Etomidate elevates intracellular calcium levels and promotes catecholamine secretion in bovine chromaffin cells

Etomidate, an intravenous imidazole general anaesthetic, is thought to produce anaesthesia by modulating or activating ionotropic Cl(-)-permeable GABA(A) receptors. Chromaffin cells are known to express functional GABA(A) receptors with properties similar to their neuronal counterparts. We have shown that activation of the GABA(A) receptors, with specific GABA(A) agonists, leads to cellular excitation. Our goal was to determine whether etomidate mimicked this response and to explore the functional consequences of this activation. Imaging experiments with the Ca(2+)-indicator dye fura-2 were used to assay [Ca(2+)](i). Bovine adrenal chromaffin cells were superfused with a variety of GABA(A)-selective drugs to determine their effects on [Ca(2+)](i). Amperometric measurements were used to assay catecholamine release in real-time. We show that bovine adrenal chromaffin cells were excited by etomidate at clinically relevant concentrations. Etomidate directly activated GABA(A) receptors found in chromaffin cells thereby elevating [Ca(2+)](i). The effects of etomidate were mimicked by the specific GABA(A) agonist muscimol and blocked by the specific antagonist bicuculline. Our data show that low concentrations of etomidate modulated GABA(A) receptor activation by muscimol. Blockade of voltage-dependent Ca(2+) channels prevented the elevation of [Ca(2+)](i) by GABA. Application of etomidate directly to the chromaffin cells elicited robust catecholamine secretion from these cells. The data indicate that clinically relevant concentrations of etomidate can directly activate GABA(A) receptors, which, due to the positive anion equilibrium potential, depolarizes chromaffin cells. This depolarization activates voltage-dependent Ca(2+) channels thereby stimulating catecholamine release. Our data suggest that circulating catecholamine levels may be elevated after etomidate application.

Sensitivity of 14-3-3 protein test varies in subtypes of sporadic Creutzfeldt-Jakob disease

BACKGROUND

The increase of the 14-3-3 protein in CSF is used as a diagnostic test in Creutzfeldt-Jakob disease (CJD), but the sensitivity and specificity of the 14-3-3 test are disputed. One reason for the dispute may be the recently established heterogeneity of sporadic CJD. The relationship between CSF 14-3-3 protein and sporadic CJD subtypes, distinguished by electrophoretic mobility of proteinase K-resistant prion protein (PrP(Sc)) and genotype at codon 129 of the prion protein gene, has not been elucidated.

METHODS

The authors examined the 14-3-3 protein test in 90 patients with sporadic CJD. PrP(Sc) type (type 1 or type 2) and the genotype at polymorphic codon 129 were determined in each patient. Mutations were excluded by prion gene sequencing.

RESULTS

The authors' findings indicate that the sensitivity of the 14-3-3 test is higher in patients with molecular features of the classic sporadic CJD than in patients with the nonclassic CJD subtypes. The difference appears to be related to the PrP(Sc) type and not to the codon 129 genotype. Disease duration before 14-3-3 testing might also have an influence because it was shorter in classic sporadic CJD.

CONCLUSION

The Creutzfeldt-Jakob disease clinical subtype should be considered when interpreting results of the 14-3-3 test.

25 Hydroxyvitamin D 1 alpha-hydroxylase is required for optimal epidermal differentiation and permeability barrier homeostasis

Keratinocytes express high levels of 25OHD 1alpha-hydroxylase (1OHase). The product of this enzyme, 1,25-dihydroxyvitamin D (1,25(OH)(2)D), promotes the differentiation of keratinocytes in vitro suggesting an important role for this enzyme in epidermal differentiation. To test whether 1OHase activity is essential for keratinocyte differentiation in vivo we examined the differentiation process in mice null for the expression of the 1alphaOHase gene (1alphaOHase(-/-)). Heterozygotes for the null allele were bred, and the progeny genotyped by PCR. The epidermis of the 1alphaOHase(-/-) animals and their wild-type littermates (1alphaOHase(+/+)) were examined by histology at the light and electron microscopic level, by immunocytochemistry for markers of differentiation, and by function examining the permeability barrier using transepidermal water loss (TEWL). No gross epidermal phenotype was observed; however, immunocytochemical assessment of the epidermis revealed a reduction in involucrin, filaggrin, and loricrin-markers of differentiation in the keratinocyte and critical for the formation of the cornified envelope. These observations were confirmed at the electron microscopic level, which showed a reduction in the F (containing filaggrin) and L (containing loricrin) granules and a reduced calcium gradient. The functional significance of these observations was tested using TEWL to evaluate the permeability barrier function of the epidermis. Although TEWL was normal in the basal state, following disruption of the barrier using tape stripping, the 1alphaOHase(-/-) animals displayed a markedly delayed recovery of normal barrier function. This delay was associated with a reduction in lamellar body secretion and a failure to reform the epidermal calcium gradient. Thus, the 25OHD 1OHase is essential for normal epidermal differentiation, most likely by producing the vitamin D metabolite, 1,25(OH)(2)D, responsible for inducing the proteins regulating calcium levels in the epidermis that are critical for the generation and maintenance of the barrier.

Calcium and 1,25(OH)2D: interacting drivers of epidermal differentiation

Both calcium and 1,25(OH)(2)D promote the differentiation of keratinocytes in vitro. The autocrine or paracrine production of 1,25(OH)(2)D by keratinocytes combined with the critical role of the epidermal calcium gradient in regulating keratinocyte differentiation in vivo suggest the physiologic importance of this interaction. The interactions occur at a number of levels. Calcium and 1,25(OH)(2)D synergistically induce involucrin, a protein critical for cornified envelope formation. The involucrin promoter contains an AP-1 site essential for calcium and 1,25(OH)(2)D induction and an adjacent VDRE essential for 1,25(OH)(2)D but not calcium induction. Calcium regulates coactivator complexes that bind to the Vitamin D receptor (VDR). Nuclear extracts from cells grown in low calcium contain an abundance of DRIP(205), whereas calcium induced differentiation leads to reduced DRIP(205) and increased SRC 3 which replaces DRIP in its binding to the VDR. In vivo models support the importance of 1,25(OH)(2)D-calcium interactions in epidermal differentiation. The epidermis of 1alphaOHase null mice fails to form a normal calcium gradient, has reduced expression of proteins critical for barrier function, and shows little recovery of the permeability barrier when disrupted. Thus in vivo and in vitro, calcium and 1,25(OH)(2)D interact at multiple levels to regulate epidermal differentiation.

Mice lacking 25OHD 1alpha-hydroxylase demonstrate decreased epidermal differentiation and barrier function

Keratinocytes express high levels of 25OHD 1alpha-hydroxylase (1OHase). The product of this enzyme, 1,25(OH)(2)D, promotes the differentiation of keratinocytes in vitro. To test whether 1OHase activity is essential for keratinocyte differentiation in vivo we examined the differentiation process in mice null for the expression of the 1alphaOHase gene (1alphaOHase(-/-)) by light and electron microscopy, by immunocytochemistry for markers of differentiation, by ion capture cytochemistry for calcium localization, and by function using transepidermal water loss (TEWL) to assess barrier integrity. Levels of involucrin, filaggrin, and loricrin-markers of differentiation in the keratinocyte and critical for the formation of the cornified envelope-were reduced in the epidermis of 1alphaOHase(-/-) mice. Calcium in the outer epidermis was reduced with loss of the calcium gradient from stratum basale to stratum granulosum. TEWL was normal in the resting state, but following disruption of the barrier, 1alphaOHase(-/-) mice had a markedly prolonged recovery of barrier function associated with a reduction in lamellar body secretion and a failure to reform the calcium gradient. Thus 1,25(OH)(2)D is essential for normal epidermal differentiation, most likely by inducing the proteins and mediating the calcium signaling in the epidermis required for the generation and maintenance of the barrier.

Role of Cl- co-transporters in the excitation produced by GABAA receptors in juvenile bovine adrenal chromaffin cells

GABA is the primary inhibitory neurotransmitter in the adult mammalian brain. However, in neonatal animals, activation of Cl(-)-permeable GABA receptors is excitatory and appears to depend on the expression of a Na(+)-K(+)-2Cl- cotransporter (NKCC) that elevates intracellular Cl- levels, leading to a depolarized Cl- equilibrium potential (ECl). The change from excitation to inhibition appears to involve the expression of the K+/Cl- co-transporter, KCC2, which lowers intracellular Cl- levels resulting in a hyperpolarized ECl. In this study, we show that bovine chromaffin cells from 4- to 5-mo-old animals are excited by GABA. Activation of GABAA receptors depolarizes the cells, opens voltage-dependent Ca2+ channels, elevates [Ca2+]i, and promotes the release of catecholamines. Blockade of voltage-dependent Ca2+ channels prevents the elevation of [Ca2+]i by GABA. The extrapolated anion reversal potential in these cells is approximately -28 mV, indicating a resting intracellular anion concentration of approximately 50 mM. Expression of KCC2 protein was not detected in the juvenile chromaffin cells. In contrast, clear expression of NKCC1 was observed. Blockade of NKCC1 should reduce the intracellular Cl- concentration and hyperpolarize ECl. Bumetanide, an NKCC1 blocker, reduced the elevation of [Ca2+]i by GABA. In some cells, activation of GABAA receptors inhibits responses to excitatory neurotransmitters, even though GABA itself is depolarizing. Co-activation of cholinergic and GABAA receptors in chromaffin cells produced elevations in [Ca2+]i that were comparable to those produced by cholinergic receptors alone. Our data showing the selective expression of chloride co-transporters and the resulting strongly depolarized anion reversal potential may help explain how activation of GABAA receptors causes sufficient excitation to elicit catecholamine release from chromaffin cells.

Inhibition of phosphatidylinositol 3-kinase dephosphorylates BAD and promotes apoptosis in myeloid leukemias

The phosphatidylinositol 3-kinase (PI3K)/AKT protein kinase pathway is involved in cell growth, proliferation, and apoptosis. The functional activation of PI3K/AKT provides survival signals and blockade of this pathway may facilitate cell death. Downstream targets of PI3K-AKT include the proapoptotic protein BAD, caspase-9, NF-kappaB, and Forkhead. We have previously reported that BAD is constitutively phosphorylated in primary acute myeloid leukemia (AML) cells, a post-transcriptional modification, which inactivates its proapoptotic function. In this study, we tested the hypothesis that the inhibition of PI3K by LY294002 results in the dephosphorylation of AKT and BAD, and thus promote leukemia cell apoptosis. We investigated the effects of LY294002 in megakaryocytic leukemia-derived MO7E cells, primary AML and normal bone marrow progenitor cells. In MO7E cells, LY294002 reduced AKT kinase activity, induced dephosphorylation of AKT and BAD, and increased apoptosis. Concomitant inhibition of mitogen-activated protein kinase signaling or combination with all-trans retinoic acid further enhanced apoptosis of leukemic cells. In primary AML samples, clonogenic cell growth was significantly reduced. Normal hematopoietic progenitors were less affected, suggesting preferential targeting of leukemia cells. In conclusion, the data suggest that the inhibition of the PI3K/AKT signaling pathway restores apoptosis in AML and may be explored as a novel target for molecular therapeutics in AML.

Vitamin D regulated keratinocyte differentiation: role of coactivators

1,25 Dihydroxyvitamin D (1,25(OH)(2)D) regulates the differentiation of keratinocytes. 1,25(OH)(2)D raises intracellular free calcium (Cai) as a necessary early step toward stimulating differentiation. 1,25(OH)(2)D induces the calcium sensing receptor (CaR) in keratinocytes and enhances the calcium response of these cells. Activation of the CaR by calcium increases intracellular free calcium by a mechanism involving phospholipase C (PLC) cleavage of phosphatidylinositolbisphosphate into inositoltrisphosphate (IP(3)) and diacylglycerol (DG). 1,25(OH)(2)D induces the family of PLCs. PLC-gamma1 has a DR6 VDRE in its promoter which binds and is activated by VDR/RAR rather than VDR/RXR. The involucrin gene, which encodes a critical component of the cornified envelope, contains a DR3 VDRE in its promoter that acts in conjunction with a nearby AP-1 site. The sequential regulation of these genes is critical for the differentiation process. In undifferentiated keratinocytes, the VDR binds preferentially to the DRIP complex of coactivators. However, with differentiation DRIP 205 is no longer produced, and the VDR switches partners to the SRC family (SRC2 and 3). These studies suggest that at least part of the sequential activation of genes required during keratinocyte differentiation is regulated by the change (availability) of these different coactivator complexes.

[Antagonism of the novel cholinolytic tricyclopinate on nicotinic and muscarinic cholinergic receptors]

Tricyclopinate hydrochloride(TCPN.HCl) and methiodide(TCPN.CH3I) have been identified as new chemical entities. The effects of these two compounds on central and peripheral nicotinic and muscarinic cholinergic receptor activities were investigated. Excitation of the central nicotinic receptors by nicotine produced convulsions in mice. The dose-response curves of nicotine for producing convulsions were shifted rightward by TCPN.CH3I in a paralled manner. Excitation of the central muscarinic receptors by arecoline produced tremors in mice. TCPN.HCl was shown to prevent arecoline-induced tremors. In isolated guinea-pig ileum preparations. TCPN.HCl was found to antagonize nicotine-induced contractions due to excitation of ganglionic nicotinic receptors. In xenopus laevis embryo neuron-muscle co-cultured cells, TCPN.HCl blocked spontaneous miniature endplate currents, and showed preference to blocking the nicotinic receptor ion channels, which had a long open time, and high current amplitude. The anticholinergic effects of TCPN.CH3I were weaker than those of TCPN.HCl. In conclusion, TCPN.HCl has potent effects against nicotinic and muscarinic receptors in the central and periphery nervous systems.

[Protective effects of ischemic preconditioning on ischemia reperfusion injuries of kidney: experimental studies]

We studied the serum levels of SOD and creatinine(Cr) of venous blood and changes in renal tissue structures under electromicroscope in the ischemia referfusion(I/R), the ischemic preconditioning(PC1, PC2, PC3), and the control groups in rabbits. The results were that the serum levels of SOD and Cr in the I/R group were obviously higher than that in the PC and control groups after one-hour ischemia and one-hour reperfusion(P < 0.001). There were no significant difference in Cr levels between the PC2 and control groups; there were significant degenerate and necrotic changes under the electromicroscope in renal tissues in the I/R group, but there were no significant change in the PC and control groups. The results suggest that PC plays a role in protecting the kidney from injury induced by ischemia and reperfusion.

[Electrocardiographic T-wave amplitude of normal population and its correlation with age, sex and race]

OBJECTIVE

To establish a normal electrocardiographic T wave amplitude standard in Chinese population according to age and sex.

METHODS

The electrocardiographic T wave amplitudes in 4,322 persons among normal population; aged from birth to eighty-five years old divided into 11 age-groups, were analyzed. The 97.5th percentile(P97.5) and 2.5th percentile(P2.5) were considered as the upper and the lower limit of normal T wave amplitudes and T/R ratio. Wilcoxon rank sum test was used to determine whether the normal electrocardiographic T wave amplitude and the T/R ratio were different in P97.5 value versus mean + 1.96 s value, in men versus women, and in Chinese versus Americans. The linear correlation analysis was used to examine the association between normal T amplitude and age as well as between T/R ratio and age.

RESULTS

The normal T wave amplitudes and T/R ratio in all leads were greater in P97.5 value than in mean + 1.96 s value and were greater in men than in women. The normal T wave amplitudes of adults were greater in Chinese than in Americans except V1 lead in which the amplitudes were greater in Americans than in Chinese. There was moderate or marked correlation of normal T wave amplitude and T/R ratio with age in most of the leads.

CONCLUSION

There are marked differences of age, sex and race in normal electrocardiographic T wave amplitudes.

[Study on cytotoxicity to leukemia cell and enhancement of immunologic functions of jiexinkang]

Cytotoxicity to leukemia cell and enhancement of immunologic functions of jiexinkang (JXK, traditional Chinese medicine) were observed in 34 cases of leukemia in vitro. The results showed that the leukemia cytotoxicity in the group of vincristine combined with JXK was significantly higher than that in vincristine alone. It was also found among all the observed cases that 20 refractory or recurred patients resistant to vincristine showed an obvious intention of the anti-toxicity efficiency when JXK was added. Jiexinkang alone had anti-leukemia cell effect, too. We explored JXK effects on immunologic functions in mice, and found that IFNr and NK activities of normal and experimental model mice were significantly higher than those of control group(P < 0.01). The results indicate that JXK has an effect of anti-leukemia cell and may improve the cell-immunologic functions.

Determination of acetone, 2-butanone, diethyl ketone and BTX using HSCC-UV-IMS

A combination of a custom-designed ion mobility spectrometer (IMS) with a UV ionization source and a high speed capillary column (HSCC) has been developed as an analytical device for the sensitive detection of volatile organic compounds (VOCs), e.g. 2-propanone (acetone), 2-butanone and 3-pentanone (diethyl ketone) in the gas phase. A fast separation of the three selected substances and benzene, toluene and m-xylene (BTX) - all of which occur in human breath - has been achieved within less than four minutes at a carrier gas flow rate of 4.5 mL x min(-1). Multi-dimensional correlations presented support the interpretation of the acquired spectra of mixtures. Method detection limits were 2.7 microg x L(-1) for acetone and 2-butanone and 3.0 microg x L(-1) for diethyl ketone in nitrogen, respectively. The assay linear dynamic range is 4-320 microg x L(-1).

Insomnia associated with thalamic involvement in E200K Creutzfeldt-Jakob disease

BACKGROUND

Insomnia with predominant thalamic involvement and minor cortical and cerebellar pathologic changes is not characteristic of familial Creutzfeldt-Jakob disease (CJD) but is a hallmark of fatal familial insomnia.

OBJECTIVE

To report a 53-year-old woman with intractable insomnia as her initial symptom of disease.

METHODS

The authors characterized clinical, pathologic, and molecular features of the disease using EEG, polysomnography, neurohistology, Western blotting, protein sequencing, and prion protein (PrP) gene (PRNP) analysis.

RESULTS

The patient developed dysgraphia, dysarthria, bulimia, myoclonus, memory loss, visual hallucinations, and opisthotonos, as well as pyramidal, extrapyramidal, and cerebellar signs. Polysomnographic studies showed an absence of stages 3 and 4, and REM. She died 8 months after onset. On neuropathologic examination, there was major thalamic involvement characterized by neuronal loss, spongiform changes, and prominent gliosis. The inferior olivary nuclei exhibited chromatolysis, neuronal loss, and gliosis. Spongiform changes were mild in the neocortex and not evident in the cerebellum. PrP immunopositivity was present in these areas as well as in the thalamus. PRNP analysis showed the haplotype E200K-129M. Western blot analysis showed the presence of proteinase K (PK)-resistant PrP (PrP(sc)) with the nonglycosylated isoform of approximately 21 kd, corresponding in size to that of type 1 PrP(sc). N-terminal protein sequencing demonstrated PK cleavage sites at glycine (G) 82 and G78, as previously reported in CJD with the E200K-129 M haplotype.

CONCLUSIONS

Insomnia may be a prominent early symptom in cases of CJD linked to the E200K-129M haplotype in which the thalamus is severely affected.

[The significance of nm23 gene expression in embryonic tissues and lung cancer tissues]

BACKGROUND

To clarify the relationship between nm23-H1 gene and differentiation of embryonic tissues and the significance of its expression in pulmonary carcinoma.

METHODS

nm23-H1 protein ( NM23-H1) was detected in the embryonic tissues of SD rats and human being, as well as in human lung cancer tissues, by immunohistochemistry method.

RESULTS

Only embryonic tissues with definite configuration ( organ structure) expressed NM23-H1 constantly. Positive rate of NM23-H1 was 34. 7% in 49 cases of human lung cancer tissues, and 27. 3% in squamous cell carcinoma, 50. 0% in adenocarcinoma. The positive rate of NM23-H1 was 22. 2% in 27 cases of hilar lymph node metastatic foci, and 34. 8% in primary tumour foci ( P > 0. 05) . There was no significant difference of lymphatic metastatic rates between NM23-H1 positive and negative primary tumors.

CONCLUSIONS

There is positive correlation between accumulation of NM23-H1 and differentiation of embryonic tissues and lung carcinoma. NM23-H1 may play an important role in maintaining a stable epithelial structure. It doesn't show that NM23-H1 can directly inhibit the metastasis of lung cancer cells.

[Relationship between serum CA125 level and prognosis in the patients with uterine endometrial carcinoma]

OBJECTIVE

To study the relationship between serum CA125 level and prognosis of uterine endometrial carcinoma.

METHODS

The serum CA125 levels in 71 patients with uterine endometrial carcinoma were measured by using microparticle enzyme immunoassay. The relationship between preoperative CA125 levels and surgical pathologic staging, histologic classification, and other prognostic factors was investigated.

RESULTS

(1) The positive rate of serum CA125 in postmenopausal patients was significantly higher than in premenopausal patients. (2) The positive rate of serum CA125 was related to surgical pathologic staging. (3) Serum CA125 level was correlated not only with histological classification but also with other prognosis factors. (4) Increase of serum CA125 after operation predicted the possibility of relapse.

CONCLUSION

CA125 is a useful marker in predicting the prognosis of uterine endometrial carcinoma.

Highly frequent frameshift DNA synthesis by human DNA polymerase mu

DNA polymerase mu (Polmu) is a newly identified member of the polymerase X family. The biological function of Polmu is not known, although it has been speculated that human Polmu may be a somatic hypermutation polymerase. To help understand the in vivo function of human Polmu, we have performed in vitro biochemical analyses of the purified polymerase. Unlike any other DNA polymerases studied thus far, human Polmu catalyzed frameshift DNA synthesis with an unprecedentedly high frequency. In the sequence contexts examined, -1 deletion occurred as the predominant DNA synthesis mechanism opposite the single-nucleotide repeat sequences AA, GG, TT, and CC in the template. Thus, the fidelity of DNA synthesis by human Polmu was largely dictated by the sequence context. Human Polmu was able to efficiently extend mismatched bases mainly by a frameshift synthesis mechanism. With the primer ends, containing up to four mismatches, examined, human Polmu effectively realigned the primer to achieve annealing with a microhomology region in the template several nucleotides downstream. As a result, human Polmu promoted microhomology search and microhomology pairing between the primer and the template strands of DNA. These results show that human Polmu is much more prone to cause frameshift mutations than base substitutions. The biochemical properties of human Polmu suggest a function in nonhomologous end joining and V(D)J recombination through its microhomology searching and pairing activities but do not support a function in somatic hypermutation.

Effects of uremic serum on isolated cardiac myocyte calcium cycling and contractile function

BACKGROUND

Diastolic dysfunction occurs in patients with chronic renal failure. Moreover, serum from uremic patients contains one or more inhibitors of the plasmalemmal Na,K-ATPase (sodium pump). We hypothesized that a circulating substance present in uremic sera contributes to both sodium pump inhibition and diastolic dysfunction.

METHODS

Serum samples were obtained from six patients with chronic renal failure and diastolic dysfunction.

RESULTS

Their serum samples caused marked inhibition of Na,K-ATPase purified from dog kidney at all concentrations studied (all P < 0.01) and also impaired ouabain-sensitive rubidium uptake by myocytes isolated from Sprague-Dawley rats (P < 0.01). These cardiac myocytes were studied for their contractile function with video-edge detection and calcium metabolism with indo-1 fluorescence spectroscopy after exposure to these uremic sera. These uremic sera caused increases in myocyte fractional shortening (P < 0.01) as well as an increase in the time constant of relengthening (P < 0.01). Examining the calcium transient, the time constant for calcium recovery was also increased (P < 0.01). Exposure of these cells to sera from age- and sex-matched healthy subjects did not result in significant changes in contraction or calcium cycling. Extracts of uremic serum samples inhibited isolated Na,K-ATPase whereas extracts of normal serum samples did not. The effect of uremic serum extracts on contractile function and calcium cycling were quite similar to that of intact serum or the addition of ouabain. Co-incubation of uremic serum extract with an antibody fragment directed against digoxin markedly attenuated the inhibition of Na,K-ATPase activity and completely prevented any effects on calcium cycling or contractile function.

CONCLUSION

These data show that one or more substances are present in uremic sera that acutely cause increased force of contraction and impaired recovery of cardiac myocyte calcium concentration as well as impaired relaxation. As these effects are similar to that seen with ouabain and can be prevented by co-incubation with an antibody fragment to digitalis, which also attenuates the sodium pump inhibitory effect, we suggest that this (these) substance(s) circulating in uremic sera and inhibiting the sodium pump also causes the acute diastolic dysfunction seen in our system.

A convenient and rapid method for genetic transformation of E. coli with plasmids

A convenient and rapid method for the genetic transformation of Escherichia coli with plasmids is proposed. By mixing the recipient cells and plasmid DNA and spreading them directly on selective medium plates containing Ca2+, the so-called 'plate transformation' could achieve almost the same transformation efficiency as the classical transformation method with calcium. The whole protocol takes only about 2 min, its simplicity compared favorably, not only to the usual protocol, but also to all other documented modifications.

Role of protein kinase C in the signal pathways that link Na+/K+-ATPase to ERK1/2

We have shown before that Na(+)/K(+)-ATPase acts as a signal transducer, through protein-protein interactions, in addition to being an ion pump. Interaction of ouabain with the enzyme of the intact cells causes activation of Src, transactivation of EGFR, and activation of the Ras/ERK1/2 cascade. To determine the role of protein kinase C (PKC) in this pathway, neonatal rat cardiac myocytes were exposed to ouabain and assayed for translocation/activation of PKC from cytosolic to particulate fractions. Ouabain caused rapid and sustained stimulation of this translocation, evidenced by the assay of Ca(2+)-dependent and Ca(2+)-independent PKC activities and by the immunoblot analysis of the alpha, delta, and epsilon isoforms of PKC. Dose-dependent stimulation of PKC translocation by ouabain (1-100 microm) was accompanied by no more than 50% inhibition of Na(+)/K(+)-ATPase and doubling of [Ca(2+)](i), changes that do not affect myocyte viability and are known to be associated with positive inotropic, but not toxic, effects of ouabain in rat cardiac ventricles. Ouabain-induced activation of ERK1/2 was blocked by PKC inhibitors calphostin C and chelerythrine. An inhibitor of phosphoinositide turnover in myocytes also antagonized ouabain-induced PKC translocation and ERK1/2 activation. These and previous findings indicate that ouabain-induced activation of PKC and Ras, each linked to Na(+)/K(+)-ATPase through Src/EGFR, are both required for the activation of ERK1/2. Ouabain-induced PKC translocation and ERK1/2 activation were dependent on the presence of Ca(2+) in the medium, suggesting that the signal-transducing and ion-pumping functions of Na(+)/K(+)-ATPase cooperate in activation of these protein kinases and the resulting regulation of contractility and growth of the cardiac myocyte.

Coronary reperfusion following ischemia: different expression of bcl-2 and bax proteins, and cardiomyocyte apoptosis

The aim of this work was to examine factors that could be involved in the occurrence of apoptosis in rat hearts subjected to coronary occlusion followed by reperfusion. To this end, we studied the expression of the pro- and anti-apoptotic factors, bax and bcl-2, respectively, in reperfused ischemic hearts and in hearts injected with bFGF or saline. In anesthetized rats the left coronary artery was occluded for 45 min, the anesthesia withdrawn and the occlusion removed to allow reperfusion; in sham-operated rats the occlusion was omitted. After 4 hours the rats were decapitated and the heart excised. Sections from the left ventricle were stained with anti-bcl-2-antibody and anti-bax-antibody using the TUNEL method which detects apoptosis. Fragmentation of DNA isolated from reperfused ventricles was examined by agarose electrophoresis. In reperfused hearts no bcl-2 staining was observed in the discrete area in which many cardiomyocyte nuclei were stained by the TUNEL method; outside this area staining for bcl-2 was more marked than in sham-operated rats. Sections from reperfused hearts were stained for bax protein over a wide area including the apoptotic region; sham-operated hearts showed little reaction. Staining for bcl-2 was demonstrable in some nuclei in hearts from saline-injected rats; the numbers were unaffected by i. v. bFGF. Ischemia/reperfusion increases the overall expression of both bcl-2 and bax proteins, but bcl-2 is lost from the reperfused area as indicated by TUNEL staining. Accordingly, the ratio of bcl-2 to bax was reduced in the reperfused area, indicating a pro-apoptotic trend. The marked increase in bcl-2 outside the reperfused area could be a mechanism with which to salvage surviving cardiomyocytes.