Effects of lens extirpation with anterior vitrectomy on vitreous three-dimensional mesh structure

AIM： To investigate the changes in vitreous gel structure after lens extirpation combined with anterior vitrectomy in rabbit eyes. METHODS： Twenty-eight chinchilla rabbits were divided into three groups. The control group （Group I） included 16 eyes from eight rabbits who did not receive any treatment. Group II included 20 eyes from 10 rabbits that underwent lens aspiration only. Group III included 20 eyes from 10 rabbits that underwent lens aspiration combined with posterior capsulotomy and anterior vitrectomy. Eyes were harvested on the 30th and 60th day postoperatively, respectively. Changes in vitreous gel stretch length due to gravity and the rate of vitreous liquefaction were observed. The collagen content in the vitreous body was examined using the L-hydroxyproiine test. Electronic microscopic images were obtained from each eyeball. RESULTS： On both the 30th and 60th day postoperatively, the vitreous gel length of group III was significantly shorter than group I and group II （P〈0.05）, while the rate of liquefaction of the vitreous body in group III was significantly higher than group I and group II （P〈0.05）. The collagen content in group Ul was also higher than that in group I and group II （P〈0.05）. CONCLUSION： Loss of vitreous gel mass is more likely to occur in the eyes of rabbits receiving anterior vitrectomy. Lensectomy combined with anterior vitrectomy may damage the stable three-dimensional mesh structure of collagen, which could aggravate vitreous gel liquefaction.

Improving Sustainability by Privatizing Wildlife Conservation

The purpose of this study is to improve environmental sustainability by identifying the most sustainable/least fragile of the three major wildlife conservation access models—open, government, and private—under varying environmental and socioeconomic conditions. The private access model is the most sustainable of the three major conservation models because it provides the best information and incentives to balance the needs of humans and wildlife, maintain general wildlife habitat, and adapt quickly to changing environmental and/or socioeconomic conditions. Government-controlled access, however, can be employed as a model of last resort if the private access model shows signs of failing to protect specific species from local extirpation or extinction, which it is most likely to do for migratory species, species with close commercial substitutes, and species with no direct commercial value. Government regulators may also be needed to enforce property rights arrangements like catch shares and to monitor resources that remain open access in case socioeconomic or environmental conditions change sufficiently to trigger the tragedy of the commons. Most treatments of wildlife regulation default to various iterations of the government access model and fail even to consider the costs and benefits of private and open access models. The analysis here instead shows the conditions in which each conservation access model is most appropriate: open when a resource is in high supply and low demand, private most of the time, and government when the others fail to slow resource depopulation/depletion.

Spatiotemporal distribution of seasonal bird assemblages on land-bridge islands: linking dynamic and static views of metacommunities

Background: Although assessing temporal dynamics of populations is crucial for understanding metacommunities, empirical studies have primarily analyzed only static snapshots of communities. Here, we present a holistic view of how species traits and habitat characteristics relate to metacommunity dynamics and use it to test for differences in the spatiotemporal distribution of seasonal bird assemblages. Methods: We surveyed forest birds in breeding and winter seasons within 36 islands for 9 years. We then grouped birds into four landbird assemblages, selected on the basis of published differences in biology or ecology: winter residents, migratory winter visitors, breeding summer residents, and migratory summer visitors. We estimated dynamic species colonization and extirpation through the 9-year period, and evaluated the associations among island attributes, species attributes and community composition. Results: Overall, winter and summer residents showed strong associations between composition and habitat structure of the islands. In addition, winter and summer residents on large islands had lower extirpation and turnover than winter and summer visitors. Visitor assemblages showed no significant habitat associations, and in winter had high extirpation rates and small body sizes. By contrast, local extirpation of summer visitors was correlated with local species richness, indicating a likely effect of competition on extirpation. Conclusions: Our results demonstrated repeated patterns among species composition, bird traits, habitat/island characteristics and observed metacommunity dynamics. Winter and summer residents best matched species sorting and patch dynamics, respectively, due to differences in resource availability and requirements of overwinter survival versus breeding. Summer visitors were consistent with species sorting and winter visitors were randomly distributed, likely because of interactions with resident competitors. Our results highlight that coexisting seasonal migrant and resident assemblages differ in their spatial dynamics, with consequences for relevant conservation and management strategies.

Brain Metastases: Epidemiological, Clinical, Diagnosis, Treatment and Outcome Features in Dakar

Brain metastases (BM) are the most frequent brain cancer. There are few studies on BM in Senegal. The aim of this study was to describe epidemiological, clinical, diagnosis, treatment and outcome features of patients diagnosed with BM. We conducted a retrospective and descriptive study of patients diagnosed with brain tumors and regularly followed at the neurosurgery department of the “Fann Teaching Hospital (CHNU-Fann)” of Dakar (Senegal) between from January 2010 to December 2017. The medical records of all the patients with evidence histologically diagnosed with BM were reviewed. In our study, 682 medical records of patients with brain tumors were reviewed, and only 20 showed histological evidence of BM (2.9%). The mean age was 45.45 years. The sex-ratio was 0.43. Brain CT scan was performed in all the patients (100%) and brain MRI in 3 patients. The brain lesions were multiple in 70% of the patients and single in 30%. The histological type of BM was adenocarcinoma (55%) and squamous cell carcinoma (45%). Five types of primary cancers were found: lung cancer (50%), breast cancer (30%), colorectal cancer (10%), melanoma (5%) and one undetermined cancer. All the patients had extirpation surgery;50% of the patients died 7 days after the surgery;25% had a survival of 3 months after the surgery and 25% of the patients were lost of sight. Conclusion: The improvement of the screening and diagnosis tests, and the use of the radiation treatment and chemotherapy could allow early management and decrease the death’s frequency of the patients with BM in Senegal.