A natriuresis receptor at the carotid bifurcation specifically activated by oxytocin

Summary Rats anaesthetised with Inactin, body temp. maintained at 37°C, were infused with mannitol-saline until both urine flow rate and conductivity reached a balanced state. In separate experiments under analogous conditions cardiac output was measured by dye dilution and organ flow rates by⁸⁶Rb distribution. Doses of oxytocin of 3 ng or less, injected at or just below the carotid bifurcation, caused a highly significant natriuresis with increased tubular rejection, but no measureable haemodynamic changes. The same oxytocin dose given into the internal or external carotid artery above the bifurcation caused neither haemodynamic changes nor natriuresis. Injection of vasopressin, angiotensin and -MSH at the sensitive site did not result in natriuresis in the same dosage range. Section of the sinus nerve significantly decreased the natriuretic response to oxytocin. It is suggested that the carotid body contains a specific oxytocin receptor capable of eliciting natriuresis in the rat.     

采用高脂饲料加空气干燥术建立颈动脉粥样硬化动物模型

目的:利用高脂饮食加空气干燥术建立一种稳定、重复性好、有较典型动脉粥样硬化病理改变的动物模型。方法:32只日本大耳白兔随机分为模型组(n=24)、对照组(n=8)。模型组给予高脂饲料喂养加空气干燥术,术中结扎左侧颈动脉分支血管,对照组正常饲料喂养,分别于术后第2、4、8、12周处死动物。取颈动脉组织切片HE染色,光镜下观察。结果:(1)75%兔颈总动脉存在细小血管分支,暂时结扎侧支血管后干燥效果更好。(2)对双侧颈动脉实施手术,结扎左侧分支,成模率更高。部分斑块显示出不稳定性。结论:采用改进后高脂饮食加空气干燥术可成功建立兔颈动脉粥样硬化模型,其病理特点适合于目前临床研究。     

Fine structure of the carotid body of the midterm human fetus

Summary The human fetal carotid body was studied using both histochemical and electron microscopic methods. The glomus cells of a mid term fetal carotid body evidently contain catecholamines. This was demonstrated both by formaldehyder-induced fluorescence of the cells and by the presence of typical dense-cored vesicles (diameter 1430–3200 Å) in the cytoplasm of the chief cells. The glomus cells were densely innervated and the synapses found on their surface were probably cholinergic in type, containing agranular synaptic vesicles measuring 400–700 Å in diameter with a few dense-cored vesicles measuring 900 to 1300 Å. Synapses were not found in any other cell type within the glomus caroticum. The prominent feature of the glomus cell cytoplasm was the presence of the dense-cored vesicles. The density of the vesicular core varied only slightly from cell to cell. There were no perceptible differences in vesicular size between the different cells. The glomus cells were mostly surrounded by the processes of the sustentacular cells, which usually also surrounded the capillary walls. No glomus cells were ever found in direct contact with the capillary wall. The capillaries were wide and very numerous over the restricted area of the organ. They formed sinusoidal loops, probably anastomosing with each other. Finally, the features of the fine structure are discussed, correlating the present findings with our knowledge about the adult functional carotic body.     

Two unusual benign lesions of the neck masquerading as malignancy on fine-needle aspiration cytology

Two cases of unusual benign tumors of the neck are described, both of which were initially misdiagnosed on cytology as carcinomas. Fine-needle aspiration findings in each case demonstrated a pleomorphic population of cells including bizarre multi-nucleated giant cells, the latter raising the false impression of malignancy. However, on review the cytological appearances of the tumors, a pleomorphic lipoma and a carotid body tumor, were characteristic. the correct diagnosis in each case would have been made or suggested if the pathologist had been familiar with the cytologic features characteristic of the lesion and the differential diagnosis of the head and neck tumors. in addition, the point is made that adequate clinical information is essential for the pathologist if all relevant conditions are not to be missed in the differential diagnosis.     

An association of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphism and common carotid atherosclerosis

Plasma homocysteine (Hcy) concentration has been shown to be influenced by a mutation in the gene coding methylenetetrahydrofolate reductase (MTHFR). Although plasma Hcy is related to atherosclerotic disorders, conflicting results have been reported about the association between MTHFR gene polymorphism and sclerotic lesions of the common carotid arteries. The effect of age–gene interaction on carotid arterial remodeling was investigated in elderly subjects with several risk factors for atherosclerosis. We evaluated sclerotic lesions of the common carotid arteries by ultrasonography in 326 patients (mean age ± standard deviation, 73 ± 12 years) and studied relations among the known risk factors for atherosclerosis, including MTHFR gene polymorphism and its interactions with age and sex. Of the 326 subjects studied, 136 had MTHFR genotype CC, 136 genotype CT, and 54 genotype TT. The three groups did not differ with respect to background factors such as age, history of cigarette smoking, blood pressure, lipids or uric acid, or in the incidence of atherosclerotic diseases. Spearman's rank correlation revealed a significant relationship between gender, age, Brinkman index, systolic blood pressure, triglycerides, HDL-cholesterol (HDL-C), uric acid, and MTHFR gene polymorphism. Multiple regression analysis using intima-media complex thickness (IMT) as a criterion variable and risk factors, including MTHFR gene polymorphism as explanatory variables showed that MTHFR gene polymorphism (P = 0.039) was a significant independent explanatory variable for IMT, along with gender (male) (P < 0.001), age (P < 0.001), systolic blood pressure (SBP) (P = 0.047), total cholesterol (T-C) (P < 0.001), and HDL-C (P < 0.001). Furthermore, a general linear model analysis revealed that interaction between age and MTHFR gene polymorphism was significantly associated with IMT, independently of age, SBP, T-C, and HDL-C in male subjects. However, age–gene interaction was not observed in female subjects. The findings of the present study confirm an association between MTHFR gene polymorphism and common carotid atherosclerosis in the Japanese population and further support the role of risk factor–gene interaction in common carotid atherosclerosis. Received: May 14, 2001 / Accepted: June 8, 2001     

The effects of blood osmolality changes on cat carotid body chemoreceptors in vivo

The possibility that carotid chemoreceptors respond to changes in plasma osmolality was investigated in the cat, perfusing the carotid artery with blood made hyper- or hypo-osmotic and recording chemoreceptor activity from carotid nerve fibers. Blood made hyperosmotic with sucrose or NaCl reduced the chemoreceptor discharge, while hypoosmotic blood increased chemoreceptor activity. The minimal osmolality variation necessary to obtain a detectable frequency change was 3–8% of the control. Frequency changes of 30% of the control were obtained with a 20% variation in osmolality. The frequency variations produced by the osmotic changes lasted as long as the infusion was maintained (up to 15 min). In some instances a rebound was observed when iso-osmotic saline was perfused again. A transient change in frequency and a clear rebound were obtained when blood made hyperosmotic with glycerol was perfused. These effects probably reflect a rapid change in intracellular osmolality due to the free passage of glycerol across cellular membranes.The modifications in chemoreceptor activity consecutive to osmolality variations are the opposite of those observed in isolated and superfused carotid bodies. As it is known that osmolality values affect the smooth muscle of the blood vessels, we conclude that our results are mainly produced by changes in carotid body blood flow due to a direct effect of hyper- and hypo-osmotic solutions on vascular muscle tone. Chemoreceptor excitation during a decrease in blood osmolality may contribute reflexly to the increased vascular resistance observed during acute osmolality reductions in man.     

Interaction of peripheral and central respiratory drives in cats I. Effects of sodium cyanide as a peripheral chemoreceptor stimulus at different levels of CSF pH

In cats anesthetized with chloralose-urethane, the central respiratory chemoreceptors were exposed to mock CSF of pH 7.02, 7.20, or 7.57. The right carotid body was simultaneously stimulated by intracarotid injections of 40, 80, or 160 μg sodium cyanide in 200 μl Ringer solution. The left carotid nerve and, in some animals, both vagosympathetic truncs were dissected. It could be demonstrated the the increase in ventilation produced by application of NaCN to the peripheral chemoreceptors is significantly larger at high than at low mock CSF pH (i.e. at low than at high central stimulus intensity). In vagotomized cats the responses of V_T and gelai to NaCN similarly depend upon CSF pH; they are somewhat larger, though, than in intact animals. These results are discussed as compared with results reported by different authors. Supported by the Deutsche Forschungsgemeinschaft (Be 477)     

Effects of carotid sinus nerve transection on changes in neuropeptide Y and indolamines induced by long-term hypoxia in rats

 Long-term hypoxia induces changes in neuropeptide-Y-like immunoreactivity (NPY-LI) and/or in the content of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) at the central level. To determine whether these alterations depend on the integrity of carotid body (CB) chemoreceptors, intact rats or those whose carotid sinus nerve was transected (CSNT) were exposed to hypoxia (10% O₂) or to normoxia for 14 days. Thereafter, NPY-LI, 5-HT and 5-HIAA levels in discrete brain regions were determined. The increase in NPY-LI in the ventrolateral medulla oblongata (VLM) of intact hypoxic rats was mostly abolished after CSNT and therefore is mainly mediated by CB chemoreceptors. In contrast, other hypoxia-induced changes were similar or even enhanced in CSNT as compared to intact rats and therefore do not depend on the integrity of CB chemoreceptors. This was the case for the increase of NPY-LI in the striatum and the caudal dorsomedian medulla oblongata (DMM), as well as for all the changes in 5-HT and 5-HIAA in the DMM, the VLM, the raphe nuclei, the striatum and the frontal cortex. We propose that long-term hypoxia alters brain NPY-LI and indolamine content through the stimulation of CB chemoreceptors or ancillary chemoreceptors, as well as through local biochemical or morphological mechanisms. Received: 5 May 1998 / Received after revision: 27 July 1998 / Accepted: 3 September 1998     

脑梗塞患者颈动脉粥样硬化斑块的超声研究

目的探讨脑梗塞患者颈动脉粥样硬化病变程度和特征,评价彩色多普勒超声对该粥样斑块的诊断价值.方法应用HP5500超声仪,对35例脑梗塞患者和46例正常人进行颈动脉检查.结果脑梗塞组颈动脉粥样硬化斑块检出率、斑块记分均显著高于对照组[分别为85.7%和21.7%,P＜0.01;(6.745±3.214)mm和(3.408±3.613)mm,P＜0.001],且脑梗塞组软斑比例为55.8%,显著大于对照组33.3%(P＜0.01),脑梗塞组斑块表面不规则即Ⅱ、Ⅲ度的比例亦显著大于对照组(41.9%/11.1%,11.6%/0%,P＜0.05).结论脑梗塞的发生与颈动脉粥样硬化病变密切相关;软斑块是发生脑梗塞的主要危险;超声检查对颈动脉粥样硬化具有诊断价值,可为脑梗塞的预防与治疗提供参考资料.     

颈动脉粥样斑块与冠状动脉病变

目的 研究颈动脉粥样斑与冠状动脉病变的关系。方法 将82例冠心病待排和冠心病患者按冠状动脉造影结果分成正常组和冠脉粥样病变组,同期超声检测颈动脉粥样硬化程度。结果 颈动脉粥样斑块与冠脉弱粥样硬化之间有较密切的关系。颈动脉粥样斑块对狭窄性冠状动脉病变预测的敏感性为71.7%,特异性为91.9%,阳性和阴性预测值分别为91.7%和73.9%,其准确性为81.7%。结论 颈动脉超声检测可作为预测冠状动脉粥样硬化有价值的指标。