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Biomedical subjects

E R Chen

Publications and source records attributed to E R Chen.

At least 37 records · Page 2Linked to original sources
PubMed1994

Anthelmintic effect of levamisole against Angiostrongylus cantonensis in mice.

Levamisole, in dosages of 2.5, 5, 10, and 25 mg/kg/day, was given orally by orogastric tube beginning 5, 10, 15, and 20 days after the infection of ICR mice with 50 third-stage larvae of Angiostrongylus cantonensis. Medication was given for 7, 14 or 21 consecutive days. The mice in each group were sacrificed 3 days after cessation of treatment and the brains were examined for parasites. Complete anthelmintic effects could be obtained when treatment was started 10 days post-infection with dosages as low as 2.5 mg/kg/day for 21 consecutive days. Over 90% worm reduction was achieved in the two-week treatment group with medication beginning 5 days after infection at diverse dosages. High dose were given in the treatment groups beginning 15 days post-infection. When the commencement of medication was delayed to 20 days post-infection, worm reduction rates were around 50% in spite of long periods and/or high dosages of medication.

Angiostrongylus cantonensis↗
PubMed1993

Studies on cryopreservation of third-stage larvae of Parastrongylus cantonensis.

Attempts have been made to increase the survival rate of third-stage larvae of Parastrongylus cantonensis during cryopreservation. Parasites were obtained from experimentally infected snails, Biomphalaria glabrata. The maximum non-toxic concentrations of cryoprotectants dimethyl sulphoxide (DMSO) and glycerol were determined as 10% v/v in NCTC 109 medium. Different pre-cooling times and serum additives were assayed to determine their effects on the viability of larvae. Larvae pre-cooled at -20 degrees C for 15-20 minutes before transfer to -70 degrees C had the optimum survival rate. The presence of serum was essential for further cooling to -196 degrees C. There were no differences between native and heat-inactivated sera on the larval viability. The survival of larvae recovered after storage at -196 degrees C was higher in sera collected from the rat, man, or fetal calf than in sera collected from the mouse, dog, or horse. Viability assessed by mouse-infections showed that thawed larvae retained infectivity for susceptible hosts, but it was significantly lower than that of unfrozen control worms.

Angiostrongylus cantonensis↗
PubMed1993

Vector competence of Aedes albopictus and Ae. aegypti (Diptera: Culicidae) to dengue 1 virus on Taiwan: development of the virus in orally and parenterally infected mosquitoes.

The vector competence in Ae. aegypti (L.) and Ae. albopictus (Skuse) from southern Taiwan to the dengue 1 virus was studied to elucidate the distribution of dengue infection during the 1987-1988 outbreak. The brain of Ae. aegypti was infected as early as 3 d after intrathoracic inoculation. The esophagus and the proboscis (tissues within the labium) were infected 5 d after inoculation. The salivary gland was highly susceptible to the virus, but no specific infection site was found. Gangli, muscles, and diverticula within the thorax were not infected. In the abdominal area, the ventral diverticula, Malpighian tubules, ganglia, and the dorsal vessel were not infected. However, the entire gut was susceptible to dengue 1 virus, although it was not infected simultaneously. Only a certain type of midgut epithelial cells was infected by the virus. The ovarioles, oviducts, and accessory glands frequently were infected. However, the spermathecae were not infected, perhaps because of the chitin-rich outer layer. Infections of the testes, vas deferens, seminal vesicles, and accessory glands of males also were detected in this study. The tissues of the proboscis were never infected in Ae. albopictus but frequently were infected in Ae. aegypti, indicating that the virus may escape the salivary gland barrier more efficiently in Ae. aegypti than in Ae. albopictus. When these mosquitoes were fed on hanging drops, the salivary gland infection and transmission rates of Ae. aegypti were always higher than those of Ae. albopictus. On Taiwan, Ae. aegypti appears to be a more competent vector in the transmission of the dengue 1 virus than Ae. albopictus.

Aedes↗
PubMed1993

Killing effect of gamma irradiation on Angiostrongylus cantonensis in snails.

Cobalt-60 gamma irradiation was used to kill the larvae of Angiostrongylus cantonensis in four groups of snails that were irradiated at a rate of 15.4 Gy/min for 16.23 min (0.25 kGy), 32.47 min (0.50 kGy), 48.70 min (0.75 kGy), and 64.94 min (1.00 kGy), respectively. Third-stage (infected stage) larvae were isolated from these snails and 50 were administered to each experimental animal via an esophageal tube. At a dosage of 0.25 kGy, the mean +/- SD number of worms recovered from 30 rats and 30 mice was 15.6 +/- 6.5 and 11.3 +/- 6.2, respectively. These were significantly different from the number of worms recovered from the nonirradiated (control) groups, which were 28.9 +/- 9.6 (P < 0.05) and 16.6 +/- 10.3 (P < 0.05) for rats and mice respectively. Worms and cellular infiltrations in lung tissue of rats were histopathologically identified in the 0.25-kGy-irradiated group as well as in the control group. Worms and eosinophilic meningitis were also noted in the brain tissue of mice in control groups. No worms or pathologic findings were observed in the heart, lung, or brain tissue of rats or mice infected with larvae irradiated at or exceeding 0.50 kGy. It is therefore concluded that a dosage of 0.50 kGy is sufficient to prevent successful infection in mice and rats.

Angiostrongylus cantonensis↗
PubMed1992

Antibodies of different immunoglobulin isotypes in serum and bile of patients with clonorchiasis.

Specimens of serum and bile from patients were assayed by an enzyme-linked immunosorbent assay to reveal antibodies specific to antigens from adult Clonorchis sinensis. Antibodies of the IgG isotype showed the greatest elevation during infection (Student's t-test, P < 0.001), whereas serum IgA and IgE and secretory IgA in bile were moderately elevated (P < 0.05). Major differences in the distribution of antibodies among the IgG subclasses were observed between patients who were and those who were not infected. IgG4 antibody levels were elevated in the serum and bile of infected patients, and there were significant correlations between the levels of IgG and IgG4 antibodies and the intensity of infection.

Adult↗
PubMed1992

[Clinical and scanning electron microscopic studies on Norwegian scabies infection].

Two typical cases of Norwegian scabies were studied clinically, scanning electron microscopically and histopathologically. Case 1 was a boy with Down's syndrome and case 2 was a man with adult T cell leukemia/lymphoma. Their clinical pictures showed hyperkeratotic plaques and warty crusts on hands, feet, ears, elbows and buttocks. Direct examination of the KOH preparation revealed many embryonated sarcoptic eggs, postpartum egg-shells, fecal pellets, larvae and male and female adult mites. Histopathologic examination showed several burrows inside the thick horny layer. Many sarcoptic egg-shells, mites and fecal pellets were found in the burrows. Psoriasiform hyperplasia and parakeratosis were noted, too. The size and shape of the sarcoptic eggs and the detailed structure of mites and molt were observed by using a scanning electron microscope. Besides, hook-like structures were noted at the tarsi of both forelegs and hindlegs. We suggest that the larvae crawl out from longitudinal openings in the egg-shell by the use of hook-like structures. The mites also used these hook-like structures to make the burrows. Scanning electron microscopy provides a good method to understand the dynamics of these burrowing parasites. It is helpful in illustrating the behavior of the scabies mites in their burrows in Norwegian scabies patients.

Adolescent↗
PubMed1991

Detection of antibodies to Angiostrongylus cantonensis in serum and cerebrospinal fluid of patients with eosinophilic meningitis.

Adult and young adult antigens of Angiostrongylus cantonensis were purified by immuno-affinity chromatography and used to detect antibody in serum and cerebrospinal fluid (CSF), by enzyme-linked immunosorbent assay (ELISA), in cases of human eosinophilic meningitis or meningoencephalitis. The levels of IgG, IgA, IgM and IgE antibodies to A. cantonensis in these patients were higher than levels in control subjects. Antibodies in patients detected against adult and young adult worm antigens of A. cantonensis did not differ significantly. Significantly higher IgM and IgE antibody levels were observed in serum compared with CSF from infected patients (Student's t-test, P less than 0.05). Both adult and young adult A. cantonensis antigens proved to be highly sensitive in ELISA for serum antibodies; however, the sensitivity was significantly lower in tests on CSF.

Angiostrongylus↗
PubMed1991

Experimental infection routes of Angiostrongylus cantonensis in mice.

Stomach intubation is the most common method used in the experimental infection of animals with Angiostrongylus cantonensis. In order to compare the effectiveness of other possible transmission methods, groups of BALB/c mice were given infective third-stage larvae of A. cantonensis by different routes including intraperitoneal or subcutaneous injections, and penetration of anal mucosa, vaginal mucosa, conjunctival mucosa, lacerated skin, unabraded skin, foot pad and tail skin, while stomach intubation was used as control. Recovery of fifth-stage larvae was higher in mice inoculated with third-stage larvae subcutaneously. Successful infections were established through all experimental transmission routes except tail skin penetration. This study suggests that oral infection may not be the only route for the transmission of human angiostrongyliasis, and subcutaneous infection may be a better method for experimental infection.

Anal Canal↗
PubMed1991

Clonorchiasis in Taiwan.

Since Ohi in 1915 found clonorchiasis patients in Taiwan, many surveys have shown that Miao-li in the north, Sun-moon Lake in the middle and Mei-nung in the south of Taiwan are three important endemic areas of clonorchiasis. In recent studies, the disease showed a tendency to extend its endemicity. Rats, cats, dogs and pigs are the natural reservoir hosts, and 17 species of fresh water fish are also infected with metacercaria. One definitive snail host, Parafossarulus manchouricus, and two other suggested snails, Semisulcospira libertina and Thiara granifera, may serve as the first intermediate host. The human incidence is about 20-50% in endemic areas and 10-20% in newly infected localities. Higher infection rates and more intensities of the worm burden are observed in the adult males. A higher incidence is also observed in the Hakkanense ethnic group. The infection according to the occupation has changed from merchants and government employees to farmers. Praziquantel, 60 mg/kg body weight divided into three doses by oral route in one day, has been given to 356 patients and revealed a 96% cure rate and a 99% egg reduction rate. This regimen is highly recommended for the treatment of clonorchiasis.

Animals↗
PubMed1991

Clinical studies on angiostrongyliasis cantonensis among children in Taiwan.

Angiostrongyliasis cantonensis is a disease commonly seen in Taiwan, especially in children during the summer rainy season. Most of the cases reported in other countries were adults and their clinical manifestations were different from children. Studies on special clinical characteristics of angiostrongyliasis cantonensis among 82 children in Taiwan were performed. Thirty-eight (46.3%) were male and 44 (53.7%) females, and 87% could be traced to a history of contact with the intermediate host, the giant African snail, Achatina fulica, which plays a major role in transmission. The incubation period (average: 13.2 days) was shorter in children than in adults (average: 16.5 days). In about one-third (30.5%) of the total cases, the clinical form was meningoencephalitis, which was higher than in adult cases seen in Thailand (5%). The most common clinical symptom was fever (91.5%), followed by vomiting and headache. The percentages of sixth and seventh cranial neuropathy associated with the disease were 19.5% and 11.0% respectively. Ophthalmologic fundoscopy showed that 25.0% with papilledema which was significantly higher than seen in adults (12%) in Thailand. Most of the cases in this study had peripheral leukocytosis (above 10,000/mm3) and eosinophilia (above 10%); the percentages were 82.9% and 84.1%, respectively. The worm recovery rate from cerebrospinal fluid by lumbar puncture of 82 cases was 41.5%; 141 worms were collected from one female patient using a pumping method. In the recent 2 years, albendazole and levamisole were used clinically with good result.

Adolescent↗
PubMed1991

Current status of food-borne parasitic zoonoses in Taiwan.

More than 50 species of zoonotic parasites (nematodes-18 spp., trematodes-19 spp., cestodes-10 spp., protozoa-2 spp., and arthropods-2 spp.) have been reported in Taiwan. Among them, Angiostrongylus cantonensis, Clonorchis sinensis and Taenia saginata are the most important and most common food-borne parasites. Angiostrongyliasis is highly endemic in southern and eastern Taiwan. About 80% of patients are children below 15 years of age, mostly infected after eating Achatina fulica during May and September. Patients residing in the mountainous and remote areas are more susceptible than those in the urban districts. Cipangopaludina chinensis and Ampullarium canaliculatus are additional important sources of infection. Albendazole is effective in treating infections in animals. Levamisole has been shown to shorten and lighten the course and symptoms in clinical trials. Clonorchiasis is endemic in Miao-li in northern, Sun-moon lake in central, and Mei-nung in southern Taiwan. Recent surveys, however, have shown endemic areas to be more extensive. Hakkanese and farmers have a greater tendency of infection than other groups. Praziquantel, 3 doses of 20 mg/kg body weight for one day, is an effective treatment. Taeniasis saginata is mainly caused by eating raw beef or viscera of wild animals by the aborigines. A single dose of 150 mg praziquantel cures almost 100%.

Animals↗
PubMed1991

Clinical and electrophysiological assessment of cerebral malaria.

From January 1980 to December 1990, six cases of malaria were observed; three cases were caused by plasmodium (P.) vivax and three by P. falciparum. Following a malaria episode, two cases (33.3%), developed cerebral malaria. Both of them were infected by P. falciparum. Neurological and electrodiagnostic investigations were scheduled throughout their clinical course. The first case manifested as a grand mal seizure, followed by myoclonic jerk and a comatous state. A suppression burst EEG observed before anti-malarial therapy was initiated. In the second case, a manifestation of encephalo-myelo-neuropathy was confirmed clinically and electrophysiologically. Although both cases occurred suddenly and were extremely severe, early anti-malarial therapy resulted in good responses without sequelae. The complete reversibility of the pathological event depends on early recognition and comprehensive therapy. Further, electrophysiological assessment is recommended for the detection of regional involvement in cerebral malaria.

Adult↗
PubMed1991

Clinical experience on malaria.

The 11 cases of malaria admitted to Kaohsiung Medical College Hospital in the past 10 years were analyzed to assess the characteristics of patients who acquired malaria parasite infection. Nine of the patients contracted malaria in Southeast Asia. Two men had received antimalarial chemoprophylaxis before they went abroad and another two men relapsed after antimalarial treatment. The initial symptoms and signs were nonspecific, including fever, chills, abdominal pain and hepatosplenomegaly. Seven patients responded well to the antimalarial regimens. Two persons developed meningeal malaria. Resistance to chloroquine and primaquine and even to quinine was noted in another two cases. Hypoglycemia was diagnosed in one of latter two patients who developed heavy parasitemia (26%), acute renal failure and died 5 days after treatment. Peripheral blood smear examination is a simple and quick method to make a diagnosis in any suspicious case. Resistance to chloroquine and primaquine is not uncommon, especially in those who acquired the infection in Southeast Asia. Changing to more potent agents and aggressive management in complicated cases is necessary.

Adult↗
PubMed1991

Medical treatment of malaria.

Eleven patients with 14 episodes of malaria have been admitted to Kaohsiung Medical College Hospital in the past 10 years and have been evaluated in this study. All of the patients were male and had traveling history to Africa or Southeast Asia. Eight of them were suffering from falciparum malaria and three vivax malaria. Initially they were treated with chloroquine (900 mg + 300 mg x 2 d) and primaquine (15 mg x 14 d). Quinine (650 mg q8h x 7-10 d) was used in one severe and another reinfected case of falciparum malaria. Cerebral malaria was noted in two falciparum cases with good response to treatment. One severe patient who also suffered from black water fever died of acute renal failure, even though quinine had been given immediately. It is concluded that chloroquine combined with primaquine is effective and safe in the treatment of vivax and falciparum malaria in Taiwan. Quinine should be given as soon as possible in a severe case of falciparum malaria. Supportive management and basic knowledge of epidemiology is also very important in the medical treatment of malaria.

Adult↗
PubMed1990

Characterization of monoclonal antibodies to young-adult worms of Angiostrongylus cantonensis.

Three IgG1 and one IgG2a monoclonal antibodies were obtained by fusion of NS-1 cells with spleen cells of BALB/C mice immunized with young-adult worm antigen of A. cantonensis. These 4 monoclonal antibodies were specific to A. cantonensis without cross-reactivity to any antigens of Toxocara canis, Ascaris suum, Clonorchis sinensis, Dirofilaria immitis, Paragonimus westermani, Gnathostoma spinigerum, Strongyloides stercoralis and Anisakis spp. detected by ELISA. The affinity constants of monoclonal antibodies specific to young-adult worms antigen of A. cantonensis were in the range of 10(7) M-1 to 10(9) M-1. The immunoblots showed that the 4 monoclonal antibodies recognized epitope on molecular weight of 204 kiloDaltons. They will be utilized to purify their corresponding antigen by an immunoaffinity column for the specific immunodiagnosis.

Angiostrongylus↗
PubMed1990

[Immunological screening of clonorchiasis].

Crude antigens of Clonorchis sinensis adult worms were purified by Sephadex G-200 column chromatography. A purified antigen was then applied to detect clonorchiasis patients and parasite-free subjects by an enzyme-linked immunosorbent assay (ELISA) and an intradermal test (IDT). The results of the ELISA showed that specific antibody levels of IgG, IgM, IgA, IgE and total IgE in 371 infected patients were significantly higher than those of 181 parasite-free subjects (Student's t-test, p less than 10(-6) or p less than 0.005). The sensitivity was 92.8% and the specificity was 89.0%. Significant correlations between the intensity of infection, expressed as egg per gram feces, and specific IgG, IgA and total IgE concentration were observed (linear regression, p less than 0.0005). Among the 309 subjects tested intradermally with Clonorchis antigen, 128 showed a positive reaction while all of the 60 parasite-free subjects showed negative results. By this test, the sensitivity was 49% and the specificity of IDT was 100%. The specific IgG, IgA and total IgE antibody levels of the IDT positive patients were significantly higher than those of the negative subjects (Student's t-test, p less than 0.0005). There was no correlation between the induced swelling diameter and the intensity of infection in IDT positive clonorchiasis patients. Cross reactions in ELISA were observed in patients infected with Capillaria philippinensis, Sparganum proliferum and Toxocara canis, when the antigens prepared in the present study were used.

Animals↗
PubMed1990

Fate of ingested immunoglobulin G in the mosquito Aedes aegypti (Diptera: Culicidae).

The amount of bloodmeals ingested by Aedes aegypti was estimated to be 3.00 +/- 1.05 mg (2.84 +/- 0.99 microliters) in average. The feeding time of a mosquito was not necessarily associated with the quantity of the bloodmeal. Nevertheless, the number of egg laid after bloodfeeding was apparently dependent on the volume of ingested bloodmeals. The change of immunoglobulin G (IgG) in the ingested bloodmeals of Aedes aegypti was also evaluated by ELISA. To detect the survival of ingested IgG, 5-day-old adult female mosquitoes were allowed to feed on a human arm. After completion of feeding, 3 engorged mosquitoes were selected on the basis of 6-hour intervals until the 54th hour post ingestion. Selected specimens were deprived of their legs and wings, homgenized and centrifuged. The supernatants were collected for ELISA procedure. The control groups included the blank (PBS) and unfed mosquitoes. All OD405 values representing the amount of IgG in the ingested bloodmeal were evaluated as 1.702 +/- 0.017, 0.469 +/- 0.046, 0.414 +/- 0.084, 0.231 +/- 0.012, 0.180 +/- 0.025, 0.172 +/- 0.006, 0.163 +/- 0.012, 0.173 +/- 0.007, 0.168 +/- 0.012, and 0.169 +/- 0.014, respectively for each interval. A blood sample taken from the same person fed to mosquitoes was evaluated to be 1.716 +/- 0.012. The OD405 values of the blank and the unfed group were 0.156 +/- 0.019 and 0.159 +/- 0.009, respectively. The result showed that IgG ingested by Aedes aegypti may be digested vigorously within 6 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗