PubMed Health⌕ Search

Biomedical subjects

A T Santos

Publications and source records attributed to A T Santos.

At least 19 recordsLinked to original sources
PubMed2001

Development of a DNA-based method aimed at identifying the fish species present in food products.

Analysis of restriction fragment length polymorphism (RFLP) profiles of a 464 bp amplicon obtained from the mitochondrial cytochrome b gene was used to differentiate between several different fish species. The method was tested by a collaborative study in which 12 European laboratories participated to ascertain whether the method was reproducible. Each laboratory was required to identify 10 unknown samples by comparison with RFLP profiles from authentic species. From a total of 120 tests performed, unknown samples were correctly identified in 96% of cases. Further work attempting to use the method to analyze mixed and processed fish samples was also performed. In all cases the species contained within mixed samples were correctly identified, indicating the efficacy of the method for detecting fraudulent substitution of fish species in food products.

Animals↗
PubMed2001

Identification of Hake species (Merluccius Genus) using sequencing and PCR-RFLP analysis of mitochondrial DNA control region sequences.

The use of DNA-based methodologies in identification of hake species belonging to the Merluccius genus was shown to be successful. A short fragment of the left hypervariable domain of the mitochondrial control region was amplified, sequenced, and digested from 11 hake species. The hake-specific PCR product, due to its limited size, was obtained in a variety of tissue samples with different levels of DNA concentration and degradation, including sterilized food products. On the basis of this phylogenetically informative 156-bp sequence were selected four restriction enzymes (ApoI, DdeI, DraIII, and MboII) that allow the hake species discrimination. Species identification by phylogenetic analysis of sequences or by PCR-RFLP methodologies is useful in a variety of scenarios including authentication of thermally processed food, detection of food components, and species determination of individuals whose morphological characters are removed.

Animals↗
PubMed2001

Identification of flatfish (Pleuronectiforme) species using DNA-based techniques.

Identification of flatfish species using a DNA-based methodology was studied. The polymerase chain reaction was employed to obtain a 464 bp amplicon from mitochondrial cytochrome b gene. The sequences from this fragment belonging to 24 species were analyzed using a genetic distance method, and polymorphic sites were determined. The fragment was found to be highly polymorphic (231 sites), and this permitted the differentiation of most of the species. Phylogenetic tree construction was employed to allow the identification of flatfish species. As a result, each species was grouped in a well-differentiated clade, except for two pairs: Limanda ferruginea and L. limanda, and Solea impar and S. lascaris, which could not be differentiated. On the basis of the sequences obtained, restriction enzymes were selected to provide specific restriction profiles, which allow the differentiation of 21 species of flatfish in a faster and less expensive manner than sequencing. This polymerase chain reaction-restriction fragment length polymorphism methodology (PCR-RFLP) was tested using commercial samples.

Animals↗
PubMed2000

Use of restriction fragment length polymorphism to distinguish between salmon species.

Identification of 10 salmon species using DNA-based methodology was investigated. Amplification of DNA was carried out using a primer set which amplified a region of the mitochondrial cytochrome b gene. Sequences of PCR-amplified DNA from the salmon species were used to select six restriction enzymes allowing species to be uniquely classified. RFLP patterns generated following analysis with each enzyme were resolved using polyacrylamide gel electrophoresis and visualized by silver staining. Results indicate that it is possible to differentiate between all 10 salmon species and that the technique could be easily adopted by the food industry for analysis of processed salmon products.

Animals↗
PubMed1989

Schistosomiasis on Bohol Island, Philippines, with special emphasis on the successful discovery of new habitats of the vector snail, Oncomelania quadrasi, and area-wide mollusciciding.

In the endemic area of schistosomiasis on Bohol Island, we succeeded in locating seven new colonies of the vector snail, Oncomelania quadrasi, four in Trinidad and three in Talibon, in addition to six locations from which the snails were previously recorded. We were led by the proximity of the snail habitat to the residence of the infected individuals. In northern Bohol the continuous wet season would appear to make the major differences between the places that do and those that do not support O. quadrasi. Twice-yearly weed clearance and applying chemical molluscicides (niclosamide and phebrol) for the control of O. quadrasi have been extensively in effect over the snail colonies, since July 1986. Although it has not yet yielded satisfactory results in certain colonies, snails have been eliminated from six habitats in a period of two and a half years.

Animals↗
PubMed1987

Negative conversion of COP (circumoval precipitation) reactions after selective mass chemotherapy on schistosomiasis japonica with praziquantel in Bohol, Philippines.

For the longitudinal survey of human schistosomiasis japonica in the villages of Sto. Tomas and San Vicente in the province of Bohol, Philippines, the circumoval precipitin (COP) test was used for case detection. Plasma collected by finger prick from the community people and lyophilized eggs of Schistosoma japonicum were used for the assay. Degree of precipitation at type 2 or 3 of Yokogawa et al. [1] was considered as positive. Selective mass chemotherapy with praziquantel was given to the patients including cases with only positive COP reactions. San Vicente and Sto. Tomas villages were examined in 1984 and 1982, respectively and followed up in 1986. Positive COP reactions were converted to negative in 82.1% or 55 out of 67 cases treated in 1984 and 1985 at San Vicente. Similarly, negative conversion was observed in 75.4% or 43 out of 57 cases treated in 1981 and 1982 at Sto. Tomas. The cases with persistent positive COP reaction after treatment were considered as incomplete cure or reinfection. The concentrated distribution of positive cases around the habitat of Oncomelania snails was observed at San Vicente where the prevalence of COP positives declined from 22.2% to 14.0% in 2 years. These results suggest that in the area with selective mass chemotherapy on schistosomiasis japonica, COP reactions of treated cases are converted to negative at high proportions in 2 years, and the positives detected by subsequent survey after 2 years are considered mostly as new infections or reinfections.

Animals↗
PubMed1986

Population studies on Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum, in the Philippines. 5. Quantitative analysis on successful snail control by land reclamation.

For the control of Oncomelania quadrasi, environmental modifications, i.e., clearing of vegetation, leveling of swampy depression and draining of stagnant water by channeling and excavation were carried out at 3 areas in Leyte, Philippines from 1974 to 1977. The change of snail population resulted in the land reclamation was evaluated by the methods previously developed by the population studies on this snail. As a result of statistical analysis based on y = log(x + 0.01) transformation and the antilogarithmic mean density A-y = (antilog -y) -0.01, the reduction of snail population was observed at 13 out of 18 sites studied at 3 project areas and the significant reduction was statistically confirmed at 9 sites of them. Particularly at Dagami area, which was a wide and heavily snail-infested land adjacent to Dagami Poblacion, the reduction rate of snail density reached 87.7% to 99.2% and some wet depressions have been converted into good rice fields with little snail infestation at the last survey.

Animals↗
PubMed1986

An attempt to study the case fatality rate in Schistosoma japonicum infection in the Philippines.

As a sequence to a cross-sectional study on the clinical gradient of the disease by Pesigan et al., (1965) a follow-up of the subjects in that study was made after 12 years. Of the 135 untreated cases followed up, 23 (17.04%) died from various causes of which 12 (8.89%) had signs and symptoms attributable to schistosomiasis as the immediate cause or one of the main causes of death. This occurred in 1 to 11 years with an average of 5 years, which corresponds roughly to 1.78% of the infected cases per year. This is considered a conservative estimate because in the other deaths due to other diseases, schistosomiasis is a contributory cause. A diminishing severity of the disease was observed among the surviving patients which could imply that they must have developed some degree of immunity to the disease.

Adolescent↗
PubMed1985

The cercarial emergence of Schistosoma japonicum from Oncomelania quadrasi under outdoor conditions in the Philippines.

The cercarial emergence of Schistosoma japonicum from Oncomelania quadrasi was observed under outdoor conditions in Leyte, Philippines. Nocturnal periodicity of the emergence within 24 hours was recognized. Peak emergence usually occurs between 18:00 and 20:00 and occasionally between 8:00 and 10:00. The peaks were usually synchronized with a sudden lowering of water temperature and light intensity and occasionally with their increase. As the nocturnal periodicity of the emergence was observed in the dark and outdoors, it was suggested that emergence might be dependent on temperature, which is secondarily influenced by photoperiodicity and light intensity.

Animals↗
PubMed1985

Longitudinal study on Schistosoma japonicum infections in the Philippines. 4. Effect of mass-chemotherapy with praziquantel on incidence at Dagami, Leyte.

The effect of selective mass-chemotherapy with praziquantel at a dose of 60 mg/kg a day on the annual incidence of Schistosoma japonicum infection was examined by a follow-up study of 1,800 school children enrolled at 9 primary schools at Dagami Area, Leyte, Philippines. The incidence rates before mass-chemotherapy were 22.2, 24.2, 26.9, 9.6 and 28.4% in a period from school year (SY) 1975/76 to 1979/80, respectively, where the incidence of 9.6% in SY 1978/79 was probably due to extraordinary drought in the previous year. Egg positives including village people were treated and the numbers treated yearly were 22, 943, 273, 300 and 341 from SY 1978/79 to SY 1982/83, respectively. The incidence was reduced drastically as early as one year following the start of mass-chemotherapy, i.e., 8.4, no survey, 6.8 and 15.4%, from SY 1980/81 to SY 1983/84, respectively, and which demonstrated the efficacy of mass-chemotherapy on reduction of transmission.

Child↗
PubMed1984

Phase III clinical trials with praziquantel in S. japonicum infections in the Philippines.

Following successful Phase II clinical studies with praziquantel (2-cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino [2,1-a]isoquinolin-4-one, EMBAY 8440, Biltricide), expanded field trials of Phase III were conducted in Mindoro Oriental, Leyte and Davao Norte, to reassess efficacy, safety and acceptability of the drug on a larger scale. A total of 6,134 cases were treated with the best tolerated and effective dose of 60 mg/kg bwt which for practical purposes was given in 2 instead of 3 divided doses as applied in the earlier trials. Two aliquots of one stool from each individual were examined quantitatively by a modification of the thick smear method one week before, six and twelve months after treatment. Although 67.8% were noted to have drug-related side effects, most were mild to moderate, with only 1.2% considered as severe. Severe reactions consisted mainly of colicky abdominal pain, occurring about 1 h after drug intake, usually accompanied by fever, sweating, urge to defecate, and occasionally by discharge of bloody stool. These reactions, however, required only symptomatic treatment with antispasmodics and antipyretics. Stool follow-up 6 months after treatment showed 89.2% of EPG (eggs per gram of faeces) negativity, with an overall egg reduction of 91.1%. Twelve months after treatment, practically the same results were obtained with 87.5% still negative cases and an egg reduction of 90.5%. This study confirms safety and efficacy of the drug as well as its acceptability when given on a community wide scale.

Adolescent↗
PubMed1984

Experimental infection of Oncomelania quadrasi with Paragonimus ohirai.

Two hundred Oncomelania quadrasi collected from Leyte, Philippines were exposed to infection with Paragonimus ohirai, a rodent type lung fluke. In a group, each snail was exposed individually to 10 miracidia hatched from eggs which were brought from Japan to the Philippines. In another group, 100 snails were placed in a Petri dish and P. ohirai miracidia were added to provide 10 per snail. The observations were made each successive week after exposure. All the snails examined were positive for the larvae of P. ohirai. Nine-ten weeks after exposure, many cercariae were recognized. It was proved that O. quadrasi is highly susceptible to P. ohirai.

Animals↗
PubMed1983

Evaluation of micro-ELISA for schistosomiasis japonica using crude egg antigen.

Procedures of micro-ELISA for detecting antibody of Schistosoma japonicum infection were improved by using crude egg antigen, peroxidase-labeled antibody and O-phenylenediamine on a micro-ELISA plate (M129A, Dynatech). Reactions were performed with 0.1 ml of reagents in 0.3 ml wells at each step and 0.3 ml of substrate was placed at the final procedure. The endpoint of reaction was defined as the upper limit of 99% critical range of absorbance in negative sera at 1:40 dilution which was approximately twice the absorbance of a pooled negative serum at 1:40. Using this endpoint, appropriate concentrations of antigen and conjugate were determined. Cross-reactions of egg antigen were observed with sera at 1:40 from the infections with other schistosomes, Trichobilharzia brevis, Fasciola hepatica, Echinococcus multilocularis and Trichinella spiralis were diminished at 1:200 serum dilutions except for other schistosomes. Among 177 egg positives, 171 (96.6%) showed the titer of 200 or higher while 67 old cases at Kofu, Japan showed low titers where 22 (31.9%) were lower than 40, 44 (63.7%) were between 40 and 160 and 3 (4.4%) were 320 or higher. The proven non-infected controls of 93 cases from Leyte and Manila, Philippines, Tokyo and Kofu, Japan were all negative. The result of ELISA for schistosomiasis japonica by crude egg antigen was satisfactory after standardization and stabilization of the procedures which were considered to be as important as using defined antigens.

Animals↗
PubMed1983

Longitudinal study on Schistosoma japonicum infections in the Philippines. 3. Incidence and environmental modification at Dagami, Leyte.

The yearly change of incidence of schistosomiasis japonica was observed among 1800 children enrolled in 9 schools situated within a 5 km radius around Dagami Poblacion, Leyte, Philippines from School Year (SY) 1974/75 to 1979/80. The purpose of this observation was to know the effect of environmental modification undertaken in about 50 ha of snail-infested and abandoned rice field which is the most depressed and central portion of this project area. Children were examined by egg detection from stool and by circumoval precipitin test. Coverage of examination among the school population ranged from 40 to 80% yearly and the ratio of re-examination after about 1 year was from 30 to 60%. The annual incidence in the different schools differed greatly from 12.15 to 42.86% in contrast to the annual prevalence which differed only slightly. There was corresponding increase of incidence with age from 18.6% at age 7 to 33.9% at age 12 while no significant difference was observed between sexes. The overall annual incidence rates for 9 schools during the 5-year follow-up period (SY 1975/76 to 1979/80) were 22.2, 24.2, 26.9, 9.6 and 28.4%, respectively. Those of Dagami Central II, the nearest school to the reclaimed site, were 15.7, 18.2, 19.3, 5.2 and 11.6%, respectively, for the same period. Obviously, the incidence was increasing while the reclamation was going on except in SY 1978/79. Analysis of the sudden drop of incidence in that year in all the 9 schools showed that it was not due to the effect of reclamation, but was most likely due to scanty rainfall in the previous year (1977). These observations indicated that small scale environmental modification had doubtful effect on outlying endemic areas in reducing the danger of Schistosoma infection but may have a little effect on the immediate surroundings as shown by a lesser elevation of incidence after the abrupt decrease at the nearest school as compared to those of schools located farther from the reclamation area.

Age Factors↗