Neuropeptide Y-like immunoreactivity in the diencephalon of the little brown bat (Myotis lucifugus): localized variations with physiological state.

The current study used light microscopic immunocytochemistry to demonstrate and compare neuropeptide Y-like immunoreactivity (NPY-IR) in the diencephalon of the little brown bat (Myotis lucifugus) at different stages in its annual cycle of activity and hibernation. Animals were sacrificed in each of three discrete physiological states: euthermic, hypothermic, and hibernating. In general, NPY-IR was abundant in the hypothalamus and sparse in other diencephalic areas. Immunoreactivity was present in a number of pathways which project to or originate from diencephalic nuclei; these include the ansa peduncularis, medial forebrain bundle, inferior thalamic peduncle, stria terminalis, stria medullaris, mammillary peduncle, and dorsal longitudinal fasiculus. Dense fiber plexuses were present throughout the hypothalamus; however, NPY-IR was conspicuously absent from the suprachiasmatic nucleus. Immunoreactive perikarya were located in the supraoptic, dorsomedial, ventromedial, and arcuate nuclei, in the external division of the ventral lateral geniculate nucleus, and in the pineal gland. Localized changes in density and/or distribution of NPY-IR were correlated with changes in physiological state.     

冠心病患者QT离散度与冬眠心肌关系的初步探讨

目的　探讨冠心病患者 QT离散度 (QTd)与冬眠心肌的量化关系。方法　 5 3例存在节段心肌收缩功能不全的冠心病患者行超声心动图、心电图和核素心肌显像 ,经皮腔内冠状动脉成形术 (PTCA)术后 1周复查超声心动图和心电图。结果　 1全组 QTd从术前的 65 .85± 2 5 .83 ms降至术后的 5 6.79± 2 9.73 m s(P<0 .0 0 1)。2有节段收缩功能改善的病人 (IP组 ) QTd显著小于无节段功能改善的病人 (NIP组 ) (P<0 .0 0 1) ;术前 QTd与术后左心室整体室壁运动指数 (WMSI)的变化呈中度负相关 (r=- 0 .48,P<0 .0 0 1)。 3术后 IP组 QTd显著降低 (P<0 .0 0 1) ,而NIP组无显著变化 ;术后 QTd降低的幅度与 WMSI的降低程度呈中度正相关 (r=0 .63 ,P<0 .0 0 1)。4冬眠心肌检测阳性组 QTd显著小于检测阴性组 (P<0 .0 0 1)。结论　 QT离散度与冠心病患者的冬眠心肌数量有关 ,并可预测PTCA术后冬眠心肌的恢复程度     

Coronary artery surgery for ischaemic heart failure: the surgeon's view

Recent advances in medical therapy have improved outcomes for patients with severe heart failure. However, overall survival remains poor. Transplantation is an established therapy for these patients but is limited by the large mismatch between demand and donor organ availability.Recently it has been recognised that not all ventricular dysfunction secondary to coronary artery disease is irreversible. Revascularisation in certain patients would appear to improve ventricular function. These patients are said to demonstrate myocardial hibernation. Revascularisation in these patients may provide a further treatment option in the treatment of heart failure.     

Left ventricular function and prognosis after myocardial infarction: Rationale for therapeutic strategies

Prognosis after acute myocardial infarction is strongly associated with left ventricular dysfunction. However, asynergy does not necessarily imply loss of viability and myocardial necrosis. In fact, two different patterns of contractile dysfunction, possibly coexisting, have been shown after acute myocardial infarction: Stunning and hibernation represent distinct patterns of contractile dysfunction that share the character of reversibility. It is noteworthy, then, to identify the presence of these two conditions at the bedside and to develop medical treatment to effect recovery of myocardial dysfunction. This strategy has the potential to ameliorate the outcome of patients after acute myocardial infarction by improving left ventricular function. Beta-blocker therapy significantly reduces mortality and the incidence of reinfarction after an acute myocardial infarction: These benefits result from the prevention of sudden death, the reduction of the extent of myocardial injury during the acute phase, and a further antiischemic action. Nevertheless, beta-blocker therapy increases left ventricular dilatation. Recent experimental and clinical data show that ACE inhibitors confer positive therapeutic effects after myocardial infarction by reducing the extent of left ventricular dilation, by reducing mortality, and by improving the clinical outcome. Not all patients, however, can be subjected to this therapeutical approach because of the possible detrimental effects produced by hypotension and by block of neurohormonal activation, sometimes truly compensatory in the early phase. Therefore, it would be interesting to suggest a combination therapy of a beta-blocker with a vasodilator agent (ACE inhibitor or calcium-channel blocker).     

经皮冠状动脉腔内成形术对冬眠心肌收缩功能的近期影响

目的　探讨经皮冠状动脉腔内成形术 (PTCA)对冬眠心肌收缩功能的近期影响。方法　对 5 3例存在节段心肌收缩功能不全的冠心病患者行超声心动图和核素心肌显像 (SPECT) ,PTCA术后1周复查超声心动图 ,比较手术前后左室整体及节段的收缩功能变化。结果　 (1)术前收缩功能不全而经PTCA获得血运重建的 16 7个节段中 ,术后有 87段 (5 2 1% )功能改善 ;而未经PTCA获得血运重建的 5 9个节段中 ,术后仅有 2段 (3 4% )功能好转 (P <0 0 0 1)。血运重建区域的室壁运动指数(WMSI)从术前的 1 85± 0 96降至术后的 1 5 1± 0 80 (P <0 0 0 1) ,而非血运重建区域的WMSI在手术前后差异无显著性。 (2 )有节段收缩功能改善的患者左室射血分数 (LVEF)从术前的 5 2 1± 11 9提高至术后的 5 4 8± 11 2 (P <0 0 5 ) ,而无节段功能改善者LVEF手术前后差异无显著性 ;术后近期LVEF的提高幅度与左室整体WMSI的降低程度呈显著正相关 (r =0 73,P <0 0 0 1)。结论　成功PTCA术能在近期内改善冬眠心肌的收缩功能 ,且左室整体泵功能的变化与冬眠心肌收缩功能密切相关。     

成肌细胞移植治疗缺血性心脏病机制的研究

目的 :研究成肌细胞是否可在体内建立新的收缩组织 ,是否可促进因缺血导致的冬眠及顿抑心肌细胞功能的恢复 .方法 :成年新西兰兔结扎冠状动脉左前降支建立心肌缺血损伤模型 ,体外培养扩增自体骨骼肌成肌细胞并用BrdU标记 ,将 (3.5～ 5 .0 )× 10 7细胞移植到自体急性心肌梗死区域 .对照组将自体内皮细胞、骨骼肌细胞移植入急性心肌梗死区 .2 ,4 ,8wk后行大体、组织形态学、细胞学检测 .结果 :梗死区部位观察到带荧光的成肌细胞及肌纤维 ,部分已分化成横纹肌 .正常心肌细胞随梗死时间增长 ,可见细胞切面积及体积增加 ,呈现肥大趋势 .骨骼肌成肌细胞移植治疗组梗死区残存冬眠、顿抑心肌细胞数量、细胞代谢活性、局部微血管网数量与对照组比较差异有显著意义 (P <0 .0 5 ) .结论 :在改善微血管网恢复微环境的条件下 ,存活的成肌细胞分泌多种细胞因子 ,使已经顿抑、冬眠的心肌细胞得到激活 ,从而改善心功能 .     

Hibernating myocardium: clinical and functional response to revascularisation

Objective: We assessed the effects of coronary bypass grafting on left ventricular (LV) function, exercise capacity and symptom profile in patients with LV impairment and evaluated the role of identifying myocardial hibernation in a prospective non-randomised study. Methods: Of 120 patients screened, 47 patients with LV ejection fraction <35% and three vessel coronary artery disease were studied. All underwent stress/redistribution and separate day rest/redistribution Tl-201 imaging together with cine MRI at enrolment, and cine MRI at follow-up. Group 1, 30 patients undergoing bypass surgery, underwent symptom limited treadmill exercise testing with peak VO₂ measurement, and symptom profile evaluation less than 3 months before, and 3–6 months after operation. Revascularisation was assessed by post-operative Tl-201 imaging and repeat coronary angiography. Group 2, 17 patients treated on medical therapy alone underwent symptom profile assessment at enrolment and follow-up for those who survived. Segmental hibernation was defined as the equivalent of greater than 50% of maximal Tl-201 uptake where wall motion was severely impaired on resting imaging. Patients were considered to be hibernating where two of nine LV segments fulfilled these criteria. Results: In group 1, five patients died (17%), peri-or post-operatively, two defaulted and 23 attended follow-up studies. In group 2, three patients died prior to follow-up (18%). In the surgical group there was an increase in mean LVEF from 24.0±8% to 29.7±11% (P<0.05) while in the medical group there was a fall from 25.7±10% to 20.6±8% (P<0.05). In group 1, the mean NYHA dyspnoea grade improved from 2.7 to 1.4 while in the medical group it was unchanged, 2.6 to 2.5. In patients with myocardial hibernation identified pre-operatively, 18/19 (95%) improved LVEF after CABG compared with 2/4 (50%) of patients without hibernation. 17/19 (86%) patients with hibernation improved NYHA dyspnoea class compared with 2/4 (50%) of patients without. 60/93 (65%) of hibernating segments improved function after revascularisation while 47/53 (89%) hibernating segments showed no improvement on medical therapy alone. Conclusion: In patients with severe LV impairment with myocardial hibernation, coronary artery bypass grafting improves both global and regional systolic LV function, and symptom profile. Medical treatment of patients with LV impairment and myocardial hibernation does not improve LV contractile function or symptoms. Both surgical and medical therapy carry a high mortality rate.     

The relationship between regional blood flow and contractile function in normal, ischemic, and reperfused myocardium

During normoperfusion, both myocardial blood flow and contractile function are heterogeneously distributed throughout the left ventricle, in that midwall segment shortening is higher at the apex than at the base of the left ventricle, and greater in the anterior than in the posterior wall. Also, transmural heterogeneity of myocardial deformation exists with greater segment shortening and wall thickening occurring in inner than in outer myocardial layers. A transmural heterogeneity of myocardial blood flow – with greater inner as compared to outer wall perfusion – exists which is not simply related to temporal fluctuations since the heterogeneous flow pattern is stable over at least a few minutes. While an increase in myocardial contractile function will lead to a metabolically mediated increase in regional coronary perfusion within or above the autoregulatory range does not increase regional myocardial contractile function. During hypoperfusion, the reduction in subendocardial blood flow is more pronounced than that in subepicardial blood flow, and contractile function in the inner myocardial layers ceases more rapidly than in the outer myocardial layers. The reduced regional myocardial contractile function is closely matched to the reduced regional myocardial blood flow; however, such a coupling between reduced flow and function is lost when ischemia is prolonged for several hours in that function for a given flow is further reduced. During reperfusion, regional myocardial contractile function remains depressed for a prolonged period of time, depending on the severity, duration, and location of the preceding ischemic episode, while regional myocardial blood flow is restored to almost normal. Recovery of contractile function in the outer myocardial layers is faster than in the inner myocardial layers. Received: 30 April 1998, Accepted: 28 May 1998     

EVOLUTION OF DAILY TORPOR AND HIBERNATION IN BIRDS AND MAMMALS: IMPORTANCE OF BODY SIZE

1. The evolution of hibernation and daily torpor in mammals and birds remains a controversial subject. The original view was that use of torpor reflects a primitive thermoregulation, as it occurs in ancestral groups of mammals. 2. This view is no longer widely supported. However, the interpretation of a polyphyletic derivation of torpor also has been challenged because of the astonishing similarity of torpor patterns among various orders and even the two classes. 3. A recent argument is that mutations required for torpor and hibernation are unlikely to occur simultaneously and that torpor must be plesiomorphic (ancestral), although it is not functionally primitive. Homeothermy is interpreted as a loss of the ability to enter torpor in those groups that could survive without the requirement of heterothermic periods for energy conservation. 4. Interestingly, while torpor in mammals occurs in the phylo-genetically old groups, lending support to the hypothesis of an ancestral derivation of torpor, the opposite is the case for birds. Modern bird groups and ancestral mammal groups contain mainly small species that often rely on fluctuating food supply, whereas modern mammalian orders and ancient bird orders contain the largest species with low energy requirements for maintenance and thermoregulation. 5. It is, therefore, possible that not phylogenetic position but size and diet determine the occurrence of heterothermy. Moreover, because endothermy and torpor in birds has apparently evolved separately from that in mammals and because it is possible that daily torpor and hibernation represent two distinct torpor patterns that evolved separately, a convergent evolution of torpor in endotherms cannot be excluded.