Yoshitaka Oyamada

Anatomical and functional pathways of rhythmogenic inspiratory premotor information flow originating in the pre-Bötzinger complex in the rat medulla.

The pre-Bötzinger complex (preBötC) of the ventrolateral medulla is the kernel for inspiratory rhythm generation. However, it is not fully understood how inspiratory neural activity is generated in the preBötC and propagates to other medullary regions. We analyzed the detailed anatomical connectivity to and from the preBötC and functional aspects of the inspiratory information propagation from the preBötC on the transverse plane of the medulla oblongata. Tract-tracing with immunohistochemistry in young adult rats demonstrated that neurokinin-1 receptor- and somatostatin-immunoreactive neurons in the preBötC, which could be involved in respiratory rhythmogenesis, are embedded in the plexus of axons originating in the contralateral preBötC. By voltage-imaging in rhythmically active slices of neonatal rats, we analyzed origination and propagation of inspiratory neural activity as depolarizing wave dynamics on the entire transverse plane as well as within the preBötC. Novel combination of pharmacological blockade of glutamatergic transmission and mathematical subtraction of the video images under blockade from the control images enabled to extract glutamatergic signal propagations. By ultra-high-speed voltage-imaging we first demonstrated the inter-preBötC conduction process of inspiratory action potentials. Intra-preBötC imaging with high spatiotemporal resolution during a single spontaneous inspiratory cycle unveiled deterministic nonlinearities, i.e., chaos, in the population recruitment. Collectively, we comprehensively elucidated the anatomical pathways to and from the preBötC and dynamics of inspiratory neural information propagation: (1) From the preBötC in one side to the contralateral preBötC, which would synchronize the bilateral rhythmogenic kernels, (2) from the preBötC directly to the bilateral hypoglossal premotor and motor areas as well as to the nuclei tractus solitarius, and (3) from the hypoglossal premotor areas toward the hypoglossal motor nuclei. The coincidence of identified anatomical and functional connectivity between the preBötC and other regions in adult and neonatal rats, respectively, indicates that this fundamental connectivity is already well developed at the time of birth.

Solitary pulmonary metastasis from prostate sarcomatoid cancer

BackgroundPulmonary metastasis from prostate cancer is considered to be a late event, and patients can be treated with chemotherapy or hormonal manipulation. However, there has been only a few reports on surgical resection for pulmonary metastasis from prostate cancer.Case PresentationWe present a surgical case of solitary pulmonary metastasis from prostate cancer. A 73-year-old man underwent pelvic evisceration for prostate cancer. Histopathological examination revealed a poorly differentiated adenocarcinoma with a sarcomatoid carcinoma component. During postoperative follow-up, chest computed tomography showed a nodular shadow in the lung, and thoracoscopic wedge resection of the lung was performed. Histopathological examination revealed a histological appearance similar to that of the prostate sarcomatoid carcinoma. This is the first reported case of solitary pulmonary metastasis from prostate sarcomatoid cancer.ConclusionIsolated pulmonary metastasis from prostate sarcomatoid cancer is extremely rare, but surgery could be the treatment of choice.

Effect of Antioxidants on Hyperoxia-Induced ICAM-1 Expression in Human Endothelial Cells

The regulating mechanism of hyperoxia-induced ICAM-1 expression has not been elucidated. We studied the effect of antioxidants, including superoxide dismutase (SOD), catalase and N-acetylcysteine (NAC), on hyperoxia-induced ICAM-1 expression in human pulmonary artery endothelial cells (HPAEC) and human umbilical vein endothelial cells (HUVEC). Cells were cultured to confluence and exposed to either hyperoxic or normoxic gas with or without various kinds of antioxidants. The levels of ICAM-1 expression in the endothelial cells and the concentrations of reduced (GSH) and oxidized glutathione (GSSG) in the media were examined by flow cytometry and by spectrophotometry, respectively. After 48-hour exposure to hyperoxia, ICAM-1 expression was increased (HPAEC; 161 +/- 21% and HUVEC; 163 +/- 16%) and total glutathione concentration in the media was decreased as compared with normoxia. SOD did not change the GSH and GSSG concentrations in the media. Catalase dose-dependently decreased the supernatant GSSG concentration in both HPAEC and HUVEC, while the GSH concentration was nearly constant. NAC dose-dependently increased the supernatant GSH concentrations in both HPAEC and HUVEC. There was no difference in the supernatant GSSG concentrations between the NAC-treated HPAEC and HUVEC. There was no difference in ICAM-1 expression in either HPAEC or HUVEC with SOD treatment. ICAM-1 expressions in 100 U/ml (236 +/- 20%) and 1,000 U/ml (315 +/- 36%) of catalase were increased in HPAEC, and that in 1,000 U/ml (440 +/- 209%) of catalase was increased in HUVEC. Five and 10 U/ml of NAC decreased ICAM-1 expression in HPAEC (141 +/- 26% and 113 +/- 11%) and HUVEC (119 +/- 23% and 106 +/- 7%), respectively. These results suggest that extracellular glutathione may play a role in regulating hyperoxia-induced ICAM-1 expression in HPAEC and HUVEC.

Optical mapping of pontine chemosensitive regions of neonatal rat.

We analyzed the neuronal response to hypercapnic acidosis, using an optical recording technique with a fluorescent voltage-sensitive dye (di-4-ANEPPS), in pontine slice preparations of neonatal rats, containing the locus coeruleus (LC), which has been electrophysiologically demonstrated to be chemosensitive. The dye-stained preparation was continuously superfused with artificial cerebrospinal fluid. Epifluorescence of the slice was detected using a high-sensitivity optical recording system. Changes in the intensity of fluorescence were serially analyzed while switching artificial cerebrospinal fluid from control to hypercapnic acidosis, or vice versa. The optical recording method revealed that the LC, as reported in previous studies, reversibly showed a depolarizing response to hypercapnic acidosis in 56% of the examined preparations. The A5 area (56%) also exhibited a reversible, depolarizing response to hypercapnic acidosis. The response was preserved under conditions in which chemical synaptic transmission was blocked by low Ca(2+)-high Mg(2+) solution. These results suggest that the optical recording method is applicable to identification of potentially chemosensitive areas, which deserve further electrophysiological analysis, and that the A5 area could be chemosensitive.

Role of Kir2.2 in hypercapnic ventilatory response during postnatal development of mouse.

In order to determine the role of Kir2.2 in the hypercapnic ventilatory response (HCVR) during postnatal development, we measured the response of the Kir2.2-knockout (Kir2.2-/-) mouse in an unanesthetized unrestrained state by means of pressure plethysmography on postnatal days 9-10, 14-15 and 18, and compared the response with that in its wild counterpart, the FVB mouse. We also examined developmental changes in m-RNA expression of Kir2.2 in the brainstem of the FVB mouse using quantitative real-time PCR assay. Kir2.2-/- exhibited a smaller increase in tidal volume and minute ventilation volume than the FVB mouse in response to hypercapnic challenge on days 14-15. Meanwhile, the FVB mouse showed a transient increase in m-RNA expression of Kir2.2 in the brainstem on days 14-15. These findings suggest that Kir2.2 in the brainstem plays a transient role in HCVR, possibly through central ventilatory chemosensitivity, during postnatal development.

Effects of inactivation and stimulation of locus coeruleus on respiratory activity of neonatal rat

We examined the effects of pharmacological inactivation and electrical stimulation of the locus coeruleus (LC) on the respiratory rate (RR) in isolated brainstem-spinal cord preparations of the neonatal rat. The brainstem and spinal cord were isolated en bloc from neonatal (days 1-4) Sprague-Dawley rats and superfused with artificial cerebrospinal fluid (ACSF) equilibrated with a gas mixture containing 2% CO(2) (pH 7.8). Pharmacological inactivation of the bilateral LC by means of microinjection of tetrodotoxin or noradrenaline elicited a significant decrease in RR in preparations obtained from rats aged 3-4 days, but not in preparations of rats aged 1-2 days. Stimulation of the bilateral LC with a train of electrical pulses (25-50 microA, 30 ms, 0.5 Hz, 3-4 min) caused a marginal but significant increase in RR on days 3-4, but not on days 1-2. These results indicate that the LC exerts an excitatory effect on the medullary respiratory rhythm generator in an age-dependent manner.

Morphological analysis of developmental changes in pontine noradrenergic neuronal groups in the neonatal rat

We examined the morphological changes in two pontine noradrenergic neuronal groups, area A5 and the locus coeruleus (LC), in neonatal Sprague-Dawley rats between postnatal day 1 and day 10. The volume of the unilateral LC exhibited no significant developmental change. Meanwhile, the number of A5 neurones counted unilaterally was significantly larger on days 1-2 than on days 3-4 or day 10.

Age-dependent chemosensitive pontine inhibition of medullary respiratory rhythm generation in the isolated brainstem of the neonatal rat

Age-dependence and chemosensitivity of the pontine inhibitory effect on medullary respiratory rhythm generation were examined in the isolated brainstem-spinal cord of the neonatal rat. In early preparations (days 1-2), the increase in RR (Delta RR) induced by the pons resection was larger in 8% CO(2) (pH 7.2) than in 2% CO(2) (pH 7.8). That difference was not found in late preparations (days 3-4). Under a given pH, the Delta RR was larger in early preparations than in late preparations.

Age-dependent involvement of ATP-sensitive potassium channel Kir6.2 in hypoxic ventilatory depression of mouse

In order to examine whether ATP-sensitive potassium channel Kir6.2 is involved in hypoxic ventilatory responses, especially in hypoxic ventilatory depression (HVD), and whether the involvement shows age-dependence, we measured the hypoxic ventilatory response in the Kir6.2-knockout mouse (Kir6.2-/-) in an unanesthetized unrestrained state by means of pressure plethysmography in the 2nd and 4th postnatal weeks, and compared the response with that of its wild type counterpart, the C57BL6/J mouse. In the 4th postnatal week, but not in the 2nd week, the Kir6.2-/- exhibited a larger and longer initial augmentation and a weaker subsequent depression of respiratory frequency and ventilation in response to hypoxia (FIO(2)=0.12 in N(2)). These findings suggest that Kir6.2 is involved in HVD of the mouse at a certain point during the postnatal development.

Ventilation-perfusion inequality and diffusion impairment in acutely injured lungs

To assess the significant role of diffusion impairment and its unequal distribution in acutely injured lungs with alveolar flooding, oleic acid was intravenously injected into twenty-five mongrel dogs. The animals were divided into two groups, A and B. 0.1% CO in air was delivered, as an inspired gas, to the animals of group A. Simultaneously, saline containing a trace amount of six foreign inert gases was infused through a peripheral vein. While allowing the animals in group B to breathe air, saline containing ethylene, acetylene and freon 22 was infused. After injection of oleic acid, group A revealed increase in intrapulmonary shunt accompanied by a marked broadening of ventilation-perfusion (VA/Q) and diffusing capacity-perfusion (G/Q) distributions. A considerable amount of total cardiac output was received by the lung areas with low G/Q ratios where significant diffusion limitation was predicted to occur. Group B showed that excretion of freon 22 (gas with lower diffusivity) in injured lungs was considerably distorted as compared to those of ethylene and acetylene (gases with higher diffusivities), again ascertaining the importance of diffusion limitation in lungs with exudate in alveolar regions.