Diatom Detection Using Enzyme Combined with Strong Acid Digestion Method / 法医学杂志

OBJECTIVES@#To detect diatom in the organs of drowners by enzyme combined with strong acid digestion method, and evaluate its application value.@*METHODS@#A total of 40 cases which have been identified as drowning in local region were collected. Samples of the lung, liver, kidney, and the water of the scene were also gathered from each case. Strong acid digestion method, enzyme combined with strong acid digestion method, and enzymic digestion method were respectively performed to detect the diatom in the samples. The comparative analysis was made on digestion time, digestive power and detection rate of diatom, etc.@*RESULTS@#Enzyme combined with strong acid digestion method was significantly better than enzymic digestion method on digestion time and digestive power; enzyme combined with strong acid digestion method were obviously superior to strong acid digestion method on the detection rate of diatom.@*CONCLUSIONS@#Enzyme combined with strong acid digestion method combines the advantages of strong acid digestion method and enzymic digestion method. It has the characters of operation safety with little pollution to environment, which is worthy of further popularization and practice.

Progress on Diatom Test in Drowning Cases / 法医学杂志

In drowning cases, it is difficult to judge whether the deceased died from drowning or throwing into the water after killed or identificate the cause of death of the decomposed corps in forensic practices. The diatom test is still considered as the important assistant evidence in drowning cases. This paper reviews research progress on technologies in recent years of forensic diatom test, and the application value of the new developing approach in the field of forensic medicine.

Diatoms in drowned and postmortem immersed rabbits' lungs / 法医学杂志

OBJECTIVE@#To investigate the numbers, sizes and types distribution of diatoms in drowned and postmortem immersed rabbits' lungs.@*METHODS@#Sixty-two rabbits were randomly divided into drowning group (n = 30), postmortem immersion group (n = 30) and land death group (n=2), and the diatoms in each lung lobe were analyzed quantitatively and qualitatively by microwave digestion and scanning electron microscopy.@*RESULTS@#In the drowning group, the diatoms were detected in each lung lobe with Cyclotella and Melosira in the majority. In the postmortem immersion group, Cyclotella was in the majority. And the diatoms weren't detected in some lung lobes in postmortem immersion. There were significant differences in the detection rates of upper lobe of left lung, middle lobe and cardiac lobe of right lung in two groups (P < 0.05).@*CONCLUSION@#Based on the microwave digestion and scanning electron microscopy, the numbers, sizes and types distribution of diatoms in drowned and postmortem immersed rabbits' lungs can be analyzed and used as references for testing theory.

Comparative analysis between diatom nitric acid digestion method and plankton 16S rDNA PCR method / 法医学杂志

OBJECTIVE@#To compare and explore the application value of diatom nitric acid digestion method and plankton 16S rDNA PCR method for drowning identification.@*METHODS@#Forty drowning cases from 2010 to 2011 were collected from Department of Forensic Medicine of Wenzhou Medical University. Samples including lung, kidney, liver and field water from each case were tested with diatom nitric acid digestion method and plankton 16S rDNA PCR method, respectively. The Diatom nitric acid digestion method and plankton 16S rDNA PCR method required 20 g and 2 g of each organ, and 15 mL and 1.5 mL of field water, respectively. The inspection time and detection rate were compared between the two methods.@*RESULTS@#Diatom nitric acid digestion method mainly detected two species of diatoms, Centriae and Pennatae, while plankton 16S rDNA PCR method amplified a length of 162 bp band. The average inspection time of each case of the Diatom nitric acid digestion method was (95.30 +/- 2.78) min less than (325.33 +/- 14.18) min of plankton 16S rDNA PCR method (P < 0.05). The detection rates of two methods for field water and lung were both 100%. For liver and kidney, the detection rate of plankton 16S rDNA PCR method was both 80%, higher than 40% and 30% of diatom nitric acid digestion method (P < 0.05), respectively.@*CONCLUSION@#The laboratory testing method needs to be appropriately selected according to the specific circumstances in the forensic appraisal of drowning. Compared with diatom nitric acid digestion method, plankton 16S rDNA PCR method has practice values with such advantages as less quantity of samples, huge information and high specificity.

Distribution of diatoms in central city of Beijing / 法医学杂志

OBJECTIVE@#To explore the quantity and distribution of diatoms in main rivers and lakes in Xicheng, Dongcheng, Chaoyang, Haidian, Fengtai and Shijingshan Districts of the city of Beijing.@*METHODS@#Water samples were examined through the method of disorganizing, which were collected from 16 rivers and lakes in the central city of Beijing in September and October 2011. Diatom species and proportions of water samples were analyzed using DotSlide microscope station.@*RESULTS@#A total of 10 species of diatoms were detected. Cyclotella, Synedra and Melosira etc. were found to be the dominant species via quantitative analysis. Significant differences were observed for diatom species and proportions among the different rivers and lakes. Melosira was found to be the dominant species in the Chang River; Synedra, in the Zhuan River, the Kunyu River and the Taoranting Park; Cyclotella, in the East Moat River, the Ba River, the Liangshui River and the Yongding River; and Navicula, in the Liangma River; Nitzschia, in the diversion canal of the Yongding River.@*CONCLUSION@#The features of distribution of diatoms in the central city of Beijing are outlined. The morphological and relative constituent ratio database of diatoms are established in central city of Beijing.

Diatom test in lung tissue of corpses in water and causes of death / 法医学杂志

OBJECTIVE@#To explore potential application of diatom test of lung tissue in investigation of cause of death in victim found in the water.@*METHODS@#Four hundred and seven cases were collected and analyzed for cause of death and the nature of case. Diatom test was performed in tissues and the amount was quantified. Forty-five rabbits died in the water (antemortem, postmortem and different seasons drowning) were randomly divided into 9 groups and the diatom content in lung tissue were tested with the method of nitric acid.@*RESULTS@#In 407 drowning cases, 372 cases showed a positive result of diatom test. In positive cases, the amount of accidents or suicide were 35 and homicide were 21. Thirty-five cases showed negative result of diatom test and majority were homicide in which bodies were thrown into the water after killing. Some drowning cases were in special circumstances. Animal experiments confirmed that a large amount of diatoms in lung tissue were detected in drowning victim and showed the same type in water. The amount of diatom in lung tissue was usually lower in the summer and winter comparing with spring and autumn.@*CONCLUSION@#The diatom test could be considered as an auxiliary evidence in determination of cause of death in body found in the water. The test results were related with manner of death. The nature of case should be synthetically determined based on autopsy, criminal scene and details of the cases, etc.

Improved nitric acid digestion method for detecting diatom in autopsy tissue / 法医学杂志

OBJECTIVE@#To investigate the advantages of nitric acid digestion method and its differences with the traditional method.@*METHODS@#Ethanol was used to fully fix the testing sample. About 80-100 g of the testing samples were cut into pieces and digested with nitric acid. It was then centrifuged and washed to remove organic components. Smears were prepared and examined under the light microscope.@*RESULTS@#The diatom had been identified with clear striations, counted conveniently and classified easily.@*CONCLUSION@#The improved nitric acid digestion method is not only simple with a higher successful rate of detection, but also can prevent interference from contamination. It can improve the stability of the experimental results, avoid harm to human and environment, and provide higher safety in the course of experiment.

Advances in research of diagnosis of drowning in forensic medicine / 法医学杂志

The current macroscopical and microscopical signs in the fresh drowning victim are non-specific. Moreover, putrefaction will vanish these autopsy findings quite rapidly. The study of additional detecting methods to diagnose drowning has become one of the hottest topics in forensic medicine. This article reviewed several methods commonly used in the determination of drowning in forensic practice. The advantages and disadvantages of various methods were also discussed.

Proliferaciones algales de la diatomea toxigénica Pseudo-Nitzschia (Bacillariophyceae) en el Golfo de Nicoya, Costa Rica / Algal blooms of the toxigenic diatom Pseudo-Nitzschia (Bacillariophyceae) in the Golfo de Nicoya, Costa Rica

En el mes de noviembre de 2001, se aisló de una marea roja cerca de la Isla San Lucas, las diatomeas Pseudo-Nitzschia pungens f. pungens seguida por Skeletonema costatum, Chaetoceros lorenzianus y en menor concentración Thalassiosira spp. las cuales fueron caracterizadas por microscopía electrónica de rastreo y transmisión, siendo esta la primera vez que se describe la presencia de estas especies produciendo proliferaciones en Costa Rica. Actualmente existe un aumento en el reporte de mareas rojas donde predominan las diatomeas, y los conteos celulares indican el aumento en el número de las especies conocidas como Pseudo-nitzschia pungens f. multiseries. A estas se les atribuye la producción del ácido domóico, un aminoácido de bajo peso molecular. Las intoxicaciones amnésicas por mariscos (IAM) que afectan a los humanos, se producen por la ingesta de mariscos contaminados con este ácido. En Costa Rica, hasta la fecha, solo se han reportado casos de intoxicación paralítica por mariscos contaminados por los dinoflagelados Pyrodinium bahamense var. compressum y Gymnodinium catenatum, sin embargo existe la posibilidad de producirse intoxicaciones humanas por la ingesta de mariscos y peces contaminados con toxinas amnésicas las cuales son hidrosolubles y termoestables. Debe entonces considerarse el peligro potencial de aparición de casos de intoxicaciones amnésicas y se sugiere la inclusión de estas especies en los programas de monitoreo permanente para tomar las medidas preventivas de salud pública

Water samples were collected during a red tide event in November 2001, near San Lucas Island (Gulf of Nicoya, Costa Rica). Superficial temperature was 27ºC and water was turbid, with no fetid smell. One sample was treated with negative staining and observed using a transmission electron microscope (TEM); another sample was observed using a scanning electron microscope (SEM). Samples had high concentrations of the diatom Pseudo-Nitzschia pungens f. pungens (characterized by two rows of poroids in the external channel), and lower concentrations of Skeletonema costatum (chains joined by external microtubules) and Chaetoceros lorenzianus (oval apertures and long chains, having setae with distinctive transverse rows and spines). This is the first time that the first species was described producing red tides in Costa Rica. However, reports about red tides with high concentration of species like P. pungens (variety multiseries) are increasing. These species have been related to the production of domoic acid, a low molecular weight amino acid which in humans can cause amnesic intoxications with seafood. Previously, Costa Rican reports of toxic accidents only referred to seafood contaminated with Pyrodinium bahamense var. compressum and Gymnodinium catenatum dinoflagellates. The increase in the number of Pseudo-Nitzschia causing harmful algae blooms is of interest for scientists around the world and must be documented. Similarly, some Chaetoceros species have been reported to be harmful to fish. We strongly recommend the establishment of a permanent surveillance program monitoring the presence of these species new at Costa Rican Pacific coast. Since the amnesic toxin is soluble in water and heat-resistant, we want to stress the possibility of having human cases of amnesic intoxication

The use of water chemistry and benthic diatom communities for qualification of a polluted tropical river in Costa Rica

The water quality of several sections of a tropical river subjected to severe pollution was studied through physico-chemical water analysis and benthic diatom assemblages. The methodology follows the concept of differential species groups and that of its modification for the groups of nutrient-differentiating species for rivers rich in both oxygen and inorganic nutrients. The trophic indication of the latter authors correspond clearly with the results of chemical observations made in this study. The most abundant species found in this river were Navicula goeppertiana, Gomphonema parvulum, Gomphonema sp. aff. pumilum, Nitzschia palea, Nitzschia amphibia, Nitzschia clausii Nitzschia inconspicua, Navicula seminulum, Navicula sp. aff. cryptocephala, Navicula schroeterii var. escambia, Cymbella sinuata and Surirella sp. aff. roba. These species are known to be tolerant to organic pollution and eutrophication. Therefore we may conclude that diatoms are useful for biological monitoring of disturbed tropical rivers

Characterization of drowning by diatom test.

Examination by the diatom test, of different organs of corpses of individuals who died of drowning revealed the presence of frustules in all the visceral organs. Diatom load of different organs was found to be positively related with breadth/diameter of the frustule. Relatively larger diatoms were encountered in the lungs, heart and kidneys as compared to the other organs. Smaller diatoms up to 10 mu diameter were found in the brain, and bone marrow samples. However, diatoms were also recovered from the lungs, heart and kidneys of corpses of individuals in whom the cause of death was not drowning. Brain and bone marrow were considered reliable samples for executing the diatom test.