| Objective:This study was respectively designed to conduct statistical analysis on the data of the sizes of diatoms about samples in animal experiments and in drowning cases,to explore the effects of digestive tract and respiratory tract barriers on the sizes of diatoms entering the systemic circulation.It provides the references for the establishment of diatom test standard for diagnosis of drowning.Methods:1.Four kinds of standardized diatom solution were mixed in proportion according to the concentration of Nitzschia,Stephanodiscus,Coscinodiscus(small)and Coscinodiscus(large)(provided by the Freshwater Algae Culture Collection at the Institute of Hydrobiology),and the mixture was prepared into 500 ml of standardized diatom solution so that the concentration of the four diatoms in the diatom mixture was the same.2.Digestive tract barriers:(1)The blank group:there were 10 New Zealand white rabbits and each rabbit was sacrificed immediately.Three portions(about 2g each)of lung tissue,three portions(about 3g each)of liver tissue,three portions(about 3g each)of kidney tissue,one portion(about 1g)of spleen tissue,one portion(about 2g)of blood,and one portion(about 0.05g)of stomach contents were taken from each rabbit respectively.(2)Treatment group:there were 29 New Zealand white rabbits and the rabbits were fed a mixture of standardized diatoms and sacrificed after 24 hours,then three portions(about 2g each)of lung tissue,three portions(about 3g each)of liver tissue,three portions(about 3g each)of kidney tissue,one portion(about 1g)of spleen tissue,one portion(about 2g)of blood,and one portion(about 0.05g)of stomach contents were taken from each rabbit respectively.(3)The numbers and sizes of Nitzschia,Stephanodiscus,Coscinodiscus(small)and Coseinodiscus(large)in the samples from the blank group and treatment group were tested using the Microwave Digestion-Vacuum Filtration-Automated Scanning Electron Microscopy method and all types of diatoms(classified into genera)were recorded.3.Respiratory tract barriers:(1)There were 100 drowning cases and one portion(about 2g)of lung tissue,three portions(about 3g each)of liver tissue,three portions(about 3g each)of kidney tissue,and one portion(about 10-50ml)of water sample were taken for each case respectively.(2)The numbers,sizes and types of diatoms(classified into genera)were recorded in the samples from 100 drowning cases using the Microwave Digestion-Vacuum Filtration-Automated Scanning Electron Microscopy method.Statistical analyses were performed by SPSS 24.0.Results:1.Digestive tract barriers(The blank group and The treatment group)1.1 The types of diatoms:In the blank group,a total of 44 diatoms were detected and 12 were Nitzschia,accounting for 27.3%,Stephanodiscus,Coscinodiscus(small)and Coscinodiscus(large)were not detected.In the treatment group,Nitzschia and Stephanodiscus were detected in the lung tissues,liver tissues,kidney tissues,spleen tissues and blood and Coscinodiscus were detected only in the lung tissues and the blood1.2 Diatom detection rate:In the blank group,Nitzschia were detected in 4/10 of experimental rabbits,and in the treatment group,Nitzschia,Stephanodiscus,Coscinodiscus(small)and Coscinodiscus(large)were detected in 22/29 of experimental rabbits.The difference between the two groups was statistically significant(P=0.048<0.05),suggesting that the detection rate of the blank group was different from that of the treatment group,and the detection rate of the treatment group was higher.1.3 The numbers of diatoms:In the blank group,the numbers of diatoms in the lung,liver,kidney tissues and blood were 1.20±2.05 valves/10g,1.05±3.31 valves/10g,0.43 ± 0.91 valves/10g,3.21 ± 10.14 valves/10g,respectively.In the treatment group,the numbers of diatoms in the lung,liver,kidney,spleen tissues,blood and stomach contents were 2.63±4.74 valves/10g,0.22± 0.64 valves/10g,0.35± 0.93 valves/10g,0.95± 3.69 valves/10g,0.71± 2.11 valves/10g,66.93± 103.34 valves/10g,respectively.1.4 The length of diatoms:In the blank group,the length of diatoms in the lung liver,kidney tissues were 18.16± 8.95 um,11.93 ± 2.04 um,23.21 ± 2.51 um,respectively.In the treatment group,the length of diatoms in the lung,liver,kidney,spleen tissues,blood and stomach contents were 47.70±54.72 um,12.39± 3.17 um,15.05 ± 5.38 um,8.43 ± 2.35 um,43.89± 58.98 um,25.00 ± 13.81 um,respectively.1.5 The width of diatoms:In the blank group,the width of diatoms in the lung liver,kidney tissues were 3.80 ± 1.12 um,2.71 ± 0.32 um,4.01 ± 0.31 um,respectively.In the treatment group,the width of diatoms in the lung,liver,kidney,spleen tissues,blood and stomach contents were 45.60 ± 56.17 um,5.95 ± 5.93 um,5.43± 3.60 um,3.68 ± 1.85 um,40.88 ± 61.64 um,25.00 ± 13.81 um,respectively.1.6 The distribution of the sizes of diatoms:75%of diatom valves in the lung,liver,kidney,spleen tissues and blood have a maximum length of less than 40 um and 75%of diatom valves in the stomach contents have a maximum length of less than 30 um.75%of diatom valves in the lung,liver,kidney,spleen tissues and blood have a maximum width of less than 40 um and 75%of diatom valves in the stomach contents have a maximum width of less than 30 um.There were no statistical differences between the length of diatoms in the tissues(lung,liver,kidney,spleen and blood)and stomach contents(P=0.101>0.05).There were no statistical differences between the width of diatoms in the tissues(lung,liver,kidney,spleen and blood)and stomach contents(P=0.053>0.05).It can be concluded that digestive tract barriers is not selective to the length and width of standardized diatom.2.Respiratory tract barriers2.1 The numbers of diatoms:The numbers of diatoms in the liver tissues were 17.01±31.48 valves/10g.The numbers of diatoms in the kidney tissues were 15.12±20.42 valves/10g.The numbers of diatoms in the lung tissues were 103,688.16 ±251,457.30 valves/10g.The numbers of diatoms in the water.samples are were 10,488.39± 15,449.16 valves/10g.The lung tissues have the largest number of diatoms that is approximately 10 times the average number of diatoms in the water samples.The numbers of diatoms in the liver and kidney tissues are about 16 valves/10g,much less than that in the lung tissues and water samples2.2 The length of diatoms:The length of diatoms in the liver tissues were 17.39 ±10.00 um.The length of diatoms in the kidney tissues were 16.75±11.26 um.The length of diatoms in the lung tissues were 19.49± 17.21 um.The length of diatoms in water samples were 22.20 ± 21.93 um.The length of diatoms in water samples was the longest among all samples.The length of diatoms in water samples and lung tissues was longer than that in liver and kidney tissues with statistical differences.There were no statistical differences between the length of diatoms in the liver and kidney tissues2.3 The width of diatoms:The width of diatoms in the liver tissues were 6.06 ±4.43 um.The width of diatoms in the kidney tissues were 5.82± 4.11 um.The width of diatoms in the lung tissues were 7.76± 5.45 um.The width of diatoms in water samples were 7.30 ± 5.63 um.The width of diatoms in lung tissues was the largest among all samples.The width of diatoms in water samples and lung tissues was larger than that in liver and kidney tissues with statistical differences.The differences between the width of diatoms in the liver and kidney tissues were not statistically significant.2.4 The distribution of the sizes of diatoms:The length of diatoms is more widely distributed than the width.However,the distribution of the width is more concentrated.More than 90%of diatom valves have a maximum length of less than 50 um,and over 45%have a maximum length of less 15 um.Over 90%of diatoms have a maximum width of less than 15 um,and over 75%have a maximum width of under 10 um.2.5 The distribution of the types of diatoms:The percentage of centric diatoms in the closed organs(liver and kidney)is 31%while that of pennate diatoms is 69%.The percentage of centric diatoms in lung and water samples is 55%and 54%respectively while that of pennate diatoms is 45%and 46%respectively.The percentage of pennate diatoms in the closed organs are higher than that in the lung and water samples with statistical differences.The top three pennate diatom genus in quantities are Navicula,Nitzschia and Cymbella.Conclusion:(1)Diatoms can enter the body through the digestive tract barrier and the digestive tract barriers is not selective to the length and width of standardized diatom(2)In drowning cases,the length and the width of the diatoms in the liver and kidney tissues are smaller than that in the lung tissues and water samples and that means the alveoli-capillary barrier has a selectivity for the size of diatoms.(3)In drowning cases,it is easier for pennate diatoms to be inhaled into the alveoli,to penetrate through the alveoli-capillary barrier,and reach distant organs such as the liver and kidney tissues.(4)Our results provided the evidence to support the theory of diatoms penetrating the alveoli-capillary barrier. |
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