Coronary microcirculation: autoregulation and metabolic control

The majority of studies axamining the regulation of coronary blood flow and vascular resistance have considered the coronary circulation as being composed of large conduit vessels and resistance vessels. Recently, it has become apparent that regulation of coronary microvascular resistance is not distributed uniformly, but varies across different segments or microdomains of the vasculature. Generally, small arterioles, those less than 100 m in diameter, respond differently than larger arterioles and small arteries. There are major differences in the level of autoregulatory control, myogenic control, endothelial modulation and control by metabolic factors across these various microvascular domains. There are also transmural variations which may account for some of the differences in coronary blood observed between epicardial and endocardial regions. In addition, interactions between these various regulatory mechanisms further complicate the understanding of coronary microvascular regulation. Importantly however, it may be these complex interactions and heterogeneous regulatory mechanisms which allow for adequate perfusion of the myocardium under an extreme range of metabolic conditions. This segmental distribution of regulation suggests an integrative hypothesis of regulation whereby a variety of mechanisms play a role in the overall response.Invited Contributions to the Symposium Regulation of coronary blood flow, held at the XV. World Congress of the International Society for Heart Research in Prague 1995     

Anaesthetic management of a child with Bartter’s syndrome

We report the anaesthetic management of an eight-year-old asthmatic boy with Bartter’s syndrome who had bilateral orchidopexy with caudal epidural analgesia. Bartter’s syndrome is a rare congenital disorder characterized by hypokalaemic hypochloraemic metabolic alkalosis, hyperaldosteronism, hyperreninaemia and hyperplasia of the juxtaglomerular apparatus of the kidneys. Characteristically, although these patients are normotensive they may be hypovolaemic. They may have unstable baroreceptor responses and show marked resistance to vasopressors. Hence, fluid, acid-base and electrolyte imbalances along with haemodynamic instability pose particular problems in their anaesthetic management. Previous case reports have described the management of these patients with general anaesthesia, our patient had his orchidopexy with caudal epidural analgesia using plain bupivacaine 0.5%. The patient was haemodynamically stable throughout surgery and was comfortable with caudal analgesia as the sole anaesthetic. Hypovalaemia, acid-base status and electrolyte imbalance were treated before instituting caudal epidural analgesia. We present this case report which describes the anaesthetic considerations in the light of the pathophysiology of Bartter’s syndrome.     

Evaluation of myocardial energy status in vivo by NMR spectroscopy

Summary NMR spectroscopy is a powerful and non-invasive technique with which to study cardiac energy metabolism in vivo. This mcthod makes use of the "spin" properties of certain atomic nuclei. The naturally occurring phosphorus nucleus (P-31) is visible by NMR and phosphorus-31 NMR spectra contain signals from the major components of energy metabolism. In vivo, the phosphocreatine to ATP ratio (PCr/ATP) is used as an index of the energy status and viability of the myocardium. However, it is the response of this metabolic index to differing physiological and pharmacological stresses that has helped to elucidate the mechanisms that regulate cellular respiration and to highlight abnormalities in heart failure. As there are many technical difficulties involved with cardiac NMR, 31-phosphorus studies of skeletal muscle have provided an indirect way of studying abnormalities in myocardial metabolism in vivo.One of the unique features of NMR is that it permits in vivo measurements of fluxes through key enzymes in energy metabolism using magnetization transfer. Determination of the rates of energy transfer through the creatine kinase reaction and energy turnover in vivo will provide new insights into the control of energy metabolism in health and disease. Alternatively, carbon-13 NMR can be used to measure fluxes through the different metabolic pathways of synthesis and catabolism following administration of selectively labelled carbon-13 substrates. In conclusion, the non-invasive and versatile nature of NMR spectroscopy makes it an ideal method to assess and evaluate energy metabolism in vivo.     

Laminar organization of the extraocular muscles of the rabbit.

Studies of bilateral hemispheric somatosensory evoked potentials (SEP) were carried out on 17 comatose patients following closed-head injury. Control evoked potentials were obtained from 74 normal volunteers. A prognosis of potential recovery or nonrecovery from coma was made in all 17 patients based on the SEP analyses. All subjects underwent bilateral median and peroneal nerve stimulation and responses were averaged from scalp electrodes placed over the somatotopic sensory cortex for the wrist and leg. The prognostic outcome of all 17 patients was accurately predicted following SEP analysis. Results show that 4 of 17 patients with prognoses of “positive recovery” had eight defined SEP peaks present within a time base analysis of 300 ms. Twelve patients with prognoses of “negative recovery” had five or less SEP peaks present within a time base of 500 ms. The majority of the “negative recovery” patients showed only SEP primary waveform components consisting of two peaks. The data suggest a potentially useful method using SEP analysis to prognosticate the possible recovery from clinical coma.     

Plasma levels and half lives of thioridazine and some of its metabolites

Summary Plasma-levels of thioridazine, mesoridazine, sulphoridazine and two other metabolites were determined in ten older chronic psychotic patients on thioridazine therapy. The plasma-level before the morning dose of thioridazine was the most reliable parameter for clinical studies. An intra-individual relationship between lower doses of thioridazine and plasma-levels was found. The percentage contribution of psychoactive compounds to the total sum of thioridazine plus metabolites ranged from 43–74%. The mean early disappearance half-life of thioridazine was 5 hours, and its mean late disapperance half-life was 26 hours.     

癌性恶病质代谢的研究现状

恶病质是癌症病人死亡的常见原因之一。与单纯性饥饿引起的营养不良不同．它的主要代谢改变是葡萄糖合成率的变化，糖异生、糖酵解增加，脂肪动员和氧化加速．蛋白质合成减少。     

药物代谢中的药酶特性与临床研究近况

目的:为了促进药物代谢酶在临床上的深入研究。方法:以近几年国内外大量有代表性的论文为依据进行分析、归纳、整理。结果:药物代谢酶大多具有遗传多态性,其活性受相关药物影响,遗传多态性和药物之间代谢性相互作用是临床药物反应千变万化的重要因素。结论:药物代谢酶的认识和研究有助于临床合理用药和减少药物不良反应。     

Metabolic risk factors in patients with ureteropelvic junction obstruction and renal calculi

PURPOSE: We performed a prospective study to determine the incidence and spectrum of metabolic abnormalities predisposing to stone formation in patients with ureteropelvic junction obstruction and renal calculi. MATERIALS AND METHODS: A total of 47 consecutive patients with congenital ureteropelvic junction obstruction underwent metabolic evaluation of stone risk factors. Of these patients 21 had associated stones (study group), while 26 did not (control group). Logistical regression, Wilcoxon rank sum and Fisher's exact tests were performed to determine whether there was a significant difference between these groups in regard to the presence of metabolic risk factors. RESULTS: Demographically and symptomatically the 2 groups were equivalent except that the study patients were older. The 24-hour urinary excretion of calcium was significantly higher in study than in the control patients (p = 0.007). While the incidence of hypercalciuria and hyperuricosuria was also higher in the study population, these differences were not significant (p = 0.08 and 0.07, respectively). CONCLUSIONS: Metabolic abnormalities predisposing to stone formation are present more frequently in patients with ureteropelvic junction obstruction who have associated stones compared to those who do not. As such, urinary stasis alone does not explain stone formation in these cases. Rather, the local physiological environment of urine likely has a predisposing role. In addition to restoring unobstructed urinary flow, consideration should be given to metabolic evaluation and prophylactic treatment for affected patients.     

焦炉作业与代谢综合征的相关性研究

[目的]探讨焦化厂焦炉作业与代谢综合征之间的相关性。[方法]以焦炉作业工人为研究对象,选取男性焦炉作业工人432名,其中炉顶工208名、炉侧工161名和炉底工63名。112名对照选自机电车间工人。检测所有研究对象的身高、体重、血压、血糖、高密度脂蛋白以及三酰甘油水平,按照中华医学会糖尿病分会(CDS)建议的标准诊断代谢综合征。[结果]采用多元Logistic回归分析对各组间年龄、工龄、吸烟和饮酒状况等因素进行校正后,发现炉顶组及炉侧组与对照组相比患代谢综合征的危险度升高,调整OR值分别为3．33(95％可信区间为1．07-10．34)和3．43 (95％可信区间为1．13-10.37);且炉顶组及炉侧组高血压患病率也显著高于对照组(P<0．05),而炉底组危险度未见升高。[结论]炉顶和炉侧作业可增加该作业人群患代谢综合征的危险度。     

干休所代谢综合征流行病学调查及生活方式强化干预

目的:调查北京136个军队老年集聚社区居民代谢综合征(m etabolic syndrom e,MS)的患病率及危险因素;探讨生活方式强化干预对MS患者早期治疗及降低危险因素的效果。方法:于2004年5~6月对北京136个以离退休干部为主体的军队社区、2 335名医疗体系属于我院的常住居民通过健康体检后进行MS的筛查和评价;对明确诊断MS患者实施健康教育、饮食和运动等生活方式强化干预。结果:在被调查的2 335人中MS患病率为28.7%,具有4个危险因素者占6.9%。饮食、运动干预后饮食结构趋于合理,中、老年组平均体重指数下降2~4 kg。结论:对MS高危人群进行常规筛查和评价,可促进MS的早期临床诊断;生活方式强化干预可增强老年人维护健康的意识,积极的防治有利于MS的转归及防止并发症的发生及发展。