水稻纹枯病(Pellicularia sasakii (Shirai) Wei)菌丝的活动与病害发生的关系

纹枯病菌絲在田間稻株上的消长受水稻各生育期、及当时气候条件影响很大;一般在孕穗职前菌絲量少,孕穗至乳熟初期分布量大、蔓延速度快;抽穗期后10天达到最高峯。早稻成熟期菌絲停止蔓延或消失;晚稻(尤其連作晚稻)抽穗期后因寒潮或低温而停止蔓延;乳熟期趋于消失。纹枯病菌核的发育一般要通过四个时期,无休眠期。病情的水平扩展速度以孕穗至抽穗期最快,乳熟期几停止;而垂直扩展速度以水稻分蘖期最慢,抽穗至乳熟期最快。矮稈品种2—3天,高稈品种3—5天便可士升一个叶位,乳熟后緩慢。晚稻則以抽穗期最快,抽穗后緩慢,乳熟后病势停滞不前。在水稻易感期(孕穗—抽穗),遇到梅雨的两端低温,职及矮稈品种、多肥、密植,在一定有效菌核量下,是本病流行期、流行程度的关鍵因素。防治适期应以菌絲蔓延前期,卽在分蘖期至孕穗期施药,以杀伤菌絲为主;有必要时可在抽穗期再施药一次,保护剑叶,以抑制菌核形成、兼杀菌絲为主。如对矮稈品种、多肥栽培的水稻,于分蘖期施药保护是很必要的。     

小麦对条锈病的水平抗病性研究初报

将小麦品种采用随机区组的田间设计种于小种病圃中,以鉴定和测定其水平抗性。根据各个“品种——小种”组合的相对病情指数的方差分析的结果,有些品种,如农大311、西农6028和丰产3号,其品种——小种互作高度显著,被鉴定为具有垂直抗性,另外一些品种,对试验所用的小种并无专化性,并且在大田生产中已显出20多年的持久的中度抗性,初步推测为属水平抗性。在后一类中,有些品种,如平原50,表现为中等反应型,其余则属于呈典型感病的迟锈慢锈类型。在迟锈慢锈品种的病指的对数矫正值(logits)和病圃的锈病强度(以感病对照品种的病指表之)的对数矫正值之间发现了直线回归。     

Novel Alkaloids from Marine Actinobacteria: Discovery and Characterization

The marine environment is an excellent resource for natural products with therapeutic potential. Its microbial inhabitants, often associated with other marine organisms, are specialized in the synthesis of bioactive secondary metabolites. Similar to their terrestrial counterparts, marine Actinobacteria are a prevalent source of these natural products. Here, we discuss 77 newly discovered alkaloids produced by such marine Actinobacteria between 2017 and mid-2021, as well as the strategies employed in their elucidation. While 12 different classes of alkaloids were unraveled, indoles, diketopiperazines, glutarimides, indolizidines, and pyrroles were most dominant. Discoveries were mainly based on experimental approaches where microbial extracts were analyzed in relation to novel compounds. Although such experimental procedures have proven useful in the past, the methodologies need adaptations to limit the chance of compound rediscovery. On the other hand, genome mining provides a different angle for natural product discovery. While the technology is still relatively young compared to experimental screening, significant improvement has been made in recent years. Together with synthetic biology tools, both genome mining and extract screening provide excellent opportunities for continued drug discovery from marine Actinobacteria.     

Approach to the patient in respiratory distress

Respiratory distress is a very common presenting complaint in emergency practice. It is essential that the clinician rapidly determine the underlying cause of the clinical signs using physical examination findings and nonstressful diagnostic tests. Oxygen therapy will often stabilize a patient, allowing for a more complete physical examination and diagnostics, including thoracocentesis, thoracic radiographs, and blood collection for laboratory analysis. The disease processes that cause respiratory distress can be grouped according to anatomic location: the airways, pulmonary parenchyma, pleural space, or thoracic wall. The choice of diagnostic and therapeutic techniques will be dependent on the suspected anatomic origin of disease. Techniques useful in diagnosing airway disorders include oral examination, cervical and thoracic radiographs, fluoroscopy, and bronchoscopy. Therapeutic techniques include intubation and tracheostomy. For parenchymal disease, thoracic radiographs, echocardiography, ultrasound of the thorax, and transtracheal or endotracheal wash can be useful. When the disease process is in the pleural space, thoracocentesis can be both diagnostic and therapeutic. Chest tube placement may be necessary for continuous removal of air or fluid from the pleural space. Monitoring of the respiratory patient can involve serial physical examination, pulse oximetry, and arterial blood gas analysis. It is essential to minimize stress on patients with respiratory distress because decompensation can occur easily, leading to respiratory arrest.     

Assessing performance of feedlot operations using epidemiology.

The progressive feedlot veterinarian must be well versed not only in individual production animal medicine, but also in population-based medicine. Feedlot health programs must be goal oriented, and evaluation of these goals is accomplished through diligent use of record systems and analytic evaluation of these record systems. Basic feedlot monitoring parameters include health and economic parameters in addition to the use of bench marking parameters between and among feed yards. When these parameters have significant changes, steps should be initiated to begin field investigations. Feedlot epidemiology uses several novel applications such as partial budgeting, risk assessment, and packing plant audits to provide scientifically sound and economically feasible solutions for the feeding industry.     

Protein engineering of Sulfolobus solfataricus maltooligosyltrehalose synthase to alter its selectivity

Maltooligosyltrehalose synthase (MTSase) is one of the key enzymes involved in trehalose production from starch and catalyzes an intramolecular transglycosylation reaction by converting the alpha-1,4- to alpha,alpha-1,1-glucosidic linkage. Mutations at residues F206, F207, and F405 were constructed to change the selectivity of the enzyme because the changes in selectivity could reduce the side hydrolysis reaction of releasing glucose and thus increase trehalose production from starch. As compared with wild-type MTSase, F405Y and F405M MTSases had decreased ratios of the initial rate of glucose formation to that of trehalose formation in starch digestion at 75 degrees C when wild-type and mutant MTSases were, respectively, used with isoamylase and maltooligosyltrehalose trehalohydrolase (MTHase). The highest trehalose yield from starch digestion was by the mutant MTSase having the lowest initial rate of glucose formation to trehalose formation, and this predicted high trehalose yield better than the ratio of catalytic efficiency for hydrolysis to that for transglycosylation.