Excitatory mechanism of deflationary slowly adapting pulmonary stretch receptors in the rat lung.

The excitatory responses of deflationary slowly adapting pulmonary stretch receptor (SAR) activity to lung deflation ranging from approximately -15 to -25 cm of H(2)O for approximately 5 s were examined before and after administration of flecainide, a Na(+) channel blocker, and K(+) channel blockers, such as 4-aminopyridine (4-AP) and tetraethylammonium (TEA). The experiments were performed in anesthetized, artificially ventilated rats after unilateral vagotomy. The deflationary SARs increased their activity during lung deflation and its effect became more pronounced by increasing the degree of negative pressure. During lung deflation the average values for the deflationary SAR adaptation index (AI) were below 40%. Intravenous administration of veratridine (50 microg/kg), an Na(+) channel opener, stimulated deflationary SAR activity: one maintained excitatory activity mainly during deflation and the other receptors showed a tonic discharge during both deflation and inflation. Despite the difference in deflationary SAR firing patterns after veratridine administration, flecainide treatment (6.0 mg/kg) blocked veratridine-induced deflationary SAR stimulation and also caused strong inhibition of the excitatory responses of deflationary SARs to lung deflation. Under these conditions, the average values for deflationary SAR AI were over 90%. The responses of deflationary SARs and deflationary SAR AI to lung deflation were not significantly altered by pretreatment with either 4-AP (0.7 and 2.0 mg/kg) or TEA (2.0 and 6.0 mg/kg). These results suggest that the excitatory effect of lung deflation on deflationary SAR activity is mediated by the activation of flecainide-sensitive Na(+) channels on the nerve terminals of deflationary SARs.     

N10 potential as an antidromic motor evoked potential in a median nerve short-latency somatosensory evoked potential study.

When stimulating the mixed nerve to record evoked potential, both sensory and motor fibers are activated before entering the spinal cord. The N10 potential has been described as an antidromic motor evoked potential based on results obtained by recording at the anterior midneck. In the present study, we examined the changes in latencies of Erb's potential, N10, and N13 by stimulating the median nerve distally at the wrist and proximally at the elbow. The conduction velocity of N10 calculated by the difference between N10 latencies at the two stimulation points was consistent with motor conduction velocity, although N13 conduction velocity estimated by the same method reflected a sensory conduction velocity. A positive relation was also observed between the indirect latency from the stimulation point to the anterior root as calculated using the equation (F - M - 1) / 2 (ms) and the direct latency to the negative peak of the N10 potential. Our data support the notion that N10 represents antidromic motor potential originating in the spinal entry zone of the anterior root.     

Familial spontaneous pneumothorax in three generations and its HLA

We experienced a case of familial spontaneous pneumothorax in three generations. Six of 13 family members had episodes of spontaneous pneumothorax. It is well established that there are some diseases associated with human leukocyte antigen (HLA). We performed HLA phenotyping for HLA of A, B and C. In our study, we detected the HLA haplotype A2, B61 in three of 4 who had episodes of spontaneous pneumothorax. The HLA haplotype A2, B70 were also detected in three of 4 who had episodes. This suggests that familial spontaneous pneumothorax might have hereditary factors.     

Leukocyte-Endothelium Interaction in the Rat Mesenteric Microcirculation during Halothane or Sevoflurane Anesthesia

Background: The effects of inhalational anesthetics on the microcirculation, including leukocyte dynamics, remain to be clarified. The authors investigated halothane and sevoflurane anesthesia to determine if these agents evoked leukocyte adhesion through endothelial cell-dependent mechanisms involving such adhesion molecules.

Methods: Rats were anesthetized with halothane or sevoflurane in 100% oxygen and the lungs were mechanically ventilated. Leukocyte behavior in mesenteric venules was recorded through intravital video microscopy under monitoring microvascular hemodynamics. To examine the mechanisms for leukocyte rolling and adhesion, these studies were repeated after animals were pretreated with a monoclonal antibody against P-selectin (MAb PB1.3) or against intracellular adhesion molecule-1 (ICAM-1; MAb 1A29): P-selectin required for rolling of circulating leukocytes and ICAM-1 for firm adhesive interactions with leukocyte integrins.

Results: Under baseline anesthetic conditions (1 minimum alveolar concentration [MAC]), venular wall shear rates, an index of the disperse force on marginating leukocytes, in the sevoflurane-treated rats were about two times higher than those with halothane. At 2 MAC, halothane caused a marked arteriolar constriction and decreasing shear rates concurrent with an increasing density of venular leukocyte adhesion. Sevoflurane at 2 MAC induced leukocyte rolling and adhesion, which were attenuated by PB1.3 and 1A29, without alterations in the wall shear rates. Halothane-induced leukocyte adhesion was not prevented by PB1.3 but it was by 1A29.     

Effects of dietary restriction on age-related immune dysfunction in the senescence accelerated mouse (SAM)

The effects of age and dietary restriction on immune response were investigated using an animal model of accelerated senescence (senescence accelerated mouse, SAM). The experimental groups consisted of control (ad libitum fed) and restricted groups (fed 60% of energy intake of the controls). Spleen weight and total number of splenic cells were significantly lower in the food-restricted group at 8 mo of age. Percentages of T (Thy-1.1+) and B (surface Ig+) cells in the splenic cells were not significantly different between the two groups. The number of direct hemolytic plaque-forming cells per 10(6) spleen cells 4 d following immunization with sheep red blood cells and dinitrophenyl-Ficoll was significantly greater in the 8-mo-old mice in the food-restricted group than in the control group. In the latter group, antibody responses Progressively decreased with age. Mitogen responses to concanavalin A and lipopolysaccharide were maintained in the food-restricted group but were depressed in the control group at 8 mo. In addition, though autoantibody to single-stranded DNA increased in the control group with advancing age, there was a steady decrease in the food-restricted group until 8 mo. Serum immunoglobulin (IgA and IgM) concentrations were significantly lower in the food-restricted group than in controls at 8 mo of age. Therefore, our results suggest that when senescence accelerated mice are subjected to food restriction, there may be a modulatory effect on the immune dysfunction associated with advancing age.     

CT导引下肝肾囊肿抽吸硬化治疗

目的：总结CT导引下肝肾囊肿穿刺抽吸硬化治疗的疗效和操作经验。材料和方法：肝囊肿11，肾囊肿15例，多囊肾1例，囊肿大小为3．5－12cm，均用15cm长20GGreene针穿刺治疗，抽出囊液量为21－550ml，囊液抽净后注入99．7％的无水酒精。结果：治疗后症状均有明显好转或消失，本组随访肝囊肿7例、肾囊肿11例，疗效指数I级1例（多囊肾），Ⅱ级肝肾囊肿各2例，Ⅲ级肝囊肿5例肾囊肿8例。穿刺操作顺利，无严重并发症发生。结论：CT导引下肝肾囊肿抽吸硬化治疗操作简便、创伤小、疗效高可作为替代外科手术的有效的治疗方法，多囊肾的单纯抽吸治疗可明显减轻症状，改善肾功能，是一种较好的治疗手段。     

Effect of external high-frequency oscillation on severe cardiogenic pulmonary edema

Effective gas exchange can be maintained in animals without endotracheal intubation using external high-frequency oscillation (EHFO). The aim of this study was to evaluate the effect of EHFO in patients with respiratory failure due to severe cardiogenic pulmonary edema. Seven patients were ventilated with EHFO for 2h at 60 oscillations·min⁻¹, with a cuiras pressure of 36 cmH₂O (−26 to +10) and an inspiratory to expiratory ratio of 1:1, with EHFO. Blood gas values and hemodynamic parameters were measured. Significant increases were noted in cardiac index (2.3±0.5 to 2.5±0.5 l·m⁻²;P<0.05), stroke volume index (24±7 to 28±8 ml·m⁻²;P<0.05), and arterial O₂ pressure (Pao₂) (70±4 to 95±23 mmHg;P<0.01) without a change in pulmonary artery wedge pressure at 1 h after EHFO. The respiratory rate decreased from 28±3 to 22 ±3 breaths·min⁻¹ at 5 min after the termination of EHFO (P <0.01). Arterial CO₂ pressure (Paco₂) did not, however, decrease. Increased stroke volume without a change in pulmonary artery wedge pressure (preload) suggests either improved inotropic function of the left ventricle or reduced left ventricular afterload with EHFO. The use of EHFO may be effective not only for gas exchange but also for left ventricular function in patients with severe cardiogenic pulmonary edema.     

Dynamic gadolinium-enhanced echo-planar MR imaging of the liver: Effect of pulse sequence and dose on enhancement

To develop guidelines for clinical magnetic resonance imaging of the liver, the authors undertook an animal study to investigate the effect of dose and pulse sequence on liver signal intensity in gadopentetate dimeglumine—enhanced echo-planar imaging. Serial imaging of the liver was performed in anesthetized rats after intravenous administration of five different doses (0.01, 0.05, 0.1, 0.2, and 0.5 mmol/kg) of contrast agent, with six different pulse sequences. The results show that gadopentetate dimeglumine—enhanced echo-planar images obtained during the perfusion phase can yield either positive (due to increased T1 relaxation rates) or negative (due to susceptibility-induced increased T2 relaxation rates) liver enhancement depending on choice of pulse sequence and dose. At the current clinically recommended dose of 0.1 mmol/kg, maximal liver signal enhancement was seen with a T1-weighted inversion-recovery sequence, while maximal liver signal diminution was seen with a T2*-weighted gradient-echo sequence. The authors conclude that gadopentetate dimeglumine—enhanced echo-planar imaging can provide T1, T2, and T2* contrast that may be exploited for both lesion detection and lesion characterization.