Agonist-specific differential changes of cellular signal transduction pathways in senescent human diploid fibroblasts

Changes in the signal transduction efficiency of senescent cells led us to compare the signaling events induced by two mitogenic agonists, platelet-derived growth factor (PDGF) and lysophosphatidic acid (LPA) in presenescent and senescent or near-senescent human diploid fibroblasts. When the changes in intracellular [Ca(2+)](i) were analyzed, both PDGF and LPA generated a rhythmic increase in [Ca(2+)](i) in presenescent cells. The frequency of calcium response was reduced and desensitized in PDGF-stimulated senescent cells, while response to a LPA-induced calcium signal was also reduced in frequency, though its magnitude was unaltered. PDGF treatment increased the fibrous actin (F-actin) level in presenescent cells but not in senescent cells in contrast to a reduced but visible increase in F-actin in LPA-treated senescent cells. The effect of PDGF on phospholipase D (PLD) activation was also reduced significantly, as a ca. 60-80% reduction of PLD activity was observed in PDGF-stimulated cells but only a little reduction in LPA-induced cells. Agonist-specific differential changes of cellular signaling events caused a differential effect on DNA synthesis after growth factor stimulation. We observed a dramatic (80-90%) reduction of [3H]thymidine incorporation into DNA in the PDGF-stimulated near-senescent cells. LPA resulted in a 2-3-fold increase in thymidine incorporation even in the near-senescent cells. These differences in the responses of senescent or near-senescent cells to PDGF- and LPA-stimulation raised questions about the differential changes of the respective signaling apparatuses induced by aging. Since PDGF signaling event was affected greatly by aging, we further examined the protein contents involved in PDGF signal transduction pathway. PDGF receptor (PDGFR), protein kinase C-alpha (PKC-alpha), phospholipase C-gamma1 (PLC-gamma1), and PLD1 were examined by Western blot analysis. The protein levels of PKC-alpha and PLC-gamma1 were unchanged, but those of PLD1 and PDGFR were reduced with age. The reduced content of PDGFR protein may be one of the important contributors to the failure of PDGF-stimulated signal transduction in human senescent fibroblasts. Our results strongly suggest that age-dependent agonist-specific changes in signaling events might be in charge of the functional deterioration of senescent cells through imbalance of signal responses.

Effect of pretreatment reagent and hydrogen peroxide on enzymatic hydrolysis of oak in percolation process

The effect of pretreatment reagent and hydrogen peroxide on enzymatic digestibility of oak was investigated to compare pretreatment performance. Pretreatment reagents used were ammonia, sulfuric acid, and water. These solutions were used without or in combination with hydrogen peroxide in the percolation reactor. The reaction was carried out at 170 degrees C for the predetermined reaction time. Ammonia treatment showed the highest delignification but the lowest digestibility and hemicellulose removal among the three treatments. Acid treatment proved to be a very effective method in terms of hemicellulose recovery and cellulose digestibility. Hemicellulose recovery was 65-90% and digestibilities were >90% in the range of 0.01-0.2% acid concentration. In both treatments, hydrogen peroxide had some effect on digestibility but decomposed soluble sugars produced during pretreatment. Unlike ammonia and acid treatments, hydrogen peroxide in water treatment had a certain effect on hemicellulose recovery as well as delignification. At 1.6% hydrogen peroxide concentration, both hemicellulose recovery and digestibility were about 90%, which were almost the same as those of 0.2% sulfuric acid treatment. Also, digestibility was investigated as a function of hemicellulose removal or delignification. It was found that digestibility was more directly related to hemicellulose removal rather than delignification.

Histone cross-linking by transglutaminase

Transglutaminases irreversibly catalyze covalent cross-linking of proteins by forming isopeptide bonds between peptide-bound glutamine and lysine residues. Among several transglutaminases, tissue-type transglutaminase (tTGase) is most ubiquitously found in every type of cells and tissues in animals, but its natural substrate has yet to be identified. In an attempt to identify the natural substrate for tTGase, we examined in vitro if core histones were subject to cross-linking by tTGase. We found core histone subunits, H2A and H2B, were specifically cross-linked by tTGase. The cross-linking was between either one or both glutamines at C-terminal end of H2A (-VTIAQ104 GGVLPNTQ112 SVLLPKKTESSKSK-C' end) and the first and/or third lysine from C-terminal end of H2B (-AVESEGK116 AVTKYTSSK125-C' end). The cross-linking occurred only when these subunits were released from nucleosome but not when these were organized in nucleosome. Most interestingly, in chicken erythrocyte the cross-linked H2A-H2B was present in a significant amount. From these results, it can be proposed that tTGase-mediated cross-linking is an another form of core histone modification and it may play a role of chromatin condensation during erythrocyte differentiation.

Elafin expression in human fetal and adult submandibular glands

Elafin, a bifunctional protein, has the NH(2)-terminal domain functions as a transglutaminase substrate for crosslinking to lysine-containing proteins and the COOH-terminal whey acidic protein domain as a potent anti-elastase. Human fetal submandibular glands (n=100) and adult submandibular glands (n=10) were used to elucidate the expression pattern of elafin in the developmental processes of human submandibular gland by immunohistochemistry, in situ hybridization, and western blot analysis. Elafin mRNA was expressed both in the gland epithelium and intralobular mesenchymal tissue of fetal submandibular gland in an early developmental stage (10-18 weeks) and an early intermediate developmental stage (EIDS; 19-24 weeks). The elafin antigen was also found in the intralobular mesenchyme of submandibular gland in the same stages. Thereafter, elafin was transitionally expressed in the ducts and acini of submandibular glands. In the late intermediate developmental stage (LIDS; 25-32 weeks) and the late developmental stage (LDS; 33-40 weeks), elafin became markedly positive in the excretory and striated ducts but weakly positive in the intralobular mesenchymal tissue. The elafin was heavily present in the excretory and striated ducts of adult submandibular gland, while it was sparse in the intralobular mesenchymal tissues. Western blot analysis showed the protein extracts from submandibular glands of EIDS, LIDS, and LDS, adult submandibular gland, fetal tissues (8 weeks), and adult parotid saliva migrated into multiple bands, about 25, 50, 65, and 140 kDa, which were higher than the putative size of elafin protein, 12 kDa. These data suggest that elafin, anti-elastase, is an essential component highly utilized during the morphogenetic processes of fetal salivary gland development and continuously plays a role for the protection of the tubuloalveolar structures of adult salivary gland.

Functional recovery of senescent cells through restoration of receptor-mediated endocytosis

The functional deterioration of an organism with age causes the major problem of maintaining the quality of life at old age. Degenerative changes in the organism may to some extent reflect alterations that can be observed in cells during in vitro replicative senescence. At the cellular level, the receptor-mediated endocytosis in the membrane might be emphasized as a responsible mechanism for functional decay, since the endocytosis is in charge of many important biological phenomena: nutrient uptake, growth factor sensitivity, immune response, protection from environment and pathogen uptake, etc. We found that two major endocytotic pathways, i.e. clathrin-mediated and caveolae-dependent endocytosis, are down regulated in senescent cells. For the down regulation of the clathrin dependent receptor-mediated endocytosis, the reduction of amphiphysin-1 was found responsible, which was confirmed by Western blot analysis, dominant negative mutant transfection and restoration of gene activity by microinjection. With respect to the hypo-responsiveness of senescent cells to growth factors, the upregulation of caveolins has been suggested to be a causal factor. The overexpression of caveolins caused senescent-like changes in epidermal growth factor (EGF) response of the young cells, while down regulation of caveolins by use of antisense-oligonucleotides restored the EGF response in old cells, suggesting that caveolin system would be one of the major mechanisms responsible for decreased responses to growth factors in the senescent cells. Based on these results, it can be suggested that the functional deterioration of the senescent cells may be explained in terms of the down regulation of receptor mediated endocytosis, at least in part, and that the restoration of endocytosis apparatus either with amphiphysin supplementation or with reduction of caveolins might lead to functional recovery of the senescent cells.

Down-regulation of receptor-mediated endocytosis is responsible for senescence-associated hyporesponsiveness

Human diploid fibroblasts (HDF) do not divide indefinitely and eventually lead to an arrest of cell division by a process termed cellular or replicative senescence. Irreversible growth arrest of senescent cells is strongly related to the attenuated response to growth factors. Recently, we reported that up-regulation of caveolin in the senescent cells is responsible for the attenuated response to growth factors. Senescent cells did not phosphorylate Erk-1/2 after EGF stimulation, whereas young cells did. In those senescent cells, we found an increased level of caveolin proteins and strong interactions between caveolin-1 and EGFR. When we overexpressed caveolin-1 in young HDF, the activation of Erk-1/2 on EGF stimulation was significantly suppressed. These results suggest that the hyporesponsiveness of senescent fibroblasts to EGF stimulation might be due to the overexpression of caveolin. In addition, the clathrin-dependent endocytosis system plays the more active and dominant role over the caveolae system. Therefore, we monitored the efficiency of clathrin-dependent receptor-mediated endocytosis in the senescent cells in order to elucidate the exact mode of the attenuated response to growth factors in the senescent cells. Using a transferrin-uptake assay and Western blot analysis of endocytosis-related proteins, we found a significant decrease of amphiphysin-1 in human diploid fibroblasts of multipassages. By adjusting the level of amphiphysin, we could modulate the efficiency of receptor-mediated endocytosis either in young or old cells toward growth factors: that is, a dominant negative mutant of amphiphysin-1 blocked the endocytosis in the young cells, while microinjection of the gene resumed its activity in the old cells. Taken together, we conclude that the loss of endocytotic activity of senescent cells is directly related to the down-regulation of amphiphysin-1 and/or up-regulation of caveolins. This opens a new field of functional recovery of the senescent cells simply through adjusting the receptor-mediated endocytosis capacity.

Aspartate modulates the ethanol-induced oxidative stress and glutathione utilizing enzymes in rat testes

In order to develop a preventive strategy against ethanol-induced oxidative damages on various tissues and organs, we have examined the protective effect of aspartate on the pathogenesis of testes in the ethanol treated animals. Adult male Sprague-Dawley rats were given ethanol in an amount of 36% of total calories via Lieber-DeCarli liquid diet for 6 weeks without or with aspartate (2 mM in the diet). The control group was pair-fed the diet containing isocaloric dextrin-maltose instead of ethanol. The pathogenesis of testes at post- 6 weeks of experiments were carried out by histochemistry and biochemical parameters for oxidative stress such as the level of thiobarbituric acid reactive substances (TBARS) and the activities of glutathione utilizing enzymes were also examined. Chronic ethanol administration resulted in the increased amount of thiobarbituric acid reactive substances (TBARS) in the testes, which was significantly lessened by concurrent aspartate treatment (p < 0.05). In addition to this, liver function test indicated by alkaline phosphatase activity in serum showed that the ethanol-induced hepatotoxicity was significantly ameliorated by aspartate administration. And the activities of glucose-6-phosphate dehydrogenase and glutathione transferase in testis cytosol were decreased in the ethanol treated rats (p < 0.01 and < 0.005, respectively). These data suggest that aspartate may attenuate the ethanol-induced oxidative tissue damage in rat testes possibly through a redox-related protective effect on peroxidation.

Ictal electrocorticographic findings related with surgical outcomes in nonlesional neocortical epilepsy

PURPOSE

To characterize ictal electrocorticographic features related to surgical outcomes in nonlesional neocortical epilepsy (NE).

METHODS

We analyzed 187 ictal electrocorticograms (ECoG) obtained from 18 patients who had undergone presurgical evaluation and subsequent neocortical resections (frontal: seven, parietal: one, occipital: four, multilobar: six). None of them had any MRI-detectable lesions. Various ECoG data sets recorded from eight patients who achieved a favorable surgical outcome (either seizure free or more than 90% reduction of seizure frequencies) were compared with that from ten patients with unfavorable outcome (less than 90% reduction of seizure frequencies) (follow up duration: 47+/-11 months).

RESULTS

Reproducible ictal onset zone (IOZ) in recurrent seizures (P=0.013) and persistent ictal discharges in IOZ from the onset to the end of seizure (P=0.004) were found more frequently in the patients with good outcome. Ictal onset patterns consisting of low voltage fast or high amplitude beta spikes predicted a good surgical outcome while rhythmic sinusoidal activity or rhythmic spike/sharp waves of slow frequency were predictive of poor outcome (P=0.01). The ictal onset rhythm consisting of gamma or beta frequencies was more prevalent in the favorable group (P=0.015).

CONCLUSIONS

The presence of stable ictal circuit suggested by the consistent earliest activation of specific electrodes in the repetitive seizures (reproducible IOZ) and the active participation of IOZ throughout the attack were valuable prognostic factors in addition to the morphology and frequency of ictal onset rhythm.

Radiologically confirmed de novo glioblastoma multiforme and hippocampal sclerosis associated with the first onset of nonconvulsive simple partial status epilepticus

The authors report a case of an unusual progression of glioblastoma multiforme in the temporal lobe associated with the first onset of nonconvulsive simple partial status epilepticus (SPSE), a rare form of status epilepticus. The patient underwent a left temporal craniotomy and the tumor was removed. Concurrently, the hippocampus was removed as well. The pathological diagnosis of the tumor and the hippocampus were glioblastoma multiforme and hippocampal sclerosis. The patient's postoperative course was uneventful.

Double-barreled tack suture procedure in carotid endarterectomy

The authors have developed a double-barreled tack suture procedure for carotid endarterectomy with minimal modification of a conventional needle holder. With this method surgeons can make two stitches simultaneously by using two needles threaded with double-armed suture material, which are held tightly in a parallel fashion in the jaws of a modified needle holder. This method is very effective in preventing the buckling of the intimal wall of the arterectomized distal internal carotid artery. Also, it reduces the tack suture time markedly compared with the conventional tack suture method.

Arabidopsis dynamin-like 2 that binds specifically to phosphatidylinositol 4-phosphate assembles into a high-molecular weight complex in vivo and in vitro

Arabadopsis dynamin-like (ADL) 2, a member of the high-molecular weight (M(r)) dynamin family found in Arabidopsis, has been shown to be targeted to the plastid. In the chloroplast, most of the ADL2 was present in the fraction containing the envelope membranes when analyzed by suborganellar fractionation. Sucrose gradient and gel filtration experiments showed that when associated with membranes, ADL2 existed as a high-M(r) complex, whereas the soluble form existed as a monomer. The recombinant ADL2 expressed in Escherichia coli was present as a high-M(r) form and showed higher GTPase activity at a low NaCl concentration, whereas ADL2 existed as a low-M(r) form with a low level of GTPase activity at a high NaCl concentration. Electron microscopy studies revealed that the purified recombinant ADL2 formed spiral-coiled structures or rings. In the presence of guanosine-5'-O-(3-thio)triphosphate, these structures were transformed into a long rod structure. In contrast, in the presence of GDP, these structures disassembled into oligomers that were shown to be tetramer with 4-fold symmetry. Finally, a lipid-binding assay revealed that recombinant ADL2 purified from E. coli bound specifically to phosphatidylinositol 4-phosphate. Together, these results demonstrated that the biochemical properties of ADL2 were very similar to those of dynamin and other related proteins. Based on this similarity, we propose that ADL2 may be involved in vesicle formation at the chloroplast envelope membrane.

Improvement of salt tolerance in transgenic potato plants by glyceraldehyde-3 phosphate dehydrogenase gene transfer

In the previous experiment, we isolated and characterized glyceraldehyde-3-phosphate dehydrogenase (GPD) gene of the oyster mushroom, Pleurotus sajor-caju. Expression levels of the GPD gene in the mycelia of P sajor-caju was significantly increased by exposing the mycelia to abiotic stresses, such as salt, cold, heat, and drought. We also showed that GPD confers abiotic stress resistance when introduced into yeast cells. The survival rate of the transgenic yeast cell that harbored the GPD gene was significantly higher when the yeast cells were subjected to salt, cold, heat, and drought stresses, compared with the yeast that was transformed with the pYES2 vector alone. In order to investigate the functional role of the P. sajor-caju GPD gene in higher plant cells, the complete P. sajor-caju GPD cDNA was fused into the CaMV35S promoter and then introduced into potato plants. Putative potato transformants were screened by using PCR. Twenty-one transformants were further analyzed with RT-PCR to confirm the expression of P. sajor-caju GPD. A RT-PCR Southern blot analysis revealed that 12 transgenics induced the P. sajor-caju GPD gene expression. A bioassay of these transformants revealed that the P. sajor-caju GPD gene was enough to confer salt stress resistance in the potato plant cell system. Results showed that P. sajor-caju GPD, which was continuously expressed in transgenic potato plants under normal growing conditions, resulted in improved tolerance against salt loading.

Differential activation of mitogen-activated protein kinases by methyl methanesulfonate in the kidney of young and old rats

Mitogen-activated protein kinases (MAPKs) play a critical role in the regulation of cell proliferation, differentiation and apoptosis. We evaluated MAPKs, extracellular signal-regulated kinases (ERKs), c-Jun NH2-terminal kinases (JNKs) and p38 MAPKs in the kidney of young and old rats in response to a direct-acting alkylating agent, methyl methanesulfonate (MMS). It is shown that the basal activity of ERKs was strongly down-regulated in the kidney of old rats compared to their young counterparts without a significant difference in the basal expression of ERKs. Upon treatment with MMS, ERKs were deactivated about 5-fold (P<0.05) in the kidney of young rats, whereas they were activated about 4-fold (P<0.01) in old rats. Strikingly, expression of JNKs was not detected in old animals, whereas it was clearly present and strongly activated after MMS treatment in the kidney of young animals. The basal activity of p38 significantly increased in the kidney of old rats as compared to young animals, whereas no difference in the basal expression of p38 was detected. After treatment with MMS, p38 was activated in the kidney of both young and old rats, where activation was dramatically stronger than in young animals. Taken together, these results demonstrate age-specific MAPKs signaling pathways in the rat kidney. The implications in age-related changes in susceptibility of the kidney to MMS-induced carcinogenesis are discussed.

Lack of tacrolimus-induced cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) has been reported in pediatric transplant patients receiving tacrolimus. It is unclear whether tacrolimus is associated with HCM in adult transplant recipients.

OBJECTIVE

To determine the prevalence of HCM in noncardlac adult transplant patients receiving tacrolimus.

METHODS

A retrospective analysis of nonheart transplant recipients who received tacrolimus at our institution from January 1982 to April 1996 was conducted. Patients with left-ventricular hypertrophy (LVH) defined as a posterior or septal wall thickness > or = 1.3 cm by echocardiography (ECHO) were independently evaluated.

RESULTS

There were 3609 patients who met entry criteria including 2257 liver, 1333 kidney, and 19 other organ transplants. Of the 502 patients who had undergone ECHOs after transplantation, 171 had LVH. The etiology of LVH was categorized as valvular disease (36%), hypertensive disease (29%), ischemic heart disease (17%), or multifactonal (15%). There were six patients in whom, after detailed chart review, no underlying cause of LVH was evident. Five of these patients had HCM, representing an overall prevalence of 0.1% in the entire group of tacrolimus-treated patients, and 1% in patients referred for ECHO.

CONCLUSIONS

The prevalence of HCM in our tacrolimus-treated adult transplant population is similar to that reported in general population studies. These data suggest that tacrolimus is not a risk factor for HCM in adult transplant recipients.

Thymidine-dependent attenuation of the mitochondrial apoptotic pathway in adenosine-induced apoptosis of HL-60 cells

OBJECTIVE

We previously reported that adenosine-induced apoptosis in HL-60 cells was attenuated by cotreating the cells with pyrimidine nucleosides. The mechanism involved in this adenosine-induced apoptosis by the differential supply of nucleosides is studied here with a particular focus on the regulation of apoptosis-associated mitochondrial events.

METHODS

Time-dependent changes in the mitochondrial membrane potential (MMP) after treatment with adenosine and/or thymidine were monitored.

RESULTS

The cells did not show any decrease of MMP level up to 2.5 h after 1 mM adenosine exposure, whereas cytochrome c release, caspase-9 and caspase-3 activity, and DNA fragmentation were already activated, suggesting that mitochondrial depolarization is not a prerequisite of other apoptosis-related mitochondrial events. In contrast, the translocation of Bax to mitochondria and the release of cytochrome c began within the first hour of adenosine treatment.

CONCLUSION

Thus, it is believed that adenosine-induced apoptosis is mediated by the activation of the caspase cascade by cytochrome c release with concomitant increase of Bax in the mitochondria, which implies that the translocation of Bax might be a leading event in the adenosine-induced apoptosis. Moreover, we found that most of the apoptotic parameters in adenosine-induced cellular changes, such as translocation of Bax, the release of cytochrome c, and the consequent activation of caspase-9 and caspase-3, were attenuated by thymidine supplement, thus indicating that the sensing of a nucleoside or nucleotide balance might be an upstream event of cytochrome c release. Therefore, it can be concluded that thymidine can attenuate adenosine-induced apoptosis by modulating the earliest stage of the mitochondrial apoptotic pathway.

Immunobead RT-PCR versus regular RT-PCR amplification of CEA mRNA in peripheral blood

PURPOSE

The reverse transcription polymerase chain reaction (RT-PCR) amplification of tumor-specific mRNA has been used for the detection of cancer cells in peripheral blood. More recently, an immunomagnetic isolation and reverse transcription polymerase chain reaction (immunobead RT-PCR) was developed which has reportedly significant advantages over the previous RT-PCR analysis. In our study, we compared these two methods using a model set of peripheral blood containing tumor cells under standardized conditions.

MATERIAL AND METHODS

In order to compare the false positive rate, normal peripheral blood samples from five volunteers were analyzed by both methods. A model set of peripheral blood containing tumor cells was established by adding SNUC4 human colon cancer cells to peripheral blood collected from normal volunteers not showing any nonspecific bands upon electrophoresis of the PCR products. RT-PCR amplification of carcinoembryonic antigen (CEA) mRNA was done with total RNA and mRNA prepared from this model sample. In immunobead RT-PCR analysis, mRNA was prepared from the cells isolated with anti-CEA antibody-coated magnetic beads or anti-Ber-EP4 antibody-coated magnetic beads before the RT-PCR analysis.

RESULT

The immunobead RT-PCR yielded no non-specific band, while the regular RT-PCR using total RNA did show non-specific band formation in all five samples. When mRNA rather than total RNA was used, nonspecific bands were formed in three of the five samples. Immunobead RT-PCR allowed the detection of 10(1) tumor cells in 1 ml of peripheral blood. The regular RT-PCR analysis had a detection limit of 10(2) tumor cells in 1 ml of peripheral blood.

CONCLUSION

The immunobead RT-PCR proved to be more sensitive and specific than the regular RT-PCR at least in our model system.

Bacteremia due to quinolone-resistant Escherichia coli in a teaching hospital in South Korea

Quinolone-resistant Escherichia coli (QREC) strains are being isolated with increasing frequency. From 1993 to 1998, 40 cases of QREC bacteremia were observed in a teaching hospital; 25 episodes (63.5%) were community-acquired. The incidence of QREC bacteremia increased steadily, from 6.7% to 24.6% during 5 years, and correlated with the significantly increased use of fluoroquinolones (P = .003, r = 0.98). When the 40 QREC bacteremic patients were compared with 80 patients with bacteremia due to quinolone-susceptible E. coli, prior fluoroquinolone use was the only independent risk factor for QREC bacteremia (P = .001). A high APACHE II score was the only independent risk factor for death. The rate of multidrug resistance of QREC was much higher (60%) than that of quinolone-susceptible isolates (13.8%). Pulsed-field gel electrophoresis patterns of these isolates were diverse. Therefore, the isolates revealed little evidence of clonal spread and may have emerged in direct response to the selective pressure exerted by prior fluoroquinolone use.

The protective role of HSP90 against 3-hydroxykynurenine-induced neuronal apoptosis

3-hydroxykynurenine (3HK), an endogenous metabolite of tryptophan in the kynurenine pathway, is a potential neurotoxin in several neurodegenerative disorders. Stabilizing protein structure, heat shock proteins (HSPs) have diverse roles as molecular chaperones to mediate stress tolerance. In the present study, we investigated the possible protective role of HSPs against 3HK induced neuronal cell death. Here we report that 3HK induced in a dose- and time-dependent manner neuronal cell death in neuroblastoma SK-N-SH cells. The cell death showed characteristic apoptotic features such as cell shrinkage, plasma membrane blebbing, chromatin condensation, and nuclear condensation and fragmentation. Furthermore, SK-N-SN cells were protected from 3HK induced cytotoxicity by prior elevation of HSPs expression. Our results show that the protective effect was abolished by HSP90 anti-sense oligonucleotides while not by HSP27 and HSP70 anti-sense oligonucleotides. Also, our result shows that HSP90 effectively inhibits caspases activities leading to the apoptosis. These results suggest that 3HK induces apoptosis in neuroblastoma SK-N-SN cells and that HSP90 is major contributing protein component of protection against 3HK induced apoptosis.

Evaluation of rapid immunocapture assays for diagnosis of Plasmodium vivax in Korea

The rapid immunocapture assays, OptiMal and ICT, were evaluated from 87 individuals for the diagnosis of malaria infections directly from whole blood. A total of 87 individuals was examined for malaria parasites by microscopic examination of Giemsa-stained blood smears, and 65 cases were positive for Plasmodium vivax by microscopy. Correspondingly, the OptiMal test identified malaria infection in 45 cases (69.2%) of microscopy positive cases. Of these, two cases were misinterpreted as Plasmodium falciparum, whereas ICT detected P. vivax infection in 29 (44.6%) patients. We would like to propose that rapid immuno capture assays are an easy method that can serve as a useful tool in addition to microscopy for the diagnosis of malaria, but sensitivity is not yet satisfactory for diagnosis of P. vivax in Korea.

Two-point correlation functions of the diffusion-limited annihilation in one dimension

Two-point density-density correlation functions for the diffusive binary reaction system A+A--> phi are obtained in one dimension via Monte Carlo simulation. The long-time behavior of these correlation functions clearly deviates from that of a recent analytical prediction of Bares and Mobilia [Phys. Rev. Lett. 83, 5214 (1999)]. An alternative expression for the asymptotic behavior is conjectured from numerical data.

Transglutaminase-mediated crosslinking of specific core histone subunits and cellular senescence

We observed that the transglutaminase (tTGase) level and activity increased in aged rats and senescent primary fibroblasts, suggesting that the tTGase-mediated macromolecule crosslinking may play a mechanistic role during aging. Although preliminary, our in vitro experiment suggests that the target of tTGase is core histones: H2A:H2B and H3:H4 are specifically crosslinked by tTGase. On the basis of these data, we postulate that the changes of DNA metabolism in association with cellular aging may be ascribed primarily to the crosslinking of core histone subunits. Further speculation awaits substantive data showing increased histone crosslinking in senescent cells and also what crosslinked histones in various DNA metabolisms may imply. At the moment, present data are sufficient to propose that tTGase is a senescence marker and it may be primarily responsible for the phenotypes associated with cellular senescence.