Table of Content

28 February 1994, Volume 12 Issue 1

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STUDY ON THE TRANSMISSION THRESHOLD OF FILARIASISCollaborating Research Group On the Transmission Threshold Of Filariasis

1994, 12(1):  1-6. 

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Twenty one villages from ten provinces and one autonomous region with different mf rates in population and different levels of mean mf density per 60 μl blood in positive cases and representative species of filaria and vector after DEC treatment were selected as study sites.In these villages a longitudinal investigation for a period of 3-5 years was carried out without adopting any control measure.The main results were:1.Among 279 residual microfilaremia cases,235 (84.2%) turned negative spontaneously and successively.The negative conversion rates were 86.6% (46/53) in malayan cases,60.8%(28/46) in bancroftian cases after 3 years’ follow up, and 100% (29 /29) in malayan cases, 87.4% (132/151) in bancraftian cases after 4 5 years follow up. Among 110 bancroftian cases followed up to seven years,109(99.1%)turned negative.2.Twenty two new microfilaremia cases were detected,of which,18 might be missed in previous blood examination,4 might be new infection.3. Mf rate in the population in twenty villages has been trending down,whereas in one village fluctuated around the original level.Among the 20 villages,no microfilaremia case was found in 7 villages.4. The natural infection rates of filarial larvae and infective rates in mosquito vectors were in descending trend in most of these villages,and no filarial larva was found in 12 villages.It was demonstrated that under these circumstances where the man-biting rate of mosquito vectors was within 20-50 mosquito per person and night by using the method of human bait bed net trapping, and about 40% of the population used bed-net reasonably,the mf rates in the 20 study villages were found to be ≤1.71% in areas of bancroftian filariasis,≤1.55%in areas of malayan filariasis and the mean mf density of residual microfilaremia cases in most villages was 3-10 mf per 60 μl blood,moderate mf density was found only in individual case,filariasis transmission has already been brought down below the threshold,and tended to be interrupted.In one village of malayan filariasis,the mf rate in population was 2.31% and there was one case of microfilaremia with density of 54mf/60 μl,filariasis transmission was at the critical level.

EFFECT OF EARLY TREATMENT OF ARTEMETHER AGAINST SCHISTOSOMIASIS IN MICE

1994, 12(1):  7-10. 

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When artemether(Art)was given ig to mice on the day of infection with Schistosoma japonicum cercariae at a single dose of 300 mg.kg -1 and followed by the repeated dosing at 2-3 wk intervals,the total and female worm reduction rates as compared with the control were evident.In mice treated ig with Art on d 7 at the same dosage and repeeated once every wk for 4 times,the female worm reduction rates were about or over 90%,and part of the animals was free from female worm.Nevertheless,the liver appearance of some treated animals was similar to that of the normal mouse.The results indicated that if Art was given in the early stage after infection,it could be expected to protect the host from schistosomal infection or reduce the intensity of infection.

CHARACTERIZATION OF ISOELECTRIC POINT(pI) FRACTIONS OF SOLUBLE EGG ANTIGEN OF SCHISTOSOMA JAPONICUM

1994, 12(1):  19-19. 

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The soluble egg antigen of Schistosoma japonicum was fractionated into 20 individual isoelectric point (pI) fractions with different pIs ranging from 1.86-11.40 by isoelectric focusing (IEF). The fractions were tested for humoral and cellular responses, as well as in vitro granuloma formations.The results indicated that the fractions in the acidic region(pI 3.78-5.54)may play an important role in granuloma elicitation in schistosomiasis japonica,and antibodies are also involved in the regulation of granuloma formation especially at the early stage (5 week postinfection).

MOLECULAR RECOGNITION BETWEEN GlcNAc AND PLASMODIUM FALCIPARUM MEROZOITES

1994, 12(1):  20-22. 

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In this study p aminopheny1 2 acetamido 2 deoxy β D glucopyranoside was bound covalently to bovine serum albumin(BSA)to form neoglycoprotein(GlcNAc BSA).The antigenicity of BSA and the pyranose structure of the sugar was preserved.By using the neoglycoprotein antibody against BSA and staphylococcal protein A gold(SPA gold), Plasmodium falciparum FCC 1/HN merozoites were immunolabelled.The labelled sample was observed under transmission electron microscope(TEM).The TEM pictures showed that colloidal gold pellets were distributed all over the merozoite surface.This is the first report on the direct experimental evidence of molecular recognition between GlcNAc BSA(or GlcNAc)and Plasmodium falciparum merozoites.But free GlcNAc or even GlcN can inhibit the immunolabeleation.The results support the hypothesis that,besides N acetylneuraminic acid,GlcNAc is involved as another recognized site on GPA for Plasmodium falciparum .Thus we further confirmd that N acetyl of GlcNAc is not necessary for the recognition.

CLONING AND SEQUENCING OF A DNA FRAGMENT FROM PLASMODIUM FALCIPARUM FCC1/HN ISOLATE

1994, 12(1):  23-26. 

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A specific DNA fragment isolated from Plasmodium falciparum FCC1/HN isolate has been cloned in Bam H1 site of pUC18 and first partially sequenced by Sangers method.The results show∶G+C percent of DNA sequence is 26.8%,and the cloned DNA has many restriciton sites which are conventional for subcloning.The authors suggest that this clone and sequence may be used as a guide for developing a DNA probe or PCR primers.

STUDIES ON THE COMPONENTS OF TRACE ELEMENTS AND MACRO ELEMENTS IN HEMOLYMPH OF ANOPHELES ANTHROPOPHAGUS

1994, 12(1):  27-30. 

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The elements in hemolymph of An.anthropophagus were determined by ICAP.There were 18 kinds of trace elements such as Fe,Zn,Cu,Mn,Cr,Mo,Co,Ni,V,Sr,B,Al,Ba,Zr,Cd,Pb,Ga,Li and 6 kinds of macro elements such as Ca,Mg,K,Na,S,P in the hemolymph of the mosquito.The contents of the macro elements and Fe in hemolymph of newly emerged mosquitoes were significantly higher than those of mosquitoes after taking blood meal,whereas Zn and Al were lower.Comparing elements in hemolymph of An.anthropophagus and An.sinensis ,there were 14 kinds of elements in newly emerged mosquitoes with striking significant difference,while there were 13 kinds of elements with striking significan difference in the mosquitoes after taking blood meal.Comparing elements in the hemolymph of An.anthropophagus and Ae.albopictus ,there were 13 kinds of elements with striking significant difference in the hemolymph of newly emerged mosquitoes and the mosquitoes after ta king blood meal.The results suggested that the components of elements in hemolymph were relevant to the nutritional metabolism and development of mosquitoes,and that mosquitoes of different species and with different sensibilities to malaria parasites also showed difference in the contents of elements in their hemolymph.

LONGITUDINAL SURVEILLANCE OF CHLOROQUINE RESISTANCE OF PLASMODIUM FALCIPARUM AFTER CESSATION OF MEDICATION IN SOUTH YUNNAN 

1994, 12(1):  31-33. 

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The resistance of P.falciparum to chloroquine was assayed by in vitro microtest in 1981 and after cessation of medication in 1984 , 1988- 1990 and 1992 in south Yunnan Province of China.The resistance rates were 97.4% (38/ 39) , 100% (25/ 25) , 96.1% (73/ 76) and 93.7% (59/ 63) ,respectively;ID 50 were 170,132 , 125 and 110 nmol/L ;ID 95 were 1 000,740 , 707 and 576nmol/ L;mean dosages for complete inhibition of schizont formation were 55.4 , 46.7 , 45.8 and 35.4 (pmol/well).A comparison of the results in 1981 , 1984 , 1988- 1990 and 1992 ,the resistance rate showed no marked change,ID 50 dropped 22.3% ( P 0.05) , 26.4% ( P 0.05) and 35.3% ( P 0.01) ;ID 95 declined 26.0% ( P 0.05) , 29.3% ( P 0.05) and 42.2% ( P 0.01) ;mean dosage of inhibition dropped 15.7% ( P 0.05) , 17.3% ( P 0.05) and 36.1% ( P 0.01) . The results show that the extent of resistance in chloroquine resistant P. falciparum to chloroquine in south Yunnan has been declined markedly,indicating that coresistance was variable and dropped along with the declining of drug pressure.

DIAGNOSIS OF FALCIPARUM MALARIA BY POLYMERASE CHAIN REACTION 

1994, 12(1):  37-39. 

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Polymerase Chain Reaction(PCR) method using a pair of Plasmodium falciparum specific oligonucleotides as primers was used to detect malaria patient blood samples collected from Yunnan endemic malarious area.The results showed that a DNA fragment of 492 bp was amplified in all 53 microscopically diagnosed P.falciparum samples,but negative in 8 P. vivax samples and 12 normal blood samples.This method seems to have high sensitivity and high specificity.

ROLE OF SEVERAL HOSTS IN TRANSMISSION OF SCHISTOSOMIASIS JAPONICA IN LAKE REGION

1994, 12(1):  52-55. 

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From 1989 to 1990,an investigation was conducted in three villages in Junsan township,Hanyang County,Hubei Province.The results showed that the infection rates of local residents were 55.1%,49.5%and 44.3%,respectively;the EPG were 5.6,5.2 and 2.0,respectively;the relative transmission index(RTI)were 7.1%,being highest in the age group 30-39 years.The relative index of potential contamination(IPC)was 67.2% in the age group 20-49 years,this group was considered as the main transmission source in the population.In animal hosts buffaloes,pigs and dogs,the infection rates were 35.7%,60.0% and 75.0%,respectively;MPG(miracidium per gram),0.4,0.4 and 80.4,respectively;RTI(relative transmission index),38.6%,7.7 and 46.6%,respectively.The infection rates of pigs and dogs were high in Huangshi village,while the infection rate of buffaloes was high in Chuangjiang village. These results coincided with the transmission of schistosomiasis in these villages.The results showed that dogs as the main transmission sources had important significance in the epidemiology of schistosmiasis and that buffaloes and pigs herd and fed in the snail habitats could be heavily infected.

EFFECT OF COMBINED CHEMOTHERAPY AGAINST HUMAN INTESTINAL NEMATODE EGGS

1994, 12(1):  56-59. 

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The effect of a combination of albendazole and mebendazol was evaluated by stool exa mination in 7 patients with Ascaris lumbricoides eggs,7 patients with Trichuris trichiura eggs and 9 patients with hookworm eggs.Albendazole and mebendazole were given at 300 mg and 375 mg,respectively.Both drugs were divided into 3 parts, one part b.id., and given in 1.5 days.The fecal eggs turned negative in all the patients with Ascaris infection in 3 days,while the fecal eggs were negative in all patients with Trichuris or hookworm infection in 5 days.The development rates of the eggs were remarkably lower post treatment than pre treatment.It was found that the ovicidal rates in human ascariasis,trichuriasis and ancylostomiasis were 98.8% ,100% and 100%,respectively on the second day following the initiation of treatment.The results showed that the worm repelling and ovicidal effect of the combined chemotherapy was more evident.

STUDY ON THE EFFECT OF MONOCLONAL ANTIBODIES ON GIARDIA LAMBLIA IN VITRO

1994, 12(1):  60-62. 

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Monoclonal antibodies(McAbs)were generated by fusion of SP2/0 myeloma cells with spleen cells from BALB/c mice immunized with Giardia lamblia trophozoites.To define the effect of the McAb on Giardia lamblia ,trophozoites were subcultured axenically after contact with McAb for 1 h at 37℃.The McAbs 1G 5 and 1E 2(both IgG 1)were able to inhibit the growth of trophozoite at the rate of 63.4% and 35%, respectively.The inhibitory effect was decreased along with the decreasing quantity of McAb(from dilution 1∶45 to 1∶225)added to the TYI S 33 medium.The actions of McAbs could be eliminated by absorption with trophzoites and not be influenced by complement in fresh guinea pig serum,thus the actions of McAbs appeared to be specific and complement independent.