Purely endoscopic subtemporal keyhole anterior transpetrosal approach to access the petrous apex region: surgical techniques and early results

OBJECTIVE

The anterior transpetrosal approach using a microscope to provide wider access to the petrous apex region has been described for radical resection of lesions of the middle and posterior skull base. The microscopic anterior transpetrosal approach (mATPA) requires a wide craniotomy and meticulous epidural procedures to minimize temporal lobe retraction. Recently, the clinical application of transcranial endoscopic keyhole approaches for minimally invasive surgery has been steadily expanding. In this study, the details of the purely endoscopic subtemporal keyhole ATPA (eATPA) for petrous apex lesions are described and its initial results are reported.

METHODS

Between May 2022 and May 2023, the authors performed eATPA in 10 patients with petrous apex lesions, of which 6 were meningiomas, 3 were trigeminal schwannomas, and 1 was epidermoid cyst. The surgical procedure of the purely eATPA is as follows. After a small temporal craniotomy, the endoscopic procedure is started. The anterior rim of the petrous bone and Meckel's cave are exposed via an intradural subtemporal approach. The lesion is removed with additional drilling of Kawase's triangle, cutting the superior petrosal sinus, opening Meckel's cave, and cutting the tentorium. The authors also compared the outcomes of mATPA versus eATPA for consecutive cases of petrous apex lesions.

RESULTS

Gross-total resection was achieved in 8 of the 10 patients. The average operative time was 4 hours 13 minutes. There were 3 cases of transient abducens nerve palsy and 1 case of trochlear nerve palsy in the postoperative period. No new-onset motor deficits or CSF leakage was noted in any of these patients. Only 1 patient exhibited postoperative asymptomatic temporal lobe edema. The Karnofsky Performance Scale (KPS) scores remained unchanged or improved for all patients postoperatively. Compared with mATPA, eATPA achieved a similar extent of resection and comparable postoperative KPS scores with a significantly shorter mean operative time, much smaller temporal craniotomy, and thus less mean blood loss during surgery with lower rates of new-onset temporal lobe edema in the postoperative period.

CONCLUSIONS

An eATPA allows a direct route to access Meckel's cave and posterior cranial fossa lesions similar to conventional mATPA, with shortening the operative time and reducing the risk of postoperative temporal lobe edema. This eATPA is considered one of the new surgical techniques that can be expected to develop in the future.

Rheumatologic manifestations with elevated levels of IL-6, IL-17A, and IL-23 in a patient with scurvy

Symptomatic vitamin C deficiency, scurvy, is a relatively rare disease in developed countries, but it has been reported in patients with autism spectrum disorder or developmental delay who tend to have selective diets. Patients with scurvy often demonstrate musculoskeletal manifestations with unknown pathophysiology. Herein, we report a case of scurvy in an 11-year-old boy who presented with iron-deficiency anaemia, systemic osteomyelitis, myositis predominantly in the lower extremities, and right ventricular volume overload with mild pulmonary hypertension and was diagnosed with scurvy. He had a mild developmental disorder and a selective diet, which resulted in severe vitamin C deficiency. He received intravenous and oral vitamin C supplementation, which relieved his arthralgia and muscle pain in a week. Following 4 months of vitamin C supplementation, he demonstrated no abnormal manifestations on laboratory or imaging examination and recovered without sequelae. Inflammatory cytokine and chemokine evaluations demonstrated elevated levels of interleukin (IL)-6, IL-17A, and IL-23, which are associated with T-helper (Th) 17 cell activation. This study is the first to suggest the association between the inflammation seen in scurvy, rheumatic manifestations in the patient, and Th17 cell activation. Further analysis of the association between the inflammation and vitamin C supplementation may contribute to new insights for the comprehension and treatment of other inflammatory diseases, such as rheumatic diseases.

Endoscopic Contralateral Interhemispheric Transfalcine Keyhole Approach for Large Falcine Meningiomas

OBJECTIVE

Falcine meningioma is usually approached ipsilaterally, and the technique for tumor removal has traditionally been performed under microscopy. We report a surgical procedure for large falcine meningioma by an endoscopic contralateral interhemispheric transfalcine keyhole approach.

METHODS

The study period was from September 2019 to March 2021. Study participants were patients with World Health Organization grade I meningioma showing falx attachment, excluding neurofibromatosis, who underwent initial surgery at our institution. The surgical procedure begins with a small contralateral craniotomy of about 3 cm, followed by insertion of an endoscope. The tumor attachment to the falx is excised, exposing the tumor. Internal decompression is performed, and the lesion is dissected from the surrounding brain before removal through the falx.

RESULTS

An endoscopic contralateral interhemispheric transfalcine keyhole approach was used to resect 4 cases of large falcine meningioma. The mean operation time was 265 minutes (range: 216-294 minutes), achieving Simpson grade I removal in all cases. No evidence of cerebral infarction, cerebral edema, or new neurological complaints related to impaired venous return was seen using this surgical method.

CONCLUSIONS

In the case of falcine meningioma, the endoscopic keyhole contralateral technique allows detachment of the tumor from the falx and safe manipulation in a minor field of view. In addition, because the craniotomy is smaller and the operation time is shorter, this procedure offers a less-invasive approach for the patient. This technique is thus, in our opinion, quite advantageous.

Study of Hadron Masses with Faddeev-Popov Eigenmode Projection in the Coulomb Gauge

Using SU(3) lattice QCD, we investigate role of spatial gluons for hadron masses in the Coulomb gauge, considering the relation between QCD and the quark model. From the Coulomb-gauge configurations at the quenched level on a 163 × 32 lattice at β = 6.0, we consider the A⃗ = 0 projection, where all the spatial gluon fields are set to zero. In this projection, the inter-quark potential is unchanged. We investigate light hadron masses and find that nucleon and delta baryon masses are almost degenerate. This result suggests that the N-Δ mass difference arises from the color-magnetic interactions, which is consistent with the quark model picture. Next, as a generalization of this projection, we expand spatial gluon fields in terms of Faddeev-Popov eigenmodes and leave only some partial components. We find that the N – Δ and 0++ – 2++ glueball mass splittings are almost reproduced only with 1 % low-lying components. This suggests that low-lying color-magnetic interaction leads to the hadron mass splitting.

Two-stage posterior decompression and fusion for tuberculous spondylitis after intravesical bacillus Calmette-Guerin instillation

Intravesical bacillus Calmette-Guerin (BCG) instillation is an effective treatment for nonmuscle invasive superficial bladder cancer. BCG induces a massive influx of inflammatory cells and production of cytokines in the bladder mucosa and lumen that leads to an immune response against tumor cells, acting as an immunotherapy. Cystitis, bladder ulceration, and bladder contracture are known local genitourinary complications, whereas systemic complications such as miliary pulmonary tuberculosis, mycotic aneurysms, tuberculous spondylodiscitis, and granulomatous hepatitis are very rare.

A case of tuberculous spondylodiscitis at the T8 and T9 levels following intravesical BCG instillation for bladder carcinoma is reported. The patient initially underwent decompressive laminectomy for spastic paraparesis. After reporting improvement for few weeks, the patient again presented with similar complaints and was found to have an increased kyphotic deformity, for which he underwent fixation surgery.

Osaka Sliding Knot Seals Dural Defect Simply in Extended Endoscopic Endonasal Approach

An extended endoscopic endonasal approach (EEA) has become standard for parasellar and midline skull base lesions. However, postoperative leakage of cerebrospinal fluid (CSF) can result from dural defects after lesion removal. We present a simple and effective technique, the Osaka sliding knot, to prevent CSF leakage. Between November 2018 and March 2021, a total of 41 patients underwent reconstruction of skull base defects with intraoperative high-flow CSF leaks after extended EEA by using this closure technique, of whom only 1 patient experienced postoperative CSF leakage. This technically simple and efficient method seals the dural defect to prevent CSF leakage after surgeries using an extended EEA.

Pediatric giant cell reparative granuloma of the lower clivus: A case report and review of the literature

Giant cell reparative granuloma (GCRG) is a benign nonneoplastic granulomatous lesion and is rare in the cranial bone. We present a pediatric case of this lesion arising from the condyle and lower clivus. A 9-year-old girl presented with slowly progressive hoarseness and dysphagia. She showed left glossopharyngeal, vagus, and hypoglossal nerve palsy. An osteolytic lesion around the lower clivus and condyle joint was accompanied by deformation of the craniovertebral junction. An endoscopic endonasal approach was used to decompress the cranial nerve and confirm the pathological finding. The lesion around the condyle was not resected to preserve occipito-cervical stability. The residual lesion has been observed carefully for 6 months, and regrowth has not occurred. GCRG is a rare granulomatous lesion in the cranial bone. This case is the first report of a pediatric clival GCRG. Treating pediatric GCRG may be helpful.

Minimal anterior and posterior combined transpetrosal approach for large petroclival meningiomas

OBJECTIVE

Petroclival meningiomas (PCMs) remain difficult to remove, and radical tumor resection continues to pose a relatively high risk of neurological morbidity in patients with these lesions because of the proximity of the tumor to neurovascular structures. The anterior and posterior combined (APC) transpetrosal approach allows resection of a large petroclival lesion with minimal retraction of the temporal lobe. However, this approach is thought to be complex and time-consuming. The authors simplified this approach by minimizing the petrosectomy and used this method for large PCMs. This retrospective study describes the surgical technique and surgical outcomes of large PCMs.

METHODS

Between 2014 and 2019, 23 patients (19 women and 4 men) with benign (WHO grade I) PCMs were treated using the minimal APC (MAPC) transpetrosal approach. The mean age at surgery was 54.0 years (range 37-74 years). The mean tumor diameter was 40.3 mm (range 30-74 mm). The surgical technique consisted of a temporo-suboccipital craniotomy and minimal drilling of the petrous ridge. After opening Meckel's cave and removing the lesion at the prepontine cistern, drilling of the petrous apex with superior mobilization of the trigeminal nerve was performed through the subdural space for further tumor resection around the petrous apex. Finally, the tumor was removed as much as possible.

RESULTS

The mean preoperative and postoperative tumor volumes were 26.8 and 1.3 cm3, respectively. The mean extent of resection was 95.4% (range 62%-100%). Postoperative impairments included facial numbness in 7 patients, trochlear nerve palsy in 3 patients, mild oculomotor nerve palsy in 2 patients, and transient abducens nerve palsy in 1 patient. Preoperative Karnofsky Performance Status was improved in 13 patients, remained stable in 9 patients, and deteriorated in 1 patient.

CONCLUSIONS

The MAPC transpetrosal approach provides sufficiently wide exposure of petroclival lesions. Maximal resection via the MAPC transpetrosal approach is a suitable surgical option for the treatment of large PCMs.

RARE-03. AGGRESSIVE RESECTION FOR PEDIATRIC CRANIOPHARYNGIOMAS VIA ENDOSCOPIC ENDONASAL APPROACH

OBJECTIVE

In recent years, the endoscopic endonasal approach (EEA) has been increasingly used for pediatric craniopharyngiomas. We here present our experience and the outcomes of the EEA resection of pediatric craniopharyngiomas.

MATERIALS AND METHODS

Between April 2014 and December 2019, 16 cases of pediatric craniopharyngiomas were operated at the Osaka city university (OCU) hospital. Eight patients were diagnosed with primary craniopharyngiomas while 8 had a recurrent tumor. There were 5 males and 11 females, with a mean age of 10.7 years (3–17 years). EEA was selected in all patients and a case of large muti-lobulated tumor was resected by combination of microscopic transcranial approach.

RESULTS

Gross total resection was achieved in 14 patients and near total resection in other 2. Post-op CSF leak occurred in 3 patients, which was treated with re-exploration. Pituitary stalk was preserved intraoperatively in 4 cases, and 15 patients developed diabetes insipidus and anterior hormonal replacement therapy was required in 15 patients at last follow-up. Visual improvement was noted in 4 patients while vision remained unchanged in the rest. Neuropsychological function status was preserved in all patients, and there was no new-onset obesity postoperatively. The mean follow-up duration was 35.1 months (2 – 69 months) and 4 of 8 recurrent cases had re-recurrence during this period, however there was no recurrent in 8 primary cases.

CONCLUSIONS

EEA should be the surgical modality of choice for treating pediatric craniopharyngiomas. It results in better visual and cognitive outcomes with a significantly increased extent of resection.

Surgical implementation and efficacy of endoscopic endonasal extradural posterior clinoidectomy

OBJECTIVEThe endoscopic endonasal approach (EEA) for skull base tumors has become an important topic in recent years, but its use, merits, and demerits are still being debated. Herein, the authors describe the nuances and efficacy of the endoscopic endonasal extradural posterior clinoidectomy for maximal tumor exposure.METHODSThe surgical technique included extradural posterior clinoidectomy following lateral retraction of the paraclival internal carotid artery and extradural pituitary transposition. In cases with prominent posterior clinoid process, a midline sellar dura cut was added to facilitate extradural exposure. Forty-four consecutive patients, in whom this technique was performed between 2016 and 2018 at Osaka City University Hospital, were reviewed. The pathology included 19 craniopharyngiomas, 7 chordomas, 6 meningiomas, 6 pituitary adenomas, 4 chondrosarcomas, and 2 miscellaneous. Utilization and effectiveness of this approach were further demonstrated with neuroimaging.RESULTSExtradural posterior clinoidectomies were successfully applied in all patients without permanent neurovascular injury and with better maneuverability and greater resection rate of the tumors. Four patients experienced transient postoperative abducens nerve paresis, and 1 patient experienced transient postoperative oculomotor nerve paresis; however, the patients with deficits recovered within 3 months. On radiological examination, the surgical field was 2.2 times wider in cases with bilateral posterior clinoidectomy than in cases without posterior clinoidectomy.CONCLUSIONSThe extended EEA with extradural posterior clinoidectomy creates an extra working space and allows adequate accessibility with safe surgical maneuverability to remove tumors that extend behind the posterior clinoid and dorsum sellae.

Safe maximal resection of primary cavernous sinus meningiomas via a minimal anterior and posterior combined transpetrosal approach

OBJECTIVE

Meningiomas arising from the cavernous sinus (CS) continue to be a significant technical challenge, and resection continues to carry a relatively higher risk of neurological morbidity in patients with these lesions because of the tumor’s proximity to neurovascular structures. The authors report the surgical outcomes of 9 patients with primary CS meningiomas (CSMs) that were surgically treated using a minimal anterior and posterior combined (MAPC) transpetrosal approach, and they emphasize the usefulness of the approach.

METHODS

This retrospective study included 9 patients who underwent surgery for CSM treatment between 2015 and 2016 via the MAPC transpetrosal approach. Two patients were men and 7 were women, with a mean age of 58.5 years (39–72 years). Five patients (55.5%) had undergone previous treatment. The surgical technique consisted of a temporo-occipito-suboccipital craniotomy and exposure of the posterolateral part of the CS via the presigmoidal MAPC approach. After opening Meckel’s cave and identifying the 3rd–5th cranial nerves in the prepontine cistern, Parkinson’s triangle and supratrochlear triangles were opened. Finally, the tumor occupying the posterolateral part of the CS was removed.

RESULTS

All lesions were safely and maximally removed, with preservation of external ocular movements and preoperative Karnofsky Performance Scale scores. The mean extent of resection was 77.0% (range 58.7%–95.4%). Six patients underwent adjuvant therapy in the form of stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) during the follow-up period; none of these patients experienced recurrence.

CONCLUSION

The authors conclude that the MAPC transpetrosal approach could be superior to other approaches for CSMs, as it provides direct visual access to the posterolateral portion of the CS. In their experience, this approach is an alternative and better option for safe maximal resection of CSMs.

Contralateral Minimum Anterior and Posterior Combined Petrosal Approach for Retrochiasmatic Craniopharyngiomas: An Alternative Technique

Retrochiasmatic craniopharyngiomas (RC) are a challenge for the neurosurgeon to treat surgically, restrained by their location in the interpeduncular fossa, surrounded by vital neurovascular structures, narrow corridor and poor visibility. Many approaches are possible and elucidated in the literature, which the surgeon chooses, based on multiple factors, such as the size of tumor, calcification, laterality, preoperative neurological deficits and the endocrine function status, recurrence, postradiotherapy status, or significant superior and/or posterior extension. 1 2 We describe a contralateral minimum anterior and posterior (CL-MAPC) petrosal approach for a case of recurrent RC, in a 37-year-old female patient operated before using a pterional approach, now presented with left homonymous hemianopia and panhypopituitarism ( Fig. 1 ). We preferred a contralateral approach to protect the ipsilateral optic tract (OT) from retraction injury, which formed an obstacle to the tumor from ipsilateral side. Apart from various benefits described by the author previously for RC, using MAPC petrosal approach, the CL-MAPC offers a safe corridor, protecting the ipsilateral OT, visualization of tumor origin usually posterior to chiasm, wider corridor if PCoM could be sacrificed, as it was done in this case, and pituitary stalk identification, with a probability of its functional preservation, unlike a necessity of pituitary transposition in EEA, though the endocrine outcome is poor after a radical resection irrespective of the approach chosen. 1 3 4 There was complete excision of the tumor with preservation of visual function postoperatively. We recommend the use of CL-MAPC as an alternative to EEA in some specific indications when the tumor is large, calcified, obscuring OT on the ipsilateral side and with significant lateral extension, which may be limiting factors in EEA ( Fig. 2 ). The link to the video can be found at: https://youtu.be/gWCJmh4_evs .

Genetic and prenatal findings in two Japanese patients with Schinzel-Giedion syndrome

We report two Japanese patients with Schinzel–Giedion syndrome. When polyhydramnios is observed, additional fetal findings such as overlapping fingers, hydrocephalus, hydronephrosis, and very characteristic facial appearance comprising high, prominent forehead, hypertelorism, and depressed nasal root may suggest Schinzel–Giedion syndrome.

Cholangiocyte senescence caused by lysophosphatidylcholine as a potential implication in carcinogenesis

BACKGROUND

The incidence of biliary tract cancer in patients with pancreaticobiliary maljunction or intrahepatic cholelithiasis is markedly high with undefined mechanism. In these diseases, biliary lysophosphatidylcholine (LPC) level is reportedly increased. This study investigated the influence of LPC on cholangiocytes focusing on cellular senescence and its potential contribution to carcinogenesis.

METHODS

Cultured MMNK-1, an immortalized human cholangiocyte was treated with LPC in vitro and its effect was evaluated.

RESULTS

Lysophosphatidylcholine demonstrated cytotoxicity with generation of intracellular reactive oxygen species. Accordingly, LPC provoked oxidative DNA injury, whereas the gene expressions of DNA repair enzyme (OGG1, MUTYH, MTH1) remained unchanged. Interestingly, LPC caused global DNA hypomethylation, which is frequently observed in cancer tissues. Microarray analysis identified differentially regulated genes in response to LPC, which included the components of senescence-associated secretory phenotype (SASP) including interleukin-8 (IL-8), IL-6, transforming growth factor-β and plasminogen activator inhibitor-1. Significant induction of these genes was further confirmed by quantitative real-time polymerase chain reaction. In addition to upregulation of p21 gene expression, senescence-associated beta-galactosidase activity, a widely used marker of cellular senescence was significantly induced by the treatment of LPC.

CONCLUSIONS

Based on these data, cholangiocyte senescence and SASP caused by LPC are potential pathogenic mechanisms in the development of biliary tract cancer.

Differential expression of VAMP2/synaptobrevin-2 after antidepressant and electroconvulsive treatment in rat frontal cortex

The biological basis for the therapeutic mechanisms of depression is still unknown. We have previously performed expressed-sequence tag (EST) analysis to identify some molecular machinery responsible for antidepressant effect. Then, we developed our original cDNA microarray, on which cDNA fragments identified as antidepressant-related genes/ESTs were spotted. In this study, with this microarray followed by Western blot analysis, we have demonstrated the induction of vesicle-associated membrane protein 2(VAMP2/synaptobrevin-2) in rat frontal cortex not only after chronic antidepressant treatment, but also after repeated electroconvulsive treatment. On the other hand, expression of SNAP-25 and syntaxin-1 was not changed by these treatments. These components make a soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor complex with VAMP2 and mediate the synaptic vesicle docking/fusion machinery. In conclusion, it is suggested that VAMP2/synaptobrevin-2 plays important roles in the antidepressant effects. Our results may contribute to a novel model for the therapeutic mechanism of depression and new molecular targets for the development of therapeutic agents.

Corticotropin-releasing factor as well as opioid and dopamine are involved in tail-pinch-induced food intake of rats

Several kinds of stress such as psychological stress, restraint, and foot shock inhibit feeding behavior through corticotropin-releasing factor (CRF). In contrast, a mild tail pinch increases food intake in rats. Although dopamine and opioid are thought to be involved in tail-pinch-induced food intake, it is unknown whether CRF participates in this phenomenon. Therefore, we attempted to clarify this issue using rats. A 30-s tail pinch increased food intake in 30 min after the tail pinch, and this increase was blocked by intraperitoneal injection of CRF receptor type 1 selective antagonist. CRF increased food intake in 30 min after intracerebroventricular injection at a dose of 2 or 10 ng, and this increase was also blocked by CRF receptor type 1 antagonist. Tail-pinch- or CRF-induced food intake was blocked by naloxone, pimozide, and spiperone. These results suggest that CRF, through CRF receptor type 1 as well as opioid and dopaminergic systems, are involved in the mechanism of tail-pinch-induced food intake. The results also suggest that brain CRF has dual effects on food intake, hyperphagia and anorexia, in a stress-dependent manner.

Changes in calcitonin gene-related peptide, atrial natriuretic peptide and brain natriuretic peptide in patients undergoing coronary artery bypass grafting

The initiation of cardiopulmonary bypass creates significant derangements in cardiovascular volume status and both endocrine and autonomic nervous system function. To examine whether such derangements might differ in patients with different pre-operative physical status scores, we measured the plasma concentrations of calcitonin gene-related peptide, atrial natriuretic peptide and brain natriuretic peptide, catecholamines and antidiuretic hormone, as well as haemodynamic variables, during and after cardiopulmonary bypass in 27 consecutive patients undergoing coronary artery bypass grafting. The pre-operative levels of atrial natriuretic peptide and brain natriuretic peptide differed significantly between ASA II patients and III and IV patients [mean (SD) brain natriuretic peptide levels = 14 (8.2) vs. 129 (51) pg.ml-1]. Plasma calcitonin gene-related peptide increased significantly in both groups after the initiation of cardiopulmonary bypass, and remained increased throughout cardiopulmonary bypass. The changes in plasma epinephrine, norepinephrine and antidiuretic hormone were similar to those reported previously. The changes in plasma calcitonin gene-related peptide, atrial natriuretic peptide and brain natriuretic peptide did not correlate with any changes in haemodynamic variables before or after cardiopulmonary bypass. Measurement of plasma brain natriuretic peptide might usefully be included in the pre-operative evaluation of patients with cardiac disease.

Ketamine, not propofol, attenuates cerebrovascular response to carbon dioxide in humans with isoflurane anesthesia

STUDY OBJECTIVES

To investigate the effects of ketamine and propofol on the cerebrovascular response to carbon dioxide (CO(2)) in humans during isoflurane anesthesia.

DESIGN

Randomized clinical investigation.

SETTINGS

University hospital of a medical school.

PATIENTS

30 ASA physical status I and II adult, elective surgical patients.

INTERVENTIONS AND MEASUREMENTS

With each patient given air/oxygen/isoflurane anesthesia, the flow velocity in the middle cerebral artery (Vmca) and pulsatility index were measured using the transcranial Doppler method under hypocapnic [arterial CO(2)tension (PaCO(2)) 28-32 mmHg], normocapnic (PaCO(2) 38-42 mmHg), and hypercapnic conditions (PaCO(2) 48-52 mmHg). PaCO(2) was altered by supplementing the inspired gas with CO(2) without changing the respiratory conditions. Patients were then randomly assigned to receive either ketamine 1 mg. kg(-1) or propofol (2 mg. kg(-1)followed by an infusion of 6-10 mg. kg(-1). hr(-1)) (n = 15 for each drug), and the measurements were repeated.

MAIN RESULTS

Ketamine reduced both absolute and relative cerebrovascular reactivity to CO(2) significantly [2.9 +/- 0.8 (control) vs. 2.6 +/- 1.0 (ketamine) cm. sec(-1). mmHg(-1): p < 0.05; and 3.5 +/- 0.7 (control) vs. 2.8 +/- 0.9 (ketamine) %. mmHg(-1): p < 0.01, respectively]. However, ketamine did not reduce Vmca during hypercapnic conditions (117 +/- 29 cm. sec(-1)) compared with controls (120 +/- 28 cm. sec(-1)). Although propofol decreased Vmca during all conditions, it did not cause any change in either absolute or relative CO(2) reactivity [2.5 +/- 0.8 (control) vs. 2.5 +/- 1.0 (propofol) cm. sec(-1). mmHg(-1), and 3.3 +/- 1.3 (control) vs. 4.1 +/- 1.0 (propofol) %. mmHg(-1), respectively].

CONCLUSIONS

In humans given isoflurane anesthesia, a) ketamine reduced cerebrovascular response to CO(2), but cerebral blood flow (CBF) during hypercapnic conditions was comparable with controls, and b) although propofol decreases CBF, it maintains the cerebrovascular response to CO(2).

The differential effects of stereoisomers of ropivacaine and bupivacaine on cerebral pial arterioles in dogs

We investigated whether the stereoisomers of ropivacaine and bupivacaine exert differential effects on the cerebral microcirculation. Pentobarbital-anesthetized dogs (n = 16) were prepared for measurement of cerebral pial vessel diameters by using a closed cranial window preparation. We administered three different concentrations (10(-7), 10(-5), and 10(-3) M) of each of three drug solutions [R(+), racemic, and S(-) forms of ropivacaine (n = 8) or bupivacaine (n = 8)] under the window in a randomized manner and measured cerebral pial arteriolar diameters. Various physiologic data were obtained before and after topical application of each test solution. All three forms of ropivacaine constricted cerebral pial arterioles, each in a concentration-dependent manner. The rank order for degree of vasoconstriction was S(-) ropivacaine > racemic ropivacaine > R(+) ropivacaine. In contrast, R(+) and racemic bupivacaine dilated, but S(-) bupivacaine constricted, cerebral pial arterioles, each in a concentration-dependent manner. We could find no difference in vascular reactivity to these drugs between large (> or = microm) and small (<100 microm) arterioles. Topical application of these drugs induced no changes in mean blood pressure or heart rate. The observed differences in the microvascular alterations induced by the stereoisomers of ropivacaine and bupivacaine suggest that the vasoactive effects of these drugs on cerebral arterioles could, at least in part, depend on their chirality.

IMPLICATIONS

The differential effects of the stereoisomers of ropivacaine and bupivacaine on cerebral pial vessels could, at least in part, depend on their chirality.

Lysophosphatidic acid enhances airway response to acetylcholine in guinea pigs

Inhalation of lysophosphatidic acid (LPA, 1-100 microg/ml) for 2 min enhanced the airway response induced by intravenous injection of ACh in guinea pigs. At 30 min after inhalation of LPA, the airway response to ACh was two fold higher than that before inhalation. This enhancement of airway response to ACh was partially inhibited by capsaicin desensitization or bilateral vagotomy. These results suggested that the enhancement of airway response to ACh induced by LPA may be due to the activation of capsaicin-sensitive fibers. It can be also contribute to bronchial asthma or other types of pulmonary disease such as cough variant asthma and atopic cough.

Physiological and pharmacological role of lysophosphatidic acid as modulator in mechanotransduction

The mechanotransduction mechanism is believed to play an important role in maintenance of cellular homeostasis in a wide variety of cell types. In particular, the mechanotransduction system in vascular endothelial cells may be an essential mechanism for local hemodynamic control. Elevations in intracellular free Ca2+ concentration ([Ca2]i) are an important signal in the initial step of mechanotransduction and mechanosensitive (MS) cation channels are thought to be a putative pathway; however, the molecular mechanisms remain unclear. We found that lysophosphatidic acid (LPA), a bioactive phospholipid, sensitizes the response of [Ca2+]i to mechanical stress in several cell types. Employing real-time confocal microscopy, local increases in [Ca2+]i in several regions within the cell during application of mechanical stress were clearly visualized in bovine lens epithelial and endothelial cells in the presence of LPA. The phenomenon was termed "Ca2+ spots". Pharmacological studies revealed that Ca2+ spots arise due to influx through MS channels. In this report, our data indicating the possible significance of LPA as an endogenous factor involved in regulation of mechanotransduction is reviewed. Furthermore, our findings suggest that the Ca2+ spot is a novel phenomenon occurring as an elementary Ca2+-influx event through MS channels directly coupled with the initial step in mechanotransduction.

A mechanism of Ca2+ release from Ca2+ stores coupling to the Na+/Ca2+ exchanger in cultured smooth muscle cells

We previously observed Ca2+ release from intracellular Ca2+ stores caused by reduction in extracellular Na+ concentration ([Na+]o). The purpose of this study was to determine whether lowering [Na+]o can elicit Ca2+ release from Ca2+ stores via the Na+/Ca2+ exchanger and to elucidate the mechanisms related to the Ca2+ release pathway in cultured longitudinal smooth muscle cells obtained from guinea pig ileum. Low [Na+]o-induced Ca2+ release was inhibited by antisense oligodeoxynucleotides for Na+/Ca2+ exchanger type 1 (anti-NCX). Application of anti-NCX to cells attenuated both the number of Ca2+ responding cells and the expression of the exchanger. Moreover, microinjection of heparin, a blocker of inositol 1,4,5-trisphosphate (IP3) receptors, into the cells inhibited low [Na+]o-induced Ca2+ release. These findings suggest that low [Na+]o-induced Ca2+ release occurs through an IP3-induced Ca2+ release mechanism due to changes in the Ca2+ flux regulated by the Na+/Ca2+ exchanger.

Effect of tributyltin chloride on the release of calcium ion from intracellular calcium stores in rat hepatocytes

The effects of tri-n-butyltin chloride (TBT), an environmental pollutant, on the release of Ca(2+) from intracellular stores were investigated in isolated rat hepatocytes. Isolated hepatocytes permeabilized with digitonin were suspended in solution, and the concentration of extracellular Ca(2+) was measured, using a fluorescent Ca(2+) dye, fura-2. In the solution containing permeabilized hepatocytes that had been preincubated with 4.0 microM TBT for 30 min, the extracellular Ca(2+) concentration was high, but the inositol 1,4,5-trisphosphate (InsP(3))-induced increase in Ca(2+) concentration was suppressed, suggesting that the extracellular release of Ca(2+) in response to TBT treatment was from intracellular stores. Images of the Ca(2+) concentration in the intracellular stores of primary cultured hepatocytes loaded with fura-2 were obtained after digitonin-permeabilization, using digitalized fluorescence microscopy. The permeabilized hepatocytes that had been preincubated with 4.0 microM TBT for 30 min had a very low fura-2 fluorescence ratio (340/380 nm), suggesting that stored Ca(2+) was released. When the hepatocytes were treated with 4.0 microM TBT after digitonin-permeabilization, the decrease in the fura-2 fluorescence ratio was very small. However, when the permeabilized hepatocytes were incubated with 4.0 microM TBT and 2.0 microM NADPH, the decrease was enhanced, raising the possibility that TBT might be metabolized to the active form(s), thus releasing Ca(2+) from intracellular stores. When the hepatocytes were preincubated with 0.1 microM TBT for 30 min and then were permeabilized, the fura-2 fluorescence ratio was almost the same as that in the control permeabilized hepatocytes. However, the InsP(3)-induced decrease in the fluorescence ratio was suppressed significantly in the permeabilized hepatocytes. These results suggest that TBT released Ca(2+) from the intracellular stores at high concentrations, and suppressed the InsP(3)-induced Ca(2+) release at non-toxic low concentrations. It is probable that the latter effect was responsible for the previously reported suppression of Ca(2+) response induced by hormonal stimulations (Kawanish et al., Toxicol Appl Pharmacol 1999;155:54-61).

The effects of topical and intravenous ketamine on cerebral arterioles in dogs receiving pentobarbital or isoflurane anesthesia

To evaluate the effects of ketamine on cerebral arterioles, we used a closed cranial window technique in mechanically ventilated, anesthetized dogs. Fourteen dogs were assigned to one of the following two basal-anesthesia groups: pentobarbital 2 mg. kg(-1). h(-1) or isoflurane 0.5 MAC (n = 7 each). We administered three different concentrations of ketamine (10(-7), 10(-5), and 10(-3) M) under the window and measured arteriolar diameters. For comparison, in another 14 dogs we examined the effect of systemic (IV) ketamine (1 mg/kg and 5 mg/kg) using the same two basal anesthetics. We measured diameters before and after ketamine administration, and we evaluated the effect of ketamine on CO(2) reactivity of the cerebral arterioles. Neither topical nor systemic ketamine dilated pial arterioles in either basal-anesthesia group. CO(2) reactivity of pial arterioles was reduced under systemic ketamine in both basal-anesthesia groups. The results indicate that although ketamine does not dilate pial arteriolar diameters when topically or IV administered, IV ketamine does attenuate hypercapnic vasodilation in dogs under basal pentobarbital or isoflurane anesthesia. These results provide some insight that ketamine is suitable for supplementary neurosurgical anesthesia.

Lysophosphatidic acid positively regulates the fluid flow-induced local Ca(2+) influx in bovine aortic endothelial cells

Using real-time confocal microscopy, we have demonstrated that lysophosphatidic acid (LPA), a bioactive phospholipid existing in plasma, positively regulates fluid flow-induced [Ca(2+)](i) response in fluo 4-loaded, cultured, bovine aortic endothelial cells. The initial increase in [Ca(2+)](i) was localized to a circular area with a diameter of <4 microm and spread concentrically, resulting in a mean global increase in [Ca(2+)](i). The local increase often occurred in a stepwise manner or repetitively during constant flow. The percentage of cells that responded and the averaged level of increase in [Ca(2+)](i) were dependent on both the concentration of LPA (0.1 to 10 micromol/L) and the flow rate (25 to 250 mm/s). The response was inhibited by removing extracellular Ca(2+) or by the application of Gd(3+), an inhibitor of mechanosensitive (MS) channels, but not by thapsigargin, an inhibitor of the endoplasmic reticular Ca(2+)-ATPASE: It was also inhibited by 8-bromo-cGMP, and the inhibition was completely reversed by KT5823, an inhibitor of protein kinase G (PKG). These results suggest that the [Ca(2+)](i) response arises from Ca(2+) influx through Gd(3+)-sensitive MS channels, which are negatively regulated by the activation of PKG. The spatiotemporal properties of the [Ca(2+)](i) response were completely different from those of a Ca(2+) wave induced by ATP, a Ca(2+)-mobilizing agonist. Therefore, we called the phenomenon Ca(2+) spots. We conclude that LPA positively regulates fluid flow-induced local and oscillatory [Ca(2+)](i) increase, ie, the Ca(2+) spots, in endothelial cells via the activation of elementary Ca(2+) influx through PKG-regulating MS channels. This indicates an important role for LPA as an endogenous factor in fluid flow-induced endothelial function.

Visualization of elementary mechanosensitive Ca2+-influx events, Ca2+ spots, in bovine lens epithelial cells

Local increases in the intracellular Ca2+ concentration ([Ca2+]i) in several regions within the bovine lens epithelial cell during application of mechanical stress were clearly visualized in the presence of lysophosphatidic acid (LPA), a bioactive lysophospholipid, using real-time confocal microscopy. We called the phenomenon 'Ca2+ spots'. Ca2+ spots started in a circular area with a radius of about 1.5 m. These Ca2+ spots spread concentrically, resulting in a mean global increase in [Ca2+]i. The local increase often occurred in a stepwise manner or repetitively at the same region. The spatiotemporal properties of the Ca2+ spots were completely different from those of the Ca2+ wave induced by ATP, a Ca2+-mobilizing agonist. Ca2+ spots were inhibited by decreasing the extracellular Ca2+ concentration or by the presence of Gd3+, an inhibitor of mechanosensitive (MS) channels, but not by thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ pump, suggesting that Ca2+ spots arise from Ca2+ influx through Gd3+-sensitive MS channels. On the assumption that, in lens epithelial cells, the open probability of the MS channel is 0.4, the membrane potential is 56 mV and the channel conductance is 50 pS, the estimated maximum flux of Ca2+ in a Ca2+ spot (0.4 x 10-17 to 4.7 x 10-17 mol x s(-1)) was comparable to currents of one or a few MS channels. On real-time three-dimensional confocal imaging analysis, which permitted simultaneous imaging of basal and apical planes of cells at 37.6 ms intervals, Ca2+ spots on the apical plane were more clearly visualized than those on the basal plane. From these results, we propose that the Ca2+ spot is an elementary Ca2+-influx event through MS channels directly coupled with the first step in mechanoreception In addition, our results strongly suggest that LPA functions as an endogenous factor affecting mechanotransduction systems.

Changes in Ca2+ signaling and contractile protein isoforms in smooth muscle cells from guinea pig ileum during culture

Single smooth muscle cells (SMCs) isolated from guinea pig ileum using collagenase and papain were cultured on laminin-coated dishes in MEM containing fetal calf serum. Temporal changes in intracellular calcium ion concentration in response to carbachol and to ATP were investigated using fluo-3/AM and fluorescence microscopy. It was observed that carbachol caused an increased intracellular calcium ion in freshly isolated single SMCs but a reduced or negative response of cultured SMCs before confluence. On the other hand, ATP was observed to cause an increase in the calcium ion content of SMCs throughout the culture. SDS-PAGE and Western blot analyses revealed changes in the expression of contractile proteins as follows. l-Caldesmon and non-muscle type myosin heavy chain (NMHC) (considered to be marker molecules for dedifferentiation in smooth muscle cells) and non-muscle type tropomyosin were not observed in freshly isolated single SMCs. l-Caldesmon and NMHC appeared in the cultured SMCs within 2 days and the tropomyosin isoform was observed 6 days following seeding. Simultaneously, smooth muscle type myosin heavy chain (SMHC) decreased strikingly and the 41 kDa tropomyosin monomer was lost. The content of alpha-actin decreased gradually to a minimum on day 6 when non-muscle type tropomyosin appeared, and the cells began to proliferate rapidly. These results suggest that the loss of contractility in cultured smooth muscle cells is more closely related to changes in contractile protein profiles than to receptor-mediated signal transduction and that in addition to NMHC and l-caldesmon, non-muscle type tropomyosin may be useful as a marker molecule for de-differentiation of smooth muscle cells.

[Silent myocardial ischemia and exercise-induced arrhythmia detected by the exercise test in the total health promotion plan (THP)]

We investigated the prevalence and characteristics of ischemic heart disease especially silent myocardial ischemia (SMI) and arrhythmia in need of careful observation in the exercise stress tests in the Total Health Promotion Plan (THP), which was conducted between 1994-96 for the purpose of measuring cardiopulmonary function. All workers (n = 4,918, 4,426 males) aged 18-60 yr old in an occupational field were studied. Exercise tests with an ergometer were performed by the LOPS protocol, in which the maximal workload was set up as a presumed 70-80% maximal oxygen intake, or STEP (original multistage protocol). ECG changes were evaluated with a CC5 lead. Two hundred and fifteen people refused the study because of a common cold, lumbago and so on. Of 4,703 subjects, 17 with abnormal rest ECG and 19 with probable anginal pain were excluded from the exercise tests. Of 4,667 who underwent the exercise test, 37 (0.79%) had ischemic ECG change, and 155 (3.32%) had striking arrhythmia. These 228 subjects then did a treadmill exercise test with Bruce protocol. Twenty-two (0.47% of 4,703) showed positive ECG change, 9 (0.19%) of 22 had abnormal findings on a 201Tl scan. 8 (0.17%) were diagnosed as SMI (Cohn I), in which the prevalence of hypertension, hyperlipidemia, diabetes mellitus, smoker and positive familial history of ischemic heart disease was greater than that of all subjects. In a 15-30 month follow up, none has developed cardiac accidents. Exercise-induced arrhythmia was detected in 11 (0.23%) subjects. Four were non-sustained ventricular tachycardia without any organic disease, 4 were ventricular arrhythmia based on cardiomyopathy detected by echocardiography, 2 were atrial fibrillation and another was WPW syndrome. It is therefore likely that the ergometer exercise test in THP was effective in preventing sudden death caused by ischemic heart disease or striking arrhythmia.

Spontaneous and flow-induced Ca2+ transients in retracted regions in endothelial cells

Changes in intracellular calcium concentration ([Ca2+]i) and focal adhesion sites of cultured bovine aortic endothelial cells (BAECs) were simultaneously visualized in real time. Local [Ca2+]i transients were observed at the rear edges of spontaneously migrating BAECs. Furthermore, the majority of starting regions of [Ca2+]i transients retracted continuously. Frequency of [Ca2+]i transients increased with the application of fluid flow. The majority of starting regions of flow-induced [Ca2+]i transients retracted following the occurrence of [Ca2+]i transients. In addition, retracted areas were distributed in the upstream regions of the cell. Application of GdCl3, a mechanosensitive cation channel blocker, resulted in a clear reduction of [Ca2+]i transients and rear retractions in cases of spontaneous and flow-induced BAEC migration. Flow-induced directional rear retractions were also inhibited. Consequently, we conclude that local [Ca2+]i transients play an important role in the migration of BAECs with respect to rear retraction. Furthermore, flow-induced [Ca2+]i transients regulate directional rear retraction under flow conditions.

[Molecular structure and function of mechanosensor mechanisms: an alternative prospect for the development of new drugs]

Mechanical stress to cells induces various physiological cellular responses and pathophysiological changes in many cell types. However, the molecular mechanisms remain unclear. Clarification of the mechanosensor mechanisms on the molecular level may provide an alternative approach for the development of new drugs. In the 73rd Annual Meeting of The Japanese Pharmacological Society, the latest studies performed by the following five departments were reported and discussed: 1) Expression of putative stretch sensitive nonselective cation channels of mammal, by M. Suzuki et al. (Department of Pharmacology, Jichi Medical School); 2) Mechanosensitive ATP release in aortic endothelial cells, by M. Oike et al. (Department of Pharmacology, Graduate School of Medical Science, Kyushu University); 3) Lysophosphatidic acid acts as an endogenous modulator on mechanotransduction, by H. Ohata et al. (Department of Pharmacology, School of Pharmaceutical Sciences, Showa University); 4) Stretch-induced myosin light chain phosphorylation without force development in canine basilar artery, by K. Obara et al. (Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka); and 5) Transcriptional regulation of smooth muscle phenotypic modulation, by R. Nagai (Department of Cardiovascular Medicine, University of Tokyo). This article reviews these reports.

Urocortin in the ventromedial hypothalamic nucleus acts as an inhibitor of feeding behavior in rats

Urocortin (UCN), a member of the corticotropin-releasing factor (CRF) family, inhibits food intake when it is injected intracerebroventricularly in rats. To explore the site of action of UCN in feeding behavior, we examined the effects of injection of UCN into various hypothalamic nuclei on food and water intake in 24-h fasted rats. Injection of UCN into the ventromedial hypothalamic nucleus (VMH) significantly inhibited food and water intake over 3 h without sedative effect, but no significant effect was observed following injection either into the lateral hypothalamic area, or the paraventricular nucleus of the hypothalamus. To further explore the physiological significance of endogenous UCN of the VMH in feeding behavior, the effect of immunoneutralization of hypothalamic UCN on food intake was examined. Injection of anti-rat UCN rabbit gamma-globulin into the bilateral VMH in freely fed rats significantly potentiated food and water intake compared with rats that received normal rabbit gamma-globulin. These results suggest that endogenous UCN in the VMH exert inhibitory control on ingestive behavior.

Optical recording study of granule cell activities in the hippocampal dentate gyrus of kainate-treated rats

In the epileptic hippocampus, newly sprouted mossy fibers are considered to form recurrent excitatory connections to granule cells in the dentate gyrus and thereby increase seizure susceptibility. To study the effects of mossy fiber sprouting on neural activity in individual lamellae of the dentate gyrus, we used high-speed optical recording to record signals from voltage-sensitive dye in hippocampal slices prepared from kainate-treated epileptic rats (KA rats). In 14 of 24 slices from KA rats, hilar stimulation evoked a large depolarization in almost the entire molecular layer in which granule cell apical dendrites are located. The signals were identified as postsynaptic responses because of their dependence on extracellular Ca(2+). The depolarization amplitude was largest in the inner molecular layer (the target area of sprouted mossy fibers) and declined with increasing distance from the granule cell layer. In the inner molecular layer, a good correlation was obtained between depolarization size and the density of mossy fiber terminals detected by Timm staining methods. Blockade of GABAergic inhibition by bicuculline enlarged the depolarization in granule cell dendrites. Our data indicate that mossy fiber sprouting results in a large and prolonged synaptic depolarization in an extensive dendritic area and that the enhanced GABAergic inhibition partly masks the synaptic depolarization. However, despite the large dendritic excitation induced by the sprouted mossy fibers, seizure-like activity of granule cells was never observed, even when GABAergic inhibition was blocked. Therefore, mossy fiber sprouting may not play a critical role in epileptogenesis.

Attenuated additional hypocapnic constriction, but not hypercapnic dilation, of spinal pial arterioles during spinal ropivacaine

Ropivacaine constricts spinal vessels. Because the CO2 response of spinal vessels is similar to that of cerebral vessels, we tested to see if hypocapnia would cause further spinal vasoconstriction during ropivacaine administration. In 12 pentobarbital-anesthetized dogs, spinal pial arteriolar diameter was measured using a closed spinal window preparation. Either ropivacaine solution (0.1%; n = 6) or artificial cerebrospinal fluid (n = 6) was infused continuously into the spinal window. After a period of hypocapnia (Paco2, 20-25 mm Hg) had been induced, inspired CO2 levels were adjusted to produce normocapnia (35-40 mm Hg) followed by hypercapnia (55-60 mm Hg). When the desired Paco2 was reached, measurements were made of the arteriolar diameter and physiological variables. During normocapnia, ropivacaine infusion produced a significant constriction of pial arterioles, whereas artificial cerebrospinal fluid caused no change. Hypocapnia induced a much smaller (almost nonexistent) additional vasoconstriction in the ropivacaine group than in the control group (P < 0.01). The final hypercapnic vasodilation was somewhat greater during ropivacaine (P < 0.05 versus control group). Topical ropivacaine induced no change in hemodynamic variables. We conclude that hypocapnia of the magnitude tested did not cause further constriction in spinal vessels during spinal ropivacaine.

IMPLICATIONS

During topical application of the local anesthetic ropivacaine in dogs, hypocapnia (Paco2, 20-25 mm Hg) induced almost no additional constriction of spinal arterioles, and the hypercapnic vasodilation was maintained. These data suggest that an additional constriction in spinal vessels is unlikely when hypocapnia occurs during spinal ropivacaine.

Prevention of reactive oxygen-induced endothelial cell injury by blocking its process

Endothelial cell (EC) injury induced by reactive oxygen species (ROS) was investigated and effects of Ca(2+) channel blockers, agents which elevate intracellular cAMP levels ([cAMP](i)), and protein kinase inhibitors on H(2)O(2)-induced EC injury were analyzed using human umbilical vein EC cultures. Exposure to H(2)O(2) increased intracellular Ca(2+) levels and decreased [cAMP](i). Ca(2+) channel blockers, [cAMP](i)-elevating agents, and protein kinase inhibitors significantly inhibited H(2)O(2)-induced EC injury. Data suggest that H(2)O(2)-induced EC injury is mediated by extracellular Ca(2+) influx, intracellular cAMP efflux, and intracellular signaling, each of which is blocked by Ca(2+) channel blockers, [cAMP](i)-elevating agents, or protein kinase inhibitors. It is suggested that ischemia/reperfusion injury induced by ROS may be prevented by Ca(2+) channel blockers, [cAMP](i)-elevating agents, and protein kinase inhibitors.

Hemodynamic responses induced by dopamine and dobutamine in anesthetized patients premedicated with clonidine

To test the hypothesis that the pharmacological effects of dopamine (DOA) and dobutamine (DOB) are altered when there is inhibition of the release of norepinephrine from nerve endings, we examined the hemodynamic responses to DOA and DOB in anesthetized patients premedicated with oral clonidine. Seventy adult patients were assigned to one of two groups (oral premedication with clonidine 5 microg/kg or no premedication). After the induction of general anesthesia, heart rate and systemic blood pressure (BP) were measured for 10 min after each of five IV infusions (3 and 5 microg x kg(-1) x min(-1) of DOA; 0.5, 1, and 3 microg x kg(-1) x min(-1) of DOB) in a randomized, double-blind manner. In patients given clonidine, the mean BP increases induced by DOA 5 microg x kg(-1) x min(-1) were significantly attenuated (P < 0.01), whereas the mean BP increases induced by DOB-0.5, 1, or 3 microg x kg(-l) x min(-1) were significantly enhanced (P < 0.01 or 0.05). The heart rate responses to DOA and DOB did not differ between patients with or without clonidine. Premedication with clonidine alters the effects on BP to both DOA and DOB. When small doses of DOA or DOB are used in clonidine-premedicated patients, differences of pharmacological profiles need to be considered for perioperative management.

IMPLICATIONS

Our randomized, double-blind study suggests that premedication with clonidine may enhance the effect on blood pressure response to a small dose of dobutamine (direct-acting) and attenuate that to a small dose of dopamine (mixed direct-and indirect-acting) in patients anesthetized with fentanyl and nitrous oxide.

Sensitizing effect of lysophosphatidic acid on Ca2+ response to hypotonic stress in cultured lens epithelial cells

The effects of lysophosphatidic acid (LPA), a bioactive phospholipid, on the response of the cytosolic free Ca2+ concentration ([Ca2+]i) to hypotonic stress were studied in cultured bovine lens epithelial cells, to test whether LPA affects cellular swelling-mediated increase in [Ca2+]i, which may relate to formation of sugar cataracts. Exposure of the cells to a 30% hypotonic stress caused only a slight increase in [Ca2+]i. Pretreatment with LPA (10 microM) significantly augmented the hypotonic stress-induced [Ca2+]i response, whereas addition of LPA to the cells did not affect [Ca2+]i. The hypotonic stress-induced increase in [Ca2+]i in the presence of LPA was inhibited by Gd3+, a blocker of mechanosensitive cation channels, but not by nicardipine, a L-type Ca2+ channel blocker, or thapsigargin, an inhibitor of endoplasmic reticulum-ATPase pump. These results show that LPA sensitizes the response to hypotonic stress via increase in Ca2+ influx through Gd3+-sensitive stretch-activated ion channels, and not via Ca2+ release from intracellular stores. On the other hand, LPA did not affect the [Ca2+]i response to ATP, a Ca2+ mobilizing agonist. Therefore, LPA sensitizes the hypotonic stress-induced [Ca2+]i response in lens epithelial cells, suggesting that LPA potentiates the development of cataracts induced by cellular swelling such as sugar cataract.

Effect of amino acids on the plasma concentration and urinary excretion of uric acid and uridine

To determine the effect of amino acids on the plasma level and urinary excretion of uric acid and uridine, 200 mL 12% amino acid solution, and 2 weeks later, 100 mL physiological saline solution containing glucagon (1.2 microg/kg weight), was infused into five healthy men. Both increased the urinary excretion of uric acid and the concentration of glucagon, insulin, and glucose in plasma and pyruvic acid in blood, whereas they decreased the concentration of uridine and inorganic phosphate in plasma. However, neither the amino acid infusion nor glucagon infusion affected the concentration of purine bases (hypoxanthine, xanthine, and uric acid), cyclic adenosine monophosphate (cAMP) in plasma, or lactic acid in blood or the urinary excretion of oxypurines (hypoxanthine and xanthine), uridine, or sodium. These results suggest that glucagon may have an important role in the amino acid-induced increase in urinary excretion of uric acid and decrease in plasma uridine.