Negative phototaxis in the photosymbiotic sea anemone Aiptasia as a potential strategy to protect symbionts from photodamage.

Photosymbiotic cnidarians generally seek bright environments so that their symbionts can be photosynthetically active. However, excess light may result in a breakdown of symbiosis due to the accumulation of photodamage in symbionts causing symbiont loss (bleaching). It is currently unknown if photosymbiotic cnidarians sense light only to regulate spawning time and to facilitate predation, or whether they also use their light-sensing capacities to protect their symbionts from photodamage. In this study, we examined how the sea anemone Aiptasia changes its behaviour when exposed to excess light. We reveal that Aiptasia polyps, when carrying symbionts, contract their bodies when exposed to high light intensities and subsequently migrate away in a direction perpendicular to the light source. Interestingly, this negative phototaxis was only evident under blue light and absent upon UV, green and red light exposure. Non-symbiotic Aiptasia did not exhibit this light response. Our study demonstrates that photosymbiotic Aiptasia polyps display negative phototactic behaviour in response to blue light, and that they also can perceive its direction, despite lacking specialized eye structures. We postulate that Aiptasia uses blue light, which penetrates seawater efficiently, as a general proxy for sunlight exposure to protect its symbionts from photodamage.

Semi-in vitro detection of Mg2+-dependent DNase that specifically digest mitochondrial nucleoids in the zygote of Physarum polycephalum.

The maternal/uniparental inheritance of mitochondria is controlled by the selective elimination of paternal/uniparental mitochondria and digestion of their mitochondrial DNA (mtDNA). In isogamy, the selective digestion of mtDNA in uniparental mitochondria is initiated after mating and is completed prior to the elimination of mitochondria, but the molecular mechanism of the digestion of uniparental mtDNA remains unknown. In this study, we developed a semi-in vitro assay for DNase, wherein the digestion of mitochondrial nucleoids (mt-nucleoids) was microscopically observed using isolated mitochondria from Physarum polycephalum and the DNase involved in uniparental inheritance was characterized. When myxamoebae of AI35 and DP246 are crossed, mtDNA and mt-nucleoid from only the DP246 parent are digested. The digestion of mt-nucleoids was observed in zygotes 3 h after plating for mating. During the digestion of mt-nucleoids, mitochondrial membrane integrity was maintained. In the semi-in vitro assay, the digestion of mt-nucleoids was only observed in the presence of Mg2+ at pH 7.5-9.0. Moreover, such Mg2+-dependent DNase activity was specifically detected in mitochondria isolated from zygotes 3 h after plating for mating. Therefore, Mg2+-dependent DNase is potentially involved in uniparental inheritance. Our findings provide insights into the DNase involved in uniparental inheritance and its regulatory mechanism.

Loss of symbiont infectivity following thermal stress can be a factor limiting recovery from bleaching in cnidarians.

Increases in seawater temperature can cause coral bleaching through loss of symbiotic algae (dinoflagellates of the family Symbiodiniaceae). Corals can recover from bleaching by recruiting algae into host cells from the residual symbiont population or from the external environment. However, the high coral mortality that often follows mass-bleaching events suggests that recovery is often limited in the wild. Here, we examine the effect of pre-exposure to heat stress on the capacity of symbiotic algae to infect cnidarian hosts using the Aiptasia (sea-anemone)-Symbiodiniaceae model system. We found that the symbiont strain Breviolum sp. CS-164 (ITS2 type B1), both free-living and in symbiosis, loses the capacity to infect the host following exposure to heat stress. This loss of infectivity is reversible, however, a longer exposure to heat stress increases the time taken for reversal. Under the same experimental conditions, the loss of infectivity was not observed in another strain Breviolum psygmophilum CCMP2459 (ITS2 type B2). Our results suggest that recovery from bleaching can be limited by the loss of symbiont infectivity following exposure to heat stress.

Correlation between FDG-PET/CT findings and solid type non-small cell cancer prognostic factors: are there differences between adenocarcinoma and squamous cell carcinoma?

OBJECTIVES: The maximum standardized uptake value (SUVmax) of FDG-PET/CT is commonly used as an indicator to evaluate the invasiveness and prognosis of non-small-cell lung cancers (NSCLC). We investigated the correlation between SUVmax and tumor invasiveness or postoperative recurrence of solid type NSCLC and compared squamous cell carcinoma (SCC)/adenosquamous carcinoma (ASC) to adenocarcinoma (AC). METHODS: A retrospective review of preoperative PET/CT, thin-section CT, and postoperative pathological records obtained over a 5-year period was conducted. Solid type NSCLC tumors on thin-section CT with confirmed diagnosis from surgical resection (diameter ≤3 cm) were included. Multivariate logistic regression was used to evaluate the correlation between tumor characteristics and pathological prognostic factors or postoperative recurrence. RESULTS: 150 patients (111 males, 39 females; mean age 67 years; 106 cases of AC, 36 cases of SCC, and 8 cases of ASC) were included. SUVmax was significantly correlated with pleural involvement (p = 0.047), lymphatic permeation (p = 0.003), lymph node metastasis (p = 0.027), and tumor invasiveness (p < 0.001). Receiver operating characteristic analysis indicated an optimal SUVmax threshold of 5.0 for tumor invasiveness. Histopathological type was significantly correlated with pleural involvement (p = 0.042), but not with other types of invasiveness. Twenty-nine patients experienced postoperative recurrence. SUVmax was significantly correlated with tumor recurrence (p = 0.004), but size and histopathological type were not (p = 0.502 and p = 0.351, respectively). CONCLUSION: SUVmax of the primary lesion in solid type NSCLC was significantly correlated with tumor invasiveness and postoperative recurrence. No differences in tumor invasiveness were observed between solid type AC and SCC/ASC. However, in solid type AC, SUVmax of the primary lesion was more significantly correlated with recurrence.

Prognostic evaluations of small size lung cancers by 18F-FDG PET/CT and thin-section CT.

PURPOSE: Primary lung cancers have varying prognoses, even for tumors ≤3cm in diameter. Thus, a thorough evaluation is necessary for therapeutic planning. Two imaging biomarkers have been shown to be useful for predicting primary lung cancer prognosis: maximum standardized uptake values (SUVmax) on fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) and the consolidation/tumor (C/T) ratio defined as the maximum diameter of consolidation within a tumor to the maximum tumor diameter on thin-section computed tomography (TSCT). We compared these biomarkers for predicting post-surgical recurrence in patients with small lung cancers. MATERIALS AND METHODS: Clinical records, post-operative pathologic findings, and pre-operative PET/CT and TSCT images were reviewed. Solitary primary lung cancers of ≤3cm in diameter after surgical resection were selected for analysis. SUVmax and C/T ratios were recorded. Kaplan-Meier survival curves and Cox hazards ratios were used to identify independent predictors of lung cancer recurrence from among age, gender, surgical procedure, lesion size, C/T ratio, and SUVmax. RESULTS: A total of 169 patients (114 males and 55 females; age range: 34-87 years) with solitary lung cancers were evaluated. The median post-operative follow-up period was 42 months. Twenty-eight patients had cancer recurrence with significantly higher SUVmax (p<0.001) and C/T ratios (p<0.001) than patients without recurrence. Disease-free survival was significantly reduced for SUVmax of ≥2.5 vs. SUVmax of <2.5 (p<0.001) or for a C/T ratio of ≥50% vs. a C/T ratio of <50% (p=0.030). For 19 patients with C/T ratios of <50%, none had a post-operative recurrence. A Cox hazards ratio model showed that only SUVmax was an independent predictor of recurrence (hazards ratio=1.324; p<0.001). CONCLUSION: SUVmax on FDG-PET/CT was a significant imaging biomarker relevant to the prognosis of patients with lung cancers, and was superior to the C/T ratio on TSCT for predicting postoperative recurrence, particularly for solid type lung cancer.

Prediction of pathologic prognostic factors in patients with lung adenocarcinomas: comparison of thin-section computed tomography and positron emission tomography/computed tomography.

BACKGROUND: The ratio of the maximum diameter of consolidation to the maximum tumor diameter (C/T ratio) on thin-section computed tomography (TSCT) and the maximum standardized uptake value (SUVmax) on 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) are often used as preoperative independent variables to evaluate the invasiveness of lung adenocarcinoma. We investigated the associations between these independent variables and pathologic invasiveness in pulmonary adenocarcinomas. METHODS: We selected patients with peripheral lung adenocarcinomas, definitively diagnosed by surgical resection, with diameters of ≤ 30 mm over a 4-year period ending in December 2010. The association between 3 independent variables (tumor size, SUVmax, and C/T ratio) and pathologic prognostic factors was evaluated using logistic analysis. RESULTS: We evaluated a total of 163 primary lung adenocarcinomas in 148 patients (93 males and 55 females; age range: 34 to 84 years). Using multivariate logistic regression analysis, SUVmax and the C/T ratio were significantly associated with tumor invasiveness (odds ratio [OR] = 1.227; p = 0.025 and OR = 1.019; p = 0.008, respectively). Tumor size was not associated with invasiveness (OR = 1.003; p = 0.925). For solid type adenocarcinomas, only SUVmax was significantly associated with invasiveness (OR = 1.558; p = 0.003). For subsolid type adenocarcinomas, only the C/T ratio was significantly associated with invasiveness (OR = 1.030; p = 0.009). CONCLUSIONS: Both the C/T ratio and the SUVmax are significantly correlated with pathologic invasiveness in patients with small lung adenocarcinomas, while there was a difference between the 2 evaluations. Solid type adenocarcinomas with SUVmax values of ≥ 4.4 and subsolid type adenocarcinomas with C/T ratio ≥ 53% were so highly invasive.

Pulmonary lobar volumetry using novel volumetric computer-aided diagnosis and computed tomography.

OBJECTIVES: To compare the accuracy of pulmonary lobar volumetry using the conventional number of segments method and novel volumetric computer-aided diagnosis using 3D computed tomography images. METHODS: We acquired 50 consecutive preoperative 3D computed tomography examinations for lung tumours reconstructed at 1-mm slice thicknesses. We calculated the lobar volume and the emphysematous lobar volume < -950 HU of each lobe using (i) the slice-by-slice method (reference standard), (ii) number of segments method, and (iii) semi-automatic and (iv) automatic computer-aided diagnosis. We determined Pearson correlation coefficients between the reference standard and the three other methods for lobar volumes and emphysematous lobar volumes. We also compared the relative errors among the three measurement methods. RESULTS: Both semi-automatic and automatic computer-aided diagnosis results were more strongly correlated with the reference standard than the number of segments method. The correlation coefficients for automatic computer-aided diagnosis were slightly lower than those for semi-automatic computer-aided diagnosis because there was one outlier among 50 cases (2%) in the right upper lobe and two outliers among 50 cases (4%) in the other lobes. The number of segments method relative error was significantly greater than those for semi-automatic and automatic computer-aided diagnosis (P < 0.001). The computational time for automatic computer-aided diagnosis was 1/2 to 2/3 than that of semi-automatic computer-aided diagnosis. CONCLUSIONS: A novel lobar volumetry computer-aided diagnosis system could more precisely measure lobar volumes than the conventional number of segments method. Because semi-automatic computer-aided diagnosis and automatic computer-aided diagnosis were complementary, in clinical use, it would be more practical to first measure volumes by automatic computer-aided diagnosis, and then use semi-automatic measurements if automatic computer-aided diagnosis failed.