Displaying publications 1 - 20 of 183 in total

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  1. Yoke OP, Sudderuddin KI
    PMID: 818717
    Toxicological studies of four insecticides (malathion, carbaryl, bioresmethrin, and GH 74) against Musca domestica vicinia (Ampang strain) were undertaken with particular reference to age, sex and posttreatment temperature. It was found that bioresmethrin and GH 74, both with a negative temperature coefficient, have great potential for use against houseflies. In vitro inhibitory studies of head and body esterases showed that unlike malathion and carbaryl, bioresmethrin had only negligible effect on these enzymes. The possibilities of using bioresmethrin and GH 74 for controlling the housefly problem in the Cameron Highlands, West Malaysia are discussed.
    Matched MeSH terms: Biological Assay
  2. Foo AE, Yap HH
    PMID: 6128794
    Comparative laboratory bioassays of three formulations of Bacillus thuringiensis H-14 (IPS-78, San 402-I and Bactimos) were conducted against late 3rd/early 4th instar larvae of four species of mosquito, viz., Aedes aegypti, Culex quinquefasciatus, Anopheles balabacensis and Mansonia (Mansonioides) indiana, in Malaysia. From the average response of the mosquito larvae to the three formulations of B. thuringiensis H-14, Ae. aegypti was found to be most susceptible, followed by Cx. quinquefasciatus, An. balabacensis and M. (M.) indiana in decreasing order. The LC50 values for Ae. aegypti, Cx. quinquefasciatus, An. balabacensis and M. (M.) indiana after a 48-hour exposure to IPS-78 formulation were 50.9, 129.3, 117.8 and 169.6 International Toxic Unit (ITU) Ae. ae./l; to San 402-I formulation were 54.6, 223.1, 405.1 and 177.6 ITU Ae. ae/l and to Bactimos formulation were 57.2, 175.7, 35.6 and 514.5 ITU Ae. ae./l respectively. The efficacy of the bacterial product was also found to be determined by its formulation in relation to the feeding and resting habits of the mosquito larvae. No delayed pupation or emergence was observed on the larvae exposed to B. thuringiensis H-14 at sub-lethal concentrations.
    Matched MeSH terms: Biological Assay
  3. Serit MA, Yap HH
    PMID: 6151744
    Comparative laboratory bioassays of Tolypocladium cylindrosporum, California strain (Kal) was conducted against third instar larvae of four species of mosquito, viz. Aedes aegypti, Anopheles balabacensis, Culex quinquefasciatus and Mansonia uniformis in Malaysia. Of the four mosquito species tested, Ma. uniformis was found to be the most susceptible, followed by Cx. quinquefasciatus, An. balabacensis and Ae. aegypti, in a decreasing order. The LC50 values for Ma. uniformis, Cx. quinquefasciatus, An. balabacensis and Ae. aegypti after four days of exposure were 1.18 X 10(4), 2.02 X 10(5), 4.76 X 10(5) and 1.84 X 10(7) spores per ml test media, respectively. The high sensitivity of Ma. uniformis and its longer life cycle seems to indicate that T. cylindrosporum Kal has good potential as a biocontrol agent for this species of mosquito. But, for Ae. aegypti, this fungus appears to be less effective.
    Matched MeSH terms: Biological Assay
  4. Ismail A
    Biochem Biophys Res Commun, 1988 Jan 15;150(1):18-24.
    PMID: 2962581
    This study was initiated to determine the mechanism of iron-uptake in Salmonella typhi. When stressed for iron, microorganisms produce siderophores to obtain the necessary nutrient. Generally two types of siderophores exist: the phenolate-type predominantly produced by bacteria and the hydroxamate-type commonly secreted by fungi. Results of this investigation showed that S. typhi produced siderophores of the phenolate-type since culture supernatant of the organism grown under iron-deprivation supported the growth of the phenolate-dependent auxotroph. The culture supernatant when extracted for phenolate siderophores, also supported the growth of the phenolate auxotroph but not the hydroxamate auxotroph. Production of phenolate-type siderophores were further confirmed using biochemical assays. These results showed that S. typhi utilized the high-affinity iron transport system to obtain the necessary iron.
    Matched MeSH terms: Biological Assay
  5. Lee HL, Seleena P
    PMID: 2237596
    A nationwide screening program searching for microbial control agents of mosquitos was initiated in Malaysia in 1986. A total of 725 samples were collected and 2,394 bacterial colonies were isolated and screened for larvicidal activity. From such screening, 20 Bacillus thuringiensis, 6 B. sphaericus, 1 Clostridium bifermentans and 2 Pseudomonas pseudomallei larvicidal isolates were obtained. Of these, a new B. thuringiensis named as subspecies malaysianensis was found, while the C. bifermentans was also a new anaerobe individualized as serovar malaysia. It was concluded that this screening program was highly successful.
    Matched MeSH terms: Biological Assay
  6. Tan NH, Armugam A
    Toxicon, 1990;28(10):1193-8.
    PMID: 2264068
    The in vivo interactions between alpha-neurotoxin, cardiotoxin and two phospholipases A2 (sputa-phospholipase A2-1 and 3) isolated from Malayan cobra venom were assessed by examining the effects of simultaneous injection of sub-LD50 dose of one toxin on (i) i.v. LD50 S of the other toxins in mice; and (ii) mean survival times of mice injected with lethal doses of the other toxins. While LD50 measurements did not reveal any interaction between the toxins in vivo, survival time measurements suggest a synergy between the neurotoxin and sputa-phospholipase A2-1 and between sputa-phospholipase A2-1 and sputa-phospholipase A2-3. Our results also suggest that both sputa-phospholipases A2 interfere with the lethal action of the cardiotoxin, resulting in prolongation of the mean survival time of mice injected with a lethal dose of cardiotoxin. The patterns of in vivo interactions between phospholipase A2 and other venom toxins appear to depend on the nature and mode of pharmacological action of the phospholipase A2.
    Matched MeSH terms: Biological Assay
  7. Vythilingam I, Chiang GL, Amatachaya C
    PMID: 1355928
    The efficacy of two formulations, wettable powder and emulsifiable concentrate, of cyfluthrin sprayed on plywood [10 mg (ai)/m2] was assessed against six species of mosquitos. The bioassay followed the WHO standard method, with some modification for the bioassay of insecticidal deposits on wall surfaces. The results indicated that these two formulations of cyfluthrin were effective against Anopheles dirus and Mansonia uniformis, moderately toxic to Aedes aegypti and Ae. albopictus in decreasing mortality through out the study period. It was least effective against Culex quinquefasciatus and An. maculatus, respectively. There was no statistically significant difference between these two formulations.
    Matched MeSH terms: Biological Assay
  8. Lee HL, Abimbola O, Singh KI
    PMID: 1488701
    Rapid enzyme microassays for the detection of resistance due to organophosphate and carbamate in individual field-collected strains of Culex quinquefasciatus adults were conducted. These tests allowed accurate differentiation by eye, on the basis of color changes of susceptible and resistant individuals. Two separate tests were conducted for the biochemical assays. In the insensitive acetylcholinesterase (AChE) test, acetylthiocholine iodide (ACTH) and 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB) were used as substrate and coupling agent respectively. The resulting yellow chromophore indicated AChE activity. Test results showed that the color intensity decreased as increasing concentrations of propoxur were added, thereby confirming the susceptibility of the enzyme to inhibitor. Assay of non-specific esterase however, indicated elevated levels which were correlated with degree of malathion resistance. Electrophoretic data revealed the presence of 2 esterase bands in all strains. It was concluded that such a pattern was not contributory to malathion resistance in adults.
    Matched MeSH terms: Biological Assay/methods
  9. Vythilingam I, Ridhawati, Sani RA, Singh KI
    PMID: 7909171
    The residual effectiveness of 0.005mg/ml of cyhalothrin applied to cattle was determined against three species of mosquitos: Anopheles maculatus Theobald. Anopheles dirus Peyton and Harrison Mansonia uniformis Theobald. Twenty-four hour post exposure mortality and the degree of successful blood engorgement were determined by exposing mosquitos for 10 minutes to cattle. Three replicated assays were conducted and mortality determined at 1, 2, 7, 14 and 21 days after each treatment. An initial mortality of 92-94% for An. dirus and Ma. uniformis and 79% for An. maculatus was obtained. Percentage mortality declined to 10%, 18% and 31% for An. maculatus, An. dirus and Ma. uniformis respectively on day 7 post application. On day 21 post application, percentage mortality was 2-3% for the three species of mosquitos.
    Matched MeSH terms: Biological Assay
  10. Lee HL, Tadano T
    PMID: 7855659
    The ability to identify the occurrence of different resistance genotypes in field populations of mosquito is considered important for the purpose of optimising chemical control operations. The recent development of rapid microassays of enzymes responsible for resistance has provided a means for rapidly assessing the genetic background of target mosquito populations. This concept is the topic of investigation in this study. Non-specific esterase activity, which is responsible for the resistance to organophosphates in Malaysian Culex quinquefasciatus Say adults, was determined in 3 field populations from Kuala Lumpur City using rapid enzyme assay. The optical density results were used to estimate the genotypic frequencies of the populations. Subsequently, time-dependent changes in the various frequencies were determined. Such techniques allowed rapid assessment of resistance genotypes for decision-making and its possible use in insect control merits further investigation.
    Matched MeSH terms: Biological Assay/methods
  11. Noah RM, Jais MR, Noh LM
    Malays J Pathol, 1994 Dec;16(2):157-60.
    PMID: 9053565
    Variable parameters in chemiluminescence assay, one of the methods used to assess the functional capacity of neutrophils, were evaluated for suitable adaptation locally. The use of pooled normal human serum as compared to single normal human serum in opsonizing particles for phagocytosis was found to exhibit lower chemiluminescence activity (reduction range of 30%-50%). A similar degree of depression was observed when the particles were opsonized using normal human serum in comparison to that using autologous serum. Different intensity of chemiluminescence was also noted when the opsonized particle used was the Oxford strain of Staphylococcus aureus (NCTC 6571) in contrast to a strain of Staphylococcus aureus isolated from a patient. The results obtained warrant clinicians to deliver appropriate samples as best they can when the chemiluminescence assay is requested.
    Matched MeSH terms: Biological Assay/methods*
  12. Law AT
    Environ Pollut, 1995;88(3):341-3.
    PMID: 15091547
    The effect of the oil-spill dispersant Corexit 9527 on egg-hatching rate of Macrobrachium rosenbergii (de Man) was studied by using an innovated flow-through bioassay technique. This bioassay method relies on the fact that M. rosenbergii fertilized eggs when detached from the mother prawn were able to hatch artificially. The flow-through system generated a stable and good water quality environment for hatching the eggs successfully. The Corexit 9527 had a pronounced effect on hatching rate of the M. rosenbergii eggs. In the control, the hatching rate of the eggs was 95.55% +/- 1.74%. However, it was reduced drastically with increasing concentrations of Corexit 9527. A 100% inhibition of egg hatchability was found when the level of Corexit 9527 was higher than 250 mg litre(-1). The EC(50) and the EC(95) values estimated by the probit method were 80.4 +/- 5.5 mg litre(-1) and 193.5 +/- 39.9 mg litre(-1) respectively (P = 0.05). The recommended safety level of Corexit 9527 for M. rosenbergii in Malaysian estuarine waters is below 40 mg litre(-1).
    Matched MeSH terms: Biological Assay
  13. Ramachandran S, Patel TR, Colbo MH
    Ecotoxicol Environ Saf, 1997 Mar;36(2):183-8.
    PMID: 9126437
    Three species of tropical estuarine invertebrates were exposed to copper sulfate and cadmium chloride to investigate their potential as test specimens for sediment toxicity assays in the South-east Asian regions. The larvae of the reef sea urchin (Diadema setosum), the oyster (Crassostrea iradalei), and the mud crab (Scylla seratta Forskall) were used in the 48-hr assays with copper and cadmium as reference toxicants. In addition the sea urchin were tested for end point measurements at different stages of the larval development and a 60-min sperm bioassay. The study revealed that the sea urchin first cleavage, which is an assay end point and which takes place about 1 hr after fertilization, was the most sensitive stage for both toxicants, with copper being more toxic than cadmium. Sensitivity comparisons between the three invertebrate larvae revealed the mud crab zoea larvae to be most sensitive for cadmium with an LC50 value of 0.078 microgram/ml, while the sea urchin was more sensitive for copper, with EC50 values of 0.01 microgram/ml at the first cleavage stage and 0.04 microgram/ml at the pluteus larva stage. All the invertebrates tested gave responses that made them suitable test organisms for metal bioassays in the tropical estuarine environment.
    Matched MeSH terms: Biological Assay/methods*
  14. Vythilingam I, Zainal AR, Hamidah T
    PMID: 10695808
    Two formulations of lambda-cyhalothrin (EC-Emulsion concentrate and MC-Microencapsulated) were impregnated into bednets made of polyethylene and polyester. The nets were treated at a dosage of 15 mg/m2. For bioassay of insecticidal efficacy, female Anopheles maculatus and Aedes aegypti were exposed to the nets for two minutes and mortality was scored 24 hours later. The nets were also tested after repeated washings with water and with soap and water. Microencapsulated (2.5CS) formulation was more effective than emulsion concentrate (2.5EC) formulation on both net materials--polyethylene and polyester. Repeated washing with water and soap reduces the efficacy of all bednet treatment combinations. Microencapsulated formulation on polyethylene gave best results; it could sustain up to five washes with water and two with soap and water.
    Matched MeSH terms: Biological Assay
  15. Ibrahim YB, Yee TS
    J Econ Entomol, 2000 Aug;93(4):1085-9.
    PMID: 10985016
    Effects of sublethal exposure to abamectin on the biological performance of Neoseiulus longispinosus (Evans) were studied under ambient laboratory conditions of 28 +/- 2 degrees C and 80 +/- 15% RH with 24 h light. The red form of the twospotted spider mite, Tetranychus urticae Koch, complex (Acari: Tetranychidae), was offered as prey. The LC50 obtained from the contact bioassay at 48 h after treatment was 0.015 ppm (AI). A big change in kill for a given variation in dosage for the regression slope probably indicated that abamectin was unlikely selective. Sublethal exposure to abamectin caused a reduction in survival with the female reaching 50% mortality by the sixth day and the male 4 d later. The mean preoviposition period was extended by almost 1 d, whereas the mean oviposition period was shortened by almost 5 d causing a reduction in the mean fecundity female-1 to almost half that of the untreated females. The net reproductive rate (Ro), the intrinsic rate of increase (rm), and the finite rate of increase (lambda) of the treated females were markedly inferior. Treated males were seriously affected; the mean life span was almost half that of the untreated.
    Matched MeSH terms: Biological Assay
  16. Ismail BS, Quirinus L
    Bull Environ Contam Toxicol, 2000 Oct;65(4):530-6.
    PMID: 10960146
    Matched MeSH terms: Biological Assay
  17. Sayyed AH, Wright DJ
    Pest Manag Sci, 2001 May;57(5):413-21.
    PMID: 11374157
    A field population of Plutella xylostella from Malaysia (SERD4) was divided into five sub-populations and four were selected (G2-G5) with the Bacillus thuringiensis insecticidal crystal (Cry) toxins Cry1Ac, Cry1Ab, Cry1Ca and Cry1Da. Bioassay at G6 gave resistance ratios of 88, 5, 2 and 3 for Cry1Ac, Cry1Ab, Cry1Ca and Cry1Da respectively compared with the unselected sub-population (UNSEL-SERD4). The Cry1Ac-selected population showed little cross-resistance to Cry1Ab, Cry1Ca and Cry1Da, (3-, 2- and 3-fold compared with UNSEL-SERD4), whereas the Cry1Ab-SEL sub-population showed marked cross-resistance to Cry1Ac (40-fold), much greater than Cry1Ab itself. In contrast, the Cry1Ca- and Cry1Da-SEL sub-population showed little if any cross-resistance to Cry1Ac and Cry1Ab. The mode of inheritance of resistance to Cry1Ac was examined in Cry1Ac-selected SERD4 by standard reciprocal crosses and back-crosses using a laboratory insecticide-susceptible population (ROTH). Logit regression analysis of F1 reciprocal crosses indicated that resistance to Cry1Ac was inherited as an incompletely dominant trait. At the highest dose of Cry1Ac tested, resistance was recessive, while at the lowest dose it was almost completely dominant. The F2 progeny from a back-cross of F1 progeny with ROTH were tested with a concentration of Cry1Ac that would kill 100% of ROTH. The mortality ranged between 50 and 95% in seven families of back-cross progeny, which indicated that more than one allele on separate loci were responsible for resistance to Cry1Ac.
    Matched MeSH terms: Biological Assay
  18. Ismail BS, Azlizan BA
    J Environ Sci Health B, 2002 Jul;37(4):345-53.
    PMID: 12081026
    The persistence of metsulfuron-methyl (methyl 2-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl]aminosul fonyl]benzoate) in nonautoclaved and autoclaved Selangor, Lating, and Serdang series soils incubated at different temperatures and with different moisture contents was investigated under laboratory conditions using cucumber (Cucumis sativus L.) as the bioassay species. Significant degradation of metsulfuron-methyl was observed in nonautoclaved soil compared with the autoclaved soil sample, indicating the importance of microorganisms in the breakdown process. At higher temperatures the degradation rate in nonautoclaved soil improved with increasing soil moisture content. In nonautoclaved Selangor, Lating and Serdang series soils, the half-life was reduced from 4.79 to 2.78 days, 4.9 to 3.5, and from 3.3 to 1.9 days, respectively, when the temperature was increased from 20 degrees to 30 degrees C at 80% field capacity. Similarly, in nonautoclaved soil, the half-life decreased with an increasing soil moisture from 20% to 80% at 30 degrees C in the three soils studied. In the autoclaved soil, the half-life values were slightly higher than those obtained in the nonautoclaved soils, perhaps indicating that the compound may be broken down by nonbiological processes. The fresh weight of the bioassay species was reduced significantly in Serdang series soil treated with metsulfuron-methyl at 0.1 ppm. However, the reduction in fresh weight of the seedlings was least in Lating series soil, followed by Selangor series soil.
    Matched MeSH terms: Biological Assay
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