ULTRASTRUCTURAL ANALYSES OF STONE HEART SYNDROME AT ONSET AND SIX DAYS LATER FOLLOWING TOTAL SUPPORT OF THE CIRCULATION WITH A PARTIAL ARTIFICIAL HEART OR LEFT VENTRICULAR ASSIST DEVICE (ALVAD)

Ischemic myocardial contracture developed in a 21-year-old man following aortic and mitral valve replacement. The patient's circulation was supported totally for 6 days with an abdominal left ventricular assist device (ALVAD). Cardiac allografting was then undertaken. Samples of myocardium taken at the original operation and 6 days later at transplantation were analyzed ultrastructurally. At the onset of ischemic cortracture, left ventricular abnormalities included hypercontraction of myofibrils, loss of normal A-band and Z-band patterns, mitochondrial swelling with fusion of cristae, interfibrillar edema and glycogen depletion. Capillaries demonstrated swelling of endothelial cells and basement membrane disruption. Six days later, ultrastructural morphology showed further degeneration. The myofibrils remained hypercontracted, but were more fragmented. Degenerative changes in mitochondria were more advanced and calcium deposition in cristae was present. No glycogen was seen. The right ventricular myocardium exhibited significantly fewer ultrastructural abnormalities. The principal right ventricular changes were endothelial swelling and basement membrane disruption. Glycogen granules were present. Ischemic contracture affects the left ventricle more than the right, and the morphology becomes more abnormal with time. To our knowledge, this is the first instance wherein morphologic progressions of the ultrastructural alterations of ischemic contracture have been documented.     

A correlative transmission and scanning electron microscopic study of the pigeon myocardial cell

Summary A comparative study of the pigeon ventricular myocardial cell has been performed by transmission electron microscopy (TEM) and by scanning electron microscopy (SEM). Three-dimensional access to the cell interior was obtained by cryo-fracturing paraffin-embedded tissue immersed in liquid nitrogen. The TEM studies revealed parallelly arranged myofibrils separated by rows of mitochondria. The sarcoplasmic reticulum is represented by a well-developed network of tubules which, at the Z- and H-band level of the sarcomere, expands to form belt-like cisternae. The cisternae at the Z-band level lie in close proximity to both myofilaments and mitochondria. Transverse tubules are absent and thus only peripheral couplings are present.SEM observations of the fractured tissue revealed the spatial relationship between the different cell organelles, the most important of these being the parallel myofibrils and the mitochondria. The conspicuous ridges transversing the myofibril at the Z-band level consist mainly of expanded Z-bands, but overlying SR-tubules also contribute to these ridges. Traces of the SR can sometimes be seen covering the myofibrils. The close proximity between the SR and the mitochondria was also confirmed in the SEM.Preparation and examination of SEM prepared tissue in the TEM confirmed that no essential damage or reorganization of cell organelles had taken place during the SEM procedure. On the other hand some shrinkage of the tissue, which was probably caused by critical point drying, was noticed.     

Pathological findings of cardiac rhabdomyomatosis in the guinea pig

Cardiac rhabdomyomatosis of Hartley guinea pigs was examined by light and transmission electron microscopy, and its incidence and distribution were also described. Cardiac rhabdomyomatosis was found in 58 cases out of 345 animals, aged from 1.5 to 17 weeks. A few small lesions were noted in many cases, but large lesions were rare. Most lesions noted in the ventricle were found to measure from 1 mm2 to 5 mm2 in area. The larger lesions were seen near the cardiac apex. In terms of distribution of the lesions, they were observed most frequently in the left ventricular free wall. They were also distributed less frequently in the ventricular septum and in the right ventricular free wall. In bilateral free walls and the ventricular septum, this lesion was frequently noted on the endocardial side and in the tunica muscularis, respectively. Light microscopically, this lesion had a characteristic nodular-reticular structure with large vacuolated cells. Electron microscopy of cardiac rhabdomyomatosis revealed two cell types, A and B. Type A cells were characterized by large aggregates of glycogen particles distributed loosely in the cytoplasm and by myofibrils and mitochondria located at the periphery of the cytoplasm. Type B cells were characterized by large aggregates of mitochondria near the nucleus and at the periphery of the cytoplasm and by large aggregates of glycogen particles with a similar distribution to those in type in type A cells. Myocardial cells in the marginal regions of rhabdomyomatosis lesions showed mitochondrial swelling and rupture of myofibrils.(ABSTRACT TRUNCATED AT 250 WORDS)     

Structural-metabolic changes in the ventricular myocardium in massive experimental pulmonary embolism]

A comparative study of hemodynamic and structural-metabolic changes in myocardium of right (RV) and left (LV) ventricles by compensative massive pulmonary embolism (MPE) and decompensated MPE was made in 29 mongrel dogs. By decompensated MPE the histoenzymological and ultrastructural methods reveal changes in RV which are not adequate to its high hemodynamic load: the catabolic enzymes activity decreases, the numeral density of mitochondrial profiles decreases too, the fraction of damaged mitochondria increases. By decompensated MPE the myocardial metabolism shifts from catabolic to biosynthetic processes, the activity of NADP.H-D and G-6-PDG increase in both ventricles.     

DNA damage of tumor-associated lymphocytes and total antioxidant capacity in cancerous patients

The purpose of this study was to assess DNA damage of tumor-associated lymphocytes (TALs) in malignant pleural effusion (MPE), the total antioxidant capacity (TAC) of plasma and MPE from patients with carcinoma, and DNA repair effect of melatonin. TAC of plasma was measured in 28 cancer patients with MPE and in 33 healthy persons, and also TAC of MPE supernatant was measured in these patients. DNA damages of peripheral blood mononuclear cells (PBMCs) and of TALs were assessed using comet assay. The TAC of plasma was remarkably lower in cancer patients (8.41+/-1.78 U/ml) than that in healthy persons (10.52+/-1.64 U/ml, P<0.001). The TAC of MPE supernatant (6.34+/-1.57 U/ml) was significantly lower than that of plasma in cancer patients (8.41+/-1.78 U/ml, P<0.001). The comet percentage of PBMCs was higher in cancer patients (16.8+/-7.9) than that in healthy persons (10.4+/-4.9, P<0.01). Within cancer patients, the comet percentage of TALs (41.9+/-11.7) was significantly higher than that of PBMCs (16.8+/-7.9, P<0.001). A negative correlation was observed between the TAC of MPE supernatant and the comet percentage of TALs in patients (r=-0.538, P<0.01). After treatment with melatonin, comet percentage of TALs declined significantly from 42.6+/-12.8 to 27.1+/-9.9 (P<0.001). These data show that lower TAC of MPE supernatant may be related to higher degree of DNA damage of TALs and that melatonin may facilitate the repair of the damaged DNA.     

慢性缺氧对大鼠左右心室功能、心肌肌原纤维Ca~（2＋），Mg~（2＋）－ATP

模拟５０００ｍ中度缺氧时,大鼠右室功能显著加强,而左室功能加强不显著;左右心室肌原纤维Ｃａ２＋,Ｍｇ２＋－ＡＴＰ酶活性下降,肌球蛋白同功酶Ｖ２和Ｖ３百分含量增加,Ｖ１百分含量减少。８０００ｍ重度缺氧时,右室功能减弱,但无统计学意义,左室功能减弱有显著性;ＡＴＰ酶活性和同功酶的变化超过５０００ｍ组。此外,右室ＡＴＰ酶活性与ＰＡＰ呈反比且有显著性,左室ＡＴＰ酶活性与ＣＡＳＰ虽也呈反比但无显著性;右室同功酶Ｖ３百分含量与ＰＡＰ呈正比,左室同功酶Ｖ３百分含量与ＣＡＳＰ不呈比例。上述结果表明,因短期突发严重缺氧引起的心肌供氧不足对左心室心肌的直接损伤作用大于右心室心肌。     

Experimental cardiac tamponade: correlation of pressure, flow velocity, and echocardiographic changes

Seven episodes of experimental cardiac tamponade were induced in five anesthetized closed-chest dogs. Simultaneous pericardial and intracavitary pressures were synchronized with superior vena caval and transvalvular pulsed-Doppler flow tracings. The earliest indication of tamponade was the development of a negative transmural right atrial pressure that occurred during early ventricular diastole and was associated with echocardiographic evidence of right atrial collapse. This was also associated with reversal of diastolic flow in the superior vena cava and with diminished early diastolic flow velocity across the tricuspid as well as the mitral valve. During more advanced cardiac tamponade, the transmural right atrial pressure became negative during both early and late ventricular diastole as well as during isovolumic ventricular systole. This was associated with a disappearance of early diastolic ventricular filling and right ventricular diastolic collapse as observed on two-dimensional echocardiography. In hypotensive cardiac tamponade (cardiac output diminished by 70%), the decreased transmural right atrial pressure that developed during ventricular systole was accompanied by diminished antegrade flow in the superior vena cava. In advanced and hypotensive tamponade, ventricular filling occurred mainly during atrial contraction.     

Coronary vasodilator reserve, capillarity, and mitochondria in trained hypertensive rats

To test the hypothesis that exercise training can reverse the decrements in coronary reserve, capillary density, and mitochondrial volume density evident during established hypertension, we trained spontaneously hypertensive (SHR) and normotensive (WKY) rats on a treadmill over a 3-mo period. At 7 mo of age we used microspheres to evaluate myocardial perfusion in conscious rats. Exercise training did not alter hypertension or left ventricular hypertrophy but did increase maximal O2 consumption in both SHR and WKY. A decrement in left and right ventricular coronary reserve in SHR, compared with WKY, was indicated by 1) a smaller increment in myocardial perfusion during maximal vasodilation with dipyridamole and 2) a higher minimal coronary vascular resistance per unit mass. Exercise training had no significant effect on any index of myocardial perfusion in SHR or WKY. A 12% decrement in capillary numerical density in the endomyocardium of SHR was not reversed by exercise training. We estimated the volume densities of mitochondria, myofibrils, and sarcoplasm using electron microscopy and point-counting stereology on perfusion-fixed hearts. None of the parameters in either SHR or WKY was changed by exercise training. It is concluded that exercise training does not reverse the decrements in coronary reserve and capillary numerical density associated with hypertension in adult rats. Moreover the previously observed enhancement of mitochondrial volume density due to exercise in young hypertensive rats was not observed in adult SHR.     

Right and left ventricular pressure-volume response to respiratory maneuvers

With respiration, right ventricular end-diastolic volume fluctuates. We examined the importance of these right ventricular volume changes on left ventricular function. In six mongrel dogs, right and left ventricular volumes and pressures and esophageal pressure were simultaneously measured during normal respiration, Valsalva maneuver, and Mueller maneuver. The right and left ventricular volumes were calculated from cineradiographic positions of endocardial radiopaque markers. Increases in right ventricular volume were associated with changes in the left ventricular (LV) pressure-volume relationship. With normal respiration, right ventricular end-diastolic volume increased 2.3 +/- 0.7 ml during inspiration, LV transmural diastolic pressure was unchanged, and LV diastolic volume decreased slightly. This effect was accentuated by the Mueller maneuver; right ventricular end-diastolic volume increased 10.4 +/- 2.3 ml (P less than 0.05), while left ventricular end-diastolic pressure increased 3.6 mmHg (P less than 0.05) without a significant change in left ventricular end-diastolic volume. Conversely, with a Valsalva maneuver, right ventricular volume decreased 6.5 +/- 1.2 ml (P less than 0.05), and left ventricular end-diastolic pressure decreased 2.2 +/- 0.5 mmHg (P less than 0.05) despite an unchanged left ventricular end-diastolic volume. These changes in the left ventricular pressure-volume relationship, secondary to changes in right ventricular volumes, are probably due to ventricular interdependence. Ventricular interdependence may also be an additional factor for the decrease in left ventricular stroke volume during inspiration.     

Myocardial lysosomes in pressure-overload hypertrophy

Summary Combined electron microscopic and cytochemical studies were used to investigate the effects of chronic-pressure overload hypertrophy on myocardial lysosomes, mitochondria, and myofibrils in the left ventricle of the cat. Myocardial hypertrophy was induced by an 84% banding constriction of the ascending aorta. After one month of aortic constriction the experimental animals demonstrated a 51% increase in left ventricular mass. No qualitative ultrastructural differences were noted between the myocardial tissues of the hypertrophy and normal group. However, the cytochemical reaction product to acid phosphatase appeared more frequently in the myocardium of the hypertrophy group compared to that of the normal group. By use of quantitative morphometry the percentage of mitochondria, myofibrils and lysosomes per myocardial cell was determined in both hypertrophy and normal groups of animals. Despite significant increases in the left ventricular mass of hypertrophy animals, a normal balance of mitochondria and myofibrils was maintained within the myocardium. Further analysis indicated an enhanced lysosomal population in the hypertrophy group compared to the normal group.This research was supported by a grant from the California Affiliate of the American Heart Association     

Micromechanical function of myofibrils isolated from skeletal and cardiac muscles of the zebrafish

The zebrafish is a potentially important and cost-effective model for studies of development, motility, regeneration, and inherited human diseases. The object of our work was to show whether myofibrils isolated from zebrafish striated muscle represent a valid subcellular contractile model. These organelles, which determine contractile function in muscle, were used in a fast kinetic mechanical technique based on an atomic force probe and video microscopy. Mechanical variables measured included rate constants of force development (k(ACT)) after Ca(2+) activation and of force decay (τ(REL)(-1)) during relaxation upon Ca(2+) removal, isometric force at maximal (F(max)) or partial Ca(2+) activations, and force response to an external stretch applied to the relaxed myofibril (F(pass)). Myotomal myofibrils from larvae developed greater active and passive forces, and contracted and relaxed faster than skeletal myofibrils from adult zebrafish, indicating developmental changes in the contractile organelles of the myotomal muscles. Compared with murine cardiac myofibrils, measurements of adult zebrafish ventricular myofibrils show that k(ACT), F(max), Ca(2+) sensitivity of the force, and F(pass) were comparable and τ(REL)(-1) was smaller. These results suggest that cardiac myofibrils from zebrafish, like those from mice, are suitable contractile models to study cardiac function at the sarcomeric level. The results prove the practicability and usefulness of mechanical and kinetic investigations on myofibrils isolated from larval and adult zebrafish muscles. This novel approach for investigating myotomal and myocardial function in zebrafish at the subcellular level, combined with the powerful genetic manipulations that are possible in the zebrafish, will allow the investigation of the functional primary consequences of human disease-related mutations in sarcomeric proteins in the zebrafish model.     

Structural and functional heterogeneity of cardiomyocytes during hemodynamic loading of the rat heart

Ultrastructural studies of cardiomyocytes during experimental aorta coarctation enabled one to divide them into 6 types: with mitochondrial swelling and enlargement of the sarcoplasmic reticulum; with primary damage to myofibrils; with disintegration of ultrastructure because of edema; with hypertrophy and hyperplasia of ultrastructures; without essential changes in organelles; and with concomitant changes in mitochondria and myofibrils. Such different reactions of cardiomyocytes are regarded as an adaptation mechanism that ensures the maintenance of heart function under extreme conditions.     

Manifestation of the stripes of minor proteins location in A-bands of rabbit cardiac myofibrils

Cardiac myofibrils were isolated from rabbit ventricular muscle by a method that preserves well the integrity of the A-band structure. For the first time electron microscopic observations using the negative staining method revealed, in cardiac A-bands, a full complement of pronounced transverse stripes which indicate the locations of minor proteins in skeletal muscles. The manifestation of some transverse stripes in the cardiac A-band was shown to depend on the duration of muscle incubation in a Ca2(+)-depleting and ATP-free solution before its homogenization into myofibrils. The clear visibility of fine structural details in electron micrographs allowed us to resolve morphological features specific for cardiac muscle at both the central and end parts of the A-bands. The myofibrils demonstrated here are expected to be useful for elucidating the fine structure of cardiac thick filaments and in particular the locations of minor proteins.     

Mavacamten has a differential impact on force generation in myofibrils from rabbit psoas and human cardiac muscle

Mavacamten (MYK-461) is a small-molecule allosteric inhibitor of sarcomeric myosins being used in preclinical/clinical trials for hypertrophic cardiomyopathy treatment. A better understanding of its impact on force generation in intact or skinned striated muscle preparations, especially for human cardiac muscle, has been hindered by diffusional barriers. These limitations have been overcome by mechanical experiments using myofibrils subject to perturbations of the contractile environment by sudden solution changes. Here, we characterize the action of mavacamten in human ventricular myofibrils compared with fast skeletal myofibrils from rabbit psoas. Mavacamten had a fast, fully reversible, and dose-dependent negative effect on maximal Ca²⁺-activated isometric force at 15°C, which can be explained by a sudden decrease in the number of heads functionally available for interaction with actin. It also decreased the kinetics of force development in fast skeletal myofibrils, while it had no effect in human ventricular myofibrils. For both myofibril types, the effects of mavacamten were independent from phosphate in the low-concentration range. Mavacamten did not alter force relaxation of fast skeletal myofibrils, but it significantly accelerated the relaxation of human ventricular myofibrils. Lastly, mavacamten had no effect on resting tension but inhibited the ADP-stimulated force in the absence of Ca²⁺. Altogether, these effects outline a motor isoform–specific dependence of the inhibitory effect of mavacamten on force generation, which is mediated by a reduction in the availability of strongly actin-binding heads. Mavacamten may thus alter the interplay between thick and thin filament regulation mechanisms of contraction in association with the widely documented drug effect of stabilizing myosin motor heads into autoinhibited states.     

A new method for isolating physiologically active Mg-protoporphyrin monomethyl ester, the substrate of the cyclase enzyme of the chlorophyll biosynthetic pathway

Mg-protoporphyrin monomethyl ester (MPE) is a biosynthetic intermediate of chlorophyll and converted by MPE cyclase to protochlorophyllide. Limited availability of MPE has so far hampered cyclase research. In a new, simplified, method MPE was prepared from freeze dried bchE mutant Rhodobacter capsulatus DB575 cells by extraction with acetone/H(2)O/25% NH(3). Isolated MPE was identified by absorption and fluorescence spectroscopy, and its purity was analyzed by HPLC. The extracted MPE was dried and redissolved in buffered DMSO and its substrate activity is shown by enzymatic cyclase assays. A linear time course was observed for MPE conversion to protochlorophyllide by enzymes from barley etioplasts. Our innovation of freeze drying the R. capsulatus cells before extraction provides a high yield method for MPE, which is significantly faster and more reproducible than previous extraction methods.     

Ultrastructural morphometry of the myocardium of Thunnus alalunga

The common ventricle in the heart of the Thunnus alalunga was studied. The ventricular myocardium consists of an outer compact layer and a thick inner spongy layer. The compact layer has slightly larger cells (4-6 microns diameter) than the spongy layer (2.5-5 microns diameter). Ultrastructurally the myocardium displays normal arrangements of myofibrils and mitochondria. The sarcoplasmic reticulum is poorly developed. The intercalated discs are simple with the fascia adherens being the most frequent junctional type observed; occasionally a desmosome was seen. Nexus type junctions are present but are unassociated with the intercalated discs. There are no t-tubules evident but the plasmalemma exhibits numerous caveolae which rarely form couplings with the sarcoplasmic reticulum. A morphometric analysis of the volume percent of mitochondria and myofibrils showed that the myocardial cells in the spongy layer of the heart have a significantly greater volume percentage of mitochondria than the compact layer. No significant differences were found between myocardial regions when the volume percentages of myofibrils were compared. The physiological studies revealed that the albacore tuna has heart rates (120 bpm) and ventricular blood pressures (100 mmHg) that are among the highest reported for fish.     

Ultrastructural histogenesis of chicken myocardium]

The structure of the ventricular myocardium of the chick embryo was studied from the 4th day of incubation until one day after hatching. Special attention was paid to the differenciation of myofibrils, their branching at the level of stria Z and their relations with desmosomes.     

超声心动图Tei指数对不同血糖控制水平妊娠期糖尿病孕妇胎儿心功能及出生后整体心功能的评估价值

目的:探讨超声心动图Tei指数对不同血糖控制水平妊娠期糖尿病(GDM)孕妇胎儿心功能及出生后整体心功能的评估价值。方法:选择2017年2月至2019年10月期间我院产科接诊的134例GDM患者,根据血糖控制水平将其分为良好组(餐前空腹血糖≤5.3 mmol/L,餐后2 h血糖≤6.7 mmol/L,睡前血糖>3.3 mmol/L,妊娠期糖化血红蛋白<5.5%,65例)和不良组(餐前空腹血糖>5.3 mmol/L,餐后2 h血糖>6.7 mmol/L,睡前血糖≤3.3 mmol/L,妊娠期糖化血红蛋白≥5.5%,69例),另选择50例正常妊娠孕妇为对照组。分别于妊娠3238周、新生儿出生后17 d采用超声心动图测量胎儿、新生儿心功能和Tei指数。比较胎儿、新生儿心功能、Tei指数的差异。结果:不良组胎儿左室射血分数(LVEF)、二尖瓣E/A峰的速度比值(E/AMV)、右室舒张末期内径(RVDd)、右室收缩末期内径(RVDs)、左室短轴缩短率(LVFS)、左心室Tei指数、右心室Tei指数均高于良好组和对照组(P<0.05),三尖瓣E/A峰速度比值(E/ATV)低于良好组和对照组(P<0.05)。良好组LVFS高于对照组(P<0.05),良好组LVEF、E/AMV、E/ATV、RVDd、RVDs、左心室Tei指数、右心室Tei指数与对照组比较无统计学差异(P>0.05)。不良组新生儿LVEF、E/AMV、RVDd、RVDs、LVFS、左心室Tei指数、右心室Tei指数均高于良好组和对照组(P<0.05),E/ATV低于良好组和对照组(P<0.05)。良好组LVFS高于对照组(P<0.05),良好组LVEF、E/AMV、E/ATV、RVDd、RVDs、左心室Tei指数、右心室Tei指数与对照组比较无统计学差异(P>0.05)。结论:超声心动图Tei指数可敏感地反映GDM孕妇胎儿以及新生儿心功能损伤,妊娠期有效控制血糖水平有助于保护胎儿心功能。     

RV filling modulates LV function by direct ventricular interaction during mechanical ventilation

During mechanical ventilation, phasic changes in systemic venous return modulate right ventricular output but may also affect left ventricular function by direct ventricular interaction. In 13 anesthetized, closed-chest, normal dogs, we measured inferior vena cava flow and left and right ventricular dimensions and output during mechanical ventilation, during an inspiratory hold, and (during apnea) vena caval constriction and abdominal compression. During a single ventilation cycle preceded by apnea, positive pressure inspiration decreased caval flow and right ventricular dimension; the transseptal pressure gradient increased, the septum shifted rightward, reflecting an increased left ventricular volume (the anteroposterior diameter did not change); and stroke volume increased. The opposite occurred during expiration. Similarly, the maneuvers that decreased venous return shifted the septum rightward, and left ventricular volume and stroke volume increased. Increased venous return had opposite effects. Changes in left ventricular function caused by changes in venous return alone were similar to those during mechanical ventilation except for minor quantitative differences. We conclude that phasic changes in systemic venous return during mechanical ventilation modulate left ventricular function by direct ventricular interaction.