An infectious viral disease of penaeid shrimp newly found in Korea

Since 1993, massive mortalities have occurred among the penaeid shrimp Penaeus orientalis cultured in Korea. The major gross findings of the naturally occurring cases were 2 to 6 mm sized white spots on the inside of the carapace and reddish discolorization. Amphophilic to basophilic intranuclear inclusion bodies were readily observed in the epithelia of epidermis, foregut, gills, and lymphoid organs. Electron microscopy revealed enveloped and non-occluded ellipsoid to rod-shaped virus particles within the nucleus of lymphoid organ cells and the interstitial cells of the hepatopancreas of both naturally and experimentally infected shrimp. The size of the virions was 375 x 167 nm and the nucleocapsid was 290 x 75 nm. The agent which caused ectodermal and mesodermal necrosis in penaeid shrimp in Korea resembled white spot syndrome virus (WSSV) found in Taiwan with respect to gross signs, histological changes and viral morphology. Its viral morphology differed from that of the rod-shaped nuclear virus of Penaeus japonicus (RV-PJ) found in Japan. However, a 643 bp PCR product with an identical sequence to that from RV-PJ was detected. The results suggested that the Korean agent combined characters described for WSSV and RV-PJ.

Time course of cell cycle-related protein expression in diethylnitrosamine-initiated rat liver

BACKGROUND/AIMS

Cell cycle control and the relationship that exists between cellular proliferation, the expression of cell cycle control proteins and cancer have been reported. This study was designed to decipher the timing of cell cycle control protein expression during the initiation of diethylnitrosamine-induced rat hepatocarcinogenesis.

METHODS

Three-week-old female Sprague-Dawley rats were intraperitoneally injected twice in 1 week with diethylnitrosamine; after the second injection, all animals were sacrificed at 1, 2 and 24 h, and 3 and 7 days. The expression of cell cycle-related proteins such as CDK2 and 4, cyclin proteins (D1, E and cdc2), proliferating cell nuclear antigen, tumor suppressor proteins (p53 and Rb), CDK inhibitory proteins (p21waf1 and p27Kip1), and apoptosis-inhibiting protein (bcl-2) following diethylnitrosamine treatment was examined.

RESULTS

The peak induction time of each cell cycle-related protein during DEN-induced cellular proliferation was diverse, and expressions of CDK2, CDK4, cdc2, p53, bcl-2, p21Waf1 and p27Kip1 appear to be of the greatest interest.

CONCLUSIONS

Data generated from this study may provide information about cell cycle-related protein expression in the initiation stage of hepatocarcinogenic signaling pathways stimulated by a genotoxic agent such as diethylnitrosamine.

Increased expression of ornithine decarboxylase by gamma-ray in mouse epidermal cells: relationship with protein kinase C signaling pathway

The correlation between ornithine decarboxylase (ODC) protein induction and specific protein kinase C (PKC) isozyme expression by gamma-ray in 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated normal and v-rasHa transformed mouse keratinocytes was examined. TPA at 100 nM was treated in primary mouse keratinocytes immediately after 4 Gy, 8 Gy and 16 Gy gamma-ray irradiation. After 4 hrs, cells were harvested and the protein expression levels of PKC isozymes (PKC alpha, -delta, -epsilon, -eta and -zeta) and ODC were examined. For v-rasHa infection, primary keratinocytes were infected with a defected retrovirus containing the v-rasHa gene. After 3 hrs of irradiation, each PKC isozyme and ODC protein expression were tested. Gamma-ray increases ODC protein expression in both TPA-treated normal and v-rasHa transformed mouse keratinocytes and this phenomenon correlated to the increased induction of PKC alpha without altering other PKC isozymes. Tyrosine phosphorylation of epidermal growth factor receptor protein was also stimulated during gamma-ray induced cellular changes in TPA-treated normal mouse keratinocytes. These results indicate that PKC alpha as an important regulator of mouse epidermal changes by gamma-radiation, contributes to the ODC expression occurring during exposure to tumor promoter, such as TPA, and epidermal neoplasia induced by ras activation.

Two-step autocatalytic processing of the glutaryl 7-aminocephalosporanic acid acylase from Pseudomonas sp. strain GK16

The glutaryl-7-aminocephalosporanic acid (GL-7-ACA) acylase of Pseudomonas sp. strain GK16 is an (alphabeta)2 heterotetramer of two nonidentical subunits. These subunits are derived from nascent polypeptides that are cleaved proteolytically between Gly198 and Ser199 after the nascent polypeptides have been translocated into the periplasm. The activation mechanism of the GL-7-ACA acylase has been analyzed by both in vivo and in vitro expression studies, site-directed mutagenesis, in vitro renaturation of inactive enzyme precursors, and enzyme reconstitution. An active enzyme complex was found in the cytoplasm when its translocation into the periplasm was suppressed. In addition, the in vitro-expressed GL-7-ACA acylase was processed into alpha and beta subunits, and the inactive enzyme aggregate of the precursor was also processed and became active during the renaturation step. Mutation of Ser199 to Cys199 and enzyme reconstitution allowed us to identify the secondary processing site that resides in the alpha subunit and to show that Ser199 of the beta subunit is essential for these two sequential processing steps. Mass spectrometry clearly indicated that the secondary processing occurs at Gly189-Asp190. All of the data suggest that the enzyme is activated through a two-step autocatalytic process upon folding: the first step is an intramolecular cleavage of the precursor between Gly198 and Ser199 for generation of the alpha subunit, containing the spacer peptide, and the beta subunit; the second is an intermolecular event, which is catalyzed by the N-terminal Ser (Ser199) of the beta subunit and results in a further cleavage and the removal of the spacer peptide (Asp190 to Gly198).

Protein kinase C regulates chondrogenesis of mesenchymes via mitogen-activated protein kinase signaling

A possible regulatory mechanism of protein kinase C (PKC) in the chondrogenesis of chick limb bud mesenchymes has been investigated. Inhibition or down-regulation of PKC resulted in the activation of a mitogen-activated protein kinase subtype Erk-1 and the inhibition of chondrogenesis. On the other hand, inhibition of Erk-1 with PD98059 enhanced chondrogenesis and relieved PKC-induced blockage of chondrogenesis. Erk-1 inhibition, however, did not affect expression and subcellular distribution of PKC isoforms expressed in mesenchymes nor cell proliferation. The results suggest that PKC regulates chondrogenesis by modulating Erk-1 activity. Inhibition or depletion of PKC inhibited proliferation of chondrogenic competent cells, and Erk-1 inhibition did not affect PKC modulation of cell proliferation. However, PKC-induced modulation of expression of cell adhesion molecules involved in precartilage condensation was reversed by the inhibition of Erk-1. Expression of N-cadherin was detected at the early period of chondrogenesis. Inhibition or depletion of PKC induced sustained expression of N-cadherin, and Erk-1 inhibition blocked the effects of PKC modulation. The expression of integrin alpha5 beta1 and fibronectin was found to be increased transiently during chondrogenesis. Depletion or inhibition of PKC caused a continuous increase of the expression of these molecules throughout the culture period, and Erk-1 inhibition abolished the modulating effects of PKC. Because reduction of the examined cell adhesion molecule expression is a prerequisite for the progression of chondrogenesis after cell condensation, our results indicate that PKC regulates chondrogenesis by modulating expression of these molecules via Erk-1 signaling.

Subgenomic RNAs of bamboo mosaic potexvirus-V isolate are packaged into virions

Purified virions of bamboo mosaic potexvirus-V isolate (BaMV-V) were found to contain three major RNA species, the 6.4 kb genomic RNA and two RNAs of 2.0 and 1.0 kb, in addition to associated satellite RNA (0.85 kb). Results of Northern blot hybridization, primer extension analysis and cDNA sequencing showed that the packaged 2.0 and 1.0 kb RNAs of BaMV-V were subgenomic RNAs. In contrast, in the BaMV-O isolate, only genomic RNA was packaged and encapsidated subgenomic RNAs were not detectable. The transcription initiation sites for the 2.0 and 1.0 kb subgenomic RNAs of BaMV-V were located 1 1 and 16 nt upstream of the initiation codon of open reading frames (ORFs) 2 and 5, respectively. The 2.0 and 1.0 kb subgenomic RNAs functioned as messengers for the ORF2 protein and capsid protein, respectively. Packaging of the 1.0 kb subgenomic RNAs resulted in the formation of rod-shaped particles about 70 nm in length. Our results indicate that BaMV isolates have evolved distinctly for packaging of subgenomic RNAs.

A new preoperative immunochemotherapy for the treatment of locally advanced esophageal cancer

A promising preoperative immunochemotherapy regimen for locally advanced esophageal cancer is herein described. A 67-year-old man suffering from severe dysphagia was diagnosed with unresectable esophageal cancer at initial examination because of a tumor of 11 cm in length and suspicion of trachea invasion. Neoadjuvant immunochemotherapy was undertaken for the down-staging. Interleukin-2 (IL-2) (3.5 x 10(5) Japan reference units), nedaplatin (7 mg/m2) and 5-FU (300 mg/m2) were administered intravenously daily for 5 days a week for three weeks. The gross findings of a barium esophagogram and esophagoscopy revealed significant tumor regression in both size and shape. The patient underwent an esophagectomy through a laparotomy followed by a right thoracotomy. The surgical specimens were serially sectioned and examined microscopically. All of the surgical margins were clear (upper and lower margins as well as the adventitia), and there was no evidence of lymph node metastasis. The surgical specimen revealed neoplastic squamous ghost cells surrounding significant lymphocyte infiltration. This appears to be a unique feature of this particular neoadjuvant immunochemotherapy.

Increased induction of Ca2+-mediated differentiation by gamma ray is mediated by endogenous activation of the protein kinase C signaling pathways in mouse epidermal cells

PURPOSE

The aim of this study was to determine whether gamma-rays can affect Ca2+-induced differentiation in normal and neoplastic mouse epidermal cells.

METHODS AND MATERIALS

After gamma-ray irradiation, primary and v-rasHa transformed mouse keratinocytes were cultured for 48 h in 0.12 mM Ca2+-containing media, and cellular translocation from cytosolic to particulated fraction of each PKC isozyme and expressions of differentiation markers were examined.

RESULTS

Morphological difference was seen at 48 h after irradiation in both Ca2+-shifted normal and v-rasHa transformed cells; v-rasHa cells were more resistant to the radiation than normal cells. Radiation potentiated granular cell-differentiation marker expressions (filaggrin, loricrin, and SPR-1) in both normal and v-rasHa transformed cells. In the case of spinous cell markers, the expression of keratins K1 and K10, which are usually blocked in v-rasHa cells was increased after irradiation. However, there was no change of K8 expression level, which can be seen only after v-rasHa transfection. Cellular fractionation and immunoblot analysis with antibodies against PKCalpha, delta, epsilon, eta, and xi revealed that PKCalpha was responsible for the differentiation marker expression.

CONCLUSIONS

These findings suggest that PKCalpha is an important component of the signaling pathway regulating radiation-induced differentiation in both normal and neoplastic epidermal cells.

Regulation of chondrogenic differentiation of mesenchymes by protein kinase C alpha

Chondrogenesis of chick limb bud mesenchymes requires the expression and activation of protein kinase C (PKC). This study was performed to identify PKC isoform(s) involved in the regulation chondrogenic differentiation of mesenchymes. Multiple PKC isoforms including alpha, epsilon, zeta and lambda/iota were expressed in mesenchymes derived from chick limb buds. Among the expressed PKC isoforms, the levels of PKC alpha and epsilon were increased during chondrogenic differentiation of mesenchymes. The increase in the expression of these isoforms is more evident in the particulate membrane fraction compared with the cytosolic fraction. Chondrogenesis was blocked by either selective inhibition or down-regulation of PKC alpha. In addition, the degree of chondrogenesis was closely correlated with the expression levels of PKC alpha but not other PKC isoforms expressed in mesenchymes. Thus, the results indicate that only PKC alpha is required for the induction of chondrogenic differentiation

Alleviation of apoptosis by serum in Chinese hamster ovary cells ectopically expressing human Fas antigen

Fas-mediated apoptosis is an important regulatory mechanism for the development of T-cells and prevention of oncogenesis. Here, we establish Chinese hamster ovary (CHO) cell lines which stably express Fas antigen, and analyzed apoptosis induced by anti-Fas IgM. While Fas-transfected hamster cells did not undergo apoptosis when stimulated with anti-Fas antibody in the presence of medium containing 10% serum, in reduced serum concentrations, anti-Fas antibody caused these cells to round up and detach from the culture dish. Analysis of the DNA content by a flow cytometry demonstrated a significant increase of cells with sub-G1 amount of DNA upon Fas stimulation in the low serum concentrations. The increase in the number of apoptosis cells was inhibited by an apopain (CPP32, caspase 3) inhibitor or insulin-like growth factor-I. In contrast, apoptosis in a Fas-transfected mouse T-cell line occurred in the presence of 10% serum. these results suggest that factors including insulin-like growth factor-I in fetal bovine serum protect CHO cells from apopain-dependent apoptosis mediated by Fas-antigen stimulation.

Reflected fourth-harmonic radiation from a centrosymmetric crystal

We present measurements of fourth-harmonic generation in reflection from the interface between two centrosymmetric media [Si(001)- SiO(2)] , using femtosecond pulses well below damage threshold. Analyses of signal amplitudes, rotational anisotropy, and sensitivity to surface roughening reveal that the surface dipole fourth-harmonic contribution dominates the bulk quadrupole contribution much more strongly than for second-harmonic generation.

A method for measuring naringenin in biological fluids and its disposition from grapefruit juice by man

The major flavonoid in grapefruit juice, naringin, has an aglycone, naringenin, that inhibits some oxidations in vitro and may have in vivo activity. We developed an HPLC method to measure naringenin using a methanol:water mobile phase with UV absorbance detection. The recovery of naringenin was 96%. Two subjects who drank grapefruit juice containing 214 mg naringin daily excreted approximately 30 mg/day of naringenin glucuronide. Thus, naringin is hydrolyzed to naringenin and then conjugated with glucuronic acid prior to excretion of the conjugate.

Gender differences in baseline variables, therapies and outcomes in Chinese patients with acute myocardial infarction

We prospectively studied the gender differences of baseline variables, therapies, and outcomes among a cohort of 369 Chinese patients with acute myocardial infarction from 1990 to 1995. There were 277 male and 92 female patients. The male gender had a younger mean (+/-SD) age (61.5+/-10.7 vs. 67.1+/-11.7 years, P<0.0001). Hypercholesterolemia (201.2+/-44.2 vs. 187.5+/-43.7 mg/dl, P=0.0111) and obesity (25.0 vs. 15.9%, P=0.0494) were more prominent in the female. Smoking was more prevalent in the male (78.3 vs. 18.5%, P<0.0001). The male group also had more frequent use of thrombolytic agents (19.1 vs. 9.8%, P=0.0377), beta-blockers (61.7 vs. 47.8%, P=0.0191) and heparin (25.3 vs. 12.0%, P=0.0075); but less use of angiotensin-converting enzyme inhibitors (6.9 vs. 15.2%, P=0.0149). The condition on admission was worse in the female group (Killip classification (1.5+/-0.9 vs. 1.9+/-1.0, P=0.0022), myocardial failure (8.7 vs. 2.9%, P=0.0178) and cardiomegaly (65.2 vs. 53.1%, P=0.0419). During a follow-up duration of 26.4+/-24.1 and 22.9+/-23.9 months respectively, the mortality rate was lower in the male (19.5 vs. 30.4%, P=0.0288). However after adjustment for the effect of age, the differences in Killip classification, myocardial failure, cardiomegaly and mortality became insignificant.

The E protein CTF4 and acetylcholine receptor expression in development and denervation supersensitivity

Motor activity blocks the extrasynaptic expression of many genes in skeletal muscle, including those encoding ion channels, receptors, and adhesion molecules. Denervation reinduces transcription throughout the multinucleated myofiber, restoring the developmental pattern of expression, especially of the genes coding for the acetylcholine receptor. A screen for trans-acting factors binding to the enhancer region of the alpha-subunit gene of the acetylcholine receptor identified CTF4, a ubiquitously expressed and alternatively spliced chicken homologue of the human E protein transcription factor HTF4/HEB. Expression of the CTF4 locus closely parallels that of myogenin and acetylcholine receptor during development and maturation of skeletal muscle, but transcription is not similarly regulated by neuronal cues. Alternative splicing within the region encoding the transactivation domain generates two CTF4 isoforms with different tissue distributions, but similar binding affinities for the acetylcholine receptor alpha-subunit enhancer and similar transcriptional potential when complexed to myogenin. Direct injection of a myogenin, but not a MyoD, antisense expression vector into denervated skeletal muscle caused a significant decrease in the transcriptional activation of a depolarization-sensitive reporter gene. Similarly, injection of a CTF4, but less so of an E12, antisense expression vector impaired the denervation response, further implicating the involvement of a myogenin/CTF4 heterodimer in the expression of AChR genes in vivo.

The region of dopamine transporter encompassing the 3rd transmembrane domain is crucial for function

Bovine dopamine transporter (bDAT) shows relatively low dopamine (DA) uptake efficacy and scant MPP+ transport and cocaine binding, while all of these activities are avid in human dopamine transporter (hDAT). In this study, we constructed a series of chimeras between human and bovine DAT to find out the structure(s) responsible for each DAT functions. DA uptake, MPP+ uptake, and cocaine binding in hDAT nearly disappeared only by the substitution of the 3rd transmembrane domain (TMD) with that of bDAT. On the contrary, the substitution of an identical region of hDAT into bDAT produced a complete shift toward the value of WT hDAT in the DA uptake, even though the MPP+ uptake and CFT binding maintained the values of WT bDAT. Collectively, these results suggest that the 3rd TMD in DAT is crucial for the function, especially for DA uptake.

Electron microscopic observations of apoptotic cells in various etiologies of human cardiovascular diseases

OBJECTIVE

To observe apoptotic process in various cardiovascular disorders with a particular attention to the ultrastructural morphology of apoptosis in cardiomyocytes, fibroblasts, vascular endothelial cells and smooth muscle cells.

METHODS

Transmission electron microscopic observations of the tissue specimens obtained from endomyocardial biopsies or surgical excisions of left ventricular myocardium or calcified aortic valves were carried out in 50 patients with various cardiovascular diseases.

RESULTS

The ultrastructural features of apoptosis was consistently observed in cardiomyocytes, fibroblasts, vascular endothelial cells and smooth muscle cells in all diseased tissues. In cardiomyopathies and rheumatic heart diseases apoptosis was commonly observed in the cardiomyocytes. It was often found that fibroblasts underwent apoptosis in calcific aortic valve tissues. Apoptosis of arterial smooth muscle cells was a frequent finding in renal arterial stenosis due to Takayasu's arteritis and fibromuscular dysplasia. Regardless of the cell types, the nuclear hallmarks of apoptosis were identical with minor modifications of the fragmentation of the condensed cells into apoptotic bodies.

CONCLUSIONS

Based on electron microscopic findings, it is suggested that the underlying disease processes determine which type of cells predominantly undergoes apoptotic changes in various cardiovascular disorders. In addition, different cells with similar structural morphology may have common ultrastructural features of apoptosis.

Genetic heterogeneity for familial hypertrophic cardiomyopathy in Chinese: analysis of six Chinese kindreds

OBJECTIVE

Familial hypertrophic cardiomyopathy (FHCM) is a primary myocardial disease characterized by unexplained ventricular hypertrophy. The application of the techniques of reverse genetics has identified at least five chromosomal loci as the major causes for FHCM in diverse ethnic populations, suggesting substantial genetic heterogeneity for FHCM. Recently, the defective gene loci of two Chinese families with FHCM have been mapped to chromosome 11 and 14q1, respectively. For further understanding of the molecular basis of FHCM in Chinese, we analyzed the linkage between four other Chinese kindreds and DNA markers from chromosome 14q1.

METHODS

Six unrelated Chinese families with FHCM, including two previously reported, were studied. Totally 90 family members were included for analysis. DNA from 80 individuals was extracted and polymerase chain reactions were performed using the primers designed according to the sequences derived from the alpha and beta myosin heavy chain gene. Totally four polymorphisms were studied, including three polymorphic microsatellite sequences and one single strand conformation polymorphism. Genetic linkage analysis were performed using the Linkage program.

RESULTS

In the six studied families, 39 of the 90 family members were found to be affected diagnosed either by echocardiography or by clinical evaluation. The pattern of inheritance in all six studied families was most consistent with an autosomal dominant trait with a high degree of penetrance. Genetic linkage analysis using polymorphisms on the alpha and beta MHC genes showed a combined maximal lod score of 6.2 for trinucleotide repeat polymorphism AMHC-I 15 at theta = 0.00 for three studied families without recombination. Exclusion of linkage to the chromosome 14q1 location was noted in two of three other families with the maximal lod score of -2 or less.

CONCLUSIONS

These results provide further evidence that FHCM in Chinese is genetically heterogeneous. Chromosome 14q1 locus, probably the beta myosin heavy chain gene, is important as the molecular basis for FHCM in Chinese.

Mechanism of regulation of 8-hydroxyguanine endonuclease by oxidative stress: roles of FNR, ArcA, and Fur

We found previously that 8-hydroxyguanine (oh8Gua) endonuclease in E. coli is induced in response to oxidative stress in a fashion similar to the oxidative response of the Mn-superoxide dismutase (MnSOD). In this study, attempts were made to identify the genes involved in the co-regulation of E. coli endonuclease and MnSOD (sodA). oh8Gua nuclease is induced by molecular oxygen and a superoxide radical generator (paraquat) but not by H2O2, suggesting that the regulation of this endonuclease is dependent on SoxRS but independent of OxyR. This enzyme was induced by paraquat in all of the soxRS mutant strains used (soxR-, soxS- and soxRc), whereas glucose-6-phosphate dehydrogenase (a member of the soxRS regulon) showed the expected responses; therefore, this possibility was excluded. The presence of metal chelators in the growth medium caused the induction of this enzyme, and this induction was suppressed by the addition of Fe++. Consistent with this finding, this enzyme was expressed under anaerobiosis in all of the mutant strains of fnr in particular, as well as fur, arcA, and combinations thereof. These findings suggest that the oxidative regulation of oh8Gua endonuclease is under control of fnr, fur, and arcA, where fnr plays a predominant role. The multiple involvement of regulatory genes as well as co-regulation with antioxidant enzyme will enhance the efficiency of cellular growth and survival in the aerobic environment.

Differential expression of protein kinase C isoforms in diethylnitrosamine-initiated rat liver

Although protein kinase C (PKC), a family of 12 related isoforms, plays an important role in carcinogenesis, little is known about the specific role of each isoform in the initiation stage of hepatocarcinogenesis. The subcellular distribution of PKC isoforms in the early stages of diethylnitrosamine (DEN)-initiated hepatocarcinogenesis was therefore examined. Three-week-old female Sprague-Dawley rats were intraperitoneally injected twice in 1 week with DEN; all animals were sacrificed at 1, 2 and 24 h and 3 and 7 days after the second injection. PKCalpha and -beta expression in both cytosolic and particulate fractions decreased as a result of 1 h of DEN treatment and this effect lasted for 7 days. In both fractions, PKCepsilon expression showed a marked increase by DEN treatment, while the expression of PKCdelta and -zeta was almost unchanged. These results suggest that differential expression of PKC isoforms may play an important role in the early stage of DEN-initiated hepatocarcinogenesis in rats.

Retroviral gene transfer in chondrogenic limb bud micromass cultures

We report development of a model of retroviral gene transduction in high-density limb bud cell micromass culture. The replication competent avian retrovirus RCAS BP (A) carrying the human placental alkaline phosphatase gene (RCAS AP) was used as a marker for retroviral infection and spread. The final protocol balances the need to allow time for retroviral integration and gene transduction against loss of chondrogenic potential when limb bud cells are plated at low density. It includes: (i) incubation of the dissociated limb bud cells with RCAS virus for 2 h followed by low-density culture for 48 h to allow retroviral gene expression; and (ii) secondary replating as high-density micromass culture to initiate chondrogenesis. The pattern and level of chondrogenesis in the retrovirus-transduced micromass cultures is similar to regular micromass cultures. At least 40%-50% of cells express the retroviral-transduced genes 24 h after high-density plating. This new approach facilitates ectopic gene expression in micromass culture, enabling molecular dissection of chondrogenesis and serves as a model for gene transduction in other organotypic cultures.

Molecular level investigation of exocytosis in cultured human pheochromocytoma cells: insights from high resolution scanning electron microscopy combined with autoradiogram and cytochemistry

OBJECTIVE

To investigate molecular events of exocytosis in cultured human pheochromocytoma cells with stimulation.

METHODS

The cultured pheochromocytoma cells prepared from human adrenal pheochromocytoma tumor were stimulated for the release of catecholamines by depolarization with the administration of 50 mmol/L KCl. Transmission electron microscopy (TEM) and high resolution scanning electron microscopy (HR-SEM) combined with autoradiography and cytochemistry were used to observe molecular mechanisms of exocytotic release of catecholamines from the stimulated cells labelled with 3H-noradrenaline and the filipin-treated cells.

RESULTS

TEM and HR-SEM observations of the stimulated cells labelled with 3H-noradrenaline revealed that the initial exocytotic fusion pores even less than 10 nm in diameter in human pheochromocytoma cells can be clearly observed in a single lipid bilayer. Furthermore, HR-SEM examinations of the filipin-treated cells showed that the derangement of the particles of the filipin-sterol complexes (FSCs) in the fused membranes of granule and plasma membranes occurred as the exocytotic fusion pores opened. In addition, the aggreates of the FSCs particles were consistently demonstrated around the openings of the differently sized closing exocytotic pores.

CONCLUSIONS

Based on our results, it is suggested that the rearrangement of the sterol molecules in the fused membranes of granule and plasma membranes plays an important role in the opening and closing mechanisms of exocytotic fusion pores. We hope that morphological data obtained in this study can provide some new insights into the understanding of molecular mechanisms of exocytosis, particularly the opening and closing of exocytotic fusion pores in relation to the distribution of the membrane sterols.

Nucleotides in the panhandle structure of the influenza B virus virion RNA are involved in the specificity between influenza A and B viruses

Influenza A and B viruses share common sequences and potentially similar panhandle structures in the terminal noncoding regions of virion RNA (vRNA). Interesting differences exist, however, in the number of conserved nucleotides at the 5' and 3' ends of the vRNAs, in base pairs constituting the panhandle duplex, and the length of uridine stretch (U stretch) juxtaposed to the RNA duplex. To analyse the contribution of these signals to the specificity between the two viruses, a transient ribonucleoprotein transfection method was used for the expression of the chloramphenicol acetyltransferase (CAT) reporter gene flanked by the noncoding nucleotides derived from influenza B vRNA. While the base pairing in the RNA duplex was primarily important for template activity, mismatch mutations G11 x G12' and C12 x A13' in the terminal RNA duplex region were utilized by influenza B virus, whereas these mutations were detrimental for influenza A virus. Different activity profiles were observed in the length preference of the RNA duplexes: maximum template activity was observed with 11 base pairs for influenza B virus, and 8 base pairs for influenza A virus. When the mutants with various lengths of U stretch were tested, highest CAT activities were observed with 5 to 7 uridine residues in influenza A virus, whereas in influenza B virus the activity was drastically decreased with 7 uridine residues. We suggest that the specific interaction of influenza virus RNA polymerase with these noncoding cis-acting signals in transcription of the RNA genome, along with unique coding strategies adopted by influenza B virus, has contributed to the divergence of these two closely related viruses.

A distinct region of chromosome 19p13.3 associated with the sporadic form of adenoma malignum of the uterine cervix

Adenoma malignum (AM) is known to be one of the malignant tumors that is commonly associated with Peutz-Jeghers syndrome. Recently, the genetic locus of Peutz-Jeghers syndrome was mapped to the telomeric region of chromosome 19p. We analyzed nine sporadic cases of AM with high-density loss of heterozygosity to study the region of chromosome 19p13.2-13.3 using eight microsatellite markers. Our deletion mapping data revealed a distinct region with 100% loss of heterozygosity frequency at marker D19S216. This result indicates that a putative tumor suppressor gene for AM is located at D19S216 on chromosomal band 19p13.3 and plays an important role in AM tumorigenesis.

Catalytic mechanism of aldose reductase studied by the combined potentials of quantum mechanics and molecular mechanics

The catalytic reduction of D-glyceraldehyde to glycerol by aldose reductase has been investigated with the combined potentials of quantum mechanics (QM) and molecular mechanics (MM) to resolve the question of whether Tyr48 or His110 serves as the proton donor during catalysis. Site directed mutagenesis studies favor Tyr48 as the proton donor while the presence of a water channel linking the N delta 1 of His110 to the bulk solvent suggests that His110 is the proton donor. Utilizing the combined potentials of QM and MM, the binding mode of substrate D-glyceraldehyde was investigated by optimizing the local geometry of Asp43, Lys77, Tyr48, His110 and NADPH at the active site of aldose reductase. Reaction pathways for the reduction of D-glyceraldehyde to glycerol were then constructed by treating both Tyr48 and His110 as proton donors. Comparison of energetics obtained from the reaction pathways suggests His110 to be the proton donor. Based on these findings, a reduction mechanism of D-glyceraldehyde to glycerol is described.