Note: Dynamic strain field mapping with synchrotron X-ray digital image correlation

We present a dynamic strain field mapping method based on synchrotron X-ray digital image correlation (XDIC). Synchrotron X-ray sources are advantageous for imaging with exceptional spatial and temporal resolutions, and X-ray speckles can be produced either from surface roughness or internal inhomogeneities. Combining speckled X-ray imaging with DIC allows one to map strain fields with high resolutions. Based on experiments on void growth in Al and deformation of a granular material during Kolsky bar/gas gun loading at the Advanced Photon Source beamline 32ID, we demonstrate the feasibility of dynamic XDIC. XDIC is particularly useful for dynamic, in-volume, measurements on opaque materials under high strain-rate, large, deformation.

Resonance measurement of nonlocal spin torque in a three-terminal magnetic device

A pure spin current generated within a nonlocal spin valve can exert a spin-transfer torque on a nanomagnet. This nonlocal torque enables new design schemes for magnetic memory devices that do not require the application of large voltages across tunnel barriers that can suffer electrical breakdown. Here we report a quantitative measurement of this nonlocal spin torque using spin-torque-driven ferromagnetic resonance. Our measurement agrees well with the prediction of an effective circuit model for spin transport. Based on this model, we suggest strategies for optimizing the strength of nonlocal torque.

Assessing the genetic relatedness of higher ozone sensitivity of modern wheat to its wild and cultivated progenitors/relatives

Modern wheat (Triticum aestivum L.) is one of the most ozone (O(3))-sensitive crops. However, little is known about its genetic background of O(3) sensitivity, which is fundamental for breeding O(3)-resistant cultivars. Wild and cultivated species of winter wheat including donors of the A, B and D genomes of T. aestivum were exposed to 100 ppb O(3) or charcoal-filtered air in open top chambers for 21 d. Responses to O(3) were assessed by visible O(3) injury, gas exchange, chlorophyll fluorescence, relative growth rate, and biomass accumulation. Ozone significantly decreased light-saturated net photosynthetic rate (-37%) and instantaneous transpiration efficiency (-42%), but increased stomatal conductance (+11%) and intercellular CO(2) concentration (+11%). Elevated O(3) depressed ground fluorescence (-8%), maximum fluorescence (-26%), variable fluorescence (-31%), and maximum photochemical efficiency (-7%). Ozone also decreased relative growth rate and the allometric coefficient, which finally reduced total biomass accumulation (-54%), but to a greater extent in roots (-77%) than in the shoot (-44%). Winter wheat exhibited significant interspecies variation in the impacts of elevated O(3) on photosynthesis and growth. Primitive cultivated wheat demonstrated the highest relative O(3) tolerance followed by modern wheat and wild wheat showed the lowest. Among the genome donors of modern wheat, Aegilops tauschii (DD) behaved as the most O(3)-sensitive followed by T. monococcum (AA) and Triticum turgidum ssp. durum (AABB) appeared to be the most O(3)-tolerant. It was concluded that the higher O(3) sensitivity of modern wheat was attributed to the increased O(3) sensitivity of Aegilops tauschii (DD), but not to Triticum turgidum ssp. durum (AABB) during speciation.

Lipid-rich carcinoma of the breast: a case report

Lipid-rich carcinoma is a rare variant and accounts for < or = 2% of all breast cancer diagnoses. We report a case occurring in a 53-year-old female. The patient presented with a painless, right breast mass. Clinical examination and mammography suggested malignancy. Subsequent modified radical mastectomy revealed the diagnosis of lipid-rich carcinoma. The morphological features, differential diagnosis and treatment along with a brief review of the literature are discussed in this article. Lipid-rich carcinoma (L-RC) is a very rare variant of breast carcinomas with an aggressive clinical course and poor prognosis. It presents only 1% to 2% of all breast cases. It is classified as a specific variety of mammary carcinoma because the tumour cells possess abundant vacuolated cytoplasm which is strongly positive when stained for neutral fat. Aboumrad first described it in 1963 as lipid-secreting carcinoma. However, Ramos and Taylor renamed it as lipid-rich breast carcinoma. In China, the first case was reported in 1984. Herein, we report a case of lipid-rich carcinoma occurring in a 53-year-old female patient, and the literature is reviewed.

Pancreatic schwannoma: CT findings

Schwannomas of the pancreas are rare tumors. We report a case of solitary schwannoma of the pancreas without von Recklinghausen disease. A 72-year-old man underwent routine abdominal ultrasound before cholecystectomy because of chronic cholecystitis and multiple gallstones, and ultrasound showed a small solitary tumor in the pancreas. Spiral computed tomography showed a 1.0-cm, well-defined homogeneous hypodense lesion with mild inhomogeneous enhancement and peripheral enhancement at the junction between the head and body of the pancreas. These computed tomographic findings are different from those in previous reports.

Current-induced excitations in single cobalt ferromagnetic layer nanopillars

Current-induced excitations in Cu/Co/Cu single ferromagnetic layer nanopillars ( approximately 50 nm in diameter) have been studied experimentally as a function of Co layer thickness at low temperatures for large applied fields perpendicular to the layers. For asymmetric junctions current-induced excitations are observed at high current densities for only one polarity of the current and are absent at the same current densities in symmetric junctions. These observations confirm recent predictions of spin-transfer torque induced spin-wave excitations in single layer junctions with a strong asymmetry in the spin accumulation in the leads.

Room-temperature ferromagnetic nanotubes controlled by electron or hole doping

Nanotubes and nanowires with both elemental (carbon or silicon) and multi-element compositions (such as compound semiconductors or oxides), and exhibiting electronic properties ranging from metallic to semiconducting, are being extensively investigated for use in device structures designed to control electron charge. However, another important degree of freedom--electron spin, the control of which underlies the operation of 'spintronic' devices--has been much less explored. This is probably due to the relative paucity of nanometre-scale ferromagnetic building blocks (in which electron spins are naturally aligned) from which spin-polarized electrons can be injected. Here we describe nanotubes of vanadium oxide (VO(x)), formed by controllable self-assembly, that are ferromagnetic at room temperature. The as-formed nanotubes are transformed from spin-frustrated semiconductors to ferromagnets by doping with either electrons or holes, potentially offering a route to spin control in nanotube-based heterostructures.

Current-driven excitations in symmetric magnetic nanopillars

We study experimentally the current-driven magnetic excitations in symmetric Co/Cu/Co nanopillars. In contrast with all the previous observations where the current of only one polarity is capable of exciting a multilayer system saturated by an externally applied magnetic field, we observe that both polarities of the applied current trigger excitations in a symmetric multilayer. This may indicate that in symmetric structures the current propels high-frequency magnetic oscillations in all magnetic layers. We argue, however, that only one layer is excited in our multilayers but, interestingly, currents of opposite polarities excite different layers. This hypothesis is supported by modeling the spin accumulation in symmetric magnetic multilayers.

Time-resolved reversal of spin-transfer switching in a nanomagnet

Time-resolved measurements of spin-transfer-induced (STI) magnetization reversal were made in current-perpendicular spin-valve nanomagnetic junctions subject to a pulsed current bias. These results can be understood within the framework of a Landau-Lifshitz-Gilbert equation that includes STI corrections and a Langevin random field for finite temperature. Comparison of these measurements with model calculations demonstrates that spin-transfer induced excitation is responsible for the observed magnetic reversal in these samples.

Changes in the rate of photosynthesis accompanying the yield increase in wheat cultivars released in the past 50 years

Photosynthetic rates in different development stages were carefully investigated in 18 cultivars of winter wheat released in the period between 1945 and 1995 in the area of Beijing, China. During this period, the recorded grain yield has increased eightfold. However, when those cultivars were planted and managed in the same environment, the difference was reduced to only 36%, indicating that agronomic practices are the most important factors for grain yield. Agronomic features have changed greatly in the past 50 years, through increasing the harvest index (R2 = 0.89, P < 0.05), shortening plant height (R2 = 0.77, P < 0.05) and slightly increasing flag leaf areas (R2 = 0.45, P < 0.05), which is mostly in agreement with many other researchers. In contrast to many reports, however, this study found a genetic increase in the rate of photosynthesis per unit leaf area. From the mid-stem elongation to soft dough stages, the average photosynthetic rates at saturated photosynthetic photon flux density (P(sat)) increased by 44%. In the process, the stomatal conductance (g(s)) also increased by 122%. Grain yield was positively related to the mean values of P(sat) (R2 = 0.61, P < 0.01) and g(s) (R2 = 0.67, P < 0.01) in the six development stages. Our experiment may suggest that increase in grain yield was associated with the elevation of leaf photosynthetic rate and stomatal conductance over the past 50 years.

Current-induced magnetization reversal in high magnetic fields in Co/Cu/Co nanopillars

Current-induced magnetization dynamics in Co/Cu/Co trilayer nanopillars (approximately 100 nm in diameter) have been studied experimentally at low temperatures for large applied fields perpendicular to the layers. At 4.2 K an abrupt and hysteretic increase in resistance is observed at high current densities for one polarity of the current, comparable to the giant magnetoresistance effect observed at low fields. A micromagnetic model that includes a spin-transfer torque suggests that the current induces a complete reversal of the thin Co layer to alignment antiparallel to the applied field--that is, to a state of maximum magnetic energy.

Tyrosine kinase receptor activation inhibits NPR-C in lung arterial smooth muscle cells

We have previously demonstrated that expression of the atrial natriuretic peptide (ANP) clearance receptor (NPR-C) is reduced selectively in the lung of rats and mice exposed to hypoxia but not in pulmonary arterial smooth muscle cells (PASMCs) cultured under hypoxic conditions. The current study tested the hypothesis that hypoxia-responsive growth factors, fibroblast growth factors (FGF-1 and FGF-2) and platelet-derived growth factor-BB (PDGF-BB), that activate tyrosine kinase receptors can reduce expression of NPR-C in PASMCs independent of environmental oxygen tension. Growth-arrested rat PASMCs were incubated under hypoxic conditions (1% O2) for 24 h; with FGF-1, FGF-2, or PDGF-BB (0.1-20 ng/ml for 1-24 h); or with ANG II (1-100 nM), endothelin-1 (ET-1, 0.1 microM), ANP (0.1 microM), sodium nitroprusside (SNP, 0.1 microM), or 8-bromo-cGMP (0.1 mM) for 24 h under normoxic conditions. Steady-state NPR-C mRNA levels were assessed by Northern blot analysis. FGF-1, FGF-2, and PDGF-BB induced dose- and time-dependent reduction of NPR-C mRNA expression within 1 h at a threshold concentration of 1 ng/ml; hypoxia, ANG II, ET-1, ANP, SNP, or cGMP did not decrease NPR-C mRNA levels in PASMCs under the above conditions. Downregulation of NPR-C expression by FGF-1, FGF-2, and PDGF-BB was inhibited by the selective FGF-1 receptor tyrosine kinase inhibitor PD-166866 and mitogen-activated protein/extracellular signal-regulated kinase inhibitors U-0126 and PD-98059. These results indicate that activation of tyrosine kinase receptors by hypoxia-responsive growth factors, but neither hypoxia per se nor activation of G protein-coupled receptors, inhibits NPR-C gene expression in PASMCs. These results suggest that FGF-1, FGF-2, and PDGF-BB play a role in the signal transduction pathway linking hypoxia to altered NPR-C expression in lung.

Environmental change in Bashang region historical periods

The Bashang region is a typical vulnerable eco-environmental zone. Our analysis of paleodunes, paleosol profiles, and lake changes taking place during last ten thousands years indicated that: (1) 10-6.9 ka B.P. was a post-glacial temperature-increasing stage, in which lakes had their high water level; (2) 6.9-3.0 ka B. P. was a large warm stage, during which four paleosol layers were developed and climate fluctuation has assumed 4-5 small cold-humid and cold-dry alternations. Since 5.4 ka B.P., the lakes tended to gradually shrink; and by 2.1 ka B.P., water level has fallen by 2.7 m; (3) since 3.0 ka B. P. a general trend of the region was to change into a dry, warm-dry and cold-dry environment.

Genetic diversity evaluation of some Chinese elite cotton varieties with RAPD markers

RAPDs analysis was used to assess the genetic diversity of some elite cotton varieties. 17 cotton varieties or breeding lines were screened with 200 arbitrary primers to generate 113 polymorphic bands. Cluster analysis and UPGMA showed that 17 varieties could be put into 3 clusters corresponding to genome difference. The genetic similarity among them ranged from 0.2000 to 0.8451. Three elite varieties Ejing-1, Sumian-3 and Zhongmiansuo-12 are highly similar in genetic base. 7581, an offspring from Gossypium hirsutum x G. hirsutum race Latifolium, is distinct from other upland cotton varieties. A trend in germplasm usage in the same research center was also shown in the study. To sustain progress in genetic improvement, we suggest that some good gene from other species should be considered in the upland cotton breeding procedure.

Intratumoral administration of endostatin plasmid inhibits vascular growth and perfusion in MCa-4 murine mammary carcinomas

Endostatin, a fragment of the COOH-terminal domain of mouse collagen XVIII is a recently demonstrated endogenous inhibitor of tumor angiogenesis and endothelial cell growth. Antiangiogenic therapy with endostatin in animals requires multiple and prolonged administration of the protein. Gene therapy could provide an alternative approach to continuous local delivery of this antiangiogenic factor in vivo. Established MCa-4 murine mammary carcinomas, grown in immunodeficient mice, were treated with intratumoral injection of endostatin plasmid at 7-day intervals. At the time of sacrifice, 14 days after the first injection, endostatin-treated tumor weights were 51% of controls (P < 0.01). Tumor growth inhibition was accompanied by a marked reduction in total vascular density. Specifically, computerized image analysis showed a 18-21% increase in the median distances between tumor cells and both the nearest anatomical (CD31-stained) vessel [48.1 +/- 3.8 versus 38.3 +/- 1.6 microm (P < 0.05)] and the nearest tumor-specific (CD105-stained) vessel [48.5 +/- 1.5 versus 39.8 +/- 1.5 microm (P < 0.01)]. An increased apoptotic index of tumor cells in endostatin-treated tumors [3.2 +/- 0.5% versus 1.9 +/- 0.3% (P < 0.05)] was observed in conjunction with a significant decrease in tumor perfused vessels (DiOC7 staining), and an increase in tumor cell hypoxia (EF5 staining). Hypoxia resulting from endostatin therapy most likely caused a compensatory increase of in situ vascular endothelial growth factor (VEGF) and VEGF receptor mRNA expression. Increased immunoreactivity of endostatin staining in endostatin-treated tumors was also associated with an increased thrombospondin-1 staining [1.12 +/- 0.16 versus 2.44 +/- 0.35]. Our data suggest that intratumoral delivery of the endostatin gene efficiently suppresses murine mammary carcinoma growth and support the potential utility of the endostatin gene for cancer therapy.

Hypoxia reduces atrial natriuretic peptide clearance receptor gene expression in ANP knockout mice

We tested the hypotheses that hypoxic exposure is associated with exacerbated pulmonary hypertension and right ventricular (RV) enlargement, reduced atrial natriuretic peptide (ANP) clearance receptor (NPR-C) expression, and enhanced B-type natriuretic peptide (BNP) expression in the absence of ANP. Male wild-type [ANP(+/+)], heterozygous [ANP(+/-)], and homozygous [ANP(-/-)] mice were studied after a 5-wk hypoxic exposure (10% O(2)). Hypoxia increased RV ANP mRNA and plasma ANP levels only in ANP(+/+) and ANP(+/-) mice. Hypoxia-induced increases in RV pressure were significantly greater in ANP(-/-) than in ANP(+/+) or ANP(+/-) mice (104 +/- 17 vs. 45 +/- 10 and 63 +/- 7%, respectively) as were increases in RV mass (38 +/- 4 vs. 26 +/- 5 and 29 +/- 4%, respectively). NPR-C mRNA levels were greatly reduced in the kidney, lung, and brain by hypoxia in all three genotypes. RV BNP mRNA and lung and kidney cGMP levels were increased in hypoxic mice. These findings indicate that disrupted ANP expression worsens hypoxic pulmonary hypertension and RV enlargement but does not alter hypoxia-induced decreases in NPR-C and suggest that compensatory increases in BNP expression occur in the absence of ANP.

[Surgical treatment for the recurrent patients after palatopharyngoplasty]

OBJECTIVE

To study the surgical treatment for the recurrent patients after palatopharyngoplasty (PPP).

METHOD

Five patients which were confirmed recurrence by sleep survey and examinations were reported.

RESULT

The pharyngeal cavity was narrower obviously ten months after ppp than before ppp. The anteroposterior and transverse distances were (4.06 +/- 2.94) mm and (11.40 +/- 4.16) mm respectively. After dilatation, the distances were (11.90 +/- 3.25) mm and (21.00 +/- 4.18) mm separately, and were increased significantly than before (P < 0.01). Two patients were cured and three cases marked, and all patients were not recurrent post-operation with no complications.

CONCLUSION

The recurrence was mainly concerned with the unsuitable manipulation in PPP. Selecting the cooperation and proper surgical treatment, the better effect was also obtained for the recurrent patients.

[Operations for laryngeal carcinoma with reservation of laryngeal function]

OBJECTIVE

To study the long term results and functional recovery of partial laryngectomy in the treatment of glottic and supraglottic types of laryngeal carcinoma.

METHOD

A series of 70 cases operated on between July 1978 and August 1998 were analysed, of whom 60 were glottic, 10 were supraglottic type laryngeal carcinoma. Among them, 22 cases underwent vocal cord resection, 22 vertical hemilaryngectomy, 17 Majer-Piquet's operation, 7 horizontal hemilaryngectomy, 2 Arslan's operation.

RESULT

1, 3, 5-year survival rates were 98.53%, 87.04% and 78.26% respectively. Decannulation rate was 100%. All patients could finally take food by mouth without inspiration, and could speak as soon as decannulated. Complication and recurrence rates were 15.71% and 13.04% separately.

CONCLUSION

Partial laryngectomy is an effective operation on laryngeal carcinoma with reservation of laryngeal function. It not only can totally excise neoplasm and prolong life, but also can better reserve laryngeal function and improve the quality of patient's life.

Stressors and rearing diseases of Trichoplusia ni: evidence of vertical transmission of NPV and CPV

Inability to consistently rear healthy Trichoplusia ni led to a study of its rearing diseases. Four diseases were designated after preliminary research which included electron microscopy: cytoplasmic polyhedrosis (due to cytoplasmic polyhedrosis virus, or CPV), nuclear polyhedrosis (due to nucleopolyhedrovirus, or NPV), "neonate death" syndrome (mortality in first or second instars), and "late-instar" syndrome (death in late instars accompanied by bacterial decomposition). Infectious agents were not detected by electron microscopy in insects with the latter two diseases. Prevalence of CPV and NPV, but not the neonate-death or late-instar diseases, in progeny was significantly associated with pairs of mating adults. In conjunction with egg-surface decontamination, this indicated that both viruses may be transmitted transovarially. Pupae killed by CPV had virions in the cytoplasm of infected cells, but polyhedra were empty, not occluding virions. None of the diseases had a consistent pattern of prevalence associated with the date on which eggs were laid after oviposition began. Prevalence rates of cytoplasmic polyhedrosis, nuclear polyhedrosis, and the late-instar disease were significantly greater at 95-100% relative humidity (RH) than at RH levels of 75% or below. These same three diseases killed significantly more insects in crowded rearing conditions (four or five larvae per cup with 10.2-cm(2) diet surface) than in uncrowded conditions (one to three larvae per cup). As a result of these experiments, healthy T. ni have been reared for 10 generations by use of a modified Pasteur method and rearing cups containing no more than two larvae.

Solute absorption from the airways of the isolated rat lung. V. Charge effects on the absorption of copolymers of N(2-hydroxyethyl)-DL-aspartamide with DL-aspartic acid or dimethylaminopropyl-DL-aspartamide

PURPOSE

To determine the effects of ionized substituents upon the pulmonary absorption of 6-8 kDa synthetic, hydrophilic polypeptides.

METHODS

Fluorophore-labeled poly (hydroxyethylaspartamide), F-PHEA (neutral at pH 7.4) and its copolymer derivatives poly (hydroxyethylaspartamide-co-dimethylaminopropylaspartamide), F-P(HEA-DMAPA) (positive at pH 7.4) and poly (hydroxyethylaspartamide-co-aspartic acid), F-P(HEA-AA) (negative at pH 7.4) were synthesized and administered in different concentrations to the airways of the isolated rat lung preparation. The time and molecular weight dependencies of polypeptide absorption into perfusate were determined at intervals by gel permeation chromatography.

RESULTS

For all polypeptides, molecular weights in perfusate were about 1 kDa less than those which were administered, due to preferential absorption of smaller molecules. The absorption, up to 70% of the administered dose over 3 h, of the anionic F-P(HEA-AA), was significantly faster than that of the neutral F-PHEA or the polycationic F-P(HEA-DMAPA). The latter derivative produced greatest edema in the lung. Absorption showed both active [dose-dependent kinetics] and passive [diffusive] components for all three polymers.

CONCLUSIONS

Pulmonary absorption of similarly sized macromolecular PHEA derivatives, either neutral, positively or negatively charged, occured via carrier-mediated and diffusive mechanisms. The highest rate of absorption was observed with the polyanionic derivative.

SPIN-DEPENDENT TRANSPORT AND LOW-FIELD MAGNETORESISTANCE IN DOPED MANGANITES

▪ Abstract  Doped manganite perovskites exhibit large magnetoresistance, but usually only in high fields (>1 Tesla). Efforts are under way to understand the underlying mechanism and to explore possibilities of achieving large magnetoresistance at low fields, which has led to focused studies of spin-dependent transport across macroscopic interfaces between manganites. We review recent experimental progress in this area.

Effect of intravenous infusions of 12-O-tetradecanoylphorbol-13-acetate (TPA) in patients with myelocytic leukemia: preliminary studies on therapeutic efficacy and toxicity

Studies by several investigators have shown that 12-0-tetradecanoylphorbol-13-acetate (TPA) is an extraordinarily potent stimulator of differentiation of cultured human promyelocytic leukemia cells in vitro. In the present study, TPA was administered to humans by i.v. infusion without irreversible toxicity, and it was shown to have pharmacological activity for the treatment of myelocytic leukemia in patients refractory to cytosine arabinoside (Ara C), retinoic acid, and other antileukemic drugs. Marked decreases in bone marrow myeloblasts as well as temporary remission of disease symptoms were observed when TPA was administered alone or in combination with vitamin D3 and Ara C. Additional studies with TPA after the determination of optimum dosing regimens are needed to determine whether long-lasting or permanent remissions of myelocytic leukemia can be achieved. Transient and reversible side effects were observed after a 1-mg i.v. dose of TPA, but these adverse effects became less intense or disappeared when a lower dose of TPA was used. The results of this study indicate a therapeutic effect of TPA in patients with myelocytic leukemia.

12-O-Tetradecanoylphorbol-13-acetate (TPA)-induced increase in depressed white blood cell counts in patients treated with cytotoxic cancer chemotherapeutic drugs

Fifty-two patients with solid tumors had depressed white blood cell and neutrophil counts because of prior treatment with cytotoxic cancer chemotherapeutic drugs. These patients were given one or more i.v. infusions of 0.125-0.25 mg of 12-O-tetradecanoylphorbol-13-acetate (TPA), and this treatment increased the low white blood cell and neutrophil counts toward the normal range. The average white blood cell and neutrophil counts were 2.55 x 10(9)/liter and 1.76 x 10(9)/liter, respectively, before treatment with TPA. After one or more i.v. infusions of TPA, the white blood cell and neutrophil counts increased to peak values of 5. 92 x 10(9)/liter and 4.76 x 10(9)/liter, respectively, within a few days. Most patients had increased levels of white blood cells and neutrophils by 24 hr after a single i.v. infusion of 0.25 mg TPA. Elevated levels were observed for at least 3 days. This study demonstrates that treatment with parenteral TPA is feasible with useful biological activity. Only mild and reversible side effects were observed.

Late preconditioning against stunning is not mediated by increased antioxidant defenses in conscious pigs

Previous studies in conscious pigs have demonstrated that a sequence of ten 2-min coronary occlusion/2-min reperfusion cycles renders the heart relatively resistant to myocardial stunning 24 h later [late preconditioning (PC) against stunning] by an unknown mechanism. Since oxygen radicals contribute importantly to myocardial stunning and since antioxidant enzymes have been reported to be upregulated 24 h after PC in dogs and rabbits, we tested the hypothesis that late PC against stunning is related to an increase in endogenous antioxidant defenses. Chronically instrumented conscious pigs underwent a sequence of ten 2-min coronary occlusion/2-min reperfusion cycles (preconditioned group, n = 11) or received no intervention (control group, n = 5). Twenty-four hours later, pigs were killed and the myocardial levels of Mn superoxide dismutase (SOD), Cu-Zn SOD, catalase, glutathione (GSH) peroxidase, GSH reductase, GSH, GSH disulfide, alpha-tocopherol, and ascorbate were measured. There were no differences in any of the enzymatic or nonenzymatic antioxidants between the ischemic and nonischemic regions in the preconditioned group or between the control and the preconditioned group. Thus, when a marked protection against stunning was present (24 h after PC), no alteration in antioxidant defenses was observed. These results indicate that, in conscious pigs, late PC against myocardial stunning is not mediated by increased endogenous antioxidant defenses, thereby refuting one of the major current hypotheses regarding this phenomenon.

The early and late phases of ischemic preconditioning: a comparative analysis of their effects on infarct size, myocardial stunning, and arrhythmias in conscious pigs undergoing a 40-minute coronary occlusion

The effectiveness of the late phase of ischemic preconditioning (PC) in protecting against myocardial infarction and the concomitant contractile dysfunction after sustained ischemia remains unclear. The early and late phases of PC have not been compared using the same protocol in the same experimental model; furthermore, the late phase of PC has not been assessed in the conscious state in a large animal preparation. The goal of this study was to directly compare the effects of early and late PC on myocardial infarct size and postischemic dysfunction in chronically instrumented, conscious pigs. Four groups of pigs were subjected to a 40-minute coronary occlusion followed by 3 days of reperfusion. Group 1 (n=7) served as control. Group 2 (n=6) was subjected to ten 2-minute occlusion/2-minute reperfusion cycles 25 minutes before the 40-minute occlusion (early PC). Groups 3 (n=7) and 4 (n=4) were subjected to 10 and 25 cycles, respectively, of 2-minute occlusion/2-minute reperfusion 24 hours before the 40-minute occlusion (late PC). Infarct size averaged 45.1+/-5.9% of the region at risk in control pigs, was reduced by 79% (to 9.4+/-3.2%) in group 2, but did not differ in groups 3 (33.3+/-4.8%) and 4 (38.8+/-8.2%) versus group 1. Power analysis demonstrated that there was an 80% probability of detecting a 40% decrease in infarct size in groups 3 and 4 versus group 1. The recovery of systolic wall thickening (measured with ultrasonic crystals) after the 40-minute occlusion was poor in groups 1, 3, and 4 but markedly enhanced in group 2 throughout the 3 days of reperfusion; this beneficial effect could have been due to limitation of infarct size, alleviation of stunning, or both. Thus, a series of ten 2-minute coronary occlusions had a profound (approximately 80%) early infarct-limiting effect, which was associated with a marked functional benefit. This protection, however, disappeared 24 hours later and could not be reinstituted by increasing the number of PC coronary occlusions to 25. The incidence and duration of ventricular tachycardia after reperfusion was not changed by either early or late PC; no conclusions could be drawn regarding ventricular fibrillation or ischemia-induced ventricular tachycardia, since these arrhythmias did not occur in control animals. Taken together, the present results demonstrate striking differences between the early and late effects of PC: In conscious swine subjected to a sustained coronary occlusion, a PC protocol that induces powerful protection during the early phase of PC fails to induce any protection during the late phase, indicating either that a late protective effect of PC does not exist or that, if it exists, it must be weaker than the early protective effect.

Time course of late preconditioning against myocardial stunning in conscious pigs

We have recently found in conscious pigs that a sequence of brief coronary occlusions induces severe myocardial stunning, but when the same sequence is repeated 24 hours later, the severity of stunning is markedly reduced (approximately 50%) ("late preconditioning against stunning"). As an initial step toward elucidating the mechanism and potential clinical significance of this powerful cardioprotective response, the present study was conducted to define the time course of late preconditioning against myocardial stunning. Conscious pigs underwent a sequence of ten 2-minute coronary occlusion/2-minute reperfusion cycles and then a second identical sequence at 6 hours (group I, n = 7), 12 hours (group II, n = 6), 24 hours (group III, n = 10), 3 days (group IV, n = 10), or 6 days (group V, n = 11) after the first. Systolic wall thickening (WTh) in the ischemic/reperfused region remained significantly depressed for at least 3 hours after the 10th reperfusion of the first sequence, indicating myocardial stunning. When the second sequence of coronary occlusions was performed 6 hours after the first (group I), the recovery of WTh was similar to the first. In contrast, when the second sequence was repeated 12 hours after the first (group II), the recovery of WTh was improved, though not consistently, and the total deficit of WTh decreased by 41% (P < .05) compared with the first sequence. When the second sequence was repeated 24 hours (group III) and 3 days (group IV) after the first, the recovery of WTh was substantially enhanced, with 52% and 49% reductions in the total deficit of WTh, respectively (P < .01 versus the first sequence). When the second sequence was repeated 6 days later (group V), the recovery of WTh was indistinguishable from the first sequence. Thus, late preconditioning against myocardial stunning requires > 6 hours to develop, lasts for at least 60 hours after its appearance (with the most effective protection present at 24 hours and 3 days), and disappears within 6 days after the preconditioning ischemia, a time course that is consistent with the synthesis and degradation of cardioprotective proteins. In view of its sustained duration, this endogenous cardioprotective mechanism is of potential clinical importance.

[Effects of high salt-loading on the regulation of angiotensin II receptor mRNA expression]

In the present study, the angiotensin II receptor subtype I-a (AT1a) and I-b (AT1b) mRNA levels in aortic smooth muscle (ASM), ventricular myocardium (VM) and adrenal from 12-week-old stroke-prone spontaneously hypertensive rats (SHRsp) and age-matched Wistar-Kyoto (WKY) rats with normal diet (control) and high salt-loading were examined by reverse transcriptase-polymerase chain reaction (RT-PCR). The results showed that: (1) The AT1a and AT1b mRNA levels in ASM and VM from SHRsp were lower than those from WKY rats (in ASM, 10% and 23%, while in VM, 23% and 40% lower, respectively). In contrast, both AT1a and AT1b mRNA levels in adrenal from SHRsp were higher (176% and 157%, respectively). (2) In the WKY rats with high salt-loading, the AT1a and AT1b mRNA levels in adrenal, as well as AT1b mRNA level in VM, increased significantly, as compared with the control (in adrenal, 167% and 401%, while in VM, 62%). However, the AT1a and AT1b mRNA levels in ASM, as well as AT1a mRNA level in VM, showed no obvious change. (3) In SHRsp with high salt-loading, the AT1b mRNA level in ASM, as well as AT1a and AT1b mRNA levels in VM, increased markedly (in ASM, 90%, while in VM, 590% and 200%); whereas the AT1a mRNA level in adrenal decreased significantly (58%). There was little influence on the regulation of AT1a (in ASM) and AT1b (in adrenal) receptor gene expression after high salt-loading. The results suggest that AT1a and AT1b receptors may be involved in the pathogenesis of salt-induced hypertension. The up-regulation of AT1b receptors in ASM may induce the remodeling of arterial wall, while that of AT1a and AT1b receptors in VM might contribute to ventricular hypertrophy in hypertension. Furthermore, there are certain differences between SHRsp and WKY rats with respect to the regulation of AT1a and AT1b receptor gene expression with or without external stimulation.

[Effects of xinshuaikang granule on cardiac function and atrial natriuretic polypeptide levels in rabbits with experimental congestive heart failure]

Xinshuaikang (XSK) granule mainly consisted of Radix Ginseng, Aconifum carmichaeli, Ligustici wallichii, Semen Lepidii seu Descurainiae, etc. Thirty-five white rabbits of Japanese strain with big ears were used and five groups were divided randomly. The models of chronic heart failure (CHF) was made by injection of adriamycin through the marginal vein of rabbit's ear. Only one group without adriamycin injection was taken as blank group. After the making of models, Xinbao (XB) was used to treat one group which was regarded as control group, XSK was used to treat two model groups, one used higher dose, the other one used lower dose. Fifteen days was taken as a course of treatment. The results were: the body weight of all model groups was heavier than that without adriamycin. After a course of treatment, the body weight of the groups treated by XSK or XB decreased rapidly, the general conditions of the three groups were improved; the two drugs could reduce heart rate and enhance heart function, at the same time they reduced the level of atrial natriuretic polypeptide (ANP) in plasma. The best results was obtained in XSK group with higher dose, the effect of XSK group with lower dose was equivalent to that of XB group. Hence, XSK granule could enhance the CHF rabbits' heart function, improve their heart endocrine activity, this drug had a reliable effect on CHF.

Nisoldipine attenuates myocardial stunning induced by multiple coronary occlusions in conscious pigs and this effect is independent of changes in hemodynamics or coronary blood flow

Recent studies suggest that calcium channel blockers attenuate reversible post-ischemic myocardial dysfunction (myocardial "stunning") in vivo. This beneficial effect, however, has been shown either in open-chest preparations, which are subject to the confounding influence of many unphysiological conditions, or in models in which treatment caused significant hemodynamic alterations. Furthermore, all of the studies have been conducted in the dog, and almost all of them have examined the effect of calcium antagonists after a single ischemic episode. The goal of the present investigation was to assess the effect of nisoldipine in a conscious pig model of repetitive ischemia, and to determine whether the drug exerts direct cardioprotection independent of hemodynamic changes. A total of 33 conscious pigs were used. Pigs underwent a sequence of 10 2-min coronary occlusions, each separated by 2 min of reperfusion, and were randomly assigned to a treated group (n = 11), in which nisoldipine was infused at a rate of 0.5 microgram/kg/min from 15 min before the first coronary occlusion till 30 min after the last reperfusion, and a control group (n = 12), which received vehicle. Results showed that there were no significant differences between the two groups with respect to ischemic bed size or hemodynamic variables throughout the experiment. Collateral blood flow to the ischemic regions was virtually nil in both groups. During the sequence of coronary occlusions, systolic thickening fraction in the ischemic region decreased similarly in the two groups. After the 10th reperfusion, however, the recovery of wall thickening was markedly enhanced in treated compared to control pigs, with the differences being statistically significant at 5, 15, and 30 min and 1, 3, 4 and 5 h. The total deficit of wall thickening after the 10th reperfusion (an integrative assessment of post-ischemic dysfunction) was 51% less in the treated compared with the control group (P < 0.001). This study demonstrates that nisoldipine markedly attenuates myocardial stunning after multiple ischemic episodes in conscious pigs, the improvement is evident immediately after the end of the ischemic episodes and is sustained throughout the recovery phase. This beneficial effect is independent of any favourable hemodynamic changes, and therefore indicates a direct cardioprotective action of nisoldipine.

Evidence for an essential role of reactive oxygen species in the genesis of late preconditioning against myocardial stunning in conscious pigs

Conscious pigs underwent a sequence of 10 2-min coronary occlusions, each separated by 2 min of reperfusion, for three consecutive days (days 1, 2, and 3). On day 1, pigs received an i.v. infusion of a combination of antioxidants (superoxide dismutase, catalase, and N-2 mercaptopropionyl glycine; group II, n = 9), nisoldipine (group III, n = 6), or vehicle (group I [controls], n = 9). In the control group, systolic wall thickening (WTh) in the ischemic-reperfused region on day 1 remained significantly depressed for 4 h after the 10th reperfusion, indicating myocardial "stunning." On days 2 and 3, however, the recovery of WTh improved markedly, so that the total deficit of WTh decreased by 53% on day 2 and 56% on day 3 compared with day 1 (P < 0.01), indicating the development of a powerful cardioprotective response (late preconditioning against stunning). In the anti-oxidant-treated group, the total deficit of WTh on day 1 was 54% less than in the control group (P < 0.01). On day 2, the total deficit of WTh was 85% greater than that observed on day 1 and similar to that observed on day 1 in the control group. On day 3, the total deficit of WTh was 58% less than that noted on day 2 (P < 0.01). In the nisoldipine-treated group, the total deficit of WTh on day 1 was 53% less than that noted in controls (P < 0.01). On days 2 and 3, the total deficit of WTh was similar to the corresponding values in the control group. These results demonstrate that: (a) in the conscious pig, antioxidant therapy completely blocks the development of late preconditioning against stunning, indicating that the production of reactive oxygen species (ROS) on day 1 is the mechanism whereby ischemia induces the protective response observed on day 2; (b) antioxidant therapy markedly attenuates myocardial stunning on day 1, indicating that ROS play an important pathogenetic role in postischemic dysfunction in the porcine heart despite the lack of xanthine oxidase; (c) although the administration of a calcium-channel antagonist (nisoldipine) is as effective as antioxidant therapy in attenuating myocardial stunning on day 1, it has no effect on late preconditioning on day 2, indicating that the ability of antioxidants to block late preconditioning is not a nonspecific result of the mitigation of postischemic dysfunction on day 1. Generation of ROS during reperfusion is generally viewed as a deleterious process. Our finding that ROS contribute to the genesis of myocardial stunning but, at the same time, trigger the development of late preconditioning against stunning supports a complex pathophysiological paradigm, in which ROS play an immediate injurious role (as mediators of stunning) followed by a useful function (as mediators of subsequent preconditioning).

Effect of the hydrophilic alpha-tocopherol analog MDL 74,405 on detection of hydroxyl radicals in stunned myocardium in dogs

We have previously shown in dogs that the hydrophilic alpha-tocopherol analog, MDL 74,405, attenuates postischemic myocardial dysfunction ("stunning") and generation of free radicals as assessed with the spin trap alpha-phenyl N-tert-butyl nitrone (PBN). However, we could not discern whether this drug acts on primary radicals (such as hydroxyl radical [.OH]) or on secondary radicals. The goal of this study was to directly determine whether the beneficial effects of MDL 74,405 result from actions against .OH. Open-chest dogs undergoing a 15-minute coronary artery occlusion and 3 hours of reperfusion received an intravenous infusion of either saline solution (control group, n = 7) or MDL 74,405 (n = 6) starting 30 minutes before coronary occlusion and ending 60 minutes after reflow at a dose of 0.3 mg/kg/hr. Formation of .OH was estimated by the technique of aromatic hydroxylation of phenylalanine. Phenylalanine was infused intravenously, and the plasma concentrations of the hydroxylated products ortho-, meta-, and para-tyrosines (o-, m-, and p-tyr) in the coronary venous effluent and in the arterial blood were measured with high-performance liquid chromatography. In the control group a dramatic increase in the myocardial release of o-, m-, and p-tyr was observed immediately after reperfusion; the release of tyrosines peaked at 1 minute of reflow and continued up to 10 minutes after reperfusion. MDL 74,405 abolished the release of o-tyr throughout the first 10 minutes of reperfusion but had a less pronounced effect on the production of m- and p-tyr. These results demonstrate that MDL 74,405 is effective in inhibiting .OH-initiated reactions in the postischemic stunned myocardium in the dog, suggesting that the anti-.OH action of MDL 74,405 is an important mechanism of action of this antioxidant.

Recurrent ischemia in the canine heart causes recurrent bursts of free radical production that have a cumulative effect on contractile function. A pathophysiological basis for chronic myocardial "stunning"

Open-chest dogs (total number used, 117) underwent 10 5-min coronary occlusions (O) interspersed with 10 min of reperfusion (R). When systolic thickening fraction was measured 9 min after each R, the first O-R cycle was found to cause the largest decrement, with only a slight additional loss during the next four cycles and no further loss during the last five cycles (group IV), suggesting that the first few episodes of ischemia preconditioned the myocardium against the stunning induced by the last five episodes. However, different results were obtained when the total deficit of wall thickening during the final 4-h R interval was measured. The total deficit was similar after one and three 5-min O (groups V and VI, respectively), indicating that the first ischemic episode did precondition against the next two episodes; however, it was approximately 2.5-fold greater after 10 O (group IV) than after 3, indicating that the first 3 episodes failed to precondition against the next 7. Thus, at some point between the 4th and 10th O, the preconditioning effect was lost and recurrent ischemic episodes started to have a cumulative effect. Measurements of free radicals with alpha-phenyl N-tert-butyl nitrone (PBN) demonstrated a burst of free radical generation immediately after the 1st, 5th, and 10th R (group VIII). The total cumulative release of PBN adducts during the initial 5 min of reflow was 58% less after the 5th R than after the 1st (P < 0.05) but did not differ significantly between the 1st and 10th R. When administered throughout the 10 O-R cycles, the .OH scavenger mercaptopropionyl glycine significantly enhanced the recovery of function (group I) and markedly suppressed the formation of free radicals (group VII). However, the beneficial effects of mercaptopropionyl glycine were completely, or largely, lost if the drug was discontinued after the first five (group II) or eight (group III) O-R cycles, respectively, implying that (a) the oxidative stress associated with the last five, or even two, cycles was sufficient to cause severe postischemic dysfunction, and (b) the cumulative injury caused by repetitive ischemic episodes is mediated by recurrent oxidative stress. This study provides direct in vivo evidence that oxygen radicals play an important role in the pathogenesis of myocardial stunning after repetitive ischemia, and implicates .OH as a primary culprit. Taken together, the data indicate that recurrent brief ischemic episodes result in recurrent bouts of oxyradical-mediated injury that have a cumulative effect on contractility, a situation that could lead to protracted or even chronic myocardial stunning.

Import of subunit VII of the cytochrome bc1 complex into yeast mitochondrial

The import of subunit VII, the so-called ubiquinol binding protein of the cytochrome bc1 complex of yeast mitochondria, has been investigated by subcloning the gene for subunit VII into the expression vector pSP64. The precursor to subunit VII synthesized in vitro by a transcription/translation system had the same molecular weight as the mature form of this protein present in mitochondria, confirming earlier reports that subunit VII does not contain a cleavable presequence. The subunit VII precursor was imported efficiently into a protease-resistant compartment of isolated yeast mitochondria in a reaction dependent upon a membrane potential and the presence of ATP both in the mitochondrial matrix and in the extramitochondrial space. After import, the radiolabeled subunit VII was bound to the mitochondrial inner membrane through protein-protein interactions and could not be detected in the matrix fraction or in the intermembrane space. Subunit VII was also imported into mitoplasts, where the protein was associated with the inner membrane facing the matrix side of the membrane. By contrast, after import into mitochondria obtained from yeast cells lacking cytochrome b, subunit VII was localized in the supernatant fraction, suggesting that the presence of cytochrome b may be required for the association of subunit VII with the inner mitochondrial membrane.

Inhibitory effect of a hydrophilic alpha-tocopherol analogue, MDL 74,405, on generation of free radicals in stunned myocardium in dogs

A previous study has demonstrated that the hydrophilic (alpha-tocopherol analogue, MDL 74,405, attenuates postischemic myocardial dysfunction ("stunning") in dogs. The present study was undertaken to determine directly whether the salutary effect of this drug on myocardial stunning results from inhibition of the generation of oxygen-derived free radicals. Open-chest dogs undergoing a 15-min coronary artery occlusion and 3 h of reperfusion received an intravenous infusion of either saline (controls, n = 7) or MDL 74,405 (n = 6) starting 30 min before coronary occlusion and ending 60 min after reflow at a dose of 0.3 mg/kg/h. To measure free radical production, all dogs received an intravenous infusion of the spin trap alpha-phenyl N-tert-butyl nitrone (PBN) and local coronary venous plasma was analyzed by electron paramagnetic resonance (EPR). In control dogs, the myocardial production of PBN adducts exhibited an initial burst immediately after the onset of reflow and remained elevated until 10 min after reperfusion. Dogs treated with MDL 74,405 demonstrated a marked decrease in PBN adduct production. This effect of MDL 74,405 could not be attributed to nonspecific factors such as differences in ischemic zone size, collateral flow, arterial pressure, heart rate, coronary flow or other hemodynamic variables. These results demonstrate that the hydrophilic vitamin E analogue, MDL 74,405, inhibits free radical generation after myocardial ischemia-reperfusion in vivo. This finding provides direct evidence that the salutary effects of MDL 74,405 on myocardial stunning are due to attenuation of oxidative stress.

Beneficial effects of N-acetylcysteine and cysteine in stunned myocardium in perfused rat heart

1. The objective of this study was to evaluate the effects of three sulphydryl (SH) compounds, N-acetylcysteine (NAC), cysteine (Cys) and cystamine, on functional recovery and ventricular arrhythmias (VF) in stunned myocardium in the isolated perfused heart of the rat. 2. Hearts (n = 7-8 per group) were perfused by the Langendorff procedure for 20 min to stabilize and then assigned to one of five groups: saline, sham, NAC, Cys and cystamine. After the stabilizing period, the drugs (at 3.6 microM min-1) or their vehicle (saline) were infused into coronary vessels throughout the experimental period. Ten min after administration of drugs, the left anterior descending coronary artery (LAD) was ligatured for 20 min and then untied to reperfuse for 30 min. In the sham group, a ligature was placed around the LAD but not tied. 3. NAC and Cys had a significant effect in attenuating myocardial stunning: the percentage recovery of rate-pressure product measured 30 min after reperfusion as an index of heart function, was improved with the NAC (98.3 +/- 4.5) and Cys groups (104.0 +/- 6.5) compared with the saline (only 73.6 +/- 3.8, P < 0.01) group. Cystamine did not show these beneficial effects. This may be due to the difference in chemical structure between NAC, Cys and cystamine since the latter does not have a free SH group with a disulphide bond formed. This phenomenon suggests that a free SH group is essential for the protective effects of compounds like NAC and Cys in myocardial injury. 4. NAC and Cys prevented the fall in coronary flow during the LAD occlusion and enhanced coronary flow during reperfusion but cystamine did not have such a beneficial effect. 5. The incidence of VF in the saline, cystamine, Cys and NAC groups was 6/8 (75.0%), 4/7 (57.1%), 3/8 (37.5%) and 2/7 (28.6%), respectively, and no significant differences (P > 0.05) were noted between the saline- and drug-treated groups. 6. An in vitro study with electron spin resonance indicated that Cys effectively scavenged the hydroxyl radical (-OH) generated by Fenton's reaction but did not scavenge superoxide generated in an irradiated riboflavin system. NAC and cystamine showed a scavenging effect on -OH to a certain extent but this effect did not reach statistical significance (P > 0.05 vs saline). 7. Our results demonstrate that NAC and Cys treatment before ischaemia and reperfusion can reduce myocardial stunning. This beneficial effect may be mainly due to their ability to preserve and enhance coronary flow during coronary occlusion and reperfusion and in part due to scavenging -OH and/or replenishing intracellular glutathione. The results also indicate that the condition of coronary perfusion can produce a great impact on postischaemic ventricular performance.

Effect of adenosine on myocardial 'stunning' in the dog

Recent evidence suggests a cardioprotective effect of adenosine in myocardial ischemia and reperfusion. The present study was undertaken to determine (1) whether adenosine attenuates myocardial stunning, (2) if so, whether the beneficial effect of adenosine takes place during ischemia or after reperfusion, and (3) whether adenosine preconditions against myocardial stunning. A total of 93 dogs were used. In phase A of the study, open-chest dogs undergoing a 15-minute occlusion of the left anterior descending coronary artery followed by 4 hours of reperfusion received an intracoronary infusion of either saline (group I [control], n = 14), 2 mg/min adenosine from 30 minutes before occlusion until 1 hour after reperfusion (group II, n = 10), or 2 mg/min adenosine from 2 minutes before reperfusion until 1 hour after reperfusion (group III, n = 11). Regional myocardial function (assessed as systolic wall thickening) was similar in the three groups at baseline and during ischemia. After reperfusion, dogs treated with adenosine before, during, and after ischemia (group II) demonstrated a significant improvement in the recovery of function that persisted throughout the 4 hours of reperfusion. In contrast, in dogs treated only during the reperfusion period (group III), the recovery of function was not statistically different from that in control dogs. The enhanced recovery effected by adenosine in group II could not be ascribed to differences in ischemic zone size, collateral flow during occlusion, coronary flow after reperfusion, arterial pressure, heart rate, or other hemodynamic variables. In phase B of the study, dogs received an intracoronary infusion of either saline (group IV [control], n = 6) or adenosine (4 mg/min from 40 to 10 minutes before occlusion [group V, n = 6]). Despite pretreatment with adenosine, the recovery of function in group V was indistinguishable from that in the control group. This study demonstrates that (1) continuous administration of adenosine before, during, and after ischemia results in a significant and sustained attenuation of myocardial stunning; (2) this improved recovery of function cannot be attributed to nonspecific variables, such as collateral flow during coronary occlusion, coronary flow after reperfusion, or other hemodynamic factors, and therefore reflects a direct cardioprotective action of adenosine; (3) the protection against stunning is lost or markedly diminished if adenosine is given only at reperfusion; and (4) administration of adenosine before ischemia does not precondition the myocardium against the stunning induced by a 15-minute occlusion.(ABSTRACT TRUNCATED AT 400 WORDS)

Late preconditioning against myocardial stunning. An endogenous protective mechanism that confers resistance to postischemic dysfunction 24 h after brief ischemia in conscious pigs

Conscious pigs underwent a sequence of 10 2-min coronary occlusions, each separated by 2 min of reperfusion, for three consecutive days (days 1, 2, and 3 of stage I). The recovery of systolic wall thickening (WTh) after the 10th reperfusion was markedly improved on days 2 and 3 compared with day 1, indicating that the myocardium had become preconditioned against "stunning." 10 d after stage I, pigs underwent again a sequence of 10 2-min coronary occlusions for two consecutive days (days 1 and 2 of stage II). On day 1 of stage II, the recovery of WTh after the 10th reperfusion was similar to that noted on day 1 of stage I; on day 2 of stage II, however, the recovery of WTh was again markedly improved compared with day 1. Blockade of adenosine receptors with 8-p-sulfophenyl theophylline failed to prevent the development of preconditioning against stunning. Northern blot analysis demonstrated an increase in heat stress protein (HSP) 70 mRNA 2 h after the preconditioning ischemia; at this same time point, immunohistochemical analysis revealed a concentration of HSP70 in the nucleus and an overall increase in staining for HSP70. 24 h after the preconditioning ischemia, Western dot blot analysis demonstrated an increase in HSP70. This study indicates the existence of a new, previously unrecognized cardioprotective phenomenon. The results demonstrate that a brief ischemic stress induces a powerful, long-lasting (at least 48 h) adaptive response that renders the myocardium relatively resistant to stunning 24 h later (late preconditioning against stunning). This adaptive response disappears within 10 d after the last ischemic stress but can be reinduced by another ischemic stress. Unlike early and late preconditioning against infarction, late preconditioning against stunning is not blocked by adenosine receptor antagonists, and therefore appears to involve a mechanism different from that of other forms of preconditioning currently known. The increase in myocardial HSP70 is compatible with, but does not prove, a role of HSPs in the pathogenesis of this phenomenon.

Mercury-Based Cuprate High-Transition Temperature Grain-Boundary Junctions and SQUIDs Operating Above 110 Kelvin

The superconducting transport characteristics of HgBa(2) CaCu(2)O(6+delta) (Hg-1212) films and grain-boundary junctions grown on (100)-oriented SrTiO(3) bicrystal substrates have been investigated. The films exhibit a zero-resistance temperature of approximately 120 kelvin and sustain large critical current densities, with values as high as 10(6) amperes per square centimeter at around 100 kelvin. On the other hand, the grain boundaries behave as weak links, with substantially lower critical currents, as is observed for other cuprate superconductors. A reduction of three orders of magnitude in critical current was observed for transport across a 36.8 degrees grain boundary. The current-voltage characteristics of bridges across such a grain boundary show weak-link behavior qualitatively resembling that of a resistively shunted junction. Single-level direct-current superconducting quantum interference devices (SQUIDs) have been fabricated with such bicrystal junctions. These SQUIDs show clear periodic voltage modulations when subjected to applied magnetic fields. The SQUIDs operate at temperatures as high as 111.8 kelvin, which makes them attractive for operation in portable sensors and devices that utilize nonconventional cooling methods.