Combined effect of 5-fluorouracil and recombinant tumor necrosis factor against human gastric carcinoma cell lines

This study was performed to investigate the direct effects of recombinant human tumor necrosis factor (rH-TNF) and recombinant human interleukin-2 (rH-IL-2), either alone or in combination, on the cytotoxicity of 5-FU measured by MTT assay against human gastric adenocarcinoma cell lines (MKN-28 and MKN-45), and also to determine the optimal schedule for their combination. The antitumor activity of rH-TNF was enhanced more than 42% by 10(2) U/ml of rH-IL-2. The enhancing effects of rH-TNF and rH-IL-2 on the cytotoxicity of 5-FU were evaluated in terms of Modification Index(MI), the MI value at 10 U/ml rH-TNF was 1.6; the MI at the same concentration of rH-TNF in the presence of 10(2) U/ml of rH-IL-2 was 2.1. These results demonstrated that the antitumor effect of 5-FU was enhanced 1.6 times by 10 U/ml of rH-TNF and further enhanced by the combined use of rH-TNF and rH-IL-2. The combined effect of equal concentrations of 5-FU and rH-TNF was superior or equivalent to that of 5-FU or rH-TNF alone. The sequence of 5-FU followed by rH-TNF and rH-IL-2 showed a higher inhibitory effect than the reverse sequence. This sequence combination seems worthy of further consideration for the treatment of gastric cancer.

Isolation and sequencing of the cDNA encoding phosphatidylinositol transfer protein from rabbit lung

The cDNA clones encoding rabbit lung phosphatidylinositol transfer protein (PI-TP) were isolated and sequenced. The putative polypeptide consisted of 270 amino acid (aa) residues, the same as human PI-TP, but one aa residue less than the PI-TP of rat and mouse. PI-TP RNA expression in various tissues of a pregnant rabbit was analyzed by Northern blot. Brain, placenta and fallopian tube had the highest PI-TP RNA expression. PI-TP RNA expression in alveolar epithelial type-II cells isolated from rabbit lung markedly increased after a 24-h culture, suggesting that PI-TP RNA expression in type-II cells can be modified by ambient factors.

Comparison of subcutaneous ring block of the penis with caudal epidural block for post-circumcision analgesia in children

A randomized, prospective, blind trial was conducted comparing caudal epidural blockade (caudal block) with subcutaneous ring block of the penis (penile ring block) in fifty healthy boys between two and twelve years of age undergoing elective circumcision. Subjects receiving caudal block had a longer duration of analgesia (P = 0.003), and took longer to first micturition (P = 0.04) but there was no difference in time taken to awaken from anaesthesia or spontaneously walk unaided. There was an 8% failure rate with the penile ring block but no local or systemic complications related to either block and a very low incidence of vomiting. It is concluded that both techniques are effective. Caudal block is more reliable and produces a longer duration of analgesia but penile ring block is inherently safer and has a lower incidence of adverse effects.

Myocardial infarction is coupled with activation of cyclins and cyclin-dependent kinases in myocytes

To determine whether the molecular components implicated in the regulation of the cell cycle are activated in myocytes after infarction, the expression of cyclins E, A, and B and the levels of their associated kinase activity were measured at 1 and 7 days following surgery. The quantity of cdk2 and cdc2 and the level of their kinase activity were also determined. Myocardial infarction was characterized by an increase in cyclins E, A, and B and cdc2 proteins in the surviving myocytes at 1 and 7 days. Cyclin E, A, and B and cdk2 and cdc2 kinase activity also increased. The quantity of cyclins E and A and the level of cyclin E-associated kinase activity in myocytes after infarction were comparable with those measured in neonatal myocytes. Moreover, cdc2 protein and cdc2 kinase activity in myocytes reached levels after infarction which were similar to those in neonatal myocytes. Thus, myocytes react to myocardial infarction by activating cyclins and cyclin-dependent kinases which may be coupled with the regeneration of muscle mass and recovery of ventricular function.

Aging does not affect the activation of the myocyte insulin-like growth factor-1 autocrine system after infarction and ventricular failure in Fischer 344 rats

To determine whether the attenuation in the growth capacity of myocytes in the overloaded aging heart is associated with an impairment in the activation of insulin-like growth factor-1 (IGF-1) and its receptor (IGF-1R) in the stressed cells, large myocardial infarcts were produced in Fischer 344 rats at 4 and 16 months of age, and the animals were killed 6 hours, 3 days, and 7 days later. After the documentation of cardiac failure, the unaffected myocytes were enzymatically dissociated, and the expression of IGF-1 and IGF-1R was measured at these three time points after surgery. The level of expression of IGF-1R mRNA increased at 3 days and remained elevated at 7 days in both age groups. In addition, an increase in IGF-1R protein in these cells was found, with no apparent difference with age. This phenomenon was coupled with an upregulation of IGF-1 mRNA of comparable magnitude in the younger and older animals. In contrast, the increases in the dimensional properties of myocytes were delayed and of smaller magnitude in the older infarcted rats. Moreover, the expression of atrial natriuretic factor, used as a molecular marker of myocyte cellular hypertrophy, was greater at 3 days in 4-month-old rats and at 7 days in 16-month-old rats. Thus, aging may affect the hypertrophic response of myocytes after infarction but has no impact on the ability of the cells to enhance the expression of IGF-1 and IGF-1R, which may sustain only in part the growth reserve mechanisms of the pathological heart.

Cutaneous stoma in the roux limb of hepaticojejunostomy (hepaticocutaneous jejunostomy): useful access for intrahepatic stone extraction

A cutaneous stoma in the Roux limb of hepaticojejunostomy (hepaticocutaneous jejunostomy) was used for stone extraction in two children who had hepatolithiasis (14.5 and 15.5 years, respectively) after operation for choledochal cysts. In constructing the hepaticocutaneous jejunostomy, a short, straight proximal limb from the skin to the bilioenteric anastomosis is mandatory. It provides a pathway, superior to the T-tube tract, for repeated stone extraction, which can be performed under sedation, thus obviating repeat laparotomies. The stoma allows flexible choledochoscopy, balloon dilatation of intrahepatic duct strictures, and extraction of intrahepatic stones using grasping forceps, baskets, and balloons. The electrohydraulic lithotriptor may be applied to fragment larger stones.

Does the amniotic fluid protein absorption contribute significantly to the fetal weight?

OBJECTIVE

This study was carried out to evaluate the significance of amniotic fluid protein ingestion and absorption on fetal growth.

METHODOLOGY

Neonates with small bowel atresia during a 30 year period were studied retrospectively.

RESULTS

There were 56 patients enlisted, 17 with duodenal atresia, 18 with jejunal atresia and 21 with ileal atresia. The percentage of mothers with polyhydramnios and the percentage of premature babies decreases as the intestinal atresia becomes more distal. The mean gestational age and the mean birthweight increase as the intestinal atresia becomes more distal. On the other hand, the percentage of the neonates with birthweight below the 50th and the 10th percentiles do not differ significantly as the intestinal atresia becomes more distal.

CONCLUSIONS

It appears that the variation of birthweights in babies with different levels of small bowel atresia may be due to the difference in gestation caused by polyhydramnios. The effect of amniotic fluid protein absorption on fetal bodyweight could not be demonstrated clinically in this study.

Apoptotic and necrotic myocyte cell deaths are independent contributing variables of infarct size in rats

Programmed cell death in the myocardium has been linked to ischemia reperfusion injury as well as to excessive mechanical forces associated with increases in ventricular loading. Moreover, hypoxia activates the suicide program of cardiac myocytes in vitro. Because the supplied portion of the ventricular wall is ischemic and subjected to high levels of systolic and diastolic stresses (acutely after coronary artery occlusion), apoptosis and necrosis may contribute independently to myocyte cell death after infarction. Therefore, myocardial infarction was produced in rats, and, after the determination of ventricular hemodynamics, the contribution of apoptotic and/or necrotic myocyte cell death to infarct size was measured quantitatively from 20 minutes to 7 days after coronary artery occlusion. Programmed cell death was assessed by the terminal deoxynucleotidyl transferase assay and by the electrophoretic detection of DNA laddering. Myocyte necrosis was evaluated by myosin monoclonal Ab labeling. Moreover, the expression of Bcl-2, Bax, and Fas proteins in myocytes was examined by immunocytochemistry. Myocyte cell death by apoptosis and necrosis comprised nearly 3 million myocytes at 2 hours. Apoptotic cell death involved 2.8 million cells and necrotic cell death only 90,000 myocytes. Apoptosis continued to represent the major independent form of myocyte cell death, affecting 6.6 million myocytes at 4.5 hours. Myocyte necrosis peaked at 1 day, including 1.1 million myocytes. DNA electrophoretic analysis confirmed these observations by showing nucleosomal ladders at 2-3 hours, 4.5 hours, 1 day, and 2 days after coronary artery occlusion. Myocytes showing both DNA strand breaks and myosin labeling were a prominent aspect of myocardial damage only after 6 hours. Finally, the expression of Bcl-2 and Fas in myocytes increased 18-fold and 131-fold, respectively. In conclusion, programmed myocyte cell death is the major form of myocardial damage produced by occlusion of a major epicardial coronary artery, whereas necrotic myocyte cell death follows apoptosis and contributes to the progressive loss of cells with time after infarction. The enhanced expression of Fas may be implicated in the activation of apoptosis in spite of the increase in Bcl-2, which tends to preserve cell survival.

Associations between ultrasound indices of follicular blood flow, oocyte recovery and preimplantation embryo quality

The aim of this study was to elucidate possible relationships between ultrasound indices of follicular blood flow, oocyte recovery and the subsequent production and morphological quality of preimplantation embryos. A total of 27 women with bilateral tubal occlusion, undergoing treatment for infertility by in-vitro fertilization and embryo transfer, contributed data from 29 cycles. Transvaginal ultrasonography with colour Doppler imaging and pulsed Doppler spectral analysis was used to obtain indices of blood flow for each follicle immediately before it was aspirated. The main outcome measures for each follicle were the pulsatility index, peak systolic velocity, recovery or non-recovery of an oocyte and the subsequent production or non-production of an embryo. A total of 126 follicles were studied, 102 oocytes were recovered and 58 embryos (49 at grades I or II) were produced. There were six clinical pregnancies (pregnancy rate 27.3% per embryo transfer, 22.2% per patient). There was a significant correlation (P < 0.0001, chi2 test) between whether or not follicular blood flow was detected and whether or not an oocyte was recovered. The sensitivity of a test based on the presence of detectable blood flow and the subsequent recovery of an oocyte was 74% and the positive predictive value was 93%. The peak systolic velocity (PSV, measured in cm/s, mean +/- SD) in follicles with detectable blood flow was significantly higher in follicles that were associated with the production of a preimplantation embryo (19.7 +/- 10.8) compared with those that were not (9.9 +/- 5.3, P < 0.0001, Student's t-test). There was a 70% chance of producing a grade I or II embryo if the follicular blood velocity was >/=10 cm/s, compared with 14% if the PSV was <10 cm/s, or 18% if no blood flow was detected. We conclude that there is a physiological relationship between follicular blood velocity, oocyte recovery and the production of a high-grade preimplantation embryo, which may form the basis of a useful clinical test.

Isolation of NAD cycle mutants defective in nicotinamide mononucleotide deamidase in Salmonella typhimurium

The NAD or pyridine nucleotide cycle is the sequence of reactions involved in the breakdown of NAD to nicotinamide mononucleotide (NMN) and regeneration of NAD. This cycle is fivefold more active during aerobic growth of Salmonella typhimurium and under this condition breaks down half of the NAD pool every 90 min. DNA ligase is known to convert NAD to NMN but is only a minor contributor to the NAD cycle during aerobic growth. The dominant aerobic route of NMN formation is otherwise uncharacterized. Accumulated NMN generated by either of these routes is potentially dangerous in that it can inhibit the essential enzyme DNA ligase. The reactions which recycle NMN to NAD may serve to minimize the inhibition of ligase and other enzymes by accumulated NMN. The predominant recycling reaction in S. typhimurium appears to be NMN deamidase, which converts NMN directly to the biosynthetic intermediate nicotinic acid mononucleotide. Mutants defective in this recycling step were isolated and characterized. By starting with a ligase-deficient (lig mutant) parent strain that requires deamidase to assimilate exogenous NMN, two classes of mutants that are unable to grow on minimal NMN media were isolated. One class (pncC) maps at 83.7 min and shows only 2% of the wild-type levels of NMN deamidase. Under aerobic conditions, a lig+ allele allows a pncC mutant to grow on NMN and restores some deamidase activity. This growth ability and enzyme activity are not found in lig+ strains grown without oxygen. This suggests that the existence of a second NMN deamidase (pncL) dependent on ligase and stimulated during aerobic growth. The second class of mutants (pncD) gains a requirement for isoleucine plus valine with growth in the presence of exogenous NMN. We propose that pncD mutations reduce the activity of an ilv biosynthetic enzyme that is naturally sensitive to inhibition by NMN.

Myocyte nuclear mitotic division and programmed myocyte cell death characterize the cardiac myopathy induced by rapid ventricular pacing in dogs

BACKGROUND

Observations in humans have raised the possibility that idiopathic dilated cardiomyopathy is characterized by myocyte cell loss and cell proliferation, which contribute to wall thinning and chamber dilation. Moreover, the mechanism of myocyte cell death in this patient population has been unclear. Because rapid ventricular pacing in dogs leads to a dilated myopathy that mimics the idiopathic form in man, this animal model was used to demonstrate whether myocyte nuclear mitotic division and programmed myocyte cell death occur in this setting. Additionally, the expression of proliferating cell nuclear antigen (PCNA) and Fas protein in myocytes was examined as a molecular indicator of the activation of the cell cycle and apoptotic cell death, respectively.

EXPERIMENTAL DESIGN

Mongrel dogs were chronically instrumented for measurements of systemic hemodynamics and for left ventricular pacing. At sacrifice, myocardial samples were obtained for the estimation of the number of myocytes and interstitial cells showing mitosis and for the detection of DNA laddering. In addition, the number of myocyte nuclei exhibiting DNA strand breaks, as well as the frequency of myocytes labeled by PCNA and Fas protein, was determined. Finally, the distribution of nuclei in enzymatically dissociated myocytes was evaluated.

RESULTS

Pacing-induced heart failure was characterized by DNA fragmentation and by 3700 myocytes per million cells undergoing apoptotic cell death. This phenomenon was accompanied by 11,000 cells per million expressing Fas protein. Concurrently, 22 and 17 myocytes and interstitial cells per million showed nuclear mitotic division, whereas no changes in the relative proportions of mononucleated and multinucleated myocytes were detected. Moreover, PCNA-labeled myocytes accounted for 40,000 cells per million.

CONCLUSIONS

In conclusion, the induction of PCNA and Fas may be linked to the activation of myocyte proliferation and programmed cell death in the myocardium with rapid ventricular pacing, and these two cellular responses may play a key role in the development of the congestive dilated myopathy.

Contribution of opening and closing of lung units to lung hysteresis

The recruitment and derecruitment of lung units is one explanation of the hysteresis observed in an excised lung during inflation and deflation. A simplified model has been proposed in which the recruitment-derecruitment process is a function of end-expiratory pressure (Frazer, D.G., K.C. Weber and G.N. Franz, Respir. Physiol. 61: 277-288, 1985). The object of this study was to test this model with three experimental procedures. During the first set of experiments, progressively larger pressure-volume (PL-VL) loops were recorded with end-expiratory pressure held at either -5 cmH2O, where all lung units are assumed to be closed, or +5 cmH2O, where all recruited lung units are assumed to be open. In the first case hysteresis is maximal, in the second, minimal. The difference in hysteresis is presumed to arise from the recruitment-derecruitment process. In the second set of experiments, excised lungs are slowly inflated and then deflated at a constant rate while constant-amplitude sinusoidal volume oscillations are superimposed. The end-expiratory pressure of the superimposed loops gradually rose as the lung was inflated and fell as the lung was deflated. Hysteresis was minimal when end-expiratory pressure was above 4 +/- 1 cmH2O even as peak-to-peak loop pressure greatly varied. This supports the notion of an end-expiratory pressure dependent mechanism of recruitment/derecruitment. During the third set of experiments lungs were inflated to either 50%, 75%, or 100% TLC. Volumes of air were then withdrawn and replaced so that the initial volume was restored in sinusoidal fashion as the amplitude of the volume excursions increased. For PL-VL loops with end-expiratory pressures between +4 and -2 cmH2O, pressure amplitudes rose and the hysteresis index (loop area/tidal volume) increased, regardless of the initial lung volume. These results are consistent with the previously described model of Frazer et al. (1985) which assumed that PL-VL curves can be divided into an 'opening' region, an 'open' region and a 'closing' region and that the demarcation of these regions depends on transpulmonary pressure, specifically end-expiratory pressure, and to a much lesser degree on lung volume.

Myocardial infarction and the myocyte IGF1 autocrine system

To determine the effects of acute myocardial infarction on the extent and distribution of mural stress on surviving myocardial tissue, coronary artery occlusion was surgically produced in rats. Following haemodynamic measurements in vivo, the characteristics of cardiac anatomy were determined and found to consist of an increase in mid-chamber lumenal diameter and a decrease in wall thickness. The combination of these phenomena resulted in an eight-fold increase in diastolic wall stress on the remaining viable portion of the wall and severe impairment of left and right ventricular performance. Since insulin-like growth factor-1 (IGF1) and its receptor (IGF1R) are required for cell growth in vitro, the possibility was raised that an autocrine IGF1-IGF1R system may be present in vivo and may become activated in viable ventricular myocytes shortly after infarction. Therefore, the unaffected myocytes of the left ventricle were enzymatically dissociated and the expression of IGF1R and IGF1 mRNAs were measured at 12 h and at 1, 2-3, and 7 days after surgery. The level of IGF1R mRNA increased at 12 h and remained elevated at 1 and 2-3 days following coronary artery ligation. In addition, an increased level of IGF1R protein was found on these cells. This phenomenon was coupled with the enhanced expression of IGF1 mRNA in the muscle cells at all points. Thus, the marked elevation in ventricular loading after coronary occlusion may activate the IGF1-IGF1R autocrine system of the unaffected cells, modulating the cellular growth processes implicated in short-term ventricular remodelling of the infarcted heart.

Identification and activation of autocrine renin-angiotensin system in adult ventricular myocytes

To date, the demonstration that the molecular components of the renin-angiotensin system (RAS) are present in adult ventricular myocytes is lacking. In addition, whether the RAS is upregulated under conditions of overload and myocyte hypertrophy in vivo remains to be determined. By employing an in vivo model of ischemic cardiomyopathy in rats, we document that adult myocytes express genes for renin, angiotensinogen, angiotensin-converting enzyme (ACE), and angiotensin II (ANG II) receptors. Moreover, renin, ACE, and ANG II receptor mRNAs increased in stressed myocytes undergoing cellular hypertrophy. At the protein level, the percentage of myocytes containing renin, ANG I, and ANG II was significantly increased in the overloaded heart. The number of binding sites for ANG II per myocyte also markedly increased under this setting. These results provide direct evidence of the existence of a myocyte RAS, which may be activated in pathological states of the heart to support myocyte growth and contractile function.

Surgical closed atrial septotomy under transesophageal guidance

An infant with pulmonary atresia and intact ventricular septum is presented who, after initial patch reconstruction of the right ventricular outflow tract and bidirectional cavopulmonary anastomosis through a fifth median sternotomy, underwent an echocardiographically guided closed atrial septotomy, which resulted in marked long-term clinical improvement. The technique of intraoperative transesophageal echocardiography as used in the presented case represents an expanded role for this diagnostic modality in congenital cardiac surgery.

Stretch-induced programmed myocyte cell death

To determine the effects of loading on active and passive tensions, programmed cell death, superoxide anion formation, the expression of Fas on myocytes, and side-to-side slippage of myocytes, papillary muscles were exposed to 7-8 and 50 mN/mm2 and these parameters were measured over a 3-h period. Overstretching produced a 21- and a 2.4-fold increase in apoptotic myocyte and nonmyocyte cell death, respectively. Concurrently, the generation of reactive oxygen species increased 2.4-fold and the number of myocytes labeled by Fas protein 21-fold. Moreover, a 15% decrease in the number of myocytes included in the thickness of the papillary muscle was found in combination with a 7% decrease in sarcomere length and the inability of muscles to maintain stable levels of passive and active tensions. The addition of the NO-releasing drug, C87-3754, prevented superoxide anion formation, programmed cell death, and the alterations in active and passive tensions with time of overloaded papillary muscles. In conclusion, overstretching appears to be coupled with oxidant stress, expression of Fas, programmed cell death, architectural rearrangement of myocytes, and impairment in force development of the myocardium.

The cellular basis of pacing-induced dilated cardiomyopathy. Myocyte cell loss and myocyte cellular reactive hypertrophy

BACKGROUND

Rapid ventricular pacing leads to a cardiac myopathy consisting of an increase in chamber dimension, mural thinning, elevation in ventricular wall stress, and congestive heart failure, mimicking dilated cardiomyopathy in humans. However, contrasting results have been obtained concerning the mechanisms of ventricular dilation and the existence of myocardial hypertrophy. Moreover, questions have been raised regarding the occurrence of myocardial damage and cell loss in the development of the experimental myopathy.

METHODS AND RESULTS

The functional and structural characteristics of the heart were studied in conscious dogs subjected to left ventricular pacing at 210 beats per minute for 3 weeks and 240 beats per minute for an additional week. At the time the animals were killed, measurements of myocardial structural integrity and myocyte shape, size, and number were determined by morphometric analysis of the myocardium in situ and enzymatically dissociated cells. The experimental protocol used was associated with overt cardiac failure documented by an increase in left ventricular end-diastolic pressure and a decrease in left ventricular systolic pressure and +dP/dt in combination with tachycardia, ascites, and pulmonary congestion. Although cardiac weights were not altered, cavitary diameter was increased and wall thickness was decreased from the base to the apex of the heart. Multiple foci of replacement fibrosis, comprising 6% of the myocardium, were detected across the left ventricular wall. Measurements of myocyte size and number documented a 39% loss of cells in the entire ventricle and a 61% increase in volume of the remaining viable myocytes. Myocyte hypertrophy was characterized by a 33% increase in cell length and a 23% increase in transverse area, resulting in a 23% increase in the cell length-to-cell diameter ratio. Pacing did not alter the relative proportion of mononucleated, binucleated, and multinucleated myocytes in the myocardium.

CONCLUSIONS

Myocyte cell loss and myocyte reactive hypertrophy are the major components of ventricular remodeling in pacing-induced dilated cardiomyopathy.

Dexamethasone enhances accumulation of cholesteryl esters by human macrophages

The effects of dexamethasone on lipid accumulation by human monocyte-derived macrophages were investigated. Preincubation of macrophages with dexamethasone for a period of 16-20 h resulted in a reproducible increase (3.5-fold) in the incorporation of oleate into cholesteryl esters. The effect was specific because no alterations were observed in oleate incorporation into triglycerides or phospholipids. Measurement of cellular cholesteryl esters indicated a fourfold increase after preincubation with dexamethasone. This increase was mediated by opposite effects on synthesis and breakdown of these lipids. Dexamethasone produced a 60% increase in activity of the enzyme acyl-CoA: cholesterol O-acyltransferase (ACAT), active in synthesis of cholesteryl esters, and a 40% decrease in that of neutral cholesteryl esterase, active in cholesteryl ester breakdown. The increased ACAT activity appeared to reflect increased mRNA for the enzyme. The effects of dexamethasone on cholesteryl ester accumulation by macrophages reached statistical significance at a concentration of 100 nM. They were dose dependent, and saturation was observed at around 1 microM. The effects were significant at low concentrations of cholesterol in the medium. At high-medium cholesterol, there was a large cholesterol-induced increase in ACAT activity that obscured most of the effect of dexamethasone. In general, the data suggest that high glucocorticoid levels enhance lipid accumulation by macrophages and thus would have an atherogenic action that is independent of serum cholesterol.

Fibroblast proliferation during myocardial development in rats is regulated by IGF-1 receptors

To determine whether the growth of cardiac fibroblasts during development is modulated by the insulin-like growth factor (IGF)-1 receptor (IGF-1R), the expression of IGF-1, IGF-2, and IGF-1R was determined in fibroblasts from fetal and postnatal hearts. The expression of proliferating cell nuclear antigen (PCNA) and DNA polymerase-alpha was also evaluated in combination with the estimation of DNA replication. In comparison with fetal hearts, at postnatal day 21, fibroblast expression of IGF-1R mRNA, IGF-2, PCNA, and DNA polymerase-alpha was reduced by 77, 70, 80, and 86%, respectively. Moreover, IGF-1R protein decreased by 48% at 21 days. Bromodeoxyuridine labeling decreased by 88 and 89% in the left and right ventricle, respectively, at this time. Two different antisense oligodeoxynucleotides to IGF-1R reduced DNA replication by 60 and 44% in fibroblasts in culture. In addition, this intervention markedly attenuated the growth response of fibroblasts to IGF-1 or serum. In conclusion, the IGF-1R system appears to play a major role in the regulation of fibroblast growth in the heart in vivo.

Programmed cell death and expression of the protooncogene bcl-2 in myocytes during postnatal maturation of the heart

To determine whether programmed myocyte cell death is a major component of the differential growth adaptation of the right and left ventricle during development, the formation of DNA strand breaks in myocyte nuclei was identified and quantitated in hearts of rats at the end of gestation and at 1, 5, 11, and 21 days after birth. Incorporation of BrdU in left and right ventricular myocytes was also evaluated. Moreover, the expression of bcl-2 in myocytes was determined. Programmed myocyte cell death was absent in the fetal heart but affected the myocardium postnatally. This phenomenon was no longer detectable at 21 days. DNA strand breaks in nonmyocyte nuclei were present at all time intervals. Quantitatively, 10.4, 6.1, and 2.5 myocyte nuclei/10,000 nuclei exhibited DNA degradation at 1 day in the right ventricle, interventricular septum, and left ventricule, respectively. Corresponding values at 5 days were 3.7, 3.5, and 2.0 myocyte nuclei/10,000 nuclei. At 11 days, programmed cell death involved 1.2, 1.5, and 0.53 myocyte nuclei/10,000 nuclei in these three regions of the heart. The 4.2-fold, 1.9-fold, and 2.3-fold greater magnitude of programmed cell death in the right ventricle at 1, 5, and 11 days was statistically significant. In contrast, BrdU incorporation in myocytes decreased in a comparable manner in the left and right ventricles with maturation. Importantly, bcl-2 mRNA levels were high in fetal myocytes, decreased markedly at 1 and 5 days, and progressively increased at 11 and 21 days. The expression of bcl-2 was lower in right than in left ventricular myocytes. In conclusion, programmed myocyte cell death is inversely related to bcl-2 expression and affects the right ventricle more than the left ventricle during postnatal development. This phenomenon may be crucial in the modulation of the number of myocytes in the two ventricles during the transition from the fetal to the adult circulatory system.

Down-regulation of the IGF-1 system parallels the attenuation in the proliferative capacity of rat ventricular myocytes during postnatal development

BACKGROUND

Insulin-like growth factor-1 receptor (IGF-1R) and its ligand (IGF-1) have been implicated in the growth of several cell types, including ventricular myocytes. However, the growth-promoting effect of this pathway on myocyte hypertrophy and hyperplasia has not been determined. During early postnatal development, myocyte cell volume increases nearly 25-fold, and myocyte proliferation is markedly attenuated, so a progressive decrease in this signaling mechanism will indicate that the IGF-1-IGF-1R system is mostly involved in cell proliferation. Conversely, a continuous increase in the expression of IGF-1 and IGF-1R in myocytes with maturation will suggest its involvement in cellular hypertrophy.

DESIGN

Myocytes were isolated from fetal rats and from rats at 1, 5, 11, 21, 35, and 60 days of age. Total RNA was extracted from these cells, and the expression of IGF-1, IGF-2, IGF-1R, and DNA polymerase alpha was measured by reverse transcriptase-PCR. IGF-1R mRNA levels were also determined by RNase protection assay, and the changes in IGF-1R protein were determined by the cross-linking technique. Finally, the expression of late growth-related genes was determined and compared with the fraction of muscle cells synthesizing DNA. These analyses were restricted to the left ventricular free wall and septum combined.

RESULTS

Myocardial development was characterized by a progressive decrease in the expression of late growth-related genes in myocytes, which was particularly evident at 21 days after birth and persisted up to 2 months of age. The expression of IGF-2 in these cells decreased at birth, whereas the attenuation in IGF-1 mRNA became apparent a few days later during postnatal development. The induction of IGF-1R at the message and protein levels decreased by 11 days, and this phenomenon was more evident at the subsequent age intervals. Moreover, DNA synthesis in myocytes was sharply reduced at 21 days after birth.

CONCLUSIONS

In conclusion, the decline in myocyte proliferation with cardiac development appears to be coupled with attenuation of the IGF-1-IGF-1R system, which may condition the changes in late growth-regulated genes, DNA replication, and cellular mitotic division in the myocardium.

Ventricular remodeling in global ischemia

To determine the effects of chronic constriction of the left coronary artery on the function and structure of the heart, coronary artery narrowing was surgically induced in rats and ventricular pump performance, extent and distribution of myocardial damage, and the hypertrophic and hyperplastic response of myocytes were examined. Alterations in cardiac hemodynamics were found in all rats, but the characteristics of the physiological properties of the heart allowed a separation of the animals into two groups which exhibited left ventricular dysfunction and failure, respectively. Left ventricular hypertrophy occurred in both groups and was characterized by ventricular dilatation and wall thinning which were more severe in the failing animals. Multiple foci of myocardial damage across the wall were seen in all animals but tissue injury was more prominent in the endomyocardium and in failing rats. The anatomical and hemodynamic changes resulted in a significant increase in diastolic wall stress which paralleled the depression in ventricular performance. Myocyte cell loss and myocyte cellular hypertrophy were more severe with ventricular failure than with dysfunction. Finally, diastolic overload appeared to be coupled with activation of the DNA synthetic machinery of myocytes and nuclear mitotic division. In conclusion, a fixed lesion of the left coronary artery leads to abnormalities in cardiac dynamics with marked increases in diastolic wall stress and extensive ventricular remodeling in spite of compensatory myocyte cellular hypertrophy and hyperplasia in the remaining viable tissue.

Cerebral blood flow during cardiopulmonary bypass: influence of temperature and pH management strategy

Because disordered autoregulation of cerebral blood flow may underlie neurologic injury associated with cardiopulmonary bypass (CPB), we studied the effects of normothermic (37 degrees C) and hypothermic (18 degrees C) CPB on cerebral vascular reactivity in 6 to 8-week-old piglets. Hypothermic CPB animals were subdivided into alpha-stat and pH-stat groups (n = 6 animals each group) according to acid-base management protocol. Cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2), cerebral vascular resistance (CVR), and CBF response to hypercapnia were examined before, during, and 1 hour after CPB and used to calculate CVR per millimeter of mercury change in arterial partial pressure of CO2: (CVRnormocapnia - CVRhypercapnia)/(PaCO2 hypercapnia - PaCO2 normocapnia). Before CPB, CBF, CMRO2, and vascular reactivity to elevated CO2 were similar in the three groups; these parameters remained unchanged by normothermic CPB. However, during hypothermic CPB, CBF and CMRO2 decreased in both alpha-stat and pH-stat groups; in the alpha-stat group, CBF decreased from 27 +/- 5 mL.min-1.100 g-1 (normothermic CPB) to 5 +/- 1 mL.min-1.100 g-1 (hypothermic CPB) (p < 0.05) and CMRO2 decreased from 1.8 +/- 0.21 to 0.24 +/- 0.04 mL.min-1.100 g-1 (p < 0.05), whereas in the pH-stat group CBF decreased from 28 +/- 2 to 9 +/- 1 mL.min-1. 100 g-1 (p < 0.05) and CMRO2 decreased from 1.63 +/- 0.07 to 0.31 +/- 0.09 mL.min-1.100 g-1 (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Myocyte performance during evolution of myocardial infarction in rats: effects of propionyl-L-carnitine

To determine whether alterations in the mechanical properties and calcium transients of myocytes are important factors in the evolution of the postinfarcted heart, these physiological parameters were measured in the viable muscle cells of the left ventricle 6 h, 2-3 days, 1 wk, and 1 mo after coronary artery occlusion and the documentation of left ventricular failure. In addition, the effects of propionyl-L-carnitine (PLC) on shortening properties and calcium dynamics of single myocytes were established to demonstrate whether the potential increase in ATP generation by this intervention improved myocyte cell function. Myocardial infarction was associated with a progressive increase in length of the spared myocytes, whereas the changes in myocyte diameter were apparent only at the 1-mo interval. Mechanically, myocyte shortening was decreased 43% at 6 h, 34% at 2-3 days, 26% at 1 wk, and 41% at 1 mo after infarction. Similar abnormalities were noted in the velocity of myocyte shortening. Peak systolic calcium was decreased at all intervals after infarction. In contrast, diastolic calcium remained within control values. PLC was capable of ameliorating the mechanical behavior and calcium transients of myocytes, particularly 1 mo after infarction. Thus alterations in muscle cell performance may be important determinants in the development and progression of ischemic cardiomyopathy, and interventions improving myocyte contractility may interfere with the unfavorable outcome of the disease.

The IGF-1-IGF-1 receptor system modulates myocyte proliferation but not myocyte cellular hypertrophy in vitro

In preliminary experiments it was established that the hypertrophic and hyperplastic responses of neonatal cardiac myocytes in culture were associated with enhanced expression of IGF-1 and IGF-1 receptors in these cells. Therefore, to determine the role of IGF-1 receptors on myocyte growth, cells were exposed to antisense oligodeoxynucleotides to IGF-1 receptor mRNA and the effects of this intervention on DNA synthesis, nuclear mitotic division, and changes in the number of myocytes were measured. Moreover, the influence of this procedure on ANF induction and myocyte cell volume was examined. Inhibition of the formation of IGF-1 receptors on myocytes suppressed DNA replication, mitosis, and cell proliferation. In contrast, the antisense treatment did not alter the expression of ANF in myocytes or cellular hypertrophy. Finally, IGF-1 stimulated DNA synthesis in myocytes cultured in serum-free medium, without inducing cellular hypertrophy. In conclusion, ligand activation of IGF-1 receptors on myocytes appears to be coupled with cell proliferation, whereas myocyte cellular hypertrophy seems to be independent from this effector pathway.

The effects of nitric oxide inhibition on regional hemodynamics during hyperdynamic endotoxemia

OBJECTIVE

To determine the effect of the inhibition of nitric oxide (NO) on selective organ blood flow in endotoxin-induced sepsis.

DESIGN

Nonrandomized, controlled experiment.

SETTING

Animal research facility in Brooklyn, NY.

PARTICIPANTS

Eleven mongrel dogs.

INTERVENTION

Eleven dogs were divided into one of two groups: a control group (n = 5) and an endotoxin-treated group (n = 6). The animals were anesthetized, and electromagnetic and ultrasonic flow probes were placed on the distal aorta, right internal carotid artery, superior mesenteric artery, and left renal artery. Sepsis was induced with a 60-mg/kg intravenous injection of Escherichia coli endotoxin. When the arterial blood pressure decreased to less than 60 mm Hg despite adequate fluid resuscitation, NO synthesis was inhibited with a 25-mg/kg intravenous administration of NG-monomethyl-L-arginine. After 15 minutes of inhibition, a 400-mg/kg intravenous administration of L-arginine, the substrate of NO synthase enzyme, was given. Physiologic measurements were continued for 15 minutes thereafter.

MAIN OUTCOME MEASURES

Heart rate, blood pressure, central venous pressure, pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac output, hematocrit, arterial and venous blood gas values, and blood flow measurements of right internal carotid artery, superior mesenteric artery, left renal artery, and distal aorta.

RESULTS

Control animals did not demonstrate a significant (P > .05) decrease in blood flow in the internal carotid artery, superior mesenteric artery, and distal aorta after the administration of NG-monomethyl-L-arginine. The endotoxin-treated group showed a significant (P < .05) decrease in organ perfusion when treated with the NO synthase inhibitor, NG-monomethyl-L-arginine.

CONCLUSIONS

Inhibition of NO production in the treatment of sepsis caused a significant decrease in blood flow to all vascular beds in vivo. The role, if any, of the inhibition of NO in the treatment of sepsis is questioned.

Colonic hyperganglionosis presenting as neonatal enterocolitis and multiple strictures

Neuronal intestinal dysplasia (NID) usually mimics Hirschsprung's disease, but rarely presents as neonatal enterocolitis. The authors report a case of colonic hyperganglionosis, which is a form of NID, presenting with postenterocolitis intestinal strictures. NID should be considered as a possible (although rare) cause of neonatal enterocolitis and may present with intestinal strictures.

Fatty acids as determinants of triglyceride and cholesteryl ester synthesis by isolated hepatocytes: kinetics as a function of various fatty acids

Triglyceride synthesis by hepatocytes is currently thought to be the rate-limiting step for lipoprotein formation. In order to determine whether triglyceride and cholesteryl ester syntheses in hepatocytes are sensitive to physiological fluctuations of serum fatty acids, the fatty acid dependence of these pathways was examined. Uptake of various fatty acids and incorporation into triglyceride and cholesteryl esters were studied in isolated rat hepatocytes. Rates were determined under conditions of linear incorporation and related to the concentrations of total and unbound fatty acid in a mixture of fatty acids and albumin. The findings were: pathways for triglyceride and cholesteryl ester synthesis saturated at unbound fatty acid concentrations (or fatty acid albumin ratios) within the range of serum values and thus would be acutely modulated by fluctuations in serum fatty acids. Addition of cholesterol to the medium increased cellular cholesterol, but did not alter rates of cholesterol esterification, suggesting that endogenous cholesterol synthesis provided the needed substrate. Oleate, palmitate, and linoleate were comparable in their saturation kinetics and ability to support triglyceride and cholesteryl ester synthesis. Consequently, their binding affinity for serum albumin would determine their lipid-incorporation rates. On this basis, in humans, oleate would yield the lowest rates as it has the lowest unbound fatty acid at each fatty acid-albumin ratio. Stearate, in contrast to the other fatty acids, was poorly esterified into neutral lipids by hepatocytes. Poor hepatic metabolism of stearate most likely explains previous findings of a hypocholesteremic effect of diets high in stearate as compared to other saturated fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for two NAD kinases in Salmonella typhimurium

The electron-carrying cofactor NADP is formed by phosphorylation of NAD. A strategy for the isolation of NAD kinase mutants revealed two classes of temperature-sensitive mutations, nadF and nadG, mapping at min 13 and 72 of the Salmonella chromosome. Both mutant types grew on nutrient broth at both 30 and 42 degrees C but on minimal medium showed a temperature-sensitive growth defect which was not corrected by any of the single nutritional supplements tested. A nadF deletion mutant grew on nutrient broth but not on minimal medium. A double mutant with the nadF deletion and a nadG(Ts) mutation showed temperature-sensitive growth on all media. We propose that Salmonella typhimurium has two NAD kinases, one encoded by the nadF and one by the nadG gene. This is supported by the fact that temperature-sensitive mutants of both genes produce kinase activity with altered heat stability. Results suggest that either one of two NAD kinases is sufficient for growth on rich medium, but that both are needed for growth on minimal media. Enzyme assays show that the nadF gene is responsible for about 70% of total NAD kinase activity, and that the nadG gene dictates the remaining 30%. While testing nutritional phenotypes of nadF and nadG mutants, we found that the biosynthetic intermediate, quinolinic acid (QA) inhibited growth of nadF mutants on nutrient broth. This suggested that the NadG enzyme might be inhibited by QA. Enzyme assays demonstrated that QA inhibits the NadG but not the NadF enzyme. This suggests the existence of a regulatory mechanism which controls NADP levels.

Coronary artery constriction in rats affects the activation of alpha 1 adrenergic receptors in cardiac myocytes

OBJECTIVE

To determine whether alpha 1 adrenergic receptor mediated myocyte contractility and growth are depressed acutely after non-occlusive coronary artery narrowing, the left coronary artery was constricted in rats and mechanical behaviour, cytosolic calcium, and regulation of alpha 1 adrenergic receptors were examined in myocytes seven days later.

METHODS

Coronary artery stenosis was surgically induced in rats and following the estimation of global cardiac performance myocytes were enzymatically dissociated and radioligand binding studies were performed. In addition, the isotonic contractile performance, cytosolic calcium transients and noradrenaline stimulated inositol phosphate generation in myocytes were measured in the presence of WB 4101 or after chlorethylclonidine treatment.

RESULTS

Estimations of cell mechanics in vitro established that peak shortening was decreased by 36% and 18% in left and right ventricular myocytes of coronary stenosed rats. Time to peak shortening was prolonged by 29% in left and 20% in right myocytes, whereas velocity of shortening was decreased by 27% in left myocytes. These alterations were associated with increases in cell length and width, indicative of myocyte hypertrophy. In addition, coronary stenosis was accompanied by reductions in the expression of alpha 1a and alpha 1b receptor subtypes in myocytes. alpha 1 Adrenergic receptor density and noradrenaline stimulated phosphoinositol turnover were decreased by 30% and 34% in left myocytes. alpha 1a Adrenergic receptor subtype mediated cytosolic calcium concentration and myocyte mechanical performance were also impaired in left myocytes only. The alpha 1a adrenergic receptor subtype antagonist WB 4101 abolished noradrenaline stimulated inositol phosphate generation in myocytes, whereas chlorethylclonidine at large doses only partially inhibited this response.

CONCLUSIONS

In conclusion, coronary narrowing leads to defects in the regulation of alpha 1 adrenergic receptors on myocytes which are coupled with attenuation in the transmission of signals, possibly affecting myocyte cell function and ongoing reactive cellular hypertrophy.

Nitric oxide inhibition in the treatment of the sepsis syndrome is detrimental to tissue oxygenation

The manifestations of the septic syndrome are thought to be mediated by cytokines through their role in the production of nitric oxide (NO). It is hypothesized that the inhibition of NO production with an inhibitor such as NG-monomethyl-L-arginine (L-NMMA) may be beneficial in the treatment of septic shock. Sepsis was induced by the intravenous administration of Escherichia coli endotoxin (60 micrograms/kg) in six conditioned mongrel dogs (20-24 kg). Mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), and pulmonary artery pressure (PAP) were continuously monitored. Cardiac output (CO), pulmonary capillary wedge pressure (PCWP), and arterial and mixed venous blood gases were obtained every 10 min. When the MAP decreased below 60 mm Hg, NO inhibitor L-NMMA was given by intravenous injection (25 mg/kg). Physiologic parameters were then measured at 2 and 5 min after L-NMMA injection. Subsequently, L-arginine (400 mg/kg), the substrate for the NO synthase enzyme, was administered and measurements were repeated at similar intervals. L-NMMA in septic canines produced a significant increase in MAP and SVR with a significant decrease in CO and tissue oxygenation (DO2 and VO2). These changes were reversed with the administration of L-arginine. There were no significant differences in the PCWP, CVP, PAP, or HR throughout the entire study. These results suggest that the inhibition of NO production by L-NMMA in a septic model produces elevated MAP and SVR at the expense of tissue oxygenation. Thus, its use, as a principal means of therapy for the septic syndrome, may not be appropriate because of detrimental effects on tissue oxygenation.

Structural organization of the human type VII collagen gene (COL7A1), composed of more exons than any previously characterized gene

The human type VII collagen (COL7A1) gene is the locus for mutations in at least some cases of dystrophic epidermolysis bullosa. Here we describe the entire intron/exon organization of COL7A1, which is shown to have 118 exons, more than any previously described gene. Despite this complexity, COL7A1 is compact. Consisting of 31,132 bp from transcription start site to polyadenylation site, it is only about three times the size of type VII collagen mRNA. Thus, COL7A1 introns are small. A 71-nucleotide COL7A1 intron is the smallest intron yet reported in a collagen gene, and only one COL7A1 intron is greater than 1 kb in length. All exons in the COL7A1 triple helix coding region that do not begin with sequences corresponding to imperfections of the triple helix begin with intact codons for Gly residues of Gly-X-Y repeats. This is reminiscent of the structure of fibrillar rather than other nonfibrillar collagen genes. In addition, the COL7A1 triple helix coding region contains many exons of recurring sizes (e.g., 25 exons are 36 bp, 12 exons are 45 bp, 8 exons are 63 bp), suggesting an evolutionary origin distinct from those of other nonfibrillar collagen genes. Sequences from the 5' portion of COL7A1 are presented along with the 3766-bp intergenic sequence, which separates COL7A1 from the upstream gene encoding the core I protein of the cytochrome bc1 complex. The COL7A1 promoter region is found to lack extensive homologies with promoter regions of other genes expressed primarily in skin.

Subacute ischemia of the colon esophageal interposition

The most devastating complication of colon interposition is acute ischemia with colon necrosis. Delayed complications of the interposed colon, including long segment stricturing develop in an occasional patient. Some investigators have speculated that these late complications result from delayed colon ischemia. We believe that these patients represent a small subgroup who have nonnecrotic vascular insufficiency (subacute ischemia) of the interposed colon, which is present from the time of the operation. We reviewed the postoperative contrast radiographic studies of 3 patients with subacute colon ischemia. The radiographic findings are characteristic, and are identical to those seen in ischemic colitis of the nonmobilized colon. They include loss of haustral folds, an ill-defined bowel wall border, and mucosal changes such as "thumbprinting," and "urticaria." Fibrosis and stricturing represent the end-stage of the ischemic process.

Myocyte cellular hyperplasia and myocyte cellular hypertrophy contribute to chronic ventricular remodeling in coronary artery narrowing-induced cardiomyopathy in rats

To determine whether cardiac failure produced by chronic coronary artery stenosis was associated with the activation of myocyte cellular hyperplasia in the myocardium, the changes in number and size of left ventricular myocytes were measured in rats 3 months after surgery. The hypertrophied left ventricle was found to possess 44%, 32%, 49%, and 48% fewer mononucleated, binucleated, trinucleated, and tetranucleated myocytes, respectively. In contrast, the hypertrophied right ventricle contained 1.49 x 10(6) more myocytes as a result of a 2.1-fold, 1.4-fold, and 1.4-fold increase in mononucleated, binucleated, and tetranucleated myocytes. Myocyte cell volume was seen to increase 49% and 21% in left and right ventricular myocytes, respectively. The process of myocyte cellular hyperplasia in the right ventricular myocardium was accompanied by capillary proliferation, and these events were responsible for the parallel addition of newly formed cells and capillaries within the wall and mural thickening. Moreover, the in-series insertion of new myocytes contributed to right ventricular dilatation after coronary artery stenosis. In view of the fact that extensive myocardial damage and cell loss may have masked the phenomenon of myocyte cellular hyperplasia in the left ventricle, the presence of DNA synthesis in myocyte nuclei was evaluated at 3 days, 1 week, 2 weeks, 1 month, and 3 months after coronary artery stenosis. Bromodeoxyuridine (BrdU) labeling markedly increased in myocyte nuclei of both ventricles, reaching its peak at 1 and 2 weeks. BrdU labeling of nonmyocyte nuclei also increased but mostly at 2 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamic cardiomyoplasty: left ventricular diastolic compliance at different skeletal muscle tensions

The possible limitation of left ventricular (LV) relaxation during diastole is a concern for clinicians and researchers utilizing dynamic cardiomyoplasty. This study was designed to evaluate the LV compliance at three different skeletal muscle tensions, in a normal heart and in a failing heart, created by propranolol infusion (11.6 mg/kg). A biventricular latissimus dorsi muscle (LDM) wrap was performed in 10 dogs. The LV pressure (Millar) and two minor axis dimensions (endocardial crystals) were measured. LV pressure-volume loops were constructed, and LV diastolic compliance was calculated. The measurements were obtained before wrap and after wrap at different LDM tensions with 0, 5, and 10 volts stimulation each time. These measurements were repeated after propranolol treatment. The results showed that LV diastolic compliance (dV/dP) was 1.79 before wrap and about 0.7 after wrap, and after propranolol, at various tensions and stimulations. LDM wrap decreased LV compliance significantly. LV compliance was not significantly affected by changing tension or voltage of stimulation in either the failing or the non-failing heart. The reduction in compliance may be an indication that LDM wrap causes a limitation of LV relaxation, which is one of wrap's deleterious effects.

Complete coding sequence, intron/exon organization, and chromosomal location of the gene for the core I protein of human ubiquinol-cytochrome c reductase

Core I protein is a nuclear-encoded component of the ubiquinol-cytochrome c reductase complex of the mitochondrial respiratory chain. We have located the gene for the human core I protein in the p21 region of chromosome 3, just upstream of the COL7A1 gene which encodes type VII collagen. The core I gene, which has been sequenced in its entirety, is comprised of 10,417 base pairs, from the major transcription start site to the polyadenylation signal, and contains 13 exons. The predicted polypeptide contains 480 amino acids, of which the first 34 are predicted to constitute a typical mitochondrial leader peptide containing 6 positively charged arginine residues. The predicted human protein shows significant homology with core I protein from Saccharomyces cerevisiae, rather high homology (64% similarity, 46% identity) with the processing enhancing protein, which functions as core I protein in Neurospora crassa, and, surprisingly, highest homology with the small subunit of the mitochondrial processing peptidase of rat (74% similarity, 55% identity). The predicted human sequence is 87% identical to the reported bovine core I sequence predicted from cDNA cloning, up to residue 298, but the two predicted sequences are widely divergent after that point.

Regulation of angiotensin II receptors on ventricular myocytes after myocardial infarction in rats

To determine the effects of acute myocardial infarction on the regulation of angiotensin II (Ang II) receptors and contractile performance of left and right ventricular myocytes, coronary artery ligation was surgically induced in rats, and Ang II receptor density and affinity and the mechanical properties of surviving muscle cells were examined 1 week later. Physiological determinations of cardiac pump function revealed the presence of ventricular failure, which was associated at the cellular level with a depression in the velocity of myocyte shortening and relengthening, a prolongation of time to peak shortening, and a reduction in the extent of cell shortening. These abnormalities in single-cell function were more prominent in left than in right ventricular myocytes. Cellular hypertrophy was documented by increases in cell length and width, which were also greater in the spared myocytes of the infarcted left ventricle. Reactive hypertrophy was accompanied by a 1.84- and 1.85-fold increase in the density of Ang II receptors on left and right myocytes, respectively. On the other hand, the affinity of Ang II receptors for the radiolabeled antagonist was not altered. However, Ang II-stimulated phosphoinositol turnover was enhanced by 3.7- and 2.5-fold in left and right myocytes, respectively, after infarction. Ventricular myocytes were found to possess the AT1 receptor subtype exclusively. In conclusion, myocardial infarction leads to impairment in the contractile behavior of the remaining cells and to the activation of Ang II receptors and effector pathway associated with these receptors, which may be involved in the reactive growth adaptation of the viable myocytes.

Effects of cardiomyoplasty on biventricular function in canine chronic heart failure

Dynamic cardiomyoplasty, the use of skeletal muscle to assist the heart, is a new therapy for the treatment of heart failure. However, the effects of cardiomyoplasty on biventricular function and the synchrony of ventricular contraction are not fully known. We assessed the efficacy of latissimus dorsi muscle (LDM) dynamic cardiomyoplasty in a chronic model of biventricular failure. Five dogs received doxorubicin (1 mg.kg-1.wk-1) for up to 12 weeks to induce heart failure and then underwent a biventricular cardiomyoplasty. After operation, the muscle was progressively stimulated according to an established protocol. When training was complete (10 weeks), radionuclide ventriculographic and catheterization data were obtained. Peak left ventricular (LV) systolic pressure and its first derivative were unchanged, whereas LV end-diastolic pressure decreased slightly with LDM assistance (11.0 +/- 1.6 to 9.6 +/- 1.5 mm Hg; p < 0.05). Right ventricular (RV) systolic pressure increased significantly with LDM assistance from 21 +/- 2 to 26 +/- 3 mm Hg (p < 0.05), whereas its first derivative and RV end-diastolic pressure were unchanged. Dynamic cardiomyoplasty significantly improved LV ejection fraction from 0.18 +/- 0.07 without LDM assistance to 0.31 +/- 0.05 with LDM assistance (p < 0.05); similarly RV ejection fraction increased from 0.32 +/- 0.07 to 0.45 +/- 0.06 with LDM assistance (p < 0.05). The temporal sequence of LV wall motion was assessed by phase analysis of the radionuclide ventriculograms. With skeletal muscle assistance, standard deviation ("spread") decreased from 31.6 +/- 17.4 to 20.0 +/- 15.4 degrees (p < 0.06), whereas skewness ("symmetry") was unchanged. Dynamic cardiomyoplasty improved both LV and RV ejection fractions without increasing diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

[Clinical and experimental study of left ventricular diastolic function in heart qi insufficiency syndrome]

In order to assess the left ventricular diastolic function of Heart Qi Insufficiency Syndrome (HQIS), apexcardiogram, ECG, electro-cardio-phonogram, impedance cardiogram were recorded and computerized simultaneously. A/D, PEP/LEVT, A/H were increased, while TRTI, DATI, HI, SV, CI reduced in 64 patients, 34 of them with coronary heart disease. The change was statistically significant. This study showed that DATI was more sensitive than PEP/LEVT in patients with HQIS, while there was no significant difference between abnormal ratio of them, overlapping of the two indices was showed. Replenishing Heart Mixture attained its therapeutic effect through improving abnormal left ventricular function. After treatment A/H, A/D, PEP/LEVT were reduced and DATI, SV, CI increased (P < 0.05-0.01). In experiment, HQIS was produced by acute myocardial ischemia in open-chest anesthetized dogs by left anterior descending coronary artery occlusion. It has been shown that dp/dtmax and T were more sensitive than dp/dtmax. Result of the clinical and the experimental study were consistent.

Biomechanical study of sternal closure techniques

Median sternotomy is the most commonly used incision in cardiothoracic surgery. Closure of this incision is usually performed with parasternal wires, but alternate techniques have been proposed to improve closure stability. This study compares biomechanical stability of standard wire (No. 5 stainless steel) with that of three types of band closure: 5-mm Mersilene ribbon, 5-mm stainless steel band, and 5-mm plastic band. Eight bisected cadaver sterna were reapproximated using each method of sternal fixation and tested for biomechanical stability using an MTS Bionix 858 Biomechanical Tester. Loads of 50, 100, 150, and 200 Newtons (1 Newton = 1 kg.m/s2) were applied as a distracting force across the closure. A linear regression line of displacement as a function of increasing load was determined for each closure method; the slope of this line is inversely proportional to fixation stability. Displacement and load correlated linearly for each closure (r = 0.99). Mean slopes were 0.012 mm/Newton (95% confidence limits, 0.0098 to 0.0142 mm/Newton) for No. 5 stainless steel wire, 0.014 mm/Newton (95% confidence limits, 0.0118 to 0.0162 mm/Newton) for plastic band, 0.017 mm/Newton (95% confidence limits, 0.0148 to 0.0192 mm/Newton) for Mersilene ribbon, and 0.017 mm/Newton (95% confidence limits, 0.0148 to 0.0192 mm/Newton) for 5-mm steel band. No. 5 stainless steel wire provided the most stable closure, although statistical significance was achieved only in comparison with Mersilene ribbon and stainless steel band (p < 0.05). The superior stability of stainless steel wire closure may be due to tightening of the wires by twisting, which results in more tension across the reapproximated sternal halves than with other methods.

[Effect of Equisetum hyemale on experimental hyperlipemia in rats and its toxic test]

The results of an experimental study in rats fed with Equisetum hyemale and hyperlipid food have proved that inhibiting effects on the elevation of triglyceride and cholesterol can be obviously observed in both high and low doses of Equisetum. The study also shows that Equisetum hyemale can antagonize the hyperlipemia in rats. The acute toxic test has proved its low toxicity.

Ventricular loading is coupled with DNA synthesis in adult cardiac myocytes after acute and chronic myocardial infarction in rats

To determine whether the overload associated with myocardial infarction and ventricular failure in rats is coupled with activation of DNA synthesis in the remaining left and right ventricular myocytes, flow cytometric analysis was performed on myocyte nuclei prepared from both ventricles 7 and 30 days after coronary occlusion. In addition, oral captopril was administered in separate groups of control and experimental rats to establish whether a relation existed between attenuation of ventricular loading and magnitude of DNA synthesis in myocytes. Results demonstrated that left ventricular failure and right ventricular dysfunction at 7 days after infarction were biventricularly associated with marked increases in the number of myocyte nuclei in the G2M phase of the cell cycle. In contrast, the fraction of nuclei in the G0+G1 phase decreased. In comparison with the earlier time point, the 30-day interval was characterized by a significant magnitude of cardiac hypertrophy, a moderate amelioration of ventricular pump function, and a decrease in the percentage of myocyte nuclei in the G2M phase in both ventricles. However, 30 days after infarction, the number of right ventricular myocyte nuclei in the S and G2M phases remained elevated with respect to control animals. Captopril therapy reduced the extent of ventricular loading and the population of myocyte nuclei in the cell cycle at 7 days. In conclusion, DNA synthesis in myocyte nuclei may represent an important adaptive component of the myocardial response to infarction.

Voltage-dependent performance of skeletal muscle pouches: implications for cardiomyoplasty

Cardiomyoplasty, a new therapy for heart failure, uses autologous skeletal muscle to mechanically assist the heart. The success of dynamic cardiomyoplasty is critically dependent on the contraction strength of the assisting skeletal muscle. Unlike cardiac muscle, skeletal muscle contracts in a graded response to electrical stimulation. However, in current cardiomyoplasty practice, no systematic technique exists to set the stimulating voltage effecting skeletal muscle contraction. The stimulating voltage is simply set to some multiple of the "threshold" voltage. Furthermore, researchers do not consider the role of stimulating voltage when they determine the amount of assistance afforded during cardiomyoplasty. To more accurately assess the value of this heuristic voltage-setting technique, we investigated the role of stimulating voltage on the strength of contraction of the latissimus dorsi muscle. Six New Zealand white rabbits had isovolumic hydraulic pouches constructed from the latissimus dorsi muscle. The muscles were wrapped around a compliant balloon in which isovolumic pressure development was measured during tetany-inducing burst (pulse-train) stimulation. The tetanic plateau of the pouch pressure record was used to measure the effects of stimulating voltage on skeletal muscle contraction. Results indicated that (1) increasing stimulating voltage from two to four times the "threshold" voltage increased normalized pouch pressure from 0.38 +/- 0.21 to 0.78 +/- 0.12 (mean +/- SD) (p < 0.05); (2) the threshold-normalized voltage necessary to cause maximal muscle contraction varied widely (5.7 +/- 2.0, mean +/- SD; range, 3.1 to 9.3); and (3) the current achieving maximal pressure development varied from 5.6 to 31.4 mA (19.9 +/- 10.4 mA).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of dynamic cardiomyoplasty on indices of left ventricular systolic and diastolic function in a canine model of chronic heart failure

The effects of cardiomyoplasty were evaluated with multiple-gated equilibrium radionuclide angiocardiography and catheterization in a canine model of chronic heart failure. Doxorubicin was administered to 12 dogs at a dose of 1 mg/kg/wk intravenously for 10 weeks. Left ventricular ejection fraction was reduced from a mean of 53.6% +/- 3.4% to 33.5% +/- 2.3% preoperatively. Two dogs died of presumed arrhythmia during this period. Cardiomyoplasty with the left latissimus dorsi muscle was performed on 10 dogs. The muscle was wrapped around both the left and right ventricles. Five dogs died of infection or arrhythmia after the operation. Postoperatively the muscle remained unstimulated for 2 weeks to allow adhesion to the heart. After this period, the latissimus dorsi muscle was conditioned by a progressive stimulation protocol. After the muscle was conditioned, multiple-gated equilibrium radionuclide angiocardiography studies showed that left ventricular global ejection fraction was 18.4% +/- 7.2% at 0 volts (nonstimulation), 26.2% +/- 3.7% at 5-volt stimulation (p less than 0.05), and 31.0% +/- 5.4% at 10-volt stimulation (p less than 0.05). Regional ejection fractions in low lateral, apical, and low septal regions at 5 volts and 10 volts were higher than those at 0 volts (p less than 0.05). Regional wall motion (percent radial shortening) of the low lateral region was higher than that during nonstimulation (p less than 0.05). Peak emptying rate was 2.07 +/- 0.95 end-diastolic counts per second at 0-volt, 3.10 +/- 0.67 at 5-volt, and 3.34 +/- 0.89 at 10-volt stimulation (p less than 0.05). Peak filling rate was 1.81 +/- 0.52 end-diastolic counts per second at 0-volt, 2.67 +/- 1.18 at 5-volt, and 3.11 +/- 0.65 at 10-volt stimulation (p less than 0.05). Cardiac catheterization data showed a nonsignificant increase in left ventricular rate of pressure rise with increasing voltage (1302 +/- 355 mm Hg/sec at 0 volts, 1450 +/- 413 mm Hg/sec at 5 volts, and 1568 +/- 455 mm Hg/sec at 10 volts). Left ventricular systolic pressures were unchanged. End-diastolic pressures decreased (11.2 +/- 1.48 mm Hg at 0 volts, 10.4 +/- 2.30 mm Hg at 5 volts, and 9.6 +/- 1.52 at 10 volts; p less than 0.05). These data show that cardiomyoplasty can improve indices of systolic and diastolic function in a canine model of chronic heart failure.