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Biomedical subjects

S H Ma

Publications and source records attributed to S H Ma.

14 recordsLinked to original sources
PubMed2001

Sequence analysis of hemagglutinin and nucleoprotein genes of measles viruses isolated in Korea during the 2000 epidemic.

To characterize the genetic properties of currently circulating measles viruses in Korea, the complete nucleotide sequences of hemagglutinin (H) protein and nucleoprotein (N) genes of Korean viruses were analyzed. The entire genes of H and N were directly amplified by RT-PCR from each clinical specimen and sequenced. Sequence analyses of H and N genes indicated that all Korean viruses had a high degree of homology (>99.8%) when compared with each other. The Korean viruses differed from other wild-type viruses by as much as 6.8% in the H gene and 6.5% in the N gene at the nucleotide level. The deduced amino acid variability was up to 6.4% for the H protein and up to 6.5% for the N protein. Phylogenetic analyses of nucleotide sequences and deduced amino acid sequences of the H and N genes revealed that all Korean viruses were grouped into the clade H1.

Disease Outbreaks↗
PubMed2000

Potential dengue virus-triggered apoptotic pathway in human neuroblastoma cells: arachidonic acid, superoxide anion, and NF-kappaB are sequentially involved.

Direct in vivo evidence for the susceptibility of human neuronal cells to dengue virus has not been reported. In this study, we demonstrated that type 2 dengue (DEN-2) virus infection induced extensive apoptosis in the human neuroblastoma cell line SK-N-SH. Phospholipase A(2) (PLA(2)) was activated by DEN-2 infection, which led to the generation of arachidonic acid (AA). Inhibition of PLA(2) activity by the PLA(2) inhibitors, AACOCF(3) and ONO-RS-082, diminished DEN-2 virus-induced apoptosis. In contrast, the cyclooxygenase inhibitors aspirin and indomethacin, thought to increase AA accumulation by blocking AA catabolism, enhanced apoptosis. Exogenous AA induced apoptosis in a dose-dependent manner. Superoxide anion, which is thought to be generated through the AA-activated NADPH oxidase, was increased after infection. Pretreatment with superoxide dismutase (SOD) protected cells against DEN-2 virus-induced apoptosis. Furthermore, generation of superoxide anion was blocked by AACOCF(3). In addition, the transcription factors, NF-kappaB and c-Jun, were found to be activated after DEN-2 virus infection. However, pretreatment of cells with oligodeoxynucleotides containing NF-kappaB, but not c-Jun, binding sites (transcription factor decoy) strongly prevented dengue virus-induced apoptosis. The finding that AACOCF(3) and SOD significantly block activation of NF-kappaB suggests that this activation is derived from the AA-superoxide anion pathway. Our results indicate that DEN-2 virus infection of human neuroblastoma cells triggers an apoptotic pathway through PLA(2) activation to superoxide anion generation and subsequently to NF-kappaB activation. This apoptotic effect can be either directly derived from the action of AA and superoxide anion on mitochondria or indirectly derived from the products of apoptosis-related genes activated by NF-kappaB.

Animals↗
PubMed1998

DNA immunization with Japanese encephalitis virus nonstructural protein NS1 elicits protective immunity in mice.

Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, is a zoonotic pathogen that is prevalent in some Southeast Asian countries and causes acute encephalitis in humans. To evaluate the potential application of gene immunization to JEV infection, we characterized the immune responses from mice intramuscularly injected with plasmid DNA encoding JEV glycoproteins, including the precursor membrane (prM) plus envelope (E) proteins and the nonstructural protein NS1. When injected with the plasmid expressing prM plus E, 70% of the immunized mice survived after a lethal JEV challenge, whereas when immunized with the plasmid expressing NS1, 90% of the mice survived after a lethal challenge. As a control, the mice immunized with the DNA vector pcDNA3 showed a low level (40%) of protection, suggesting a nonspecific adjuvant effect of the plasmid DNA. Despite having no detectable neutralizing activity, the NS1 immunization elicited a strong antibody response exhibiting cytolytic activity against JEV-infected cells in a complement-dependent manner. By contrast, immunization with a construct expressing a longer NS1 protein (NS1'), containing an extra 60-amino-acid portion from the N terminus of NS2A, failed to protect mice against a lethal challenge. Biochemical analyses revealed that when individually expressed, NS1 but not NS1' could be readily secreted as a homodimer in large quantity and could also be efficiently expressed on the cell surface. Interestingly, when NS1 and NS1' coexisted in cells, the level of NS1 cell surface expression was much lower than that in cells expressing NS1 alone. These data imply that the presence of partial NS2A might have a negative influence on an NS1-based DNA vaccine. The results herein clearly illustrate that immunization with DNA expressing NS1 alone is sufficient to protect mice against a lethal JEV challenge.

Animals↗
PubMed1998

Study of Dengue virus infection in SCID mice engrafted with human K562 cells.

Here we report that severe combined immunodeficient (SCID) mice engrafted with human K562 cells (K562-SCID mice) can be used as an animal model to study dengue virus (DEN) infection. After intratumor injection into K562 cell masses of PL046, a Taiwanese DEN-2 human isolate, the K562-SCID mice showed neurological signs of paralysis and died at approximately 2 weeks postinfection. In addition to being detected in the tumor masses, high virus titers were detected in the peripheral blood and the brain tissues, indicating that DEN had replicated in the infected K562-SCID mice. In contrast, the SCID mice were resistant to DEN infection and the mock-infected K562-SCID mice survived for over 3 months. These data illustrate that DEN infection contributed directly to the deaths of the infected K562-SCID mice. Other serotypes of DEN were also used to infect the K562-SCID mice, and the mortality rates of the infected mice varied with different challenge strains, suggesting the existence of diverse degrees of virulence among DENs. To determine whether a neutralizing antibody against DEN in vitro was also protective in vivo, the K562-SCID mice were challenged with DEN-2 and received antibody administration at the same time or 1 day earlier. Our results revealed that the antibody-treated mice exhibited a reduction in mortality and a delay of paralysis onset after DEN infection. In contrast to K562-SCID, the persistently DEN-infected K562 cells generated in vitro invariably failed to be implanted in the mice. It seems that in the early stage of implantation, a gamma interferon activated, nitric oxide-mediated anti-DEN effect might play a role in the innate immunity against DEN-infected cells. The system described herein offers an opportunity to explore DEN replication in vivo and to test various antiviral protocols in infected hosts.

Animals↗
PubMed1998

Antiapoptotic but not antiviral function of human bcl-2 assists establishment of Japanese encephalitis virus persistence in cultured cells.

Upon infection of Japanese encephalitis virus (JEV), baby hamster kidney (BHK-21) and Chinese hamster ovary (CHO) cells were killed by a mechanism involved in apoptosis. While readily established in a variety of cell lines, JEV persistence has never been successfully instituted in BHK-21 and CHO cells. Since stable expression of human bcl-2 in BHK-21 cells has been shown to delay JEV-induced apoptosis, in this study we investigated whether JEV persistence could be established in such cells. When constitutively expressing bcl-2, but not its closest homolog, bcl-XL, following a primary lytic infection, approximately 5 to 10% of BHK-21 and CHO cells became persistently JEV infected during a long-term culture. From the persistent bulks, several independent clones were selected and expanded to form stable cell lines that continuously produced infectious virus without marked cytopathic effects (CPE). Among these stable cell lines, the truncated nonstructural protein 1 (NS1) was also detected and was indistinguishable from the NS1 truncations previously observed in JEV-persistent murine neuroblastoma N18 cells. However, the stable expression of NS1 alone, regardless of whether it was truncated or full length, failed to render the engineered cells persistently infected by JEV, implying that aberrant NS1 proteins were likely a consequence of, rather than a cause for, the viral persistence. Enforced bcl-2 expression, which did not affect virus replication and spread during the early phase of cytolytic infection, appeared to attain JEV persistence by restriction of virus-induced CPE. Our results suggest that it is the antiapoptotic, rather than the antiviral, effect of cellular bcl-2 which plays a role in the establishment of JEV persistence.

Amino Acid Sequence↗
PubMed1997

Inhibition of Japanese encephalitis virus infection by nitric oxide: antiviral effect of nitric oxide on RNA virus replication.

The antiviral effects of nitric oxide (NO) on Japanese encephalitis virus (JEV), a member of the family Flaviviridae, were investigated in this study. In vitro, inhibition of replication of JEV in gamma interferon-activated RAW 264.7 murine macrophages was correlated to cellular NO production. When cocultured with infected murine neuroblastoma N18 cells, gamma interferon-activated RAW 264.7 cells also efficiently hindered JEV replication in contiguous bystanders, and this anti-JEV effect could be reversed by an NO synthase (NOS) inhibitor, N-monomethyl-L-arginine acetate. In vivo, the mortality rate increased as the NOS activity of JEV-infected mice was inhibited by its competitive inhibitor, N-nitro-L-arginine methyl ester. Moreover, when an organic donor, S-nitro-N-acetylpenicillamine (SNAP), was used, the NO-mediated antiviral effect was also observed in primarily JEV-infected N18, human neuronal NT-2, and BHK-21 cells, as well as in persistently JEV-infected C2-2 cells. These data reaffirm that NO has an effective and broad-spectrum antimicrobial activity against diversified intracellular pathogens. Interestingly, the antiviral effect of NO was not enhanced by treatment of N18 cells with SNAP prior to JEV infection, a measure which has been shown to greatly increase the antiviral effect of NO in infection by vesicular stomatitis virus. From biochemical analysis of the impact of NO on JEV replication in cell culture, NO was found to profoundly inhibit viral RNA synthesis, viral protein accumulation, and virus release from infected cells. The results herein thus suggest that NO may play a crucial role in the innate immunity of the host to restrict the initial stage of JEV infection in the central nervous system.

Animals↗
PubMed1997

Effect of enforced expression of human bcl-2 on Japanese encephalitis virus-induced apoptosis in cultured cells.

Infection by Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, causes acute encephalitis in humans and induces severe cytopathic effects in different types of cultured cells. This study attempted to determine whether apoptosis contributes to virus-induced cell death in a culture system by characterizing JEV lytic infection in baby hamster kidney BHK-21 cells, murine neuroblastoma N18 cells, and human neuronal progenitor NT2 cells. According to our results, the replication of JEV, and not the UV-inactivated virions per se, triggered apoptosis in these cell lines, as evidenced by nuclear condensation, DNA fragmentation ladder, and in situ end labeling of DNA strand breaks with terminal transferase (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling assay). Different strains of JEV, regardless of whether they are neurovirulent to mice, could induce apoptosis of the infected cells. In addition, enforced expression of the human protooncogene bcl-2 in BHK-21 cells, which did not influence virus production, appeared to delay the process of JEV-induced apoptosis, despite the fact that most infected cells were inevitably killed after prolonged cultures. However, Bcl-2 proteins expressed in N18 cells failed to block JEV-induced apoptosis, although they did prevent Sindbis virus-induced apoptosis from occurring in the same cells. This finding suggests that these two viruses may utilize similar but not identical mechanisms to kill their infected cells. The results presented here thus demonstrate that apoptosis can be a general mechanism for JEV-induced cell death and that enforced bcl-2 expression may be inadequate in protecting all cell types from JEV-induced apoptosis in cell cultures.

Animals↗
PubMed1996

Persistence of Japanese encephalitis virus is associated with abnormal expression of the nonstructural protein NS1 in host cells.

Persistent infection with Japanese encephalitis virus (JEV) was established in murine neuroblastoma N18 cells, and the persistency has been maintained in cell culture for over 6 months. From the persistently infected cells, a clone named C2-2 was selected and expanded to form a stable cell line. The vast majority of C2-2 cells showed viral protein staining by immunofluorescence and continuously produced low levels of virus (10(3) to 10(4) PFU/ml) without marked cytopathic effects or cyclic variations. In addition to the wild-type viral proteins, truncated forms of the viral nonstructural protein 1 (NS1) as well as its derivative NS1' were produced in C2-2 cells. Both truncated NS1 and NS1' contain deletions at their N-termini; however, the analyses by RT-PCR and direct sequencing of the viral RNA failed to detect any truncations or mutations within the NS1 region, suggesting that NS1 truncation was a result of a unique posttranslational proteolytic cleavage of NS1 in the persistently infected cells. Similar but not identical truncation of NS1 was also observed in two other persistently infected cell lines established in Vero and DBT (murine astrocytoma) cells. However, viruses released from C2-2 cells did not produce truncated NS1 upon infection of N18 cells, suggesting that NS1 truncations were the result of virus-cell interaction in persistently infected cells. These data indicate a strong association between abnormal NS1 expression and JEV persistency. A probable involvement of dysfunctional NS1 in the establishment and/or maintenance of JEV persistency in tissue culture is discussed.

Amino Acid Sequence↗
PubMed1995

Generation and characterization of Japanese encephalitis virus specific monoclonal antibodies.

Monoclonal antibodies (MoAbs) specifically against Japanese encephalitis virus (JEV) were generated by fusion of immunized mouse spleen cells with NS-1 myeloma cells. Nakayama-NIH (Na) and three Taiwan local strains of JEV, i.e., TL isolated from a patient's brain in 1965, NT109 (JE7) isolated from Cx. tritaeniorhynchus in 1985, and RP9, a plaque purified clone of NT109, were used in the immunization. The specificities of moAbs were determined by immunoprecipitation and western blotting, using JEV-infected cell lysates. They were confirmed by the same methods using recombinant JEV proteins as antigens. From Na immunization, 4 anti-E, 3 anti-NS1 and 3 anti-NS3 moAbs were generated. Seventeen anti-E, three anti-NS1 and three anti-NS3 specific moAbs were generated from mice immunized with Taiwan local JEV strains. Overall 21 anti-E, 6 anti-NS1, and 6 anti-NS3 moAbs were produced and characterized. The isotypes of these moAbs were also determined and described. Interestingly, a majority of the moAbs generated for RP9 were IgG1 isotype. In conclusion, 33 moAbs specific to JEV were generated and characterized, and some of these anti-JEV moAbs were made against Taiwan local isolates. These moAbs provide a powerful tool to study JEV, especially the antigenic properties of Taiwan's local strains.

Animals↗
PubMed1991

The anterior cavernous sinus space.

The anterior cavernous sinus space is the venous space anterior to the cavernous carotid artery. It is tetrahedral in shape with the anterior apex at the superior orbital fissure. The superomedial wall is formed by the base of the anterior clinoid process. The inferomedial wall is formed by the sphenoid bone. The lateral wall consists of two layers of dura with the oculomotor, trochlear, ophthalmic and abducens nerves in the inner layer. Medially, the posterior wall consists of the cavernous carotid artery. Laterally, it communicates with the lateral cavernous sinus space. Paraclinoid and carotid cave aneurysms may occupy this space and its microanatomy is important in the surgery of these aneurysms.

Carotid Arteries↗
PubMed1990

The effects of actinidia sinensis planch (kiwi) drink supplementation on athletes training in hot environments.

On the basis of studying the problems and experimental data of athletes training in hot environments, we designed an athletic drink choosing actinidia sinensis planch (ASP), also known as kiwi fruit, as the basic component, and assessed its effects in athletes both at site of training and in the laboratory. The main results were as follows: (1) In athletes riding on a Monark ergometer (maintaining HR at 150 beat/min), the work time to exhaustion was longer (149 +/- 3 min vs 120 +/- 1 min), and the work load was larger (947 +/- 36 KJ vs 833 +/- 28 KJ) when supplementing the ASP drik than when they drank the placebo, P less than 0.01) (2) Supplements with the ASP drink expanded the blood volume of athletes. Hematocrit increased significantly after exercise in athletes consuming placebo, but no significant changes were found in those consuming the ASP drink. (3) The ASP drink which contained 5% carbohydrate maintained the blood glucose concentration of athletes at a normal level even when training lasted more than 2.5 hours and without noticeable effect on plasma insulin levels. (4) Supplement of small amount of multi-minerals in the ASP drink helped to decrease the mineral level changes in serum and sweat after intensive training, but it did not cause kaliemia or affect urinary output. (5) Data on urinary vitamin C content indicated that the vitamin C status of athletes supplementing the ASP drink improved. The ASP drink is not only effective but also fragrant, tasty, refreshing and thirst quenching, and it appears to have no side effects.

Adolescent↗
PubMed1989

[Infusion of sclerosant through direct cannulation of the coronary vein in the prevention and treatment of esophageal varices bleeding in portal hypertension].

To control bleeding from esophageal varices in portal hypertension, infusion of sclerosant through direct cannulation of the coronary vein at splenectomy was carried out in 50 patients, either as an emergent procedure or during bleeding interval. In all cases complete obliteration of the varices was revealed by coronary venography after the infusion. Prompt control of bleeding was obtained in 94% of patients. Three Child C grade patients died within one month postoperatively. Rebleeding occurred in only 6.7% during a follow-up of 1-4 years (an average of 36.4 months). One, two, and three year complication-free survival rate was 97.5%, 95.6%, and 93.5% respectively. The procedure is thus considered satisfactory and recommendable.

Adolescent↗
PubMed1988

Cerebrovascular occlusive disease in children: a survey.

Eight cases of stroke in children treated with surgery are reported. Four of the patients had Moya-moya disease and presented with TIA. They were treated by surgically creating collaterals through the STA-MCA bypass, encephalomyosyangiosis and encephalomyoarteriosynangiosis operations. Three patients with traumatic or idiopathic carotid artery stenosis or occlusion presented with TIA and were treated with STA-MCA bypass. One patient with idiopathic carotid artery stenosis presented with a complaint of a continuous swishing noise in the ear and had a STA-MCA bypass followed by carotid artery ligation. Although stroke in children is usually secondary to systemic disease, there is a group of children with surgically treatable disease who need to be identified and treated. The potential benefit of surgery may depend on the promptness with which a definitive diagnosis is reached.

Adolescent↗