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Biomedical subjects

S Panyim

Publications and source records attributed to S Panyim.

At least 37 records · Page 2Linked to original sources
PubMed1998

Experimental transmission of white spot syndrome virus (WSSV) from crabs to shrimp Penaeus monodon.

White spot syndrome virus (WSSV) of the black tiger prawn Penaeus monodon is a recently discovered baculo-like virus disease which is currently the cause of very serious and widespread losses in the shrimp industry in Thailand and elsewhere in Asia. Three suspected crab carriers of this virus commonly found in shrimp-rearing areas were investigated. These were Sesarma sp., Scylla serrata and Uca pugilator. All these crabs could be infected with WSSV by injection and they sustained heavy viral infections for up to 45 d (confirmed by normal histology, specific in situ DNA hybridization and PCR amplification) without visible signs of disease or mortality. All of them also transferred the disease to P. monodon via water while physically separated in aquarium cohabitation tests. Transfer of the virus to the shrimp was monitored using in situ DNA hybridization and PCR assay at 12 h intervals after cohabitation began. With U. pugilator, WSSV could be detected in the shrimp cohabitants after 24 h using PCR amplification and after 60 h using in situ hybridization. With S. serrata, the shrimp were positive for WSSV after 36 h using PCR and after 60 h using DNA in situ hybridization. With Sesarma sp. they were positive after 48 h using PCR and 72 h using in situ hybridization. These laboratory studies demonstrated that crab carriers of WSSV may pose a real threat to cultivated shrimp. However, the studies were carried out in containers with a small volume and with relatively clean sea water as compared to shrimp cultivation ponds. Pond-based studies are now needed to determine whether factors such as pond volume, pond water quality and shrimp and crab behavior can influence the rate and success of transfer.

Animals↗
PubMed1998

Effects on larvicidal activity of single proline substitutions in alpha3 or alpha4 of the Bacillus thuringiensis Cry4B toxin.

The possible role of alpha-helices 3 and 4 in toxicity of the dipteran-active Bacillus thuringiensis Cry4B delta-endotoxin was investigated by employing proline substitutions via site-directed mutagenesis. Similar to the wild-type Cry4B, the mutant toxins were over-expressed in Escherichia coli as cytoplasmic inclusions and were structurally stable upon solubilization and trypsin activation. The substitution of glutamine 149 by proline in the center of helix 4 (Q149P) resulted in a nearly complete loss of toxicity against Aedes aegypti mosquito-larvae. However, single proline replacements near the center of helix 3 (V119P) and at the N-terminus of helix 4 (Q140P) did not decrease larvicidal activity. The toxicity of E. coli cells expressing the wild-type toxin was significantly reduced by two-hour preincubation with the non-toxic mutant (Q149P), thus indicating that the primary binding step was not affected by the proline substitution in helix 4. The results therefore reveal a crucial role for helix 4 of the Cry4B toxin in toxicity, possibly in membrane insertion and pore formation rather than in receptor recognition.

Aedes↗
PubMed1995

A simple, rapid and sensitive detection of salmonella in food by polymerase chain reaction.

A polymerase chain reaction (PCR) method was developed for detection of salmonella in food. A set of PCR primers was designed to amplify a 199 bp salmonella-specific DNA fragment derived from a repetitive DNA of Salmonella Weltevreden. The assay detected all 52 most prevalent serovars found in contaminated food in Thailand and no cross-reaction was observed with other non-salmonella organisms. The limit of detection was 1 fg of purified target DNA or five bacteria from pure culture. The detection of artificially contaminated food performed following a 6 h enrichment step was three bacteria per gram and the result was obtained within 4 h.

Animals↗
PubMed1995

Simple nonradioactive DNA hybridization method for identification of sibling species of Anopheles dirus (Diptera: Culicidae) complex.

A simple method was developed for species identification of mosquitoes in the Anopheles dirus complex found in Thailand using horseradish peroxidase-labeled DNA probes and a chemiluminescent detection system. Species-specific DNA probes for Anopheles dirus, species B, C, and D detected 1-5 ng of target DNA, a sensitivity that was comparable with the radioisotopic detection system. Identification of individual mosquitoes was performed by dot-blot analysis of crude mosquito DNA. The method allowed identification using third or fourth instars as well as the adult head, thorax, or abdomen. This technique successfully identified the sibling species of the A. dirus complex in field collections.

Animals↗
PubMed1995

Larval habitats of malaria vectors and other Anopheles mosquitoes around a transmission focus in northwestern Thailand.

We sampled 199 bodies of water for Anopheles larvae around a malaria-endemic village near Mae Sot, Thailand, over 2 years. Anopheles dirus species A and D occurred in 54 small, well-shaded, stream and temporary ground pools. The larval habitat of species D is reported for the first time. Anopheles minimus species A occurred in 8 samples from slow-moving streams, in 8 from rice fields, and in 2 from ground pools. Anopheles pseudowillmori occurred in one sample from a ground pool, in 3 from streams, and in 9 from rice fields.

Animals↗
PubMed1995

PCR amplification of crude blood on microscope slides in the diagnosis of Trypanosoma evansi infection in dairy cattle.

In this study, we compared four T. evansi detection tests (Direct examination, Card Agglutination mouse inoculation and Polymerase Chain Reaction (PCR) in a natural infection of dairy cattle in central Thailand. The samples for PCR amplification were collected either in microfuge tubes or on microscope slides and the amplification results were compared. Collecting the samples on slides was faster and more convenient than collection in tubes. Comparable results were obtained from PCR amplification of both tube- and slide collected samples, processed twelve to fourteen days after collection. PCR was the most sensitive of the methods under comparison, using the mouse inoculation test as golden standard. The specificity of the PCR test under study is further discussed in this paper.

Agglutination Tests↗
PubMed1994

Giant catfish Pangasianodon gigas growth hormone-encoding cDNA: cloning and sequencing by one-sided polymerase chain reaction.

cDNA clones encoding giant catfish (Pangasianodon gigas) growth hormone (GH) have been isolated using a polymerase chain reaction (PCR) strategy. Pairwise combinations of degenerate and general primers allowed for the amplification of regions both 3' and 5' to the point of entry into the message. The amplified PCR products were cloned and sequenced. The cDNA sequence was found to encode a polypeptide of 200 amino acids (aa), including a putative signal peptide of 22 aa. The 5' and 3' untranslated regions of the message are 58 and 515 nucleotides long, respectively. The giant catfish GH displays the highest aa sequence homology with the carp GH, with 80% of sequence identity. Moreover, giant catfish GH has structural features in common with both mammalian and avian GH polypeptides, and also contains the domains of conserved sequence found in other GH.

Amino Acid Sequence↗
PubMed1994

A highly sensitive, rapid, and simple polymerase chain reaction-based method to detect human malaria (Plasmodium falciparum and Plasmodium vivax) in blood samples.

A highly sensitive, rapid and simple method to detect human malaria in blood samples was developed. Malaria parasite DNA in blood from a fingerprick was directly amplified by the polymerase chain reaction (PCR) using two sets of primers to yield a 206-basepair (bp) product for Plasmodium falciparum and a 183-bp product for P. vivax. Both were easily visualized in an ethidium bromide-stained agarose gel, allowing identification of the two human malaria species in a single amplification reaction. As little as a one P. falciparum and/or P. vivax parasite per microliter of blood was detectable by this method, a sensitivity superior to that of thick blood film microscopy. The total time required for diagnosis of 48 blood samples, starting from fingerprick blood collection, was approximately 4 hr. When compared with microscopic examination by an expert microscopist, results showed a sensitivity of 89% for P. falciparum and 91% for P. vivax and an overall specificity of 94%. Six infected blood samples classified by microscopy as single species were diagnosed by the PCR method as being mixed P. falciparum and P. vivax infections. The high sensitivity, rapidity, and simplicity of the method should make it attractive for a large-scale epidemiology study, follow-up of drug treatment, and immunization trials.

Animals↗
PubMed1994

HLA class II polymorphism in Thai insulin-dependent diabetes mellitus.

Fifty-seven Thai IDDM patients were studied for HLA class I by LCT and HLA class II by LCT and PCR-RFLP. It was found that DRB1*0301, DR3, DQB1*0201, DRB3*0202, DQA1*0501 and DQ2 were significantly increased with R.R. = 10.0, 6.6, 4.2, 3.7, 3.5 and 3.2 and Pc < 0.005, 0.001, 0.01, 0.005, 0.01 and 0.005, respectively. In contrast, DQA1*0101, DRB3*0301, DR5 and DQ1 were significantly decreased with R.R. = 0.2, 0.2, 0.3 and 0.5 and Pc < 0.01, 0.05, 0.01 and 0.05, respectively. The primary factor for IDDM susceptibility is probably DRB1. The homozygous Asp57/Asp57 DQB1 genotype appears to determine resistance to IDDM while Arg52-DQA1, non-Asp57-DQB1 haplotype confers susceptibility to IDDM. The common haplotypes in Thai IDDM cases were DRB1*0301, DRB3*0202, DQA1*0501, DQB1*0201, DPB1*0401 and DRB1*0405, DQA1*0301, DQB1*0402 (or 0401 or 0302), DPB1*0401 (or 0301 or 1501). The less common haplotypes were DRB1*0406, DQA1*0301, DPB1*0302, DPB1*0501 and DRB1*1202, DRB1*0301, DQA1*0601, DQB1*0301, DPB1*0501. DR3 was increased in both gender groups with early onset (< 10 years) regardless of a family history of DM. However, DR3/DR4 genotype was increased only in female patients with a family history of DM and early onset. In conclusion, DRB1, DRB3, DQA1 and DQB1, but not DPB1 are involved in the occurrence of IDDM. The cooperation of HLA class II and X-chromosome may contribute to the development of IDDM in addition to other factors such as other genetic (chromosomes 11, 19, 14, 7), immunologic and environmental factors which require further study.

Adolescent↗
PubMed1994

Field evaluation of simplified radioactive and nonradioactive DNA probe methods for the diagnosis of falciparum malaria.

Specific DNA probe hybridization technique is one method of choice for detection of malaria infection. It provides an obvious advantage over conventional microscopy when large numbers of samples are simultaneously monitored. The method was simplified so that preparation and processing of blood specimens were all performed on membrane filters. Background signals generated from blood components were removed by treating samples spotted on the membrane with a series of buffer washes without the necessity of a protease digestion step. Hybridization was monitored using either 32P-or digoxigenin-labeled DNA probe. 849 field samples collected from various malaria endemic areas in Thailand have been evaluated by this protocol and compared with microscopic examination. Sensitivity obtained by this procedure was comparable to that of microscopy at a malaria clinic. The specificities of both types of DNA probes were better than 93%, but digoxigenin-labeled probe performed better than 32P-labeled one when the numbers of parasites were less than 25 per 200 white blood cells.

DNA Probes↗
PubMed1994

A simplified and highly sensitive detection of Trypanosoma evansi by DNA amplification.

In Southeast Asia Trypanosoma evansi infection is a disease of economic importance since it affects the health of buffalo, cattle and swine. The acute stage symptoms include abortion, central nervous system disorder and even death, and in the chronic condition working capacity and productivity of the animals are affected. A polymerase chain reaction (PCR)-based detection technique has been developed with a sensitivity of 0.5 pg of parasite DNA or one single parasite in 10 microliters of blood samples which were allowed to clot and then boiled before DNA amplification. This permitted storage of blood collection at ambient temperature for at least one month. Phosphate-saline-glucose solution, normally used as trypanosome maintenance buffer, inhibited PCR. Although DNA primers used were derived from T. evansi specific sequence, amplification of the genome of T. brucei and T. equiperdum generated the same 227 bp fragment. This method should now make it possible to detect infections in livestock in the very early stages where microscope examination is equivocal and to monitor groups of animals after trypanocidal treatment.

Animals↗
PubMed1993

Sensitive detection of Plasmodium falciparum in blood and mosquito by DNA amplification.

By means of enzymatic amplification of Plasmodium falciparum DNA using the polymerase chain reaction (PCR), we have been able to detect as little as 20 parasites in 20 ml infected human blood based on the visualization of a 206 bp fragment in ethidium bromide-stained agarose gel. Comparison, through microscopic examination of 2030 blood samples collected from various endemic areas in Thailand, indicates that the PCR-based detection system is 96% specific and 81% sensitive, with a disagreement of 6.6%. The same protocol can be applied to detect a minimum of 10 sporozoites or a single oocyst dissected from P. falciparum-infected mosquito.

Animals↗
PubMed1992

A specific DNA probe which identifies Babesia bovis in whole blood.

A genomic library of Babesia bovis DNA from the Mexican strain M was constructed in plasmid pUN121 and cloned in Escherichia coli. Several recombinants which hybridized strongly to radioactively labeled B. bovis genomic DNA in an in situ screening were selected and further analyzed for those which specifically hybridized to B. bovis DNA. It was found that pMU-B1 had the highest sensitivity, detecting 25 pg of purified B. bovis DNA, and 300 parasites in 10 microliters of whole infected blood, or 0.00025% parasitemia. pMU-B1 contained a 6.0 kb B. bovis DNA insert which did not cross-hybridize to Babesia bigemina, Trypanosoma evansi, Plasmodium falciparum, Anaplasma marginale, Boophilus microplus and cow DNA. In the Southern blot analysis of genomic DNA, pMU-B1 could differentiate between two B. bovis geographic isolates, Mexican strain M and Thai isolate TS4. Thus, the pMU-B1 probe will be useful in the diagnosis of Babesia infection in cattle and ticks, and in the differentiation of B. bovis strains.

Animals↗
PubMed1992

Detection of Plasmodium falciparum by polymerase chain reaction in a field study.

Detection of Plasmodium falciparum by polymerase chain reaction (PCR) was evaluated in 33 P. falciparum-infected patients with two different amplification systems over 5-7 days of curative treatment. In the K1-14 system, a P. falciparum DNA fragment of 206 bp was detected, and in the circumsporozoite (CS) system, a fragment of 800 bp was detected. The K1-14 and CS systems identified 95% and 93%, respectively, of 103 microscopically identified specimens; both systems detected as few as 11 parasites/microliters among these specimens. Specimens from 20 smear- and history-negative controls were all negative by both PCR systems. The K1-14 and CS systems detected P. falciparum DNA in 53% and 20%, respectively, of blood films collected on the first day and 3% and 0 of the blood films collected on the fourth day after reversion to microscopic negative. The simultaneous use of two independent PCR systems to monitor patients during curative treatment of P. falciparum infections convincingly demonstrated that P. falciparum DNA was present transiently in the blood of infected patients at a time when the parasite could no longer be detected microscopically.

Animals↗
PubMed1992

Population genetic evidence for species A, B, C and D of the Anopheles dirus complex in Thailand and enzyme electromorphs for their identification.

Mixtures of chromosomal forms A, B, C and D in natural populations of Anopheles dirus Peyton & Harrison sensu lato in Thailand show significant positive values of Wright's fixation index for six enzyme-electromorph loci. The mean value of FIS over all loci was found to be +0.28 (SD 0.02), with a range of +0.57 (Odh) to +0.10 (Idh-2). Partitioning electromorph data for the chromosomal forms reduces the mean FIS to 0.03 (SD 0.01), which suggests that positive assortative mating is a characteristic of each form. This supports the hypothesis that the chromosomal/electrophoretic forms A, B, C and D represent four distinct biological species within the An. dirus complex. An example is given of the use of enzyme electromorphs as a means of vector identification during a malaria entomological field study involving a mixture of An. dirus species A and D. Electromorph identifications of 323 sp. A and 161 sp. D were more than 98% correct when cross-referenced to specific DNA probes.

Alleles↗
PubMed1991

A novel detection of a single Plasmodium falciparum in infected blood.

Detection of Plasmodium falciparum malaria by a specific DNA probe is a highly promising means for epidemiological surveillance of human malaria. However, none of presently available DNA probe methods could detect as little as a few parasites in infected blood. By amplification of a specific 206 base pairs P. falciparum DNA sequence using the polymerase chain reaction (PCR), as little as 0.01 picogram DNA or one-half of a parasite was sufficient for a specific detection. A PCR procedure for detection of P. falciparum in infected blood without prior DNA extraction was also developed which was sensitive for a single parasite. The procedure was simple and should be applicable for a large scale epidemiological study involving a very low parasitemia situation.

Animals↗