Role of MAPK in cerebral vasospasm

Cerebral vasospasm is the major cause of mortality and morbidity in patients of subarachnoid hemorrhage. Despite intensive studies during the past five decades, the signaling pathways in cerebral arteries that lead to the pathological contraction remain elusive. The complex nature of cerebral vasospasm requires a complex signaling pathway or a group of pathways that may need to interact to initiate and maintain vasospasm. This review explores the possibility that mitogen-activated protein kinase is the elusive signaling pathway responsible for cerebral vasospasm.

Mechanism of hemolysate-induced [Ca2+]i elevation in cultured fibroblasts

Erythrocyte lysate (hemolysate) released from blood clot after subarachnoid hemorrhage is the causative agent for chronic cerebral vasospasm, a prolonged contraction of cerebral arteries. Fibroblasts, the outer layer cells of vessel wall that in contact with blood clot directly, may contribute to cerebral vasospasm. However, the effect of hemolysate on intracellular Ca2+ ([Ca2+]i) mobilization in fibroblasts has not been studied. We investigated hemolysate-induced [Ca2+]i mobilization in cultured neonatal human dermal and canine middle cerebral arterial fibroblasts by using fura-2 microfluorimetry. Hemolysate increased [Ca2+]i by releasing internal Ca2+ stores and promoting Ca2+ entry. Tyrosine kinase inhibitors partially but significantly reduced the effect of hemolysate. The major components of hemolysate, oxyhemoglobin (OxyHb) and adenosine triphosphate (ATP) failed to mimic the effect of hemolysate. In cultured canine middle cerebral arterial fibroblasts, hemolysate produced similar Ca2+ mobilization to that of dermal cells. OxyHb and ATP failed again to reproduce the effect of hemolysate. We conclude that hemolysate increases [Ca2+]i in fibroblasts and this effect of hemolysate is not mediated by OxyHb or ATP but by some unknown factors.

[Studies on the chemical components of Clematis chinensis]

AIM

To study the chemical components of the root of Clematis chinensis.

METHODS

Various chromatographic techniques were used to separate and purify the components. Their structures were determined on the basis of spectral and chemical evidence.

RESULTS

Two compounds were isolated and elucidated as: clemaphenol A (I) and dihydro-4-hydroxy-5-hyroxymethy-2(3H)- furanone (II).

CONCLUSION

Compound I and II are new compounds.

Efficacy of intrathecal liposomal fasudil for experimental cerebral vasospasm after subarachnoid hemorrhage

OBJECTIVE

To investigate the safety and efficacy of liposomal fasudil in a sustained-release form for the prevention of cerebral vasospasm after subarachnoid hemorrhage (SAH).

METHODS

Eighteen rats were divided into three groups, each of which received 2.5 mg/kg of liposomal fasudil, 5 mg/kg of liposomal fasudil, or drug-free liposomes after SAH. Next, experimental SAH was induced in 15 dogs by injection of autologous arterial blood into the cisterna magna twice after baseline vertebral angiography. In six dogs, 0.94 mg/kg of liposomal fasudil was injected into the cisterna magna (treatment group). In four dogs, drug-free liposomes were similarly injected (placebo group), and the remaining five dogs were not treated with liposomal injection after SAH (control group). Angiography was repeated on Day 7, and cerebrospinal fluid was collected before the dogs were killed.

RESULTS

A high dose of liposomal fasudil caused no significant changes in mean arterial blood pressure and did not induce seizures during the observation period. Gross and microscopic examination of the brains revealed no abnormalities, but severe vasospasm was noted in the rat basilar artery, mainly in the group treated with drug-free liposomes. Likewise, in the canine placebo and control groups, significant vasospasm occurred in the basilar artery on Day 7. In the treatment group, vasospasm in the basilar artery was significantly ameliorated (P < 0.01). In vivo, 90% of fasudil was released from liposomes in the cerebrospinal fluid.

CONCLUSION

A single injection of intrathecal liposomal fasudil is safe and effective for the prevention of vasospasm in experimental SAH.

Nuclear localization of G protein beta 5 and regulator of G protein signaling 7 in neurons and brain

The role that Gbeta(5) regulator of G protein signaling (RGS) complexes play in signal transduction in brain remains unknown. The subcellular localization of Gbeta(5) and RGS7 was examined in rat PC12 pheochromocytoma cells and mouse brain. Both nuclear and cytosolic localization of Gbeta(5) and RGS7 was evident in PC12 cells by immunocytochemical staining. Subcellular fractionation of PC12 cells demonstrated Gbeta(5) immunoreactivity in the membrane, cytosolic, and nuclear fractions. Analysis by limited proteolysis confirmed the identity of Gbeta(5) in the nuclear fraction. Subcellular fractionation of mouse brain demonstrated Gbeta(5) and RGS7 but not Ggamma(2/3) immunoreactivity in the nuclear fraction. RGS7 and Gbeta(5) were tightly complexed in the brain nuclear extract as evidenced by their coimmunoprecipitation with anti-RGS7 antibodies. Chimeric protein constructs containing green fluorescent protein fused to wild-type Gbeta(5) but not green fluorescent fusion proteins with Gbeta(1) or a mutant Gbeta(5) impaired in its ability to bind to RGS7 demonstrated nuclear localization in transfected PC12 cells. These findings suggest that Gbeta(5) undergoes nuclear translocation in neurons via an RGS-dependent mechanism. The novel intracellular distribution of Gbeta(5).RGS protein complexes suggests a potential role in neurons communicating between classical heterotrimeric G protein subunits and/or their effectors at the plasma membrane and the cell nucleus.

Dual effect of HBO on cerebral infarction in MCAO rats

Various reports in the literature have shown that hyperbaric oxygen (HBO) reduces cerebral infarction both in animals and humans. After the initial ischemic insult, however, initiating HBO treatment at different intervals has yielded conflicting results. The present study was undertaken to determine the optimal therapeutic window in which to start HBO treatment for cerebral infarction after transient focal ischemia. In this study, the operator occluded the middle cerebral artery (MCA) of anesthetized rats by introducing a blunted nylon filament into the proximal MCA from the dissected external carotid artery. When the operator removed the filament after 2 h, focal ischemia and reperfusion occurred. The operator then placed the rat in the HBO chamber and administered 3 atm absolute HBO for 1 h according to the protocol. The rat was killed 24 h after reperfusion, and the percentage of infarction (infarct ratio) was calculated by dividing the infarction area by the total area of the ipsilateral hemisphere. The results showed that the percentage of infarcted area decreased significantly (P < 0.05) both in the 3- (7.59%) and 6-h (5.35%) HBO-treatment groups compared with the control (no treatment) group (11.34%). However, the percentage of infarcted area increased significantly (P < 0.01 and P < 0.05, respectively) both in the 12- (23%) and 23-h (20%) treatment groups. The results of this study suggest that applying HBO within 6 h of ischemia-reperfusion injury could benefit the patient but that applying HBO 12 h or more after injury could harm the patient.

Orexin (hypocretin)-like immunoreactivity in the cat hypothalamus: a light and electron microscopic study

Orexin-A-like immunoreactive (OrA-ir) neurons and terminals in the cat hypothalamus were examined using immunohistochemical techniques. OrA-ir neurons were found principally in the lateral hypothalamic area (LHA) at the level of the tuberal cinereum and in the dorsal and posterior hypothalamic areas. In the LHA the majority of the neurons were located dorsal and lateral to the fornix; a small number of OrA-ir neurons were also present in other regions of the hypothalamus. OrA-ir fibers with varicose terminals were detected in almost all hypothalamic regions. The high density of fibers was located in the suprachiasmatic nucleus, the infundibular nucleus (INF), the tuberomamillary nucleus (TM) and the supra- and pre-mamillary nuclei. Ultrastructural analysis revealed that OrA-ir neurons in the LHA receive abundant input from non-immunoreactive terminals. These terminals, which contained many small, clear, round vesicles with a few large, dense core vesicles, made asymmetrical synaptic contacts with OrA-ir dendrites, indicating that the activity of orexin neurons is under excitatory control. On the other hand, the terminals of OrA-ir neurons also made asymmetrical synaptic contact with dendrites in the LHA, the INF and the TM. The dendrites in the LHA were both non-immunoreactive and OrA-ir; conversely, the dendrites in the INF and the TM were non-immunoreactive. In these regions, OrA-ir terminals contained many small, clear, round vesicles with few large, dense core vesicles, suggesting that orexinergic neurons also provide excitatory input to other neurons in these regions.

Expression of anti-neuroexcitation peptide (ANEP) of scorpion Buthus martensii Karsch in Escherichia coli

According to the cDNA sequence of anti-neuroexcitation peptide of scorpion Buthus martensii Karsch, the putative mature anti-neuroexcitation peptide (ANEP) encoding DNA fragment was obtained by a PCR method, then was cloned into expression plasmid pET28a, fused with His tag at its 3' end. When expressed in E. coli BL21 (DE3), the expression of recombinant ANEP was 15% of total cellular proteins, while most recombinant ANEP products existed in the form of insoluble inclusion bodies. Coexpression of molecular chaperones or protein disulfide isomerase could not improve its solubility. The recombinant ANEP in the cell lysate was purified to homogeneity by metal chelating affinity chromatography and Superdex 30 chromatography. In bioassay with convulsive mice model induced by thiosemicarbazide, recombinant ANEP could apparently delay the convulsion seizure of model animals by 18% and showed anti-neuroexcitatory activity.

Caspase inhibitors attenuate oxyhemoglobin-induced apoptosis in endothelial cells

BACKGROUND AND PURPOSE

Our recent study showed that oxyhemoglobin (OxyHb) induces apoptosis in cultured endothelial cells. Apoptosis requires the action of various classes of proteases, including a family of cysteine proteases known collectively as the caspases. This study was undertaken to investigate the effect of 2 caspase inhibitors, Z-VDVAD-FMK and Z-DEVD-FMK, in the protection of endothelial cells from OxyHb-induced apoptosis.

METHODS

Cultured bovine brain microvascular endothelial cells (passages 5 to 9) were exposed to OxyHb (10 micromol/L) for 24 to 72 hours with and without caspase inhibitors. Cell attachment, DNA ladder, Western blotting of poly(ADP-ribose) polymerase (PARP), and caspase activities were measured to confirm the cytotoxic effect of OxyHb and the protective effect of the caspase inhibitors.

RESULTS

(1) OxyHb produced cell detachment in a time-dependent manner. (2) OxyHb increased caspase-2 and -3 activities, produced DNA ladders, and cleaved PARP in endothelial cells. (3) Z-VDVAD-FMK and Z-DEVD-FMK (100 micromol/L) attenuated OxyHb-induced cell detachment, reduced caspase-2 and -3 activities, abolished OxyHb-induced DNA ladders, and prevented OxyHb-induced cleavage of PARP.

CONCLUSIONS

OxyHb activates caspase-2 and -3 in cultured brain microvessel endothelial cells. Caspase inhibitors attenuated the cytotoxic effect of OxyHb.

Altered expression of P(2) receptor mRNAs in the basilar artery in a rat double hemorrhage model

BACKGROUND AND PURPOSE

Extracellular ATP might induce cerebral vasospasm after subarachnoid hemorrhage through P(2) receptor. To investigate the roles of P(2) receptor subtypes in vasospasm, we examined the changes in mRNA expression of P(2) receptor subtypes in basilar arteries from double cisternal blood injection rat models.

METHODS

One hundred male Sprague-Dawley rats, each weighing 350 to 400 g, were divided into 2 groups of 50. In the first group (n=50), the autologous arterial blood (0.2 to 0.3 mL) was injected into the cisterna magna on days 0 and 2. The rats were killed on day 3, 5, or 7 (n=10 in each group). In the sham group (n=10), the rats were injected with saline (0.3 mL) instead of blood. Ten rats were killed without blood or saline injection and served as control. The basilar arteries from rats in each group were used for reverse transcription and polymerase chain reaction. In another group of 50 rats, the same experiment was conducted, and the basilar arteries were collected for transmission electron microscopic study.

RESULTS

In the subarachnoid hemorrhage groups, transmission electron microscopy showed the reduction in vessel perimeter on days 5 and 7 to be approximately 30% to 40%. The P(2X1) mRNA level was significantly decreased on day 3 and recovered on days 5 and 7. The P(2Y1) mRNA level was transiently increased on day 5, and the P(2Y2) mRNA level was elevated from day 5 to day 7 (P:<0.05).

CONCLUSIONS

The differential expression of the P(2) receptors indicates that P(2X1) subtype might not play an important role in vasospasm. The upregulation of P(2Y1) and P(2Y2) receptors might enable ATP to produce contraction at low levels of concentration.

Oxyhemoglobin produces apoptosis and necrosis in cultured smooth muscle cells

Confluent rat aortic smooth muscle cells were treated with OxyHb in a concentration- and time-dependent manner. A high concentration of OxyHb (100 microM) within 24 h decreased cell density. DNA analysis showed a smear pattern characteristic of cell necrosis. Transmission electron microscopy demonstrated disintegration of the cell membrane and destruction of cell organelles. Western blotting using PARP antibody revealed that 116 kDa PARP was not cleaved to 85 kDa, an apoptosis-related fragment. On the contrary, a low concentration of OxyHb (10 microM) produced apoptotic cell death at 72 h that was supported by DNA analysis and TUNEL staining. These results demonstrated that a high level of OxyHb induced necrosis within 24 h and a low concentration of OxyHb produced apoptosis after 72 h in cultured smooth muscle cells. Morphological alterations induced by OxyHb might contribute to the vascular wall changes in the cerebral arteries following subarachnoid hemorrhage (SAH).

Effects of AP-V and bicuculline on somatostatin-positive neurons in hypothalamus of rats subjected to acute hypobaric hypoxia

AIM

To investigate the effects of 2-amino-5-phosphonovalerate-pharmacology (AP-V) and bicuculline on somatostatin (SST)-positive neurons in hypothalamus of rats subjected to acute hypobaric hypoxia.

METHODS

SST-immunoreactivity (IR) and somatostatin mRNA (SS mRNA)-positive neurons were measured by immunohistochemistry and in situ hybridization methods.

RESULTS

Compared with control rats, SST-IR and SS mRNA-positive neurons in hypothalamic periventricular nucleus (PeV), paraventricular nucleus (PVN), and arcuate nucleus (ARC) increased after acute hypobaric hypoxia for 6 h (P < 0.01), and these effects were markedly inhibited by AP-V (10 microg, icv), a highly selective N-methyl-D-aspartate (NMDA) receptor antagonist, whereas were strongly enhanced by bicuculline (1.5 mg/kg, ip), a gamma-aminobutyric acid (GABAA) receptor antagonist.

CONCLUSION

SST possibly participates in acute hypoxic reaction in hypothalamus, furthermore, glutamate and GABA can affect somatostatin release and synthesis in hypothalamus through NMDA and GABAA receptors respectively.

Relaxant effect of U0126 in hemolysate-, oxyhemoglobin-, and bloody cerebrospinal fluid-induced contraction in rabbit basilar artery

BACKGROUND AND PURPOSE

It has been suggested that mitogen-activated protein kinase (MAPK) is involved in cerebral vasospasm after subarachnoid hemorrhage. The present study was undertaken to explore the inhibitory effect of U0126, a novel MAPK inhibitor, in the contraction of the rabbit basilar artery by 3 spasmogens: hemolysate, oxyhemoglobin, and bloody cerebrospinal fluid (CSF) from patients with vasospasm.

METHODS

The contraction and relaxation of rabbit basilar arteries were measured by isometric tension. MAPK immunoprecipitation was assessed by Western blot analysis.

RESULTS

(1) Pretreatment of the rabbit basilar arteries with U0126 reduced contractions to hemolysate, oxyhemoglobin, or bloody CSF applied subsequently. (2) In the absence of endothelial cells, U0126 produced an inhibitory effect similar to the contractions induced by hemolysate, oxyhemoglobin, or bloody CSF. (3) U0126 relaxed the sustained contraction induced by hemolysate, oxyhemoglobin, or bloody CSF. (4) Hemolysate, oxyhemoglobin, and bloody CSF enhanced MAPK immunoprecipitation. (5) U0126 reduced MAPK immunoprecipitation induced by hemolysate, oxyhemoglobin, and bloody CSF. (6) Hemolysate, oxyhemoglobin, and bloody CSF significantly increased MAPK activity in the rabbit basilar artery. (7) U0126 abolished the effect of hemolysate, oxyhemoglobin, or bloody CSF on MAPK activation.

CONCLUSIONS

This study demonstrated a role of MAPK in the contraction of rabbit basilar arteries by hemolysate, oxyhemoglobin, and bloody CSF. MAPK inhibitor U0126 may be useful in the treatment of cerebral vasospasm.

Mechanisms of [Ca2+]i elevation by H2O2 in islets of rats

Activity of reactive oxygen species is elevated in diabetes mellitus and has been implicated in the destruction of cellular components. The toxic effect of reactive oxygen species was investigated by testing the effect of H2O2 on [Ca2+]i in isolated islets of Langehans. H2O2 increased [Ca2+]i in a dose-dependent manner, which was irreversible at high concentrations. The maximum effect of H2O2 on [Ca2+]i was larger than those of KCl, glucose, ATP, carbachol and endothelin-1. The effect of H2O2 was only partially attenuated by removal of external Ca2+ and by the in-organic Ca2+ channel blocker nickel, but was not blocked by voltage-dependent or -independent Ca2+ channel blockers nimodipine, nicardipine, SK&F 96365, econazole and lanthanum. H2O2, disrupted [Ca2+]i homeostasis in islets by affecting both release and influx of Ca2+ and causing dysfunction of Ca2+ clearance systems and may contribute to the pathological process of diabetes.

[Excitatory amino acid enhance prepro-somatostatin mRNA expression induced by altitude hypoxia in the rat hypothalamus]

AIM AND METHODS

Contents of glutamate (Glu), asparate (Asp) and expression of prepro-somatostatin mRNA (PPS-mRNA) in rat hypothalamus were measured by using imitated altitude hypoxia rat model, amino acid analyzer and in situ hybridization technique.

RESULTS

After rats were subjected to altitude hypoxia, contents of Glu and Asp in hypothalamus and PPS-mRNA expression in periventricular nucleus (PeVN), paraventricular nucleus (PaVN) and arcuate nucleus (ArcN) were increased significantly. Ketamine, a NMDA receptor antagonist, could decrease the number of PPS-mRNA neurons in rat hypothalamus evoked by altitude hypoxia, but had no effect on Glu and Asp contents evoled by altitude hypoxia.

CONCLUSION

It is suggested that somatostatin maybe paticipate in altitude hypoxia reaction, Glu can enhance PPS-mRNA expression through NMDA receptor.

Optison (FS069) disrupts the blood-brain barrier in rats

Optison is a new echocardiographic contrast agent, designed for IV injection, that is very useful in delineating cardiac structures during ultrasound examination. Because Optison could be a valuable adjunct in the diagnosis and evaluation of congenital heart disease, this study was undertaken to assess its effects on the blood-brain barrier when introduced directly in the cerebral circulation, as might occur with some congenital lesions. In this study, Sprague-Dawley rats were anesthetized, and Optison, at various dosages, was injected into the carotid artery. After this, Evans blue dye, a marker for blood-brain barrier disruption, was injected at different time intervals. Gross and histologic examination of the animals' brains revealed disruption of the blood-brain barrier that appeared to be Optison-dosage-dependent. Although the mechanism for this disruption is unclear, it may be related to the use of octofluoropropane gas used in the Optison as a contrast medium. Further studies are necessary to determine the pathologic consequences of Optison's effects on the blood-brain barrier.

Role of calcium channels in oxyhemoglobin-induced apoptosis in endothelial cells

OBJECT

Oxyhemoglobin (OxyHb) released from hemolysed erythrocytes has been considered to be responsible for cerebral vasospasm after subarachnoid hemorrhage. The authors previously reported that OxyHb produced apoptosis in cultured vascular endothelial cells. The change in intracellular Ca++ homeostasis was expected to be one of the possible mechanisms of the cytotoxic effects of OxyHb. This study was undertaken to investigate the protective effects of Ca++ channel blockers on OxyHb-induced apoptosis.

METHODS

Cultured bovine coronary artery and brain microvascular endothelial cells (passages 5-9) were used. A cell density study, immunohistochemical staining, and DNA fragmentation analysis were performed to confirm apoptosis. Various concentrations (1-50 microM) of OxyHb were used for 24- to 72-hour incubations with and without Ca++-channel blockers. Oxyhemoglobin produced cytotoxicity leading to cell detachment from the culture dish in time- and concentration-dependent manners. The highest dose (50 microM) of OxyHb produced cell detachment after a 24-hour incubation, and the lower doses (1-10 microM) produced cell detachment after 48 to 72 hours. Immunohistochemical analysis showed that apoptosis occurred in cells that were still attached to the side of the culture dish after 48 to 72 hours of OxyHb treatment (5 microM). The OxyHb (10 microM) produced DNA ladders at 48 to 72 hours. Three Ca++-channel blockers were used to prevent the toxic effect of OxyHb. The voltage-dependent Ca++-channel blocker nicardipine (1 microM), the voltage-independent Ca++-channel blocker econazole (10 microM), and the inorganic Ca++-channel blocker lanthanum (100 microM) all failed to prevent cell detachment or DNA ladders produced by OxyHb. These results were similar in both cell lines.

CONCLUSIONS

Oxyhemoglobin produced apoptotic changes in cultured vascular endothelial cells, and Ca++-channel blockers did not prevent OxyHb-induced apoptosis.

Morphological changes of cerebral penetrating arteries in a canine double hemorrhage model

BACKGROUND

Morphological presentations of cerebral vasospasm, such as dystrophy and desquamation of endothelial cells, corrugation of the internal elastic layer, and necrotic changes in smooth muscle cells, are well defined in large cerebral arteries. This study was undertaken to examine pathological changes in cerebral penetrating arteries in a canine double hemorrhage model.

METHODS

Eighteen mongrel dogs were subjected to an autologous arterial blood (0.4 mL/kg) injection into the cisterna magna on day 0 and day 2 after withdrawal of an equivalent amount of cerebrospinal fluid. Angiogram was performed on day 0 before the blood injection and on the day the dogs were sacrificed. The dogs were divided into four groups: control (day 0) (n = 4), hemorrhage and sacrificed on day 3 (n = 4), day 5 (n = 5), and day 7 (n = 5). The penetrating arteries were removed and found to be spastic on days 3, 5, and 7, but not in the control group.

RESULTS

Endothelial dystrophy and partial desquamation were recorded in all dogs sacrificed on days 5 and 7. Condensation of chromatin, blebbing of the membrane, and condensation of cytoplasm were identified in many endothelial cells, features that are consistent with apoptosis. The morphological changes in the penetrating arteries were more pronounced on days 5 and 7.

CONCLUSIONS

Vasospasm occurred in cerebral penetrating arteries in a canine double hemorrhage model. The morphological change in penetrating arteries, especially apoptosis in endothelial cells, is consistent with an early phase of vasospasm. Vasospasm in a penetrating artery may contribute to the cerebral ischemia that occurs during vasospasm.

Prevention of vasospasm in penetrating arteries with MAPK inhibitors in dog double-hemorrhage model

BACKGROUND

Vasospasm in the penetrating arteries contributes to ischemic neurological deficit. It may be as important as angiographic vasospasm because it would explain the discrepancies between angiographic vasospasm and clinical symptoms in some patients. It may also underlie the different effects of vasodilators. The present study examined this hypothesis by looking at the effect of the inhibitors of mitogen-activated protein kinase (MAPK) on vasospasm of the penetrating arteries.

METHODS

Twenty-two adult mongrel dogs of either sex were used for the dog double-hemorrhage model. The dogs were randomly divided into four groups: control-hemorrhage, vehicle-treated, PD98059-treated, and U0126-treated groups. The drug injections were started on Day 3 after the first subarachnoid hemorrhage (SAH). The clinical status of the dogs was studied, based on their activity, appetite, and focal neurological symptoms. On Day 7, all the dogs were sacrificed, and the penetrating arteries from the brain stem were prepared for transmission electron microscopy.

RESULTS

(1) Severe vasospasm developed in the basilar arteries in the SAH-without-treatment group (control), in the DMSO-treated group (DMSO), and in the U0126 treatment group with mean reduction of the basilar artery diameter of 46.57%, 49.3%, and 39.6%, respectively. In the PD98059-treatment group only a mild vasospasm was observed and the mean reduction of the basilar artery diameter was 18.9%. (2) All the dogs in the control SAH and vehicle-treated groups developed severe angiographic and clinical vasospasm. The penetrating arteries were contracted, and the endothelial and smooth muscle cells were dystrophic. (3) The dogs in the U0126-treated group developed severe angiographic, but not clinical, vasospasm. The penetrating arteries were not contracted, and the endothelial and smooth muscle cells were not dystrophic. (4) The dogs in the PD98059 group developed mild angiographic vasospasm. No dog developed clinical symptoms that could be attributed to vasospasm. In morphological studies, the penetrating arteries were slightly contracted, but the cells were not dystrophic.

CONCLUSIONS

Vasospasm of the penetrating arteries, but not angiographic vasospasm, is consistent with the clinical symptoms and signs of vasospasm. MAPK may be important in maintaining vasospasm of both major and penetrating cerebral arteries. The correlation of the improvement in the clinical score with the reduction of vasospasm in the penetrating arteries demonstrated an important role of penetrating arteries in the morbidity and mortality caused by SAH.

DNA fragmentation in apoptosis

Cleavage of chromosomal DNA into oligonucleosomal size fragments is an integral part of apoptosis. Elegant biochemical work identified the DNA fragmentation factor (DFF) as a major apoptotic endonuclease for DNA fragmentation in vitro. Genetic studies in mice support the importance of DFF in DNA fragmentation and possibly in apoptosis in vivo. Recent work also suggests the existence of additional endonucleases for DNA degradation. Understanding the roles of individual endonucleases in apoptosis, and how they might coordinate to degrade DNA in different tissues during normal development and homeostasis, as well as in various diseased states, will be a major research focus in the near future.

Upregulation of rho A and rho kinase messenger RNAs in the basilar artery of a rat model of subarachnoid hemorrhage

OBJECT

Rho A, a small guanosine triphosphate-binding protein, and rho kinases have been suggested to play an important role in the agonist-induced myofilament Ca++ sensitization and cytoskeletal organization of smooth-muscle cells. To discover their possible roles in the prolonged contraction seen in cerebral vasospasm, the authors investigated the messenger (m)RNA expressions of rho A and rho-associated kinases alpha and beta in the basilar artery (BA) of a rat double cisternal blood-injection model.

METHODS

An experimental subarachnoid hemorrhage (SAH) was achieved in rats by twice injecting autologous arterial blood into the cisterna magna of each animal. The mRNAs for rho A and rho-associated kinases alpha and beta of the rat BA were analyzed using reverse transcription-polymerase chain reaction (RT-PCR). The cisternal blood injection induced a marked corrugation of elastic lamina and contraction of smooth-muscle cells observed with the aid of light and transmission electron microscopy in the rat BA on Days 3, 5, and 7. Results of the RT-PCR revealed that mRNAs for rho A and rho kinases alpha and beta were expressed in the rat BA and that they were significantly upregulated and reached their peaks on Day 5.

CONCLUSIONS

The mRNA upregulation of these proteins indicates that activation of rho A/rho kinase-related signal transduction pathways is involved in the development of long-lasting contraction of cerebral arteries after SAH.

Acute toxicity of excess mercury on the photosynthetic performance of cyanobacterium, S. platensis--assessment by chlorophyll fluorescence analysis

Measurement of chlorophyll fluorescence has been shown to be a rapid, non-invasive, and reliable method to assess photosynthetic performance in a changing environment. In this study, acute toxicity of excess Hg on the photosynthetic performance of the cyanobacterium S. platensis, was investigated by use of chlorophyll fluorescence analysis after cells were exposed to excess Hg (up to 20 microM) for 2 h. The results determined from the fast fluorescence kinetics showed that Hg induced a significant increase in the proportion of the Q(B)-non-reducing PSII reaction centers. The fluorescence parameters measured under the steady state of photosynthesis demonstrated that the increase of Hg concentration led to a decrease in the maximal efficiency of PSII photochemistry, the efficiency of excitation energy capture by the open PSII reaction centers, and the quantum yield of PSII electron transport. Mercury also resulted in a decrease in the coefficients of photochemical and non-photochemical quenching. Mercury may have an acute toxicity on cyanobacteria by inhibiting the quantum yield of photosynthesis sensitively and rapidly. Such changes occurred before any other visible damages that may be evaluated by other conventional measurements. Our results also demonstrated that chlorophyll fluorescence analysis can be used as a useful physiological tool to assess early stages of change in photosynthetic performance of algae in response to heavy metal pollution.

Differential expression of the G protein beta(5) gene: analysis of mouse brain, peripheral tissues, and cultured cell lines

A neurally expressed heterotrimeric G protein beta subunit, Gbeta(5), has been found to exhibit functional specialization with respect to its interactions with effector targets and Galpha subunits. A splice variant of Gbeta(5) that contains an N-terminal 42-residue extension, Gbeta(5)-long, has been described in the retina. To define better the potential range of its specialized interactions, analysis of Gbeta(5) gene transcript and protein expression in mouse brain and other tissues and cell lines was performed. Quantification by ribonuclease protection assay of Gbeta(5) transcript expression in the developing brain demonstrates a fivefold increase that occurs postnatally. Analysis of transcript expression by in situ hybridization and ribonuclease protection assay indicates that the Gbeta(5) gene is differentially expressed among multiple adult mouse brain regions, including the motor and occipital cortex, the olfactory bulb and associated rhinencephalic structures, hypothalamus, pontine cochlear nuclei, and Purkinje cells in the cerebellum. Gbeta(5) is also expressed in several cultured cell lines of neuroendocrine origin, including murine alphaT3-1 pituitary gonadotrophs and GT1-7 hypothalamic cells, and rat PC12 pheochromocytoma cells. Immunoblotting of tissue homogenates with antibodies to two peptides common to Gbeta(5) and Gbeta(5)-long confirmed expression of Gbeta(5) in multiple brain regions and in spinal cord and expression of Gbeta(5)-long in retina. Taken together, these results suggest that the specialized molecular properties of Gbeta(5) have been adapted to diverse neural functions in the adult brain.