Ayumu Yokochi

Vasodilatory Effects of Ketamine on Pulmonary Arteries in Rats with Chronic Hypoxic Pulmoanry Hypertension

To study the effects of ketamine on structurally remodeled pulmonary arteries from rats with hypoxic pulmonary hypertension (PH) and the effects of ketamine on endothelium-dependent and -independent relaxation, rats were exposed to hypobaric hypoxia (air at 380 mm Hg for 10 days). We measured the responses to ketamine, acetylcholine, and sodium nitroprusside (SNP) in prostaglandin F2 alpha-precontracted ring segments from a left extrapulmonary artery (EPA, 1.4-1.6 mm in outside diameter [OD]) and an intrapulmonary artery (IPA, 0.7-1.1 mm OD) obtained from control and PH rats. The effects of acetylcholine and SNP were decreased in EPA and IPA rings from PH rats compared with control rings. In contrast, ketamine produced a greater relaxation response in rings from PH rats at 3 times 10-5 -3 times 10-4 in the EPA and at 10-4 -10-3 M in the IPA compared to control rings. A nitric oxide synthase inhibitor, nitro-L-arginine (10-4 M), inhibited the relaxation in response to acetylcholine in both control and PH rats. Pretreatment with ketamine (10-4 M) had no effect on the relaxation response to any concentration of acetylcholine or SNP in either control or PH rats. We conclude that nitric-oxide-mediated relaxation, but not ketamine-induced relaxation, was impaired in structurally remodeled hypertensive pulmonary arteries. Ketamine had no effects on nitric oxide-mediated relaxation in either normal or PH rats. (Anesth Analg 1995;80:786-92)

Persistent Release of IL-1s from Skin Is Associated with Systemic Cardio-Vascular Disease, Emaciation and Systemic Amyloidosis: The Potential of Anti-IL-1 Therapy for Systemic Inflammatory Diseases

The skin is an immune organ that contains innate and acquired immune systems and thus is able to respond to exogenous stimuli producing large amount of proinflammatory cytokines including IL-1 and IL-1 family members. The role of the epidermal IL-1 is not limited to initiation of local inflammatory responses, but also to induction of systemic inflammation. However, association of persistent release of IL-1 family members from severe skin inflammatory diseases such as psoriasis, epidermolysis bullosa, atopic dermatitis, blistering diseases and desmoglein-1 deficiency syndrome with diseases in systemic organs have not been so far assessed. Here, we showed the occurrence of severe systemic cardiovascular diseases and metabolic abnormalities including aberrant vascular wall remodeling with aortic stenosis, cardiomegaly, impaired limb and tail circulation, fatty tissue loss and systemic amyloid deposition in multiple organs with liver and kidney dysfunction in mouse models with severe dermatitis caused by persistent release of IL-1s from the skin. These morbid conditions were ameliorated by simultaneous administration of anti-IL-1α and IL-1β antibodies. These findings may explain the morbid association of arteriosclerosis, heart involvement, amyloidosis and cachexia in severe systemic skin diseases and systemic autoinflammatory diseases, and support the value of anti-IL-1 therapy for systemic inflammatory diseases.

Anatomy and Clinical Implications of Ultrasound-Guided Selective Femoral Nerve Block

In this study we evaluated the anatomic basis and clinical findings of ultrasound-guided femoral nerve block performed close to the distal apex of the femoral triangle. Cadaver studies were conducted in 9 thighs of fresh bodies within 24 hours postmortem. In all cases, during injection of 10 mL of blue dye, the skin proximal to the injection site was compressed to prevent the proximal flow. In the first thigh, from the area just distal to the inguinal ligament, an epidural catheter was advanced distally beneath the fascia iliaca over the femoral nerve. In the remaining cases, 10 mL of blue dye was injected into the femoral nerve at the level of the proximal adductor canal and dye spread was evaluated after local dissection. The clinical study was conducted in 20 patients with severe varus deformities. Ten milliliters of 0.75% ropivacaine was injected as in the cadaveric series. The femoral nerve was successfully dyed in all cases of the cadaver study, whereas the muscular branch to the sartorius muscle and quadriceps muscle, with the exception of the vastus medialis muscle, evaded dyeing. All 20 patients with varus knee deformities reported analgesia; none of them experienced motor block. We conclude that local anesthetic injection at the site where the superficial femoral artery has passed beneath the medial border of the sartorius muscle (8 to 12 cm distal to the inguinal crease), combined with efforts taken to prevent proximal flow may anesthetize the sensation of the anterior-to medial aspect of the knee and motor branch of the vastus medialis muscle, without blocking the sartorius or quadriceps muscles.

Correlation of inhaled nitric-oxide induced reduction of pulmonary artery pressure and vascular changes

The purpose of the present study was to determine the relationship between hypertensive pulmonary vascular remodelling and the changes in mean pulmonary artery pressure (mPAP) during low-dose nitric oxide (NO) inhalation. Rats were exposed to chronic hypobaric hypoxia (air at 50.5 kPa (380 mmHg), 10% oxygen, for 5–29 days) to induce chronic pulmonary hypertension (PH) with pulmonary vascular structural changes. After the chronic hypoxic exposure, the rats had an indwelling pulmonary artery catheter inserted and changes in mPAP with NO were correlated to morphometrical analysis of pulmonary vascular changes. All concentrations of inhaled NO (0.1–2.0 parts per million) reduced mPAP with a similar per cent reduction from baseline mPAP in PH rats, while no changes were observed in control rats. During NO inhalation in PH rats, the absolute value of the decrease in mPAP, but not per cent reduction in mPAP, significantly correlated with baseline mPAP, the percentage of muscularised arteries at the alveolar wall level and at the alveolar duct level, and the per cent medial wall thickness of muscularised arteries. In the chronic hypoxic pulmonary hypertension model, the severity of pulmonary vascular remodelling did not alter the reactivity of the pulmonary arteries to nitric oxide and might, in part, determine the magnitude of nitric-oxide induced absolute reduction in mean pulmonary artery pressure.

Effects of the endothelin ETA receptor antagonist, TA-0201, on pulmonary arteries isolated from hypoxic rats

To investigate the roles of endothelin-1 in the pathogenesis of hypoxic pulmonary hypertension, we studied the effects of a selective endothelin ET(A) receptor antagonist, TA-0201 (N-(6-(2-(5-Bromopyrimidin-2-yloxy) ethoxy)-5-(4-methylphenyl) pyrimidin-4-yl)-4-(2-hydroxy-1,1-dimethylethyl) benzensulfonamide sodium salt sesquihydrate), on helical strips of pulmonary arteries isolated from hypoxia-induced pulmonary hypertensive rats as compared with those of normoxic rats. Endothelin-1-induced maximum contractions were significantly inhibited by exposure to hypoxia in the pulmonary arterial strips, but not in the mesenteric arterial strips. The hypoxia also induced right ventricular hypertrophy in rats. Addition of TA-0201 to the bath inhibited the endothelin-1-induced contraction of pulmonary arterial strips isolated from hypoxic rats more effectively than in those of normoxic rats. Oral administration of TA-0201 to hypoxic rats inhibited the hypoxia-induced right ventricular hypertrophy, and decreased the maximum contractile response to endothelin-1 in pulmonary arterial strips isolated from these rats. Those inhibitory effects induced by the oral administration of TA-0201 were not observed in the pulmonary arteries from normoxic rats or in the mesenteric arteries from both hypoxic and normoxic rats. These results suggest that endothelin-1 has important pathophysiological roles in hypoxia-induced pulmonary hypertension, and that TA-0201 may inhibit the endothelin-l-induced contraction through a change in the function of endothelin ET(A) receptor as well as competitive inhibition for endothelin ET(A) receptor.

Efficacy of prolonged large-dose dantrolene for severe neuroleptic malignant syndrome

N euroleptic malignant syndrome (NMS) is associated with major tranquilizer and antipsychotic administration and is characterized by hyperthermia, disorders of consciousness, and muscle rigidity (l-3). The use of dantrolene may be an effective pharmacologic intervention to reduce muscle rigidity in NMS and in malignant hyperthermia (MH), but a reliable regimen of administration has not been established. We describe a patient with severe NMS who was successfully treated by continuous infusion of dantrolene at a large dose of 6 mg * kg-r * d-l in combination with hemodialysis and continuous hemodiafiltration (CHDF). We also measured plasma dantrolene concentrations in this patient.

Thrombomodulin protects against lung damage created by high level of oxygen with large tidal volume mechanical ventilation in rats

BackgroundVentilator-induced lung injury (VILI) is associated with inflammatory responses in the lung. Thrombomodulin (TM), a component of the coagulation system, has anticoagulant and anti-inflammatory effects. We hypothesized that the administration of recombinant human soluble TM (rhsTM) would block the development of lung injury.MethodsLung injury was induced by high tidal volume ventilation for 2 h with 100% oxygen in rats. Rats were ventilated with a tidal volume of 35 ml/kg with pretreatment via a subcutaneous injection of 3 mg/kg rhsTM (HV (high tidal volume)/TM) or saline (HV/SAL) 12 h before mechanical ventilation. Rats ventilated with a tidal volume of 6 ml/kg under 100% oxygen with rhsTM (LV (low tidal volume)/TM) or saline (LV/SAL) were used as controls. Lung protein permeability was determined by Evans blue dye (EBD) extravasation.ResultsLung injury was successfully induced in the HV/SAL group compared with the LV/SAL group, as shown by the significant decrease in arterial oxygen pressure (PaO2), increased protein permeability, and increase in mean pulmonary artery pressure (mPAP) and ratio of mean pulmonary artery pressure to mean artery pressure (Pp/Ps). Treatment of rats with lung injury with rhsTM (HV/TM) significantly attenuated the decrease in PaO2 and the increase in both mPAP and Pp/Ps, which was associated with a decrease in the lung protein permeability. Lung tissue mRNA expressions of interleukin (IL)-1α, IL-1β, IL-6, tumor necrosis factor-α, and macrophage inflammatory protein (MIP)-2 were significantly higher in HV than in LV rats. Rats with VILI treated with rhsTM (HV/TM) had significantly lower mRNA expressions of IL-1α, IL-1β, IL-6, and MIP-2 than those expressions in HV/SAL rats.ConclusionsAdministration of rhsTM may prevent the development of lung injury created by high level of oxygen with large tidal volume mechanical ventilation, which has concomitant decrease in proinflammatory cytokine and chemokine expression in the lung.

A Novel Inhibitor of Inducible Nitric Oxide Synthase, ONO-1714, Does Not Ameliorate Hypoxia-induced Pulmonary Hypertension in Rats

A recent study showed that long-term administration of the inducible nitric oxide synthase (iNOS) inhibitor L-NIL reduced the development of pulmonary hypertension. The purpose of the present study was to identify the effect of an another iNOS inhibitor, ONO-1714, on the development of pulmonary hypertensive vascular changes in chronic hypoxic pulmonary hypertension in rats. ONO-1714 was administered to rats exposed to hypobaric hypoxia (air at 380 mmHg) for 10 days. Muscularization of normally nonmuscular peripheral arteries and medial hypertrophy of normally muscular arteries were assessed by light microscopy. iNOS mRNA and protein levels of the lung were assessed in normal and hypoxic rats. Chronic hypoxia induced pulmonary hypertension, right ventricular hypertrophy, and hypertensive pulmonary vascular changes. Although an acute single injection of ONO-1714 induced a significant increase in mean pulmonary artery pressure in chronic hypoxic pulmonary hypertensive rats, the increase was slight and transient. There were no significant differences among rats with and without long-term administration of ONO-1714 in pulmonary artery pressure, right ventricular hypertrophy, medial wall thickness of muscular arteries, and the percentage of muscularized arteries at the alveolar wall and duct levels. Although there was a significantly increased expression of iNOS as assessed with the reverse-transcription polymerase chain reaction in rats that were exposed to 10 days of hypobaric hypoxia, we could not detect a significant level of iNOS protein by Western blotting. ONO-1714 does not have a therapeutic role in preventing the development of chronic hypoxic pulmonary hypertension

Nitric Oxide in Pathophysiology and Treatment of Pulmonary Hypertension

All conditions causing pulmonary hypertension (PH) are characterized by three major changes in the pulmonary vasculature: vasoconstriction, vascular remodeling, and thrombosis [1,2,3]. Vascular remodeling includes muscularization of normally non-muscular peripheral pulmo‐ nary arteries, increase in medial wall thickness of muscular arteries, and increase in vascular connective tissue such as collagen and elastin [1,2,3]. Imbalance of vasoconstrictive and vasodilatory mediators might explain the increased vascular tone [1,2,3]. Endothelial cells synthesize and release prostacylin and nitric oxide for vasodilation as well as endothelin and thromboxane for vasoconstriction. Approved treatments for pulmonary arterial hypertension (PAH) include prostacyclins, endothelin receptor blockers, and phosphodiesterase-5 inhibitors as well as inhaled NO for persistent pulmonary hypertension of the neonate (PPHN) [2].