the protection of neurons, reduction of infarct size and improvement of function. Prevention of vasospasm after subarachnoid hemorrhage is one of the best candidates for vascular gene therapy. Ischemia-induced apoptosis, inflammation, and derangement of neurovascular units can be targeted by the gene transfer approach. Recent studies have shown that promotion of neurogenesis and functional recovery may also be achieved by this strategy. Furthermore, a combination of stem cell therapy with gene transfer methods may be feasible. This review describes novel approaches for the treatment of stroke using gene transfer techniques.     

Postischemic gene transfer of midkine, a neurotrophic factor, protects against focal brain ischemia

Gene therapy may be a promising approach for treatment of brain ischemia. In this study, we examined the effect of postischemic gene transfer of midkine, a heparin-binding neurotrophic factor, using a focal brain ischemia model with the photothrombotic occlusion method. At 90 min after induction of brain ischemia in spontaneously hypertensive rats, a replication-deficient recombinant adenovirus encoding mouse midkine (AdMK, n=7) or a control vector encoding beta-galactosidase (Adbetagal, n=7) was injected into the lateral ventricle ipsilateral to ischemia. At 2 days after ischemia, we determined infarct volume by 2,3,5-triphenyltetrazolium chloride staining. There were no significant differences in cerebral blood flow 1 h after ischemia between AdMK and Adbetagal groups. Infarct volume of AdMK group was 51+/-27 mm3, which was significantly smaller than that of Adbetagal group (86+/-27 mm3, P<0.05). TUNEL-positive and cleaved caspase-3-positive cells in the periischemic area of AdMK-treated rats were significantly fewer than those in Adbetagal-treated rats, suggesting that the reduction of infarct volume by midkine was partly mediated by its antiapoptotic action. Thus, gene transfer of midkine to the ischemic brain may be effective in the treatment of brain ischemia.     

Increased activity of calcium channels and Rho-associated kinase in the basilar artery during chronic hypertension in vivo

OBJECTIVES : Several factors mediating vascular responses appear to play an important role in the increased resistance of cerebral blood vessels during hypertension. The objective of this study was to elucidate the mechanisms by which hypertension increases the basal tone of the basilar artery in vivo. METHODS : Using a cranial window, we examined effects of inhibitors of L-type voltage-dependent calcium channels (nicardipine) and Rho-associated kinase (Y-27632) on the baseline diameter of the basilar artery in spontaneously hypertensive rats (SHR) and compared to the responses in normotensive Wistar-Kyoto (WKY) rats. RESULTS : Topical application of nicardipine (10(-8), 10(-7) and 10(-6) mol/l) produced dilatation of the basilar artery. Nicardipine-induced vasodilatation was enhanced in SHR compared to WKY rats. Nicardipine (10-6 mol/l) dilated the artery in WKY rats and SHR by 9 +/- 2 and 24 +/- 4%, respectively. Topical application of Y-27632 (10(-7), 10(-6) and 10(-5) mol/l) produced dilatation of the basilar artery in WKY rats in a concentration-related manner. The vasodilatation produced by Y-27632 was markedly enhanced in SHR compared to WKY rats. Y-27632 (10(-5) mol/l) dilated the artery in WKY rats and SHR by 14 +/- 2 and 45 +/- 6%, respectively. We also tested the effects of inhibitors of nitric oxide synthase (NG-nitro-l-arginine methyl ester, l-NAME), ATP-sensitive potassium channels (glibenclamide) and large-conductance calcium-activated potassium channels (tetraetyhlammonium, TEA). l-NAME and, to a lesser extent, glibenclamide produced similar constriction of the basilar artery in both strains. TEA did not affect the baseline diameter of the basilar artery in WKY rats and produced small but significant vasoconstriction in SHR. CONCLUSIONS : These results suggest that the activity of L-type calcium channels and Rho-associated kinase is enhanced in the basilar artery during hypertensionin vivo. The enhanced contractility may contribute to the increased resistance of the basilar artery during chronic hypertension in vivo.     

Long-term effects of benidipine on cerebral vasoreactivity in hypertensive rats

We tested the hypothesis that long-term application of a Ca2+ channel blocker would ameliorate the functional and morphological deterioration of the cerebral arteries during hypertension. Male spontaneously hypertensive rats (SHR) were fed a standard rat chow, containing a low (3 mg/kg/day) or high dose (6 mg/kg/day) of benidipine, a Ca2+ channel blocker, for 2 months. Using a cranial window, we examined responses of the basilar artery to acetylcholine, sodium nitroprusside, (-)-(3S,4R)-4-(N-acetyl-N-hydroxyamino)-6-cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-3-ol (Y-26763; an opener of ATP-sensitive K+ channels), and (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide (Y-27632; an inhibitor of Rho-associated kinase). Mean arterial pressure of the control group was 193+/-5 mm Hg (mean+/-S.E.M.), while that of the low-dose benidipine group was 183+/-5 mm Hg and that of the high-dose group was 159+/-4 mm Hg. Dilator responses of the basilar artery to acetylcholine and Y-26763 were impaired in SHR compared with those of normotensive Wistar-Kyoto (WKY) rats and treatment with benidipine enhanced the vasodilator responses to acetylcholine and Y-26763 in SHR. Y-27632-induced dilatation of the basilar artery was enhanced in SHR compared to that in WKY rats and the vasodilatation was reduced by benidipine in SHR. Sodium nitroprusside caused similar dilatation of the basilar artery, in both WKY rats and the SHR control group, and benidipine did not affect nitroprusside-induced dilatation of the artery in SHR. The wall of the basilar artery was significantly thicker in SHR than in WKY rats and benidipine treatment reduced the wall thickness of the artery in SHR. These findings suggest that chronic treatment with a Ca2+ channel blocker may enhance the dilator capacity and reduce contractility of the basilar artery during hypertension. Benidipine may also ameliorate the morphological changes of the basilar artery in hypertension.