Clinicopathological significance of expression of nestin, a neural stem/progenitor cell marker, in human glioma tissue.

The purpose of the study was to investigate the pathological and clinical significance of the expression of nestin, a type-VI intermediate filament transiently expressed during brain development, in glioma tissue. This study was conducted in 70 patients with newly diagnosed adult supratentorial gliomas who underwent multimodality treatment in our department, including surgery. The pathological diagnosis was grade II in 6 patients, grade III in 21 patients, and grade IV in 43 patients. Two specimen sections, one from the bulk of the removed tumor and one from the border between the tumor and normal brain tissue, were subjected to immunostaining with a mouse anti-human nestin monoclonal antibody. Analyses were performed to investigate possible correlation with pathological features, the relationship between nestin expression and the continuity of tumor with the subventricular zone (SVZ), correlation with the therapeutic prognosis, etc. Nestin was expressed specifically in astrocytoma lineage cells. In oligodendroglial tumors, nestin was expressed only in less-differentiated cells and cells suggestive of the presence of astrocytoma. In astrocytic tumors, the rate and level of nestin expression increased as the degree of malignancy increased. There was no significant correlation between the expression level of nestin and the continuity of tumor with the SVZ in the contrast-enhanced imaging before surgery. In addition, no correlation with the therapeutic prognosis was observed. Nestin, a neural stem cell marker, was specifically expressed in astrocytoma lineage cells in glioma tissue. A positive correlation was observed between the degree of malignancy and the level of nestin expression. However, the level of nestin expression was not related to the tumor localization in the SVZ and was not correlated with the therapeutic prognosis.

Usefulness of embolization of the middle meningeal artery for refractory chronic subdural hematomas.

BACKGROUND: Chronic subdural hematoma (CSDH) is generally treated by burr hole irrigation. However, sometimes repeated recurrence is observed, and treatment may consequently become difficult. We examined the efficacy of embolization of the middle meningeal artery (MMA) for such cases. METHODS: We considered embolization of the MMA for three patients who had refractory CSDH with repeated recurrence and two CSDH patients who were at risk of recurrence and showed signs of recurrence after surgery. A microcatheter was advanced through the MMA as peripherally as possible, and embolization was performed with 15-20% n-butyl-2-cyanoacrylate or 200 µm polyvinyl alcohol particles. RESULTS: EMBOLIZATION WAS PERFORMED IN THE THREE PATIENTS WHO HAD REFRACTORY CSDH WITH REPEATED RECURRENCE: The procedure was performed after burr hole irrigation of the hematoma in two patients and before the irrigation in one patient. In the two CSDH patients at risk of recurrence, embolization was performed when signs of recurrence appeared. The timing of embolization differed for each patient. However, in all the patients, the hematoma tended to decrease in size, and no recurrence was observed. CONCLUSION: Embolization of the MMA is effective for refractory CSDH or CSDH patients with a risk of recurrence, and is considered an effective therapeutic method to stop hematoma enlargement and promote resolution.

Photodynamic therapy with talaporfin sodium induces dose-dependent apoptotic cell death in human glioma cell lines.

OBJECTIVE: To investigate the kinetics of cell death in human glioma cell lines induced by photodynamic therapy (PDT) with the second-generation photosensitizer talaporfin sodium (TS) and a 664-nm diode laser. MATERIALS AND METHODS: Three human glioma cell lines (T98G, A172, U251) were studied. After incubation of the cell lines with various concentrations of TS for 4 h, PDT using diode laser irradiation at 33 mW/cm² and 10 J/cm² was performed. Cell viability and changes in cell morphology were examined by the Cell Counting Kit-8 assay and phase-contrast microscopy, respectively. In addition, to evaluate the pathology of cell death, changes in cell viability after treatment with a caspase activation inhibitor and an autophagy inhibitor were also examined. RESULTS: In all 3 human glioma cell lines, TS induced dose-dependent cell death. However, the 50% lethal dose of TS varied among these cell lines. The main morphological feature of cell death was shrinkage of the cell body, and the number of cells with this morphological change increased in a time-dependent manner, resulting in cell death. In addition, a dose-dependent improvement in cell viability by the caspase inhibitor Z-VAD-fmk was observed. CONCLUSION: PDT with TS induces dose-dependent apoptosis in human glioma cell lines. However, the sensitivity to PDT varied among the cell lines, indicating a possible difference in the intracellular content of TS, or a difference in the susceptibility to the intracellular oxidative stress caused by PDT.

Preoperative prediction of macrophage infiltration by 3-D tomographic ultrasound in endoarterectomized carotid plaques in elderly patients.

AIM: Assessment of plaque characteristics is important for the optimal treatment of carotid stenosis, particularly in elderly patients. Macrophage infiltration is reported to be involved in carotid plaque instability. However, immunohistochemical assessment of the detailed localization of macrophage infiltration in carotid plaques remains limited. We attempted to elucidate this using 3-D ultrasonography (3D-US). We compared findings of the detailed localization of macrophage infiltration with findings from the newly developed tomographic ultrasound imaging (TUI). METHODS: We obtained specimens of carotid arteries from 18 patients undergoing carotid endarterectomy (CEA), and investigated the localization of macrophages and vascular smooth muscle cells. Their localization obtained from 11 patients was compared with their preoperative TUI findings. RESULTS: We classified the localization of macrophage infiltration into four types: (i) focal infiltration in the thick fibrous cap (12 cases); (ii) subendothelial zonal infiltration (2 cases); (iii) peripheral infiltration around the lipid core (8 cases); and (iv) local infiltration near the shoulder of the fibrous cap (2 cases). Among them, preoperative TUI was available in 11 CEA cases for histological comparison. We identified two sites of focal macrophage infiltration that corresponded to local echogenic lesions without an acoustic shadow on TUI. The proliferation of smooth muscle cells failed to show an apparent echogenicity. CONCLUSIONS: TUI could not only evaluate the morphological features, but also showed the two types of focal macrophage infiltration relevant to plaque instability as an echogenic focus. TUI carried out by 3D-US is an easily applicable and non-invasive method that is considered useful for evaluating carotid plaques in elderly patients.

Symptomatic suprasellar endodermal cyst, possibly originating from the Seessel's pouch, containing fluid with a high carcinoembryonic antigen level.

A 32-year-old man presented with a rapidly progressive decrease in visual acuity and diplopia. Magnetic resonance imaging (MRI) revealed a suprasellar cystic mass extending to the upper part of the clivus. The content of this cyst showed a slightly higher signal intensity than that of his cerebrospinal fluid (CSF) on T1-weighted images. The cyst stretched the pituitary stalk, but a normal pituitary signal was observed. The cyst wall was maximally resected under neuroendoscopy, which yielded fluid contents that were white and mucous like, with a carcinoembryonic antigen (CEA) level 1,400 ng/ml or higher. On light microscopy, one to two layers of epithelial cells with cylindrical nuclei on loose connective tissue lined the cyst cavity. These cells were positive for periodic acid-Schiff, CEA, and cytokeratin 7 and negative for cytokeratin 20. On electron microscopy, epithelial cells showed many short microvilli with coating material. The cytoplasm was rich in electron-dense material, and dense intercellular adhesion was observed, but neither goblet cells nor cilia were present. On the basis of MRI features, cytokeratin expression patterns and electron microscopic findings, the patient was considered to have a suprasellar endodermal cyst derived from Seessel's pouch.

Photodynamic therapy in combination with talaporfin sodium induces mitochondrial apoptotic cell death accompanied with necrosis in glioma cells.

Photodynamic therapy (PDT) induces selective cell death of neoplastic tissue and connecting vasculature by combining photosensitizers with light. Here we clarified the types of cell death induced by PDT in combination with the photosensitizer talaporfin sodium (mono-L-aspartyl chlorine e6, NPe6) in order to evaluate the potential of this therapy as a treatment for glioma. PDT with NPe6 (NPe6-PDT) induces dose-dependent cell death in human glioblastoma T98G cells. Specifically, cell death modalities were observed in NPe6-PDT treated T98G cells, including signs of apoptosis (activation of caspase-3, expression of phosphatidylserine, and DNA fragmentation) and necrosis (stainability of propidium iodide). In addition, high doses of NPe6-PDT decreased the proportion of apoptotic cell death, while increasing necrosis. Closer examination of apoptotic characteristics revealed release of cytochrome-c from mitochondria as well as activation of both caspse-9 and caspase-3 in cells treated with low doses of NPe6-PDT. Benziloxycarbonyl-Leu-Gln(OMe)-His-Asp(OMe)-fluoromethyl-ketone (Z-LEHD-fmk), a caspase-9 specific inhibitor, and benziloxycarbonyl-Asp(OMe)-Gln-Met-Asp(OMe)-fluoromethyl-ketone (Z-DQMD-fmk), a caspase-3 specific inhibitor, showed dose-dependent prevention of cell death in NPe6-PDT treated cells, indicating that mitochondrial apoptotic pathway was a factor in the observed cell death. Further, the cell morphology was observed after PDT. Time- and NPe6-dose dependent necrotic features were increased in NPe6-PDT treated cells. These results suggest that NPe6-PDT could be an effective treatment for glioma if used in mild doses to avoid the increased necrosis that may induce undesirable obstacles.

Preliminary clinical report on safety and efficacy of photodynamic therapy using talaporfin sodium for malignant gliomas.

OBJECTIVES: To investigate the safety and efficacy of photodynamic therapy (PDT) using talaporfin sodium in patients with surgically, completely unresectable malignant gliomas with invasion into the eloquent areas of the brain associated with language and motor functions. MATERIALS AND METHODS: Subjects consisted of consecutive 14 adult patients with malignant gliomas that were shown on preoperative diagnostic imaging to have invaded the eloquent areas of the brain. Of these, 6 patients had newly diagnosed tumors and 8 patients had recurrent tumors. In 15 craniotomy and tumor resection procedures, PDT was used as additional intraoperative treatment 24 h after 40 mg/m(2) of talaporfin sodium had been injected intravenously. After the tumor bulk had been resected as extensively as possible either 1 or 2 sites of probable tumor invasion in the bottom of resection cavity were irradiated superficially with a 664-nm diode laser for 180 s (27 J/cm(2)) at a power density of 150 mW/cm(2). RESULTS: PDT achieved a response rate of 80% at the treated sites in the 6 patients with newly diagnosed malignant gliomas. In these patients, the median progression-free survival time was 23 months. The median survival time in 3 patients who died was 26 months, and the remaining 3 patients survived for more than 3 years with a good Karnofsky Performance Scale (KPS). In the 8 patients with recurrent tumors who received PDT, their response rate was low (25.0%), their gliomas recurred 3 months after PDT, and their survival time was only 9 months following PDT. No adverse events directly attributable to PDT occurred in any patients. Protection against light was only required for approximately 3 days after PDT. CONCLUSION: We examined the safety and efficacy of PDT using talaporfin sodium as an additional intraoperative treatment for malignant glioma. PDT in addition to surgical resection achieved better therapeutic results than conventional protocols, especially in patients with newly diagnosed malignant gliomas. However, the current methodology has some limitations with respect to patients with recurrent tumors. Larger-scale studies are required to confirm the clinical feasibility of PDT plus surgery.

Isoform-specific immunolocalization of 14-3-3 proteins in atherosclerotic lesions of human carotid and main cerebral arteries.

14-3-3 proteins are now recognized to have a wide range of potential functions and pathological relevance, such as regulating the intercellular signal processes of differentiation, the development and growth of cells, or preventing or mediating cell apoptosis and survival by controlling the localization of potential signaling molecules. We investigated the immunolocalization of 14-3-3 proteins in atherosclerotic lesions of human cerebral and carotid arteries using 14-3-3 isoform-specific antibodies to distinguish 7 isoforms, and confirmed the cell type localization using double immunofluorolabeling. 14-3-3 common (COM)-like immunoreactivity (IR) was intense, mainly in the foam cells and multinucleated giant cells of the carotid artery. The beta, gamma, epsilon, tau, eta, and zeta (6/7) isoform-specific antibodies showed similar results to those with anti-14-3-3 COM antibody. However, among these isoform-specific antibodies, the anti-eta isoform antibody most intensely immunolabeled multinucleated giant cells and foam cells, and the anti-zeta isoform antibody most intensely immunolabeled infiltrating vascular smooth muscle cells (VSMCs), in carotid plaques. Zeta IR was also observed in one part of the mural thrombus and in the nuclei of foam cells. Gamma isoform-like IR was relatively limited in cell components, but extracellular lesions were partly positive for this isoform. In the main cerebral arteries, the anti-epsilon isoform antibody most intensely immunolabeled infiltrating VSMCs in the intima of thickened fibrous cap plaques. Endothelial cells were also positive for the epsilon isoform. These findings may provide a basis for understanding the isoform-specific role associated with atherosclerotic lesions of the cerebral and carotid arteries.

Neuromuscular hamartoma is a possible primary pathology of oculomotor ophthalmoplegic migraine.

BACKGROUND: Oculomotor ophthalmoplegic migraine (O-OPM) occurs in many children, and in some cases MRI shows a small mass in the root exit zone (REZ) of the oculomotor nerve. This mass is considered to result from nerve hypertrophy caused by repeated demyelination. CASE RESULTS: A 51-year-old man has been on oral medication for O-OPM, which he had from 6 years of age. However, the frequency and intensity of his migraine attacks have gradually increased. Brain magnetic resonance imaging (MRI) revealed a small nodular mass in the REZ of the oculomotor nerve. The mass was initially diagnosed as oculomotor schwannoma and tumor resection was attempted. However, as the mass was tightly adhered to the oculomotor nerve and hemorrhagic, biopsy was performed. The pathological diagnosis was neuromuscular hamartoma. CONCLUSION: The small nodular mass in the REZ of the oculomotor nerve may be a hamartoma associated with congenital factors and may possibly be the primary pathology of O-OPM in this case.

Differential expression of oxidized/native lipoprotein(a) and plasminogen in human carotid and cerebral artery plaques.

OBJECTIVE: Lipoprotein(a) [Lp(a)] is a risk factor for stroke, as has recently been further confirmed by meta analysis, and consists of low-density lipoprotein and apolipoprotein(a), which shares a significant amino acid homology with plasminogen. Oxidized Lp(a) [Ox-Lp(a)] is a more pathogenic species of Lp(a). A monoclonal antibody, specific to Ox-Lp(a), distinguishes immunolocalization of Ox-Lp(a) from that of Lp(a) and that of plasminogen which carries highly homologous domains. It is worth examining their possibly differential immunolocalizations around atherosclerotic lesions in human carotid and cerebral arteries. METHODS AND RESULTS: Stage-related differences in immunolocalization of Ox-Lp(a), native Lp(a), and plasminogen were investigated in various atherosclerotic lesions of the human carotid (obtained from 13 patients undergoing carotid endarterectomy) and cerebral arteries (from 11 cadavers). Native Lp(a) was seen in the fibrous cap, extracellular matrix, endothelial cells, and subendothelial layer. Unorganized mural thrombi were positive for plasminogen, but not Lp(a). In contrast, fibrin deposits in thickened intima were positive for Lp(a), but not plasminogen. Ox-Lp(a)-like immunoreactivity was seen in endothelial cells in the early stage of atherosclerosis. Ox-Lp(a) deposition was more abundant in synthetic phase vascular smooth muscle cells (VSMC) than in contractile phase VSMC. CONCLUSION: We demonstrated differential immunoexpression patterns between native Lp(a) and plasminogen, and suggested that Lp(a)-plasminogen interaction may play a part in differential mechanisms in all atherosclerotic lesions of human carotid and cerebral arteries. The preferential presence of Ox-Lp(a) seen in endothelial cells suggests initial dysfunction of endothelial cells in atherosclerosis. The relative abundance of Ox-Lp(a) in synthetic phase VSMC is associated with their phenotypic changes during the progression of atherosclerosis.

Co-expression of somatostatin receptor subtypes and estrogen receptor-α mRNAs by non-functioning pituitary adenomas in young patients.

The expression by non-functioning adenomas (NFoma) of somatostatin receptor (SSTR) subtypes and estrogen receptor (ERα) is poorly understood. Consequently, the mRNAs of SSTR subtypes (SSTR) 1, 2, 3, and 5, dopamine receptor (D2R), and ERα were measured by real-time quantitative RT-PCR in 59 NFomas and 50 functioning adenomas; the latter included 30 GH-secreting adenomas (GHomas) and 20 prolactinomas (PRLomas). NFomas expressed higher levels of SSTR3 than functioning adenomas but had lower levels of SSTR2, SSTR5 and D2R mRNAs than GHomas. Their ERα levels were higher than those of GHomas. The SSTR subtype mRNA levels in NFomas correlated significantly with each other; there was also a good correlation between the SSTR subtypes and ERα in NFomas. These correlations were largely only observed in younger patients (<50 years). The present study describes the differential expression of SSTR subtypes in the largest number of NFoma patients studied thus far, and further proposes possible involvements of SSTR3 and estrogen in the pathophysiology of NFomas.

En bloc temporal bone resection using a diamond threadwire saw for malignant tumors.

The purpose of this study is to describe a new technique for en bloc temporal bone resection using a diamond threadwire saw (T-saw) as an alternative to cutting the temporal bone with an osteotome. This technique has been performed in 10 patients with external auditory canal and middle ear cancers without any injury to the internal carotid artery or jugular vein. The authors conclude that the use of a diamond threadwire saw after transposing the internal carotid artery anteriorly is a safe, simple, and reliable technique for en bloc temporal bone resection.

Immunohistochemical study for IgG4-positive plasmacytes in pituitary inflammatory lesions.

On histology, IgG4-related hypophysitis is essentially similar to lymphocytic hypophysitis besides massive IgG4-positive plasmacyte infiltration. This immunohistochemical study was performed to investigate the presence of IgG4-positive plasmacytes in 14 various inflammatory lesions. Five cases of lymphocytic hypophysitis and a case of granulomatous hypophysitis were either negative or showed only a few IgG4-postive cells. A case of hypophysitis associated with pachymeningitis and a case of pituitary invasion of lymphoma were IgG4 negative. On the other hand, some IgG4-positive cells that tended to accumulate were observed in every six cases of secondary inflammation. In conclusion, immunohistochemistry for IgG4 can be a clue for differentiating IgG4-related hypophysitis from lymphocytic hypophysitis. However, clusters of IgG4-positive plasmacytes could be observed in secondary inflammation. Diagnosing hypophysitis with small biopsy specimen still remains troublesome.

Mixed pial-dural arteriovenous malformation in the anterior cranial fossa--two case reports.

Most arteriovenous malformations (AVMs) associated with the meningeal artery in the anterior cranial fossa are the pure dural type, and mixed pial-dural AVMs are rare. Two types of mixed pial-dural AVM occur in the anterior cranial fossa according to the shunting point: one with the nidus in the brain parenchyma of the frontal lobe, and the other with the shunting point in the dura mater. We describe two patients with AVMs fed by the anterior ethmoidal arteries and the persistent primitive olfactory artery, with the nidus located in the pure brain parenchyma of the inferior aspect of frontal lobe, and drained via an abnormal cortical vein into the cavernous and superior sagittal sinuses. The importance of occluding the venous outflow to obliterate intracranial dural arteriovenous fistula (AVF) is emphasized. However, removal of the nidus in the brain parenchyma is required. The presence of a pial feeder should be considered before diagnosis of dural AVF of the anterior cranial fossa, and preoperative detailed evaluation for the pial supply and shunting point is mandatory.

Endocrinological and MRI features of pituitary adenomas with marked xanthogranulomatous reaction.

INTRODUCTION: The study aims to describe the endocrinological and magnetic resonance imaging (MRI) features of the rarely reported xanthogranulomas associated with pituitary adenoma. METHODS: Of 231 consecutive pituitary adenomas treated surgically, those with xanthogranulomatous reaction on histology were reviewed. RESULTS: Five patients (2.2%) had an adenoma with marked xanthogranulomatous reaction. They were all nonfunctioning macroadenomas and presented with anterior pituitary insufficiencies. On MRI, all adenomas showed mixed signal intensities on T1- and T2-weighted images with heterogeneous gadolinium enhancement, reflecting their complex histological features: Cholesterol clefts typically showed T1 high- and T2 low-signal intensities. Preoperative diagnosis was difficult in a case predominantly featuring xanthogranuloma. Although none of them had episodes of pituitary apoplexy, hemosiderin deposits and cysts with xanthochromic-like fluid were observed in five and four cases, respectively. CONCLUSIONS: Xanthogranulomatous reaction may develop in macroadenomas, probably triggered by hemorrhagic processes despite no apoplectic episodes. They typically exhibit complex mixed signal intensity on MRI, particularly T1 high- and T2 low-signal intensities, and patients present with pituitary dysfunction.

Cerebellar infarction caused by primary central nervous system angiitis of childhood: case report.

BACKGROUND: Cerebellar infarction of childhood is rare, and is difficult in pathological diagnosis. We describe a case of radiographically diagnosed primary central nervous system angiitis of childhood. SUMMARY: A 7-year-old boy experienced dizziness and headache persisting for 7 days. Diffusion-weighted images of magnetic resonance (MR) showed high signals in the left cerebellar hemisphere and vermis. The MR angiogram (MRA) findings were normal. A conventional angiogram demonstrated severe stenoses and occlusions at distal portion of left posterior inferior cerebellar artery, and irregularity in the wall of the cervical portion of the left vertebral artery (VA). Although he recovered without any neurologic deficits, an angiogram 3 months after admission showed occlusion at the cervical portion of left VA and filling of the distal VA with collateral arteries from the deep cervical artery. He was doing well, with no additional changes demonstrated on MRA, 12 months after the onset. CONCLUSION: Although MRA can detect abnormality within the proximal intracranial vessels, angiography is essential, especially in cases with distal stenoses. Repeated angiography in primary central nervous system angiitis of childhood is necessary at least 3 months after the onset, even if the patient has no symptom.

Radiopathological characteristics of cerebellar malignant glioma in adults.

Our aim was to extract the radiopathological features of cerebellar malignant glioma in adults from the four cases we encountered. All four cases (two men and two women, aged 52-80 years; mean age, 67 years) had a floating sensation or vertigo at the onset of their disease. Initially, these patients were given a diagnosis of cerebellar infarction or cavernous angioma, or had faint abnormalities in the cerebellum that were overlooked. These patients were followed up for 2-14 months (mean, 6 months), and the tumor was detected when their clinical symptoms deteriorated. The tumor was located in the hemisphere in one patient and in the vermis in three patients. MRI revealed ring-like enhancement in two patients and nodular enhancement in two patients. All patients underwent subtotal tumor resection, followed by postoperative radiochemotherapy. However, three patients died at 16 to 44 months (mean, 28 months), and cerebrospinal fluid (CSF) dissemination was observed in three patients. Two cases were classified as WHO grade III and two as WHO grade IV. The pathological features were typical of malignant glioma, partially presenting the features of low-grade glioma, such as pilocytic, astrocytic, or oligodendroglial components. Nuclear pleomorphism and vascular endothelial proliferation were prominent, and micronecrosis was relatively less evident. The MIB-1 index was 12%-40%, and most of the patients were p53 protein positive. At the onset of cerebellar malignant glioma, diagnostic imaging shows few signs of brain tumor. Thereafter, tumors grow in a short period of time, following a rapid clinical course. Because cerebellar malignant glioma is a rare disease, it is difficult to differentiate it from metastatic brain tumors and primary central nervous system lymphoma by preoperative imaging. Some patho logical features suggesting malignant transformation from low-grade glioma were detected.

Dural suturing for repair of cerebrospinal fluid leak in transnasal transsphenoidal surgery.

OBJECTIVE: Repair of a cerebrospinal fluid (CSF) leak after transsphenoidal surgery (TSS) is usually accomplished using various graft materials. These methods are effective in most, but not all, cases. METHODS: Since 2006, we have been directly suturing the sellar floor dura in patients with an intraoperative CSF leak. Fat and/or fascial grafts were utilized only when a major CSF leak developed. The incidence of postoperative CSF rhinorrhea was compared before and after the suture. RESULTS: Postoperative CSF rhinorrhea developed in 3.7% (7 out of 188) of cases before 2005, but never since the dural suture was introduced (0 out of 136, 0%; P = 0.0229). Although watertight closure was not achieved in some cases, narrowing the dural defect and supporting the intrasellar graft was attained in every case. Surgical time was approximately 30 min longer in patients who underwent dural suture (148 +/- 42 min) than those who did not (119 +/- 37 min; P = 0.0001). CONCLUSION: Direct suturing of the sellar dura is a simple, safe, and reliable surgical technique for repairing CSF leaks after TSS. Using this procedure, more than 70% of patients with an intraoperative CSF leak can avoid autologous tissue grafts.

Differential effects of an expected actin-tropomyosin binding region of heat shock protein 20 on the relaxation in skinned carotid artery and taenia cecum from guinea pig.

To explore the possible role of heat shock protein 20 (HSP20) -linked regulation of actin-myosin interaction in living vascular smooth muscle contraction, we studied the effects of HSP20p and TnIp, synthetic peptides originating from an actin tropomyosin binding region of human heat shock protein 20 [residues 110-121; GFVAREFHRRYR] and that of rabbit cardiac troponin I [residues 136-147; GKFKRPTLRRVR], respectively, on the active stress and phosphorylation level of myosin regulatory light chain (MLC(20)) during relaxation of skinned (cell membrane permeabilized) preparations from "tonic" carotid artery and "phasic" taenia cecum from guinea pig. Active stress of the skinned preparations, resulting from actin-myosin interaction, biphasically decayed following Ca(2+) removal (relaxation). Decay of MLC(20) phosphorylation level by Ca(2+) removal was much faster than active stress in an exponential manner. In skinned carotid artery, HSP20p did neither affect relaxation time course nor MLC(20) dephosphorylation, whereas, in skinned taenia cecum, the peptide slowed relaxation time course through inhibition of MLC(20) dephosphorylation and slowing "latch"-bridge dissociation. On the other hand, TnIp accelerated relaxation time course without affecting MLC(20) dephosphorylation in both skinned carotid artery and skinned taenia cecum. Our present results suggest that, HSP20p slows the relaxation processes through intracellular regulatory mechanisms such as Rho A/Rho-kinase mediated pathways, which are known to be dominant in "phasic" smooth muscles but to be recessive in "tonic" smooth muscles.