N -ethyl- N -nitrosourea induces retinal photoreceptor damage in adult rats

Seven-week-old male Lewis rats received a single intraperitoneal injection of N-ethyl-N-nitrosourea (ENU) (100, 200, 400 or 600 mg/kg), and retinal damage was evaluated 7 days after the treatment. Sequential morphological features of the retina and retinal DNA damage, as determined by a TUNEL assay and phospho-histone H2A.X (γ-H2AX), were analyzed 3, 6, 12, 24 and 72 hr, 7 days, and/or 30 days after 400 mg/kg ENU treatment. Activation of the nuclear enzyme poly (ADP-ribose) polymerase (PARP) was analyzed immunohistochemically by poly (ADP-ribose) (PAR) expression in response to DNA damage of the retina. All rats that received ≥ 400 mg/kg of ENU developed retinal degeneration characterized by the loss of photoreceptor cells in both the central and peripheral retina within 7 days. In the 400 mg/kg ENU-treated rats, TUNEL-positive signals were only located in the photoreceptor cells and peaked 24 hr after ENU treatment. The γ-H2AX signals in inner retinal cells appeared at 24 hr and peaked at 72 hr after ENU treatment, and the PAR signals selectively located in the photoreceptor cell nuclei appeared at 12 hr and peaked at 24 hr after ENU treatment. However, degeneration was restricted to photoreceptor cells, and no degenerative changes in inner retinal cells were seen at any time points. Retinal thickness and the photoreceptor cell ratio in the central and peripheral retina were significantly decreased, and the retinal damage ratio was significantly increased 7 days after ENU treatment. In conclusion, ENU induced retinal degeneration in adult rats that was characterized by photoreceptor cell apoptosis through PARP activity.     

高寒草甸类草地不同退化状态人工恢复与自然恢复经济分析

根据草地植被群落发展规律,利用数学和统计学、投入产出法等方法,对高寒草甸类不同退化状态草地自然恢复和人工恢复进行了经济预测和效益比较。数据证明:在重度→中度恢复中,人工恢复较自然恢复效益高;在中度→轻度恢复中,自然恢复较人工恢复效益高。此结果为草地建设科学决策提供了可靠依据。     

基于公共物品理论的中国西北生态脆弱区资源退化分析

不同类型的物品使生产者和消费者面临不同的激励与约束条件。公共物品理论是研究公共事务的一种现代经济理论。由于在使用上具有一定的非排他性,我国西北生态脆弱区广大的林地、草场以及有限的水资源等公共资源在很大程度上属于准公共物品。基于公共物品理论的认识,从人的行为选择与人口的增长角度深入剖析了生态脆弱区资源环境退化的机理与过程,并在此基础上探讨了公共资源的演化轨迹。分析表明:在资源的开发初期和中期,外在经济利益的刺激是导致资源开发强度不断加大,并逐步出现退化的主要原因。然而当资源的开发程度超过其可持续承载力之后,由于人口增长的惯性,长时间人口增长带来的生存压力逐渐开始显现出来,引起资源退化的动力已有外在的经济刺激演化为内在的生存压力。人口超载已经成为加速公共资源枯竭和地区贫困的最主要因素。     

Histological Changes in the Deep Branch of the Lateral Palmar Nerve of Horses With Induced Proximal Suspensory Desmitis

Desmitis of the proximal aspect of the suspensory ligament, or interosseus medius muscle, of the pelvic or thoracic limb is a commonly diagnosed cause of lameness of performance horses. Despite medical treatments available for horses with proximal suspensory desmitis (PSD), most horses treated medically for PSD of a pelvic limb remain persistently lame; this persistent lameness may be the result of a neuropathy caused by compression of nerves by an enlarged suspensory ligament. Few horses with PSD of a thoracic limb remain persistently lame. Based on the results of reports citing successful treatment of horses chronically lame because of PSD of a pelvic or thoracic limb, by excising a portion of the deep branch of the lateral plantar or palmar nerve (DBLPlN/DBLPaN), we theorized that persistent lameness of horses caused by PSD of a thoracic limb may also be due to compression of nerves that supply the ligament. The aim of this study was to determine if histological signs of compression neuropathy of the DBLPaN are present in horses with PSD in a thoracic limb. To test this hypothesis, we induced PSD by instilling collagenase into the ligament and then examined the DBLPaN after harvesting this nerve 2 months later. We found that the DBLPaNs of all treated limbs showed histologic changes suggestive of nerve compression. We conclude that studies examining the DBLPaN of horses with naturally occurring PSD for histological evidence of neuropathy are warranted.     

Retinal degeneration in nine Swedish Jämthund dogs

The Jämthund is the fourth most common breed in Sweden with approximately 1600 pups registered each year. Although it has been known that some adult dogs go blind, so they cannot hunt, the Jämthund dog has historically not been screened for hereditary eye diseases. This report describes nine Swedish Jämthund dogs with retinal degeneration. These dogs represent all Jämthund dogs diagnosed with progressive retinal atrophy (PRA) by the Swedish Eye Panel and registered with the Swedish Kennel Club from January 1998 to September 2008. The dogs were examined with indirect opthalmoscopy and slitlamp biomicroscopy. Additionally, electroretinograms (ERGs) following ECVO guidelines were performed in two dogs (one affected and one normal) and the eyes from three affected dogs were examined by light‐microscopy postmortem. Typical findings were bilateral symmetric generalized retinal degeneration with tapetal hyper‐reflectivity, attenuation of blood vessels and pigment clumping in the nontapetal fundus. These retinal findings progressed with time in two dogs after re‐examination. Visual impairment, especially under dim light conditions, was observed in the affected dogs. ERG from one affected dog showed profoundly reduced rod responses, whereas cone responses were better preserved. Microscopic changes in the eyes from three dogs were characterized by a severe diffuse predominantly outer retinal degeneration and atrophy. Re‐sequencing of the prcd‐gene for eight of the nine investigated dogs revealed that none of the individuals carried disease allele that has been associated with prcd‐PRA in other breeds. In conclusion, ophthalmoscopic, electroretinographic, and light‐microscopic alterations observed in nine Jämthund dogs were compatible with PRA. The prcd mutation was excluded as a cause of this retinopathy.     

金昌地区森林生态系统退化成因及逆转措施

通过对金昌地区森林生态系统的评价和退化成因的分析,认为该地区森林生态系统退化是自然地理条件和人为破坏共同作用的结果。因此在逆转过程中,必须考虑上述两方面的作用,用社会生态系统理论科学合理布局和开发建设每一个生态单元,以期具备一个与经济发展相适应的林业生态环境,为经济、社会可持续发展奠定基础。     

中间锦鸡儿冠层降雨再分配特征

以荒漠草原人工中间锦鸡儿(Caragana intermedia)灌丛为对象,研究降雨量及降雨强度对两类形态灌丛(健康组和退化组)穿透雨、树干茎流和冠层截留的影响。结果表明:①试验期间共观测到有效降雨33次,以中小降雨事件为主,总降雨量为251mm,次平均降雨量和平均降雨强度分别为7.6mm和1.14mm·h^-1,其中降雨量<2mm,降雨强度<1mm·h^-1的降雨事件出现次数最多。②健康组和退化组中间锦鸡儿平均穿透雨率、树干茎流率和冠层截留率分别为66.7%、8.5%、24.8%和75.4%、8.7%、16.0%,两类形态灌丛之间穿透雨和截留存在显著差异(P<0.05)。③两类形态灌丛的穿透雨量、树干茎流量、截留量与降雨量成线性函数、对数函数和幂函数关系,且其穿透雨率、树干茎流率和截留率与降雨量、降雨强度之间成对数函数和幂函数关系。灌丛形态退化显著改变了冠层降雨再分配格局,冠层截留显著降低,穿透雨显著增加,潜在提高了降水对土壤水分的直接补充,一定程度上有利于人工中间锦鸡儿稳定性的维持。     

无声的危机--荒漠化与草原退化

阐述了荒漠化与草原退化的概念，成因及相互关系，强调指出绿洲周围的“两化”，除过牧，过垦，过伐等因素外，主要是水资源减少所致；提出了以荒漠型，盐渍型，黑土滩型，毒杂草型等为代表的草原退化的主要类型，并认为荒漠化与草原退化是无声的危机，威胁着人们的生存与发展，而荒漠化危害首当其冲的是草原，要防治荒漠化首先要防止草原退化。