Identification of a 170-kDa protein over-expressed in lung cancers

Lung cancer is the leading cause for cancer death in both male and female populations. Although many molecular markers for lung cancer have been developed and useful for early detection of lung cancer, their function remains unknown. In this paper, we report our findings that a 170-kDa protein (p170) is over-expressed in all types of human lung cancers compared with normal tissues and it is identified as a subunit of translation initiation factor eIF3 by cDNA cloning. Translation initiation factors are a family of proteins that promote the initiation step of protein synthesis and are regulators of cell growth at the translational level. Further studies showed that p170 mRNA is ubiquitously expressed with higher levels in adult proliferating tissues (e.g. bone marrow) and tissues during development (e.g. fetal tissues). This study suggests that p170 and eIF3 may be important factors for cell growth, development, and tumorigenesis.

[Effects of age and ginsenoside RG1 on membrane fluidity of cortical cells in rats]

Membrane fluidity was measured using fluorescence spectrophotometer in cortical cells isolated from Wistar rats of five age groups (fetal); neonatal (3 days), young (3 months), adult (9 months) and old (27 months). Neurons were enzymatically isolated and loaded with the fluorescent dye, DPH (1,6-diphenyl-1,3,5-hexatriene). The membrane fluidity of neonatal cells was shown to be significantly higher (eta 1.485 +/- 0.211) than that in young cells (eta 2.220 +/- 0.169), and that in young cells was significantly higher than that in old cells (eta 2.842 +/- 0.143). No significant difference in fluidity, neither between fetal and neonatal cortical cells nor between young and adult ones was observed. Ginsenoside Rg1 (Rg1) is one of the important active principles of ginseng and shares many pharmacological effects of this plant. When treated with Rg1 (10, 20, 40 mg.kg-1), the membrane fluidity of old cortical cells significantly increased (eta 2.670 +/- 0.108, 2.381 +/- 0.123, 2.000 +/- 0.101). These findings indicate a substantial alteration of membrane fluidity with neuronal aging. Increment of membrane fluidity provides an aspect in elucidating the mechanisms of Rg1's antiaging action.

The multi-structural feature of the multidrug resistance gene product P-glycoprotein: implications for its mechanism of action (hypothesis)

P-glycoprotein is a member of the ATP-binding cassette (ABC) transport superfamily. It plays an important role in the development of multidrug resistance in cancers by effluxing a wide variety of anticancer drugs. A large amount of information on the structure and function of P-glycoprotein has been accumulated over recent years from studies using molecular, biochemical, and biophysical approaches. It remains unclear, however, how this protein folds in membranes and how it transports such a wide variety of hydrophobic compounds. This paper highlights the recent progress in the structural and biogenesis aspects of P-glycoprotein. A model mechanism of P-glycoprotein action is proposed as a hypothesis that is based on recent progress in studying the topological folding of P-glycoprotein.

Salvianolic acid B inhibits fibril formation and neurotoxicity of amyloid beta-protein in vitro

AIM

To observe the effect of salvianolic acid-B (SalB) on amyloid beta-protein (A-beta) fibril formation and its toxicity towards PC12 cells.

METHODS

A-beta (1 - 40) was incubated with or without SalB at 25 degrees C for 30 h, 48 h, and 100 h. Fibril formation was then viewed under an electron microscope. Toxicity of the A-beta (1 - 40) towards PC12 cells was measured with 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT). A-beta (25 - 35) was aged by incubating at 25 degrees C for 7 d, then the peptide was incubated with PC12 cells with or without SalB. Toxicity of A-beta (25-35) towards PC12 cells was observed with MTT.

RESULTS

Following incubation at 25 degrees C for 30 h, A-beta (1 - 40) (100 mg/L) aggregated and formed fibrils. SalB 10-100 nmol/L completely prevented the fibril formation within 30 h. Extension of amyloid fibrils increased with prolonging the incubation time. SalB inhibited the fibril formation process during this period. In the MTT assay A-beta (1 - 40) incubated with SalB manifested significantly lower toxicity to PC12 cells compared with that without SalB. Besides, SalB 1 micromol/L significantly attenuated the toxicity of aged A-beta (25 - 35) to PC12 cells.

CONCLUSION

SalB could inhibit A-beta aggregation and fibril formation, as well as directly inhibit the cellular toxicity of aged A-beta towards PC12 cells.

An in vitro study of the structure-activity relationships of sulfated polysaccharide from brown algae to its antioxidant effect

In this paper, the structure-activity relationships of chemically modified uronic acid polymer fragments from brown algae with regard to their antioxidant effects on H2O2-damaged lymphocyte were studied. The results indicated that the most potent antioxidant activity was obtained from the sulfated polysaccharide with ratio of mannuronate blocks (M-blocks) to guluronate blocks (G-blocks) of 3 to 1 and carboxyl residue unesterified. The sulfated G-blocks with esterified carboxyl residue also prevented lymphocyte from injury. However, the sulfated G-blocks bearing unesterified carboxyl residue hardly exerted antioxidant activity. These findings suggested that both M-blocks and esterified carboxyl residue were determinant structures in preventing lymphocyte from being oxidized by H202, indicating that the existence of M-blocks was more important in scavenging free radicals.

[Effect of ginsenoside Rg1 on learning and memory impairment induced by beta-amyloid peptide(25-35) and its mechanism of action]

AIM

To study the effect of ginsenoside Rg1 on the learning and memory impairment in mice induced by aggregated beta-AP(25-35).

METHODS

Mice were administered Rg1(5, 10 mg.kg-1, i.p.) for 10 d and control mice received daily i.p. injections of saline after the intracerebroventricular injection of aggregated beta-AP(25-35). After the final treatment, passive avoidance and performance in the Morris water maze (MWM) were assessed. and the activity of cortical and hippocampal ChAT and AchE were detected after the final behavior test.

RESULTS

Ginsenoside Rg1 (5, 10 mg.kg-1, i.p.) significantly ameliorated the learning and memory impairment induced by beta-AP(25-35). Rg1 (5, 10 mg.kg-1) decreased the latencies and swim distances of mice to reach a hidden platform and improved the corresponding changes in search strategies occurred in the Morris water maze, and Rg1 (10 mg.kg-1, i.p.), increased step-through latencies also. Biochemical analysis showed that Rg1 (5, 10 mg.kg-1, i.p.), prevented the cortical and hippocampal ChAT activity decline induced by beta-AP(25-35), and showed inhibition of the activity of AchE, although beta-AP(25-35) showed no effect on the cortical and hippocampal AchE activity.

CONCLUSION

These data showed that ginsenoside Rg1 significantly improved the learning and memory impairment induced by beta-AP(25-35), and this effect could be attributed to its inhibition of AchE and increase of ChAT activity.

[Inhibitory effects of D-polymannuronic sulfate on proliferation of rat vascular smooth muscle cells and its related mechanisms of action in vitro]

AIM

To investigate the inhibitory effects of D-polymannuronic sulfate (DPS) on the proliferation of rat vascular smooth muscle cells (VSMC) induced by basic fibroblast growth factor (bFGF) or interleukin-1 (IL-1) and its related mechanisms.

METHODS

Rat aortic smooth muscle cells pretreated with DPS in concentrations ranging from 0.001 microgram.mL-1 up to 100 micrograms.mL-1 were incubated at 37 degrees C for 24 h, followed by addition of bFGF (50 ng.mL-1) or IL-1 (50 U.mL-1) for another 24 h. The effects of DPS on the proliferation of VSMC were evaluated by MTT assays. VSMC were pretreated with DPS in concentrations ranging from 0.001 microgram.mL-1 up to 1 microgram.mL-1, followed by addition of L-NAME (0.1 microgram.mL-1) or bFGF (50 ng.mL-1) for 24 h. Supernatant nitric oxide (NO) was determined with NO assay kit, while supernatant angiotensin II (Ang II) and endothelin-1 (ET-1) were measured by radioimmunoassay.

RESULTS

DPS exerted antiproliferative effects at concentrations ranging from 0.01 microgram.mL-1 to 10 micrograms.mL-1, and its maximal effect was observed at the concentration of 1 microgram.mL-1. Also, the suppressing actions of DPS on the proliferation of VSMC were diminished by increasing the concentrations of bFGF or IL-1. Furthermore, DPS increased NO synthesis and decreased Ang II and ET-1 contents released from VSMC in a concentration-dependent manner.

CONCLUSION

DPS afforded the antiproliferative effects on bFGF- or IL-1-treated VSMC and its underlying mechanisms were associated with enhancement of NO synthesis and decrement of Ang II and ET-1 production/release in vitro.

[Effects of salvianolic acid B on beta-amyloid peptide neurotoxicity of primary cultured fetal rat cortical neurons]

AIM

To study the roles of nitric oxide (NO) and nitric oxide synthase (NOS) on the glutamate (Glu) and beta-amyloid peptide [beta-AP (1-40)] mediated neurotoxicity in primary cultured fetal rat cortical neuron and the neuroprotective effects of salvianolic acid B (Sal B) against the beta-AP (1-40) and its mechanism of action.

METHODS

With application of specific agonist and antagonist of NOS, establishment of the sodium nitroprusside (SNP), Glu and beta-AP (1-40) neurotoxicity model, the cell viability, lactate dehydrogenase (LDH) efflux and NO release were detected by using morphological observation, MTT stain, spectrophotometric measurement and Griess method, respectively, in primary cultured fetal rat cortical neurons.

RESULTS

Glu and beta-AP (1-40) were shown to increase the NO release of the neuron. Furthermore, nNOS was found to play an important role in the neurotoxicity of glutamate, iNOS may probably be involved in the neurotoxicity of beta-AP (1-40). Sal B (0.01, 0.10, 1.00 microgram.L(-1)) was shown to increase the cell viability, decrease the LDH release rate and inhibit NO release in a dose-dependent manner.

CONCLUSION

These results suggest that the neurotoxicity of Glu and beta-AP(1-40) may be partly mediated through different types of NOS. Sal B was found to prevent the beta-AP(1-40) toxicity by directly or indirectly decreasing NO release.

Antihypertensive effects of D-polymannuronic sulfate and its related mechanisms in renovascular hypertensive rats

AIM

To investigate the antihypertensive effects of D-polymannuronic sulfate (DPS), a kind of sulfated polysaccharide, and the underlying mechanisms in renovascular hypertensive rats (RHR).

METHODS

Used two-kidney one clip (Goldblatt, 2-K 1C) method to produce RHR model. DPS was given i.v. or ig for 5 wk with the initiation of establishment of RHR. Serum nitric oxide (NO) was determined with NO kit; plasma angiotensin II (Ang II) and endothelin-1 (ET-1) were measured by radioimmumoassays.

RESULTS

In acute therapeutic experiments, DPS markedly reduced systolic blood pressure (SBP) and diastolic blood pressure (DBP) dose-dependently and decreased heart rate (HR) with reduction in arterial blood pressure. In the prophylactic experiments, DPS prevented the rise in SBP and DBP in a dose-dependent manner. The hypotensive potency of DPS 50 mg/kg is comparable to that of captopril (14 mg/kg). Moreover, DPS elevated serum NO contents and lowered plasma concentrations of Ang II and ET-1.

CONCLUSION

The antihypertensive activities of DPS might be involved both in increasing the generation of nitric oxide and in decreasing the production of angiotensin II and endothelin-1 in vivo.

Role of the ribosome in sequence-specific regulation of membrane targeting and translocation of P-glycoprotein signal-anchor transmembrane segments

It is thought that the topology of a polytopic protein is generated by sequential translocation and membrane integration of independent signal-anchor and stop-transfer sequences. Two well-characterized cell-free systems (rabbit reticulocyte lysate and wheat germ extract) have been widely used to study the biogenesis of secretory and membrane proteins, but different results have been observed with proteins expressed in these two different systems. For example, different topologies of P-glycoprotein (Pgp) were observed in the two systems and the cause was thought to be the source of ribosomes. To understand how the ribosome is involved in dictating membrane translocation and orientation of polytopic proteins, individual signal-anchor sequences of Pgp were dissected and examined for their membrane targeting and translocation in a combined system of wheat germ ribosomes (WGR) and rabbit reticulocyte lysate (RRL). Addition of wheat germ ribosomes to the rabbit reticulocyte lysate translation system can enhance, reduce, or have no effect on the membrane targeting and translocation of individual Pgp signal-anchor sequences, and these effects appear to be determined by the amino acid residues flanking each signal-anchor. Ribosomes regulate the membrane targeting and translocation of Pgp signal-anchors in a polytopic form differently from the same signal-anchors in isolation. Furthermore, we demonstrated that ribosomes regulate the membrane targeting and translocation of each signal-anchor cotranslationally and that this activity of ribosomes is associated with the 60S subunit. Based on this and previous studies, we propose a mechanism by which ribosomes dynamically dictate the membrane targeting and translocation of nascent polytopic membrane proteins.

Determinant of the extracellular location of the N-terminus of human multidrug-resistance-associated protein

Multidrug-resistance-associated protein (MRP) is a member of the ATP-binding cassette (ABC) membrane-transport superfamily and is responsible for multidrug resistance in cancer cells. Distinct from other members of the ABC superfamily, MRP has three membrane-spanning domains (MSDs) and the N-terminus is located extracellularly. It has been shown that the first MSD (MSD1) with an extracellular N-terminus is important for MRP function. To address what ensures the generation of this structural organization of MRP and to understand in general the molecular mechanism of membrane folding of polytopic proteins with extracellular N-termini, the biogenesis of MSD1 in human MRP1 was examined using an in vitro expression system. Surprisingly, the second transmembrane segment (TM2) in MSD1 was found to play a critical role in the correct membrane translocation and folding of MSD1 in human MRP1. TM2 not only plays an essential role to ensure the N-terminus-outside/C-terminus-inside orientation of TM1 with an extracellular N-terminus, it can also translocate into membranes post-translationally in a signal-recognition particle and ribosome-dependent manner to provide an additional insurance for correct folding of MSD1 in MRP. These findings suggest that TM2 in a polytopic membrane protein with an extracellular N-terminus may play a critical role in controlling correct membrane translocation and folding of the protein in general.

Salvianolic acid B protects brain against injuries caused by ischemia-reperfusion in rats

AIM

To study the protective effects of salvianolic acid B (Sal B) against the ischemia-reperfusion induced rat brain injury.

METHODS

Focal cerebral ischemia-reperfusion model in rats was employed to study the protective effects of Sal B. The behavioural tests were used to evaluate the damage to the central nervous system. Spectrophotometric assay methods were used to measure the activity of superoxide dismutase (SOD), contents of reduced glutathione (GSH), malondialdehyde (MDA), adenosine 5-triphosphorate (ATP), and lactate acid (LA) in experimental rats' brain homogenate.

RESULTS

Focal cerebral ischemia-reperfusion resulted in abnormal behavior which could be alleviated by Sal B 10 mg.kg-1 i.v., and nimodipine (Nim) 4 mg.kg-1 i.p. At the same time, Sal B 10 mg.kg-1 and Nim 4 mg.kg-1 could inhibit the decrease in SOD, GSH, and ATP levels and the increase in MDA and LA levels caused by ischemia-reperfusion in brain.

CONCLUSION

Sal B showed a protective action against the ischemia-reperfusion induced injury in rat brain by reducing lipid peroxides, scavenging free radicals and improving the energy metabolism.

[Central nervous system calcium homeostasis imbalance and brain aging]

Brain aging is associated with a marked decline of memory. The calcium homeostasis imbalance hypothesis postulated that sustained changes in the regulation of intracellular Ca2+ concentration, [Ca2+]i are the major cause of brain aging. Aging may cause the increase of the [Ca2+]i through many mechanisms. These alterations would in turn affect the synaptic transduction, neurotransmitter release and signal transduction, cause memory deficit. This article reviewed the progress about this hypothesis in recent years.

Salvianolic acid B protects the memory functions against transient cerebral ischemia in mice

The objective of this work was to study the protective effects of salvianolic acid B (Sal B) on the dysfunctions of learning and memory induced by transient cerebral ischemia in mice. The mechanisms of its actions also were researched both in vivo and in vitro. The model of dysfunction of learning and memory induced by transient cerebral ischemia in mice was used. One trail passive avoidance tests were used to evaluate the learning and memory functions and experiments in vitro were employed to observe the antioxidative effects of Sal B. Cerebral transient ischemia would impair the function of memory in mice. In step down test. the error number and latency were 2.63 and 120.5 in control group and were 1.35 and 234.4 respectively in sham operated group (p < 0.05). In Sal B treated groups, the error number was less and latency was longer significantly than those of control group. Meanwhile. 3 and 10 mgkg(-1) of Sal B iv. reduced the malondialdehyde contents in cortex, hippocampus and striatum of cerebral transient ischemia rat ion vivo. Sal B 10--100 nmol L(-1) also inhibited lipid-peroxidation and scavenged free hydroxyl radicals in vitro. As conclusion. Sal B ameliorated learning and memory dysfunctions induced by cerebral transient ischemia. Its actions might be related to its antioxidant activity.

Antagonistic effects of melatonin on glutamate release and neurotoxicity in cerebral cortex

AIM

To observe the effects of melatonin (Mel) on glutamate (Glu) release from the cortical synaptosomes in old mice and on neurotoxicity induced by KCl, Glu in cultured cortical cells of fetal rat and to explore the antiaging mechanism of Mel.

METHODS

Glu release by the synaptosomes in old mouse cerebral cortex was detected in a spectrofluorophotometer. The neuronal viability in primary cultures from rat cerebral cortex was assessed using MTT stain and lactate dehydrogenase (LDH) efflux in the bathing medium.

RESULTS

Mel inhibited the K+ (30 mmol.L-1)-induced Glu release from synaptosomes either in calcium dependent or independent conditions [control (10.6 +/- 1.1), (9.2 +/- 0.7) mumol.g-1 (protein); Mel 0.1 mumol.L-1 (6.5 +/- 0.9), (7.5 +/- 0.6) mumol.g-1 (protein), respectively, P < 0.01 vs control group), increased MTT activity (control 0.67 +/- 0.04, 0.81 +/- 0.03; Mel 0.1 mumol.L-1 0.715 +/- 0.023, 0.925 +/- 0.027, P < 0.01 vs control group] and decreased LDH efflux (control 0.400 +/- 0.016, 0.379 +/- 0.016; Mel 0.1 mumol.L-1 0.345 +/- 0.021, 0.340 +/- 0.012, respectively, P < 0.01 vs control group), therefore, protected the neuronal viability against KCl and Glu-induced injury.

CONCLUSION

The inhibitory effect of Mel on Glu release from cortical synaptosome and the protective effect of Mel on cortical neurons against neurotoxicity are its antiaging mechanisms.

Membrane orientation of carboxyl-terminal half P-glycoprotein: topogenesis of transmembrane segments

Multiple topological orientations of the carboxyl-terminal half of P-glycoprotein have been observed. One orientation is consistent with the hydropathy-predicted model and contains six transmembrane (TM)-spanning regions. In another orientation, the cytoplasmic-predicted loop between TM8 and TM9 is extracellular and glycosylated. In support of this "alternative" topology, TM8 was previously established to function as a signal-anchor sequence to insert with its amino-terminal end in the cytoplasm and the carboxyl-terminal end in the extracytoplasmic space. However, it is unclear how downstream TM segments fold in the membrane when TM8 functions as a signal-anchor sequence. Here, we created several chimeric Pgp molecules to examine the membrane insertion of TM segments 9 and 10 using a cell-free system. We found that TM9 functions as a stop-transfer sequence when following the signal-anchor sequence, TM8. However, the stop-transfer activity of TM9 depends on the presence of TM10. In the absence of TM10, TM9 partially translocated across the membrane into the endoplasmic reticulum lumen. In contrast, TM9 efficiently stopped the translocation event of the nascent chain in the presence of TM10. Our results suggest that the membrane insertion of TM8 and TM9 establishes the extracellular loop between TM8 and TM9. Formation of this loop apparently involves the interactions between Pgp TM segments, which facilitate proper folding of the Pgp carboxyl-terminal half.

Inhibitory effect of resveratrol on interleukin 6 release by stimulated peritoneal macrophages of mice

In the present investigation, interleukin 6 (IL-6) activity in the supernatant of cultured mouse peritoneal macrophages was monitored using a sensitive bioassay involving the IL-6-dependent murine hybridoma B9 cell line. The effects of resveratrol on Il-6 release by mouse peritoneal macrophages stimulated with calcium ionophore A23187 and fMLP were explored. Resveratrol, at a concentration range from 5 x 10(-6) to 4 x 10(-5) mol.l-1, was found to dose-dependently inhibit IL-6 release by cultured macrophages induced by A23187 and fMLP, and showed no direct cytotoxic effect, but induced proliferation of cultured mouse thymus cells. Resveratrol, at a concentration range from 10(-8) to 10(-5) mol.l-1, was shown to dose-dependently inhibit calcium ion influx into the cells with the stimulation of fMLP (10(-6) mol.l-1). These results suggest that the blocking of calcium ion influx into cells by reveratrol is one of the possible mechanisms of the IL-6 biosynthesis inhibitory action of resveratrol.

Topogenesis of cystic fibrosis transmembrane conductance regulator (CFTR): regulation by the amino terminal transmembrane sequences

Cystic fibrosis transmembrane conductance regulator (CFTR) is a member of the ATP-binding cassette (ABC) transport superfamily. CFTR folding and assembly appear to involve several events occurred in the cytosol and ER. Misfolding of CFTR causes cystic fibrosis, and thus, understanding the folding mechanism of CFTR is extremely important. Recently, detailed study of membrane insertion process suggests that the first two transmembrane (TM) segments of CFTR have two distinct but independent mechanisms to ensure the correct membrane folding of its amino terminal end [Lu, Y., Xiong, X., Helm, A., Kimani, K., Bragin, A., Skach, W. R. (1998) J. Biol. Chem. 273, 568-576]. To understand how other TM segments are ensured to insert into membranes correctly, we investigated the topogenesis of TM3 and TM4 of CFTR in a cell-free expression system. We found that the correct membrane insertion of TM3 and TM4 of CFTR was ensured by their flanking amino acid sequences and controlled by the correct membrane insertion of their preceding TM1 and TM2. Thus, correct membrane insertion and folding of TM1 and TM2 play an essential role in the membrane insertion and folding of the subsequent TM segments of CFTR.

Effects of 7-nitroindazole on long-term potentiation induced by l-clausenamide and high-frequency stimulation in rat hippocampus in vivo

AIM

To study the antagonistic effect of selective neuronal nitric-oxide synthase (nNOS) inhibitor 7-nitroindazole on the long-term potentiation (LTP) induced by l-clausenamide (Cla) in rat hippocampus in vivo.

METHODS

Population spike (PS) of evoked potentials was determined by extracellular recording technique in the hippocampal dentate gyrus (DG) of anesthetized rats.

RESULTS

7-Nitroindazole 2 nmol icv blocked the induction of LTP elicited by high-frequency (100 Hz) stimulation or Cla 5 nmol icv (P < 0.01), and L-arginine 225 mg.kg-1 i.p. prevented the action of 7-nitroindazole (P < 0.01).

CONCLUSION

Nitric oxide produced by nNOS plays a role in the induction of Cla-induced LTP in hippocampus.

Bioequivalence evaluation of two sertraline tablet formulations in healthy male volunteers after a single dose administration

SUBJECTS, MATERIAL AND METHODS

According to a randomized two-period crossover design, 12 Chinese male volunteers were treated with 2 sertraline tablet formulations, one was made in China as test tablet, the other was made in England as reference tablet. Each volunteer received each sertraline in a single dose of 150 mg. The 2 medications were carried out by a wash-out phase of 23 days. Blood samples were obtained just before dosing and at 10 time points until 96 hours after administration, and plasma sertraline concentrations were determined by a sensitive gas-chromagraphy electron-capture method with a lower limit of quantification of 0.625 ng/ml. The bioequivalence of 2 formulations was evaluated by the shortest 90% confidence interval method which corresponds to the two one-sided test method.

RESULTS

The point estimate (90% confidence interval) of the mean ratio (test/reference) for AUC(0-96) was 97.19% (82.66% to 122.33%), for Cmax 96.27% (83.64% to 121.36%), and for t(l/2) 96.31% (85.43% to 119.57%). Regarding Tmax (test-reference), the 90% confidence interval ranged from -4 to +4 hours, but the difference between the Tmax values of 2 products is clinically of minor importance.

CONCLUSION

Therefore, it can be concluded that 2 sertraline tablet formulations are bioequivalent. administration, sertraline is slowly absorbed with peak plasma concentrations at 6 - 8 h, and has a terminal elimination half-life of approximately 26 h, indicating once-daily dosing is available. Clinically, it can be taken either in the morning or in the evening, with or without food [Ronfeld et al. 1997b]. In addition, it also exhibits higher plasma protein binding up to 97% and extensive first-pass metabolism. By demethylation, sertraline is metabolized primarily to N-demethylsertraline, and then eliminated by hydroxylation arid conjugation [Tremaine et al. 1989]. This study aimed at assessing of bioequivalence of two sertraline formulations (produced in China and England, respectively) in healthy male volunteers after a single dose administration.

Inhibitory effects of melatonin on free intracellular calcium in mouse brain cells

AIM

To study the effects of melatonin (Mel) on cortical intrasynaptosomal calcium concentration in old mice and on [Ca2+]i elevation induced by Bay-K-8644, KCl, and sodium l-glutamate in isolated brain cells of neonatal mouse, and to determine the antiaging mechanism of Mel.

METHODS

[Ca2+]i was measured in an RF-5000 recording spectrofluorophotometer by preloading the synaptosomes or cells with Fura 2-AM.

RESULTS

Long term of administrating Mel inhibited the overload of [Ca2+]i in old mouse cerebral cortex. The [Ca2+]i in both high (20 mg.L-1) and low dose (1 mg.L-1) of Mel groups was reduced from (434 +/- 32) nmol. L-1 (the older control group) to (330 +/- 41) and (313 +/- 56) nmol.L-1, respectively, P < 0.01. Mel 0.01, 0.1, 1, and 3 mumol.L-1 remarkably reduced [Ca2+]i elevations in isolated newborn mouse brain cells induced by Bay-K-8644, KCl, and Glu.

CONCLUSIONS

The inhibitory effect of Mel on neuronal [Ca2+]i overload is involved in its antiaging effect.

Effects of naloxone on l-clausenamide-induced long-term potentiation in dentate gyrus of anesthetized rats

AIM

To investigate the mechanisms of l-clausenamide-induced long-term potentiation (LTP) in the dentate gyrus of anesthetized rats.

METHODS

Extracellular recording technique was used to record the population spike (PS) in the dentate gyrus of anesthetized rats.

RESULTS

I.c.v. injection of naloxone 1 nmol, affecting neither the basal PS amplitude nor the LTP induced by tetanus, reduced the l-clausenamide-potentiated LTP only when it was administrated prior to clausenamide. Naloxone 1 nmol (i.c.v.), administrated 10 min before l-clausenamide, reduced the PS amplitude at 20 min, 55 min, and 90 min after i.c.v. injection of l-clausenamide 4 nmol from 138% +/- 10%, 170% +/- 10%, and 169% +/- 12% to 111% +/- 7%, 124% +/- 14%, and 123% +/- 11%, respectively. All P < 0.01 (n = 8). The same dose of naloxone (i.c.v.), delivered 10 min after l-clausenamide, did not affect the l-clausenamide-induced potentiation.

CONCLUSION

The activation of opioid receptors contributes to the induction of l-clausenamide-induced LTP of synaptic transmission in dentate gyrus of anesthetized rats.

Analysis of highly polar DNA adducts formed in SENCAR mouse epidermis following topical application of dibenz[a,j]anthracene

The formation of DNA adducts in mouse epidermis has been examined following topical application of dibenz[a,j]anthracene (DB[a,j]A) and its metabolites, i.e., DB[a,j]A-3,4-diol, DB[a,j]A-3,4-10, 11-bis-diol, DB[a,j]A-3,4-8,9-bis-diol, 10-OH-DB[a,j]A-3,4-diol, or 11-OH-DB[a,j]A-3,4-diol, using a 32P-postlabeling assay. At initiating doses (400-1600 nmol), DB[a,j]A produced at least 23 DNA adduct spots, including four less polar (derived from the bay-region syn- and anti-diol-epoxides) and 19 highly polar DNA adducts. DB[a, j]A-3,4-diol produced 13 DNA adduct spots, four less polar and nine highly polar DNA adducts, and DB[a,j]A-3,4-10,11-bis-diol produced nine highly polar DNA adducts. Eight and seven of the highly polar DNA adducts generated by DB[a,j]A-3,4-diol and DB[a,j]A-3,4-10, 11-bis-diol, respectively, migrated in the chromatography system like the highly polar DNA adducts produced by the parent compound. Sufficient amounts of radioactivity were associated with highly polar adduct spots 11, 13, and 22 to confirm their chromatogaphic identity in DNA samples from DB[a,j]A-, DB[a,j]A-3,4-diol-, and DB[a, j]A-3,4-10,11-bis-diol-treated mice. 10-OH-DB[a,j]A-3,4-diol and 11-OH-DB[a,j]A-3,4-diol did not produce any highly polar DNA adducts that could be detected under our experimental conditions. At an initiating dose of 400 nmol, DB[a,j]A, DB[a,j]A-3,4-diol, and DB[a, j]A-3,4-10,11-bis-diol produced 22.4 +/- 13.0, 15.6 +/- 10.1, and 5. 5 +/- 0.3 (mean +/- SD) adducts/10(9) nucleotides, of which 77, 65, and 100%, respectively, represented highly polar DNA adducts. At the same dose of 400 nmol per mouse, DB[a,j]A and its 3,4-diol were able to initiate papillomas in SENCAR mouse skin (3.08 +/- 1.89 and 3.48 +/- 2.72 papillomas per mouse, respectively, after 16 weeks of promotion with 12-O-tetradecanoyl phorbol 13-acetate), while the 3, 4-10,11-bis-diol of DB[a,j]A was inactive as a tumor initiator. A quantitative correlation (r = 0.935; p = 0.0196) between levels of less polar DNA adducts and tumor-initiating activity of DB[a,j]A, DB[a,j]A-3,4-diol, and anti-DB[a,j]ADE was observed. This study demonstrates that the highly polar DNA adducts formed from DB[a,j]A in mouse epidermis arise primarily from the DB[a,j]A-3,4-10, 11-bis-diol. However, the contribution of this metabolite to the tumor-initiating activity of DB[a,j]A appears to be small.

Antagonistic effect of nerve growth factor on neuronal injury induced by hypoxia in cultured cerebral cortical neurons of rats

AIM

To observe the effects of nerve growth factor (NGF) on neuronal hypoxic injury induced by sodium dithionite in primary cultures from gestation of 17-d rat fetal cerebral cortex.

METHODS

Neuronal death and lactate dehydrogenase (LDH) efflux in the bathing medium were measured. The homogenate of cortical cells was used to determine malonyldialdehyde (MDA) content and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities.

RESULTS

When cultures were incubated for 24 h with sodium dithionite, efflux of LDH and MDA content increased while the number of surviving neurons decreased. NGF 100 micrograms.L-1 increased the number of surviving neurons to 85% +/- 9% of normoxia level under hypoxia. NGF 1-100 micrograms.L-1 concentration-dependently attenuated hypoxia-induced increase of efflux of LDH and MDA content, with IC50 of 27 and 49 (95% confidence limits: 18-49 and 29-110) micrograms.L-1. NGF 30 micrograms.L-1 induced a 3-fold increase in SOD and GSH-Px activities. The levels of SOD and GSH-Px activities in hypoxia group were increased 2.7-fold by NGF 100 micrograms.L-1.

CONCLUSION

NGF prevented hypoxic insults in cultured cerebral cortical neurons by suppressing the generation of lipid peroxides and increasing the activities of antioxidant enzymes.