Introgressive hybridization between two non-native apple snails in China: widespread hybridization and homogenization in egg morphology.

BACKGROUND: Apple snails from the genus Pomacea have spread widely in paddy fields and other wetlands of southern China since their introduction in the 1980s. Pomacea spp. are commonly identified using mitochondrial COI sequences. However, sequencing the nuclear elongation factor 1-alpha (EF1α) gene revealed genetic introgression between field populations of P. canaliculata and P. maculata, which produce surviving hybrids in laboratory crossbreeding experiments. RESULTS: In this study, we sequenced 1054 EF1α clones to design specific primers and established a fast and accurate multiplex polymerase chain reaction (PCR) method for genotyping EF1α. Combined with genotyping P. canaliculata and P. maculata based on mitochondrial COI and nuclear EF1α, we revealed the genetic introgression patterns of 30 apple snail populations in China. Purebred and hybrid individuals of P. canaliculata were widely distributed, while pure maculata-EF1α type was detected only in a few individuals identified as P. canaliculata based on COI sequences. Each egg clutch had one to three genetic patterns, indicating multiple paternity or segregation in the progeny of hybrids. The higher percentages of hybrids in both wild populations and progeny than the homozygotes indicated a potential heterosis in the apple snail populations. Additionally, egg size and clutch size of the apple snails became homogeneous among the non-native populations exhibiting introgression hybridization. CONCLUSION: Our findings emphasize the value of apple snails as a model to study the mechanisms and impacts of introgressive hybridization on fitness traits. © 2020 Society of Chemical Industry.

Comparative mitogenome analysis on species of four apple snails (Ampullariidae: Pomacea).

The genus Pomacea contains most of the economically important Ampullariid apple snails. Five Pomacea species were reported introduced out of their native ranges, including three highly invasive species, i.e. P. maculata, P. canaliculata and an unidentified species, Pomacea sp. In this study, the mitogenome of P. maculata was determined, which carried typical gene set of metazoan mitogenomes and shared the same gene rearrangement of Ampullariidae mitogenomes. The control region of the P. maculata has a 13-bp inverted repeat unit. We compared the mitogenome of P. maculata with P. canaliculata, Pomacea sp. and the aquatic pet species, P. diffusa. The three highly invasive species showed high sequence similarity of PCGs and RNAs. atp8 and nad2 showed the lowest similarity and the highest Ka/Ks ratios, indicating that both genes have potential for studying species identification and populations genetics in apple snails. All PCGs have the Ka/Ks ratios <1, indicating the existence of purifying selection in Pomacea species. We reconstructed phylogenetic trees using 14 Caenogastropda species based on sequences of PCGs and rRNAs using Bayesian inference. Pomacea maculata grouped with other Ampullariids and was most closely related to Pomacea sp. The mitogenome of P. maculata provides useful genetic resource for exploring the genetics and evolution of P. maculata and other apple snails.

[Research progress on DNA barcoding analysis methods]. / DNAæ¡å½¢ç åˆ†æžæ–¹æ³•ç ”ç©¶è¿›å±•.

DNA barcode is a fragment of short DNA sequence from a standard part of the genome. DNA barcoding is an effective taxonomic method for species identification through analyzing the DNA barcodes. With the dramatic increasing of DNA barcode sequences, the analysis methods have developed rapidly, which promoted their applications in molecular identification for organisms. Since 2003, DNA barcoding has been widely used in species identification for animals, plants, fungi, etc. It has also robustly promoted the development of scientific disciplines, such as taxonomy, biodiversity science, and ecology. Based on review of DNA barcoding techniques, we summarized five main analysis methods on DNA barcodes, i.e. the genetic distance-, genetic similarity-, phylogenetic tree-, sequence characters-, and statistical classification-based methods. Moreover, we proposed a prospect for research and applications of DNA barcoding in the future.

Distribution and the origin of invasive apple snails, Pomacea canaliculata and P. maculata (Gastropoda: Ampullariidae) in China.

Species of Pomacea, commonly known as apple snails, are native to South America, and have become widely distributed agricultural and environmental pests in southern China since their introduction in the 1980s. However, only since 2010 have researchers recognized that at least two species, P. canaliculata and P. maculata, are present in China. Although impacts of apple snails have been extensively documented, confusion still persists regarding current distributions and origin of the species in China. To resolve this confusion, we used phylogenetic and phylogeographic methods to analyze 1464 mitochondrial COI sequences, including 349 new sequences from samples collected in southern China and 1115 publicly available sequences from snails collected in the native and introduced ranges. Pomacea canaliculata was found at all sampled localities, while P. maculata was found at only five sampled localities in the Sichuan basin and Zhejiang province. Our data indicate that Chinese populations of P. canaliculata share an Argentinian origin, consistent with multiple introductions of this species elsewhere in Asia. In addition, just a single lineage of P. maculata is established in China, which shares with populations in Brazil.

The effect of process parameters and microstructural changes on a new convenience food - quick-frozen paste-coated mushrooms (Agaricus bisporus).

The technology of quick-freezing paste-coated mushrooms (Agaricus bisporus) was studied and optimized. The best microwave pretreatment condition for 1 cm slices, regarding color protection, was 5.4 W/g, for 55, 55-60 and 60 s for mushrooms with 3, 4 and 5 cm diameter caps respectively. For a batch of paste (668.2-1034.6 g), the process parameters considered were oil content (46.6-63.4 g), water content (381-562.6 g) and flour content (166-334 g) with a constant additional content of 30 g starch, 9 g baking powder, 2.6 g carrageenan, 30 g salt and 3 g pepper. These parameters were investigated using response surface methodology (RSM) with a central composite design. The optimal levels of the major paste components were 300 g flour, 432.5 g water and 50 g oil. The freezing time and sensory acceptability for paste-coated Agaricus bisporus(PCAB) under the optimized conditions were 7.49 min and 6.2 respectively. The freezing curves of PCAB were established at different temperatures and the freezing rates were calculated to find the freezing characteristics. In addition, the cell structure of PCAB, frozen at -75 °C, the lowest freezing temperature, and studied using transmission electron microscopy, was similar in quality to that of fresh Agaricus bisporus. The results suggested that Agaricus bisporus can be quick-frozen with a paste coating to produce an acceptable and nutritious convenience food.

A treatment planning comparison between proton beam therapy and intensity-modulated x-ray therapy for recurrent nasopharyngeal carcinoma.

BACKGROUND AND PURPOSE: A comparative treatment planning study was undertaken between proton beam therapy (PBT) and intensity-modulated x-ray therapy (IMXT) for patients with recurrent nasopharyngeal carcinoma (NPC), to assess the potential benefits and limitations of the two treatment modalities. MATERIALS AND METHODS: We retrospectively analyzed seven patients with recurrent NPC treated at our proton center with PBT from 2004 to 2007. Eclipse proton treatment planning system and Eclipse inverse treatment planning system for IMXT were employed. For each patient, the IMXT plan was optimized with nine evenly spaced coplanar fields. Three coplanar beams and passive scattering mode were used for PBT. The dose prescription in cobalt Gray equivalent (CGE) for gross tumor volume (GTV) was 66CGE and for planning target volume (PTV), 62.7CGE. Dose-volume histograms (DVH) were used to evaluate the difference in dosimetric distributions for the target volume and the organs at risk (OARs). RESULTS: Optimal target volume coverage and similar target conformation were achieved in both PBT and IMXT. Median conformity index was 0.72 and 0.75 (p=0.15) and median inhomogeneity coefficient was 0.14 and 0.10 (p=0.08) for PBT and IMXT, respectively. Dose to OARs was significantly lower in PBT plans than IMXT. Median maximal dose to the brainstem was 27.89CGE(cobalt Gray equivalent) and 42.45Gy (p< 0.01), and the dose to 5% of the brainstem(D5) was 12.83CGE and 19.47Gy (p< 0.001 ), for PBT and IMXT, respectively. Median maximal dose to the spinal cord was 8.38CGE and 22.91Gy (p< 0.004), and the dose to 5% of the spinal cord was 2.18CGE and 13.62Gy (p< 0.001), for PBT and IMXT, respectively. CONCLUSIONS: The use of PBT, when compared with IMXT, resulted in similar levels of tumor conformation. PBT, however, exposed the OARs to a significantly lower dose, effectively sparing the brainstem, spinal cord, optic nerve and chiasm, temporal lobes and parotid glands. The superior dose distributions possible with PBT should translate into reduced morbidity and improved quality of life.

[Dose distributions of proton beam therapy for hepatocellular carcinoma: a comparative study of treatment planning with 3D-conformal radiation therapy or intensity-modulated radiation therapy].

OBJECTIVE: A comparative dose distribution study has been undertaken between proton beam therapy (PBT), 3-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) in the treatment of hepatocellular carcinoma (HCC), so as to assess the potential advantages of PBT. METHODS: Dose volume histograms (DVHs) were compared between PBT and 3D-CRT or IMRT planning at total dose of 66 Gy and 86 Gy in stage I patients (n = 10, diameter < or = 5 cm), 60 Gy and 72 Gy in stage IIA patients (n = 12, diameter = 5.1-10 cm). RESULTS: For patients with stage I, the mean liver dose (Dmean), V10, V20 and V30 were 13.01 Gy, 51.89%, 36.13% and 21.24% for 3D-CRT, whereas they were 6.34 Gy, 30.23%, 17.86% and 10.66%, respectively, for PBT (P < 0.002). With dose escalation to 86 Gy, the Dmean, V10, V20 and V30 were 16.91 Gy, 67.51%, 46.84% and 27.61% for 3D-CRT, whereas they were 8.26 Gy, 39.31%, 23.22% and 13.86%, respectively, for PBT (P < 0.002). Compared with 3D-CRT with dose of 66 Gy, PBT reduced the Dmean, V10, V20 and V30 even with dose escalation to 86 Gy (P < 0.042). For patients with stage IIA, the Dmean, V10, V20 and V30 were 29.18 Gy, 72.25%, 58.17%, 44.01% and 24.92 Gy, 73.32%, 56.15%, 37.75% for 3D-CRT and IMRT, respectively, with dose of 60 Gy, whereas they were 16.28 Gy, 43.93%, 33.54% and 22.78%, respectively, for PBT (P < 0.002). With dose escalation to 72 Gy, the Dmean, V10, V20, V30 were 35.02 Gy, 86.70%, 69.80%, 52.81% and 29.90 Gy, 87.98%, 67.74% and 45.30% for 3D-CRT and IMRT, respectively, whereas they were 19.54 Gy, 52.72%, 40.25% and 27.34%, respectively, for PBT (P < 0.002). Compared with 3D-CRT and IMRT with total dose of 60 Gy, PBT reduced the Dmean, V10, V20 and V30 even with dose escalation to 72 Gy (P < 0.05). In all of the 22 cases, compared with 3D-CRT, PBT reduced the doses to the nonliver OARs (organs at risks) including spinal cord, right kidney and stomach (P < 0.002). Compared with IMRT, PBT also reduced the dose to the right kidney and stomach significantly, while no significant difference was found respect to the dose to spinal cord (P > 0.05). CONCLUSION: Compared with 3D-CRT, PBT reduced the dose to the normal liver tissues and nonliver OARs significantly, even with 20 to 30.3 percent of dose escalation. Compared with IMRT, PBT reduced the dose to the normal liver tissues significantly, even with 20 to 30.3 percent of dose escalation. PBT reduced the dose to the right kidney and stomach significantly. No significant difference was observed respect to the dose to spinal cord.

Establishing the rDNA IGS structure of Cannabis sativa.

The rDNA intergenic spacer (IGS) structure of Cannabis sativa was established and can be used for classification and identification of this species. In this study, DNA fragments of rDNA IGS were amplified by PCR from Cannabis sativa plant extracts and a 1387 bp fragment was obtained. DNA sequence analysis revealed six different repeat motifs. In the middle of the IGS sequence, there were three sequence motifs, and the same three sections of DNA were then repeated with minor variation in sequence. The terminal region of the IGS was composed of another three different repeat units; multiple copies of these terminal repeat motifs were present in no discernible order. Within six repeat motifs, point variations were observed in five. The DNA sequence of the locus was compared with all the plant sequences registered in GenBank by the Fasta program of GCG software with the result that this DNA fragment was significantly different from any other DNA sequence recorded to date. The most similar sequence was that of Hops (Humulus lupulus), but with a similarity of only 88.9% over 579 bp. These specific and complex variations of IGS may be related to the species and geographic distributions.

[Value of 18F-FDG PET in clinical staging of non-small-cell lung cancer].

OBJECTIVE: To evaluate the feasibility of 18F-deoxyglucose positron emission tomography (18F-FDG PET) in the staging of non-small-cell lung cancer (NSCLC). METHODS: 105 patients with NSCLC had been examined by 18F-FDG PET and staged by PET before radiotherapy. The results of 18F-FDG PET examination were compared with those of CT. RESULTS: The staging was changed in 38 patients because of 18F-FDG PET findings with PET upstaged in 31 patients and downstaged in 7 patients. Because of distant metastasis detected by PET, 21 patients received palliative treatment. Six of the 7 downstaged patients underwent radical surgery, among which the PET findings were concordant with the operative findings in 5 patients. Distant metastasis detected by PET increased with elevation of pre-PET stage: at stage I 10.0% (2/20), stage II 14.3% (3/21) and stage III 25.0% (16/64), respectively. CONCLUSION: 18F-FDG PET, by changing clinical staging in 36.2% (38/105) NSCLC patients has impact on treatment strategy in NSCLC patients.

A highly polymorphic STR locus in Cannabis sativa.

We report on the first short tandem repeat (STR) locus to be isolated from the plant Cannabis sativa. The STR locus, isolated by a hybrid-capture enrichment procedure, was found to contain a simple sequence repeat motif of 6 bp. This 6 bp repeat motif showed no variation in repeat length but with minor variations in repeat unit sequences. The data show the locus to be highly polymorphic with the number of repeat units ranging from 3 to 40 in 108 screened samples. The observed heterozygosity was approximately 87.04%. The forward and reverse primers (CS1F and CS1R) produced no PCR products in cross-reaction study from 20 species of plants, including highly related species such as Humulus japonicus and Nicotiana tabacum. This hexanucleotide repeat DNA locus could be used to identify cannabis samples and predict their genetic relationship as the test is specific to C. sativa and is highly reproducible.