Phosphatase inhibition promotes antiapoptotic but not proliferative signaling pathways in erythropoietin-dependent HCD57 cells

Erythropoietin (EPO) allows erythroid precursors to proliferate while protecting them from apoptosis. Treatment of the EPO-dependent HCD57 murine cell line with 70 micromol/L orthovanadate, a tyrosine phosphatase inhibitor, resulted in both increased tyrosine protein phosphorylation and prevention of apoptosis in the absence of EPO without promoting proliferation. Orthovanadate also delayed apoptosis in primary human erythroid progenitors. Thus, we investigated what survival signals were activated by orthovanadate treatment. Expression of Bcl-X(L) and BAD phosphorylation are critical for the survival of erythroid cells, and orthovanadate in the absence of EPO both maintained expression levels of antiapoptotic Bcl-X(L) and induced BAD phosphorylation at serine 112. Orthovanadate activated JAK2, STAT1, STAT5, the phosphatidylinositol-3 kinase (PI-3 kinase) pathway, and other signals such as JNK and p38 without activating the EPO receptor, JAK1, Tyk2, Vav, STAT3, and SHC. Neither JNK nor p38 appeared to have a central role in either apoptosis or survival induced by orthovanadate. Treatment with cells with LY294002, an inhibitor of PI-3 kinase activity, triggered apoptosis in orthovanadate-treated cells, suggesting a critical role of PI-3 kinase in orthovanadate-stimulated survival. Mitogen-activated protein kinase (MAPK) was poorly activated by orthovanadate, and inhibition of MAPK with PD98059 blocked proliferation without inducing apoptosis. Thus, orthovanadate likely acts to greatly increase JAK/STAT and PI-3 kinase basal activity in untreated cells by blocking tyrosine protein phosphatase activity. Activated JAK2/STAT5 then likely acts upstream of Bcl-X(L) expression and PI-3 kinase likely promotes BAD phosphorylation to protect from apoptosis. In contrast, MAPK/ERK activity correlates with only EPO-dependent proliferation but is not required for survival of HCD57 cells.

[Perioperative changes of plasma ET-1 in patients undergoing coronary artery bypass grafting and the effect of nitroglycerin]

OBJECTIVE

To observe the dynamic changes of the plasma ET-1 and the effect of low dose nitroglycerin in patients with coronary artery bypass surgery.

METHODS

40 patients with coronary artery bypass surgery were divided into group A and B. Group B received intravenous nitroglycerin 1 microg x kg(-1) x min(-1) perioperatively. We used RIA to assay the plasma ET-1 level. All the hemodynamic parameters were recorded by the Swan-Ganz catheter.

RESULTS

The preoperative plasma ET-1 level in patients with coronary artery disease was significantly higher than the normal level. Five minutes after cardiopulmonary bypass in these patients the plasma ET-1 level was increased significantly until 6 to 8 hours after operation. The increased plasma ET-1 level in group B was less than in group A. There was a positive correlation between the plasma ET-1 level and the mean pulmonary pressure in group A 2 and 8 hours after operation.

CONCLUSION

In patients undergoing coronary artery bypass surgery, the increased plasma ET-1 level may be partly due to the influence of cardiopulmonary bypass. Low dose of nitroglycerin is beneficial to these patients.

Atmospheric influence of Earth's earliest sulfur cycle

Mass-independent isotopic signatures for delta(33)S, delta(34)S, and delta(36)S from sulfide and sulfate in Precambrian rocks indicate that a change occurred in the sulfur cycle between 2090 and 2450 million years ago (Ma). Before 2450 Ma, the cycle was influenced by gas-phase atmospheric reactions. These atmospheric reactions also played a role in determining the oxidation state of sulfur, implying that atmospheric oxygen partial pressures were low and that the roles of oxidative weathering and of microbial oxidation and reduction of sulfur were minimal. Atmospheric fractionation processes should be considered in the use of sulfur isotopes to study the onset and consequences of microbial fractionation processes in Earth's early history.

Anomalous 17O compositions in massive sulphate deposits on the Earth

The variation of delta 18O that results from nearly all physical, biological and chemical processes on the Earth is approximately twice as large as the variation of delta 17O. This so-called 'mass-dependent' fractionation is well documented in terrestrial minerals. Evidence for 'mass-independent' fractionation (delta 17O = delta 17O-0.52 delta 18O), where deviation from this tight relationship occurs, has so far been found only in meteoritic material and a few terrestrial atmospheric substances. In the rock record it is thought that oxygen isotopes have followed a mass-dependent relationship for at least the past 3.7 billion years, and no exception to this has been encountered for terrestrial solids. Here, however, we report oxygen-isotope values of two massive sulphate mineral deposits, which formed in surface environments on the Earth but show large isotopic anomalies (delta 17O up to 4.6%). These massive sulphate deposits are gypcretes from the central Namib Desert and the sulphate-bearing Miocene volcanic ash-beds in North America. The source of this isotope anomaly might be related to sulphur oxidation reactions in the atmosphere and therefore enable tracing of such oxidation. These findings also support the possibility of a chemical origin of variable isotope anomalies on other planets, such as Mars.

On the kinematic modelling and the parameter estimation of the human shoulder

This paper presents some results on the modelling and the corresponding parameter estimation of the human shoulder. This system consists of the clavicle, the scapula, the humerus and the various joints between these bodies and the trunk through the sternum; it will be represented as a succession of a rotational joint between the sternum and the clavicle and a constant distance joint, representing the scapula between, the clavicle and the humerus head. The parameters of this system are the components of the position vectors of the joint characteristic points (the corresponding centres of the rotations). Experimental results are presented as well as a validation of the proposed model.

On the kinematic modeling and the parameter estimation of the human knee joint

This paper presents some results on the modeling and the parameter estimation of the human knee joint. Based on the geometric characteristics of the femur condyle and the tibia plateau, a part of femoro-tibial joint model includes an involute-on-plane submodel. Data recorded by camera type device are used to analyze the kinematic characteristics of the knee joint and to estimate the corresponding submodel parameters. Experimental results are presented and the model is further validated.

Opposing actions of dehydroepiandrosterone and corticosterone in rats

The purpose of this study was to determine the impact of dehydroepiandrosterone (DHEA) and corticosterone (CORT) treatment, using implants as a route of administration, on specific hormones, metabolites, and enzymes involved in energy metabolism. Sixty male Sprague-Dawley rats, 325 g initial weight, were implanted subcutaneously for 3 weeks with time-release pellets containing either DHEA or CORT at doses of 0, 10, 25, 50, or 100 mg in this 2 x 5 factorial experiment. In general, body weights and food intakes decreased as the level of steroid hormones increased. In contrast to DHEA treatment, rats receiving the 50- and 100-mg doses of CORT had lighter thymus glands and spleens and heavier epididymal and retroperitoneal fat pads than their controls. Rats treated with 100 mg of DHEA had lowered serum levels of triglycerides and lipid hydroperoxides whereas rats treated with 100 mg of CORT had higher levels of these blood lipids compared to their respective controls. In contrast to DHEA treatment, there was a dose-dependent increase in liver lipid content and the specific activities of the hepatic lipogenic enzymes glucose-6-phosphate dehydrogenase, malic enzyme, and fatty acid synthase in response to CORT treatment. Rats treated with 100 mg of DHEA had higher serum levels of IGF-1 than control rats. Conversely, rats treated with 100 mg of CORT had lower serum levels of IGF-1 and higher serum levels of testosterone, progesterone, and insulin than their controls. These data demonstrate the lipogenic actions of corticosterone in rats. Conversely, DHEA treatment reduced serum and hepatic lipids. Furthermore, these data suggest that using implants instead of bolus injections of steroids may be a more physiological approach for studying the influence of these steroids on lipid metabolism.

Protein kinase B (c-Akt), phosphatidylinositol 3-kinase, and STAT5 are activated by erythropoietin (EPO) in HCD57 erythroid cells but are constitutively active in an EPO-independent, apoptosis-resistant subclone (HCD57-SREI cells)

We found that erythropoietin (EPO) and stem cell factor (SCF) activated protein kinase B (PKB/Akt) in EPO-dependent HCD57 erythroid cells. To better understand signals controlling proliferation and viability, erythroid cells that resist apoptosis in the absence of EPO were subcloned and characterized (HCD57-SREI cells). Constitutive activations of PKB/Akt, STAT5a, and STAT5b were noted in these EPO-independent cells. PI3-kinase activity was an upstream activator of PKB/Akt because the PI3-kinase inhibitor LY294002 blocked both constitutive PKB/Akt and factor-dependent PKB/Akt activity. The LY294002 study showed that proliferation and viability of both HCD57-SREI and HCD57 cells correlated with the activity of PKB/Akt; however, PKB/Akt activity alone did not protect these cells from apoptosis. Treatment of HCD57 cells with SCF also activated PKB/Akt, but did not protect from apoptosis. This result suggested that PKB/PI3-kinase activity is necessary but not sufficient to promote viability and/or proliferation. Constitutive STAT5 activity, activated through an unknown pathway not including JAK2 or EPOR, may act in concert with the constitutive PI3-kinase/PKB/Akt pathway to protect the EPO-independent HCD57-SREI cells from apoptosis and promote limited proliferation.

Voltage-insensitive gating after charge-neutralizing mutations in the S4 segment of Shaker channels

Shaker channel mutants, in which the first (R362), second (R365), and fourth (R371) basic residues in the S4 segment have been neutralized, are found to pass potassium currents with voltage-insensitive kinetics when expressed in Xenopus oocytes. Single channel recordings clarify that these channels continue to open and close from -160 to +80 mV with a constant opening probability (Po). Although Po is low ( approximately 0.15) in these mutants, mean open time is voltage independent and similar to that of control Shaker channels. Additionally, these mutant channels retain characteristic Shaker channel selectivity, sensitivity to block by 4-aminopyridine, and are partially blocked by external Ca2+ ions at very negative potentials. Furthermore, mean open time is approximately doubled, in both mutant channels and control Shaker channels, when Rb+ is substituted for K+ as the permeant ion species. Such strong similarities between mutant channels and control Shaker channels suggests that the pore region has not been substantially altered by the S4 charge neutralizations. We conclude that single channel kinetics in these mutants may indicate how Shaker channels would behave in the absence of voltage sensor input. Thus, mean open times appear primarily determined by voltage-insensitive transitions close to the open state rather than by voltage sensor movement, even in control, voltage-sensitive Shaker channels. By contrast, the low and voltage-insensitive Po seen in these mutant channels suggests that important determinants of normal channel opening derive from electrostatic coupling between S4 charges and the pore domain.

Effects of short and long term ethanol on the activation of signal transducer and activator transcription factor 3 in normal and regenerating liver

Interleukin-6 (IL-6) induced activation of Signal Transducer and Activator Transcription Factor 3 (Stat3) is a critical step in liver regeneration. Chronic ethanol consumption is known to increase the plasma concentration of IL-6, yet the ability of the liver to regenerate and the regenerative induction of several IL-6 initiated events are impaired in chronic alcoholic liver disease. We hypothesized that chronic ethanol consumption inhibits IL-6 dependent signal transduction. To test this hypothesis, the effect of ethanol on the Stat3 signal transduction pathway was studied in the adult rat liver. In vitro treatment of freshly isolated normal adult rat hepatocytes with 50-100 mM ethanol for 30 min blocked IL-6-induced Stat3 activation. Long-term ethanol intake in vivo significantly attenuated the activation of Stat3 induced either in vivo by partial hepatectomy or in vitro by IL-6. In contrast, short-term ethanol consumption enhanced the regenerative induction of Stat3 but inhibited IL-6 induced Stat3 activation. These data suggest that the inhibition of liver regeneration by chronic ethanol consumption is, at least in part, mediated by modulating the activation of Stat3.

[Gas chromatographic analysis of fatty acids in phosphatidylglycerol from needles of two crosses of Chinese Fir]

This paper reports a method for determination of fatty acids in phosphatidylglycerol from needles of two crosses of Chinese Fir with different cold-resistance. Some simplifications and improvements for analytical method of DEAE CL-6B column chromatography and of silica thin layer chromatography were also discussed. After being extracted with chloroform and methanol, phosphatidylglycerol was isolated from the general lipid extract by using DEAE CL-6B IEC and Silica TLC. Quantitative analysis was conducted by gas chromatography on a DB-FFAP (30m x 0.32mm i.d.) column. The results showed that there was a difference in the ratio of fatty acid (18:1+18:2+18:3)/[16:0+16:1(3t)] between the two crosses of Chinese Fir with different cold-resistance, 1.12 for that with higher cold-resistance and 1.25 for that with lower cold-resistance. A special fatty acid 16:1(3t) was found in both of the two crosses.

Cholecystokinin octapeptide reverses the inhibitory effect induced by electroacupuncture on C-fiber evoked discharges

Extracellular single unit recordings were made from spinal dorsal horn wide dynamic range neurons in spinal transected, urethane-anesthetized rats. The unit discharges elicited by noxious electrical stimulation of the hind paw were suppressed by electroacupuncture (15 Hz, 0.3 ms, 3 mA, 30 min) placed at the hind leg points (S-36 and SP-6). Local spinal superfusion with naloxone (20 micrograms/15 microliters) or CCK-8 (10 ng/15 microliters) attenuated, whereas CCK-B receptor antagonist L365,260 (2.5 micrograms/15 microliters) enhanced the electroacupuncture effect. These findings provide further evidence for the notion that CCK-8, in the spinal cord, functions as an antiopioid substrate that antagonizes opioid- or electroacupuncture-induced analgesia.

Development of intrinsic electrophysiological properties in neurons from the gustatory region of rat nucleus of solitary tract

There is no current understanding of the nature or time course of maturation of intrinsic electrophysiological properties for neurons in the gustatory region of the nucleus of the solitary tract (NST). Therefore, we used whole cell recordings in an in vitro slice preparation of the rat brainstem to characterize development of resting membrane, action potential and repetitive discharge properties of cells in gustatory NST at postnatal days 5, 10, 15, 20, and 30, and adult ages. Neurons were filled with Biocytin to verify location and characterize morphology. Membranes from younger neurons demonstrated a steeper current-voltage relation or higher input resistance, and a longer time constant than mature cells. Action potentials in younger cells had a slower rate of rise and were longer in duration. The afterhyperpolarization that typically follows the spike discharge usually had one phase in younger neurons, but was characterized by two or more phases in an increasing proportion of older cells. The repetitive discharge frequency in response to a range of depolarizing current pulses increased during development, and frequency/current plots were steeper in older compared with younger neurons. However, in all age groups there was clear accommodation of the discharge frequency. The greatest changes in resting membrane, action potential, and discharge properties were observed between P5 and P15, and mature values were generally reached by P20. At each postnatal age, neurons could be categorized in four neuron groups, based on the discharge pattern in response to a hyperpolarizing/depolarizing current protocol. Anatomical reconstructions indicated that although cells increased in overall dendritic expanse during development, neurons became less complex as illustrated by decreases in number of dendritic branch points, and in number and density of spines. The timing of major developmental differences in intrinsic electrical characteristics observed here is associated with a period of previously reported maturational changes in extracellular taste responses to number and concentration of chemical stimuli. However, further alterations in extracellular taste responses proceed after apparent maturation of intrinsic neural properties.

[Histochemical changes in Brugia malayi microfilariae-infected Anopheles sinensis]

Histochemical changes in normal and Brugia malayi microfilariae-infected Anopheles sinensis were observed using histochemical technique. The results showed that the activity of alkaline phosphatase (AKP) and acid phosphatase (ACP) and the content of glycogen and basic protein in Brugia malayi microfilariae-infected Anopheles sinensis were less obviously than those of the normal control. Esterase (EST) activity was reduced slightly and acetylcholinesterase (AChE) remained no change in infected mosquitoes compared with the normal control. It is suggested that the development of filaria larvae in vector mosquitoes has selective effect on their biochemical metabolism.

Preferred translation of human hepatitis B virus polymerase from core protein- but not from precore protein-specific transcript

In the human hepatitis B virus (HBV) genome, the 5' end of the polymerase coding sequence overlaps with the 3' end of the core protein coding sequence. Recent results obtained from genetic studies have suggested that translation of HBV polymerase initiates from the first ATG codon of the polymerase reading frame and is not a result of frameshift translation from the core protein reading frame, as in the case of retroviruses. By using in vitro-synthesized SP6 RNA transcripts, we now demonstrate that HBV core protein-specific mRNA can direct the synthesis of polymerase from the internal polymerase ATG codon in rabbit reticulocyte lysates and Xenopus oocytes. A related message with an additional 60 nucleotides at the 5' end (pre-core protein mRNA) was not as efficient as the core protein mRNA for translation of polymerase. Furthermore, translation of polymerase from the core protein mRNA was not inhibited by the cap analog m7GpppG. This result, together with the results described above, indicates that translation of HBV polymerase occurs in a novel, cap-independent manner.