Epicardial mapping of ventricular defibrillation with monophasic and biphasic shocks in dogs

To study the mechanism of defibrillation and the reason for the increased defibrillation efficacy of biphasic waveforms, the potential gradient in a 32 x 30-mm region of the right ventricle in 15 dogs was progressively lowered in four steps while a strong potential gradient field was maintained throughout the rest of the ventricular myocardium. The volume of right ventricle beneath the plaque was 10 +/- 2% of the total ventricular mass. A 10-msec monophasic (eight dogs) or 5/5-msec biphasic (seven dogs) truncated exponential shock 30% above the defibrillation threshold voltage was given via electrodes on the left ventricular apex and right atrium to create the strong potential gradient field. Simultaneously, a weaker shock with the same waveform but opposite polarity was given via mesh electrodes on either side of the small right ventricular region to cancel part of the potential difference in the region and to create one of the four levels of potential gradient fields. Shock potentials and activations were recorded from 117 epicardial electrodes in the small region, and in one dog global epicardial activations and potentials were recorded from a sock containing 72 electrodes. Each gradient field was tested 10 times for successful defibrillation after 10 seconds of electrically induced fibrillation. For both monophasic and biphasic shocks, the percentage of successful defibrillation attempts decreased (p < 0.05) as the potential gradient decreased in the small region. Defibrillation was successful approximately 80% of the time for a mean +/- SD potential gradient of 5.4 +/- 0.8 V/cm for monophasic shocks and 2.7 +/- 0.3 V/cm for biphasic shocks (p < 0.05). No postshock activation fronts arose from the small region for eight waveform when the gradient was more than 5 V/cm. For both waveforms, the postshock activation fronts after the shocks were markedly different from those just before the shock and exhibited either a focal origin or unidirectional conduction.(ABSTRACT TRUNCATED AT 400 WORDS)

Mechanisms of rubidium permeation by rabbit cortical collecting duct during potassium restriction

To examine the pathways of K permeation in the cortical collecting duct (CCD) from K-restricted rabbits, we studied the effects of the following three maneuvers: 1) luminal amiloride addition; 2) luminal Ba addition; and 3) luminal Na removal. Luminal addition of amiloride (1 mM) significantly increased the 86Rb lumen-to-bath efflux coefficient (KRb), and this effect was fully blocked by the presence of 2 mM luminal Ba. Addition of 2 mM luminal Ba reduced KRb both in the absence of luminal Na and in the presence of luminal Na. In contrast to the effect of amiloride addition, removal of luminal Na significantly increased KRb, but neither 2 mM luminal Ba nor 4 mM luminal Ba totally abolished this effect. However, simultaneous addition of luminal Ba and Sch 28080 (10 microM) fully inhibited the increase in KRb upon luminal Na removal, indicating that luminal Na removal enhances Rb efflux in part via H-K-adenosinetriphosphatase (H-K-ATPase). To test whether Na acts as a partial agonist for cation efflux via the H-K-ATPase we examined the effect of Sch 28080 on the 22Na lumen-to-bath efflux coefficient (KNa). These studies were conducted in the presence of 0.1 mM luminal amiloride to block fully apical conductive Na efflux, and the effect of Sch 28080 on KNa was examined at two different ambient K concentrations. In the presence of 0.5 mM K, Sch 28080 (10 microM) significantly inhibited KNa from 47.6 +/- 4.8 to 35.0 +/- 6.8 nm/s (P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

[Construction of an EB virus based shuttle vector plasmid pZH32]

The shuttle vector can replicate in both bacteria and eukaryotic cells. We have constructed a shuttle vector pZH32 based on the EB virus. Three component parts of the plasmid come from pSV2gpt, pS189 and pMCi5. An E. coli tyrosine suppressor tRNA gene, supF, was used as a mutagenic target in this plasmid, and a gpt gene was used as a selectable marker gene for transformed cells. This pZH32 based on EBV replicates autonomously in the nuclei of human cells. It has a low background mutation frequency. The plasmid can be used to examine the mutagenic mechanism of potential mutagens and carcinogens in mammalian cells.

In vivo priming of cytotoxic T lymphocyte responses in relation to in vitro up-regulation of major histocompatibility complex class I molecules by short synthetic peptides

Cytotoxic T lymphocytes (CTL) recognize target antigens as short peptides presented by major histocompatibility complex class I molecules (MHC-I). Externally added peptides can sensitize target cells by binding directly to MHC-I without any need for internal processing. Those which are similar in length to endogenously processed peptides are more potent in this respect than slightly longer peptides. Peptide MHC-I interactions can also be reflected as up-regulation of MHC-I in vitro on certain cells. We have compared the capacity of Db, Kb- and Ld-binding peptides, which are slightly different in length, to up-regulate MHC-I in vitro with their immunogenicity in vivo, in relation to generation of CTL responses. A clear correlation between these two different functions was found. We have also modified a 9-mer Db-binding peptide by adding cystein to the amino terminus and lysine to the amino- or carboxy terminus and studied the effects on MHC-I up-regulation and in vivo immunogenicity. Cystein and lysine contain reactive groups which are likely to influence the binding of modified peptides into the antigen-binding groove of Db. These small modifications of the optimal 9-mer peptide strongly influenced their functions but still there was a correlation between MHC-I up-regulation and CTL responses. Up-regulation of MHC-I in vitro may reflect a capacity of peptides to accumulate on the surface of particular antigen-presenting cells in vivo.

The relationship between cellular ether glycerophospholipid content and sensitivity of cancer cells to 1-O-octadecyl-2-O-methyl-glycerophosphocholine

Cancer cells are more susceptible to the growth-inhibitory effects of alkyl lysophospholipids than normal cells, but the mechanism of this selectivity is unknown. In this study we have investigated the hypothesis that the sensitivity of cells to alkyl lysophospholipids is related to the cellular ether lipid content. The order of decreasing sensitivity of the cells to the growth-inhibitory effect of 1-O-octadecyl-2-O-methyl-glycerophosphocholine (ET-18-OCH3) was MCF 7 > T84 > Malme 3M > A427 > A549, while the order of decreasing ether phospholipid content as a proportion of the total phospholipid was T84 > A427 = A549 = Malme 3M > MCF7. There was also no correlation between ET-18-OCH3-sensitivity and the proportion of ether lipid in the cholineglycerophospholipid or ethanolamineglycerophospholipid classes. Our results clearly indicate that the postulated relationship between ether phospholipid content and ET-18-OCH3-susceptibility may have very limited applicability and is unlikely to be the underlying reason for the selective effects of alkyl lysophospholipids.

In vivo primary induction of virus-specific CTL by immunization with 9-mer synthetic peptides

A primary cytotoxic T lymphocyte (CTL) response in vivo requires antigen presentation by cytosolic processing and can not in general be obtained by vaccination with soluble proteins. In the present work we have found that vaccination of mice with pre-processed synthetic peptides, corresponding to endogenous 9-mers produced in influenza A virus-infected cells, resulted in strong primary CTL responses. The generated CTL efficiently killed virus-infected target cells with preference for viral strains having the identical amino acid sequences to the peptides used for immunization. The optimal conditions for a primary in vivo CTL response was obtained with 100 micrograms peptide dissolved in incomplete Freund's adjuvant and injected s.c. at the base of tail. Spleen cells which had been primed 7-10 days earlier were restimulated for 5 days in vitro, using an optimal low peptide concentration (0.05 microM) and tested against virus-infected and peptide-treated target cells. The peptide-induced CTL were major histocompatibility complex class I restricted and CD8 positive.

Class I restricted CTL recognition of a soluble protein delivered by liposomes containing lipophilic polylysines

CD8+ cytotoxic lymphocytes recognize peptides derived from endogenous antigens complexed with class I major histocompatibility complex while CD4+ helper cells recognize peptides from exogenous antigens bound to class II MHC molecules. A soluble protein can be introduced into the class I pathway of antigen processing and presentation using an appropriate vehicle to deliver the antigen into the cytosol. Cationic liposomes containing lipophilic polylysine readily form complexes with an anionic, soluble protein ovalbumin. Mouse thymoma EL4 cells incubated with such complexes can be sensitized for killing by OVA-specific CTL effector cells. This method of target sensitization by a soluble antigen is more sensitive than the osmotic loading method previously reported.

Improved procedures for the determination of lipid phosphorus by malachite green

We have developed two procedures for the measurement of lipid phosphorus based on interaction between phosphomolybdenum and malachite green. One method, the "micro" assay uses 50-200 microliters of HClO4 and has a sensitivity range of 0.01-1.5 micrograms phosphorus. The second method, the "macro" assay, has a sensitivity range of 0.03-5.0 micrograms phosphorus with 100-500 microliters HClO4. Both assays are very reproducible with day to day standard deviations of less than 6% between triplicates irrespective of the HClO4 content used. At different concentrations of HClO4, each method was successfully used to determine the phosphorus content in phosphatidylethanolamine and sphingomyelin standards that covered the proposed sensitivity ranges. The increased range, sensitivity and greater volumes of HClO4 permitted in the procedures represent significant improvements over existing methods.

Ethanol inhibits C6 cell growth: fetal alcohol syndrome model

Maternal consumption of ethanol produces a pattern of malformations, including nervous system abnormalities, in the developing fetus, a state called Fetal Alcohol Syndrome. We report the dose-dependent inhibition by ethanol of the growth of a glioma derived cell line, C6 cells; the effects occur at ethanol concentrations commonly encountered in the blood during human intoxication. The effects occur with different morphological subtypes of the cell line and do not occur when the cells are exposed to iso-osmolar concentrations of other chemicals. The results demonstrate that C6 cells are a model for the study of the effects of ethanol on nervous system cell growth.

Sexuality in a natural population of bacteria– Bacillus subtilis challenges the clonal paradigm

Reproduction by binary fission necessarily establishes a clonal genotypic structure in bacterial populations unless a high rate of genetic recombination opposes it. Several genetic properties were examined for a wild population of Bacillus subtilis in the Sonoran Desert of Arizona to assess the extent of recombination in a natural population. These properties included allozyme variation revealed by multilocus enzyme electrophoresis, phage and antibiotic resistance, and restriction fragment length polymorphism with Southern hybridization. Evidence of extensive genetic recombination was found along with evidence of modest clonal structure. Recombination must be frequent relative to binary fission in this population. This mixed population structure provides broader options for bacterial evolution than would a purely clonal structure.

H-K-ATPase enhancement of Rb efflux by cortical collecting duct

Previous studies suggest that enhancement of rubidium tracer (86Rb) lumen-to-bath efflux following removal of luminal Na is mediated in part by a Ba-insensitive pathway. To determine the role of a primary active K pump in this response, we examined the action of known inhibitors of H-K-ATPase (Sch 28080) and Na-K-ATPase (ouabain) on the 86Rb lumen-to-bath efflux coefficient (KRb). Luminal Sch 28080 (10 microM) significantly reduced KRb by 39 +/- 8.0% (P less than 0.05), whereas luminal ouabain (0.1 mM) reduced KRb by 10 +/- 14% (P = not significant), suggesting that a luminal H-K-ATPase mediates Rb efflux. To examine whether H-K-ATPase mediates Rb in KRb following removal of luminal Na, additional experiments were conducted to examine the effect of Sch 28080 on KRb in the presence and the absence of luminal Na. In the presence of luminal Na, 10 microM Sch 28080 reduced KRb by 15 +/- 5.0%. However, in the absence of luminal Na, 10 microM Sch 28080 decreased KRb by 48 +/- 8.2%. The percentage inhibition of KRb by Sch 28080 was significantly greater in the absence of luminal Na than in its presence (P less than 0.01), suggesting that the enhancement of KRb following removal of luminal Na is mediated in part by an H-K-ATPase pathway. In either case transepithelial voltage was not significantly altered. In contrast to the lack of effect of luminal ouabain, addition of 0.1 mM ouabain to the bath increased KRb (69.8 +/- 11.1 vs. 95.9 +/- 18.7 nm/s, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[Tetrandrine on monocyte migration induced by endothelial cell-derived chemotactic factor]

The medium conditioned by cultured human umbilical vein endothelial cells (EC-CM) was used as a source of chemotactic factor, and its chemotactic activity for monocytes was tested by using micropore filter assay in modified Boyden chamber. The effects of tetrandrine, a calcium antagonist, on monocyte migration induced by EC-CM were investigated. The results showed that cultured human umbilical vein endothelial cells secreted a chemotactic factor for monocytes, and the monocyte migration induced by this chemoattractant could be inhibited by tetrandrine at the concentration of 10(-8)-10(-5) mol/L in a dose-dependent manner. Verapamil at the concentration of x10(-8) mol/L also showed the same effect. It is suggested that tetrandrine may inhibit monocyte migration into arterial subendothelial space through antagonism to calcium and thereby suppress atherogenesis.

Insertional mutation of a gene involved in growth regulation of the early mouse embryo

A transgenic mouse strain derived from embryonic stem (ES) cells infected with multiple copies of a retroviral vector carries a recessive insertional mutation resulting in prenatal lethality. A detailed histological analysis of developing embryos has shown that the mutation results in hyperplasia of both embryonic and extraembryonic ectoderm and failure of mesoderm formation in the egg cylinder stage embryo. The number of cells in each lineage of normal and mutant embryos was estimated using stereological analysis of serial sections taken from implantation sites. We observed a 2-fold increase in the number of embryonic ectoderm cells in mutant embryos at 7.5 days postcoitum (dpc). In addition, we found that mutant embryonic ectoderm cells are only 0.6 times as large as normal cells. The number of extraembryonic ectoderm cells in mutant embryos at 7.5 dpc is also increased, by almost 4-fold. Mutant extraembryonic ectoderm cells are also smaller than normal, being only two-thirds the size of wild-type cells. The mutant phenotype suggests that the gene identified by this insertional mutation plays an important role in the growth control of early embryonic lineages.

Nonoxidative ethanol metabolism: expression of fatty acid ethyl ester synthase-III in cultured neural cells

Alcohol metabolism in the human brain has been characterized as essentially nonoxidative in nature, with the esterification of ethanol with fatty acids via fatty acid ethyl ester synthase. This pathway of ethanol metabolism is related to end organ damage in the brain but the neural cell type expressing FAEES has not been identified. In this study human and rodent neuroblastoma and glioma cell lines are assayed for fatty acid ethyl ester synthase activity. Cells with neuronal properties demonstrated higher activity than glioma cell lines. We confirmed the presence of the mRNA for one type of synthase, fatty acid ethyl ester synthase-III in three neuronal cell lines--N1E115 cells, PC12 cells, and SK-N-MC cells. These results support the hypothesis that FAEES activity is expressed chiefly in cells with neuronal properties and suggest that non-oxidative ethanol metabolism is potentially related to the toxic effect of ethanol on the human brain.

[Determination of total alkaloid in seedling bulbs of Fritillaria thunbergii Miq]

This paper reports the determination of total alkaloid in the seedling bulbs and cultivars of the traditional Chinese medicine Fritillaria thunbergii. The result shows that the content of total alkaloid reaches the standard value specified in Chinese Pharmacopeia, and thus is useful for further production of sexual propagation.

Existence of both fast and slow channel activity during the early stages of ventricular fibrillation

Although sodium channels have been reported to be inactive after 5-10 minutes of ventricular fibrillation (VF), their state during early VF is unknown. In 12 open-chest dogs, a floating glass microelectrode was used to record intracellular action potentials from the right ventricle during pacing and during electrically induced VF. Before any drug was administered, an initial episode of VF was continuously recorded for at least 20 seconds followed by defibrillation. Recordings were made during VF episodes after superfusion for 15 minutes around the microelectrode site by low (2.8 x 10(-5) M) and high (10(-4) M) concentrations of tetrodotoxin (TTX) in five dogs, or by low (4 microM) and high (100 microM) concentrations of verapamil in another four dogs. In three dogs, VF was induced without drugs three times to determine if the effects observed in the previous dogs were caused by the drugs or by successive episodes of VF. Ten consecutive action potentials were analyzed at the onset and after 5, 10, 15, and 20 seconds of VF. Action potential amplitude and duration during paced rhythm or VF were not changed by the local perfusion of either TTX or verapamil. In the TTX group, the maximum upstroke rate of depolarization of an action potential (Vmax) during paced rhythm was 104 +/- 14 V/sec for control cycles before any drug was given, 86 +/- 15 V/sec for the low TTX concentration, and 55 +/- 14 V/sec for the high TTX concentration (p less than 0.05 versus other two). Vmax decreased from 55 +/- 32 V/sec at the beginning of VF to 37 +/- 27 V/sec after 20 seconds of VF for predrug VF, from 39 +/- 20 V/sec to 18 +/- 11 V/sec for low-dose TTX VF, and from 18 +/- 13 V/sec to 12 +/- 7 V/sec for high-dose TTX VF (p less than 0.05 among the three groups). In the dogs receiving verapamil, VF was still inducible with Vmax not significantly different from predrug VF at the onset and after 5 or 20 seconds of VF but with Vmax smaller (p less than 0.05) for verapamil than for predrug VF after 10 or 15 seconds of VF. In three dogs, Vmax was not significantly different during three successive episodes of VF when no drug was given between the episodes.(ABSTRACT TRUNCATED AT 400 WORDS)

Molecular cloning and characterization of a novel rat activin receptor

We report the isolation of a full-length rat cDNA for a new activin receptor. The deduced amino acid sequence of this receptor shows 67 percent overall identity with that of a previously identified mouse activin receptor. As predicted for the mouse activin receptor, the amino acid sequence of the rat receptor is consistent with a polypeptide containing an extracellular ligand binding domain, a hydrophobic transmembrane domain, and a serine/threonine kinase intracellular domain. In an expression assay, this new receptor was found to bind I125 radiolabeled activin.

The relationship between the changes in plasma atrial natriuretic peptide and renin angiotensin contents and hemodynamics in pulmonary hypertensive rats

Pulmonary artery pressure (PAP) increased significantly in rats after hypobaric hypoxic exposure for 15 days (CH15) (P less than 0.001) and was maintained at the same level after prolonged hypoxic exposure for 40 days (CH40). There were no significant changes in carotid systolic and diastolic blood pressure in CH15 and CH40 rats. The contractility of the right and left ventricles of CH15 and CH40 rats showed no difference as compared with the control group. Plasma atrial natriuretic peptide (ANP) content in CH40 rats was obviously increased (P less than 0.001), while angiotensin II (AII) dropped markedly (P less than 0.05). Plasma renin activity was increased in both hypoxic groups (P less than 0.05 respectively). These results indicate that during chronic hypoxia, plasma ANP and the renin-angiotensin system (RAS) play an important role in the modulation of pulmonary as well as systemic hemodynamics. They may work cooperatively to limit the development of pulmonary hypertension and to maintain systemic blood pressure within the normal range.

[Mechanism of the photosensitive effects of methylene blue in the inhibition of DNA synthesis in cancer cells]

In the present study, we found that various concentrations of methylene blue (38, 3.8, 0.38, 0.038, 0.0038 mumol/L) significantly inhibited DNA synthesis in ascites hepatoma (AH) cells. The inhibition increased with the concentration of methylene blue as well as with irradiation time. Photosensitization of methylene blue was not due to 1O2, OH., or O2.-, but was closely related to H2O2. The mechanism of inhibition of DNA synthesis may be attributed to the damage of DNA replication template.

[Preliminary study on the relation between serum growth hormone and 1,25-dihydroxyvitamin D3 in acromegalic patients]

Eight acromegalic patients were treated with SMS 201-995 for 12 months. At the 3rd, 6th and 12th month from the beginning of treatment, blood samples of these patients were taken for determination of growth hormone (GH), 1,25-(OH)2D3, SMC, calcium and phosphorus. The serum levels of GH decreased significantly at the 3rd, 6th and 12th months compared with the basal levels before treatment (P less than 0.01, P less than 0.05 and P less than 0.05 respectively). The concentrations of serum 1,25-(OH)2D3 and SMC also decreased significantly. Mean serum GH, 1,25-(OH)2D3 and SMC levels were reduced from 34.8 +/- 10.7 to 15.5 +/- 5.9 ng/ml (P less than 0.05), 76.2 +/- 2.7 to 45.9 +/- 8.3 pg/ml (P less than 0.05) and 8.5 +/- 1.2 to 4.4 +/- 1.0 U (P less than 0.05) respectively at the 12th month after treatment. Serum phosphorus levels reduced from 4.7 +/- 0.4 to 4.1 +/- 0.2 mg% (P less than 0.05) at the 6th month after treatment, but there was no change in the serum levels of total calcium. The treatment with SMS 201-995 directly evoked a reduction of serum GH in acromegalic patients and at the same time, the levels of serum SMC and 1,25-(OH)2D3 were decreased. The results suggest that GH may stimulate indirectly the production of 1,25-(OH)2D3 through the mediation of SMC.