Effects of carbon additions on iron reduction and phosphorus availability in a humid tropical forest soil

In the highly weathered soils of humid tropical forests, iron (Fe) plays a key role in ecosystem biogeochemical cycling through its interactions with carbon (C) and phosphorus (P). We used a laboratory study to explore the role of C quantity and quality in Fe reduction and associated P mobilization in tropical forest soils. Soils were incubated under an ambient atmosphere headspace (room air) with multiple levels of leaf litter leachate or acetate additions. Net Fe reduction occurred in all the treatments and at every time point. The more complex mixture of organic compounds in leaf litter leachate stimulated Fe reduction as much acetate, an easily fermentable C source. At the end of the experiment, Fe reduction was generally greater with higher C additions than in the low C additions and controls. The microbial biomass P had increased significantly suggesting rapid microbial uptake of P liberated from Fe. This occurred without increases in the available (NaHCO₃) P pool. The immobilization of P by microbes during the incubation provides a P conservation mechanism in these soils with fluctuating redox potential, and may ultimately stimulate more C cycling in these highly productive ecosystems. Iron cycling appears to be an important source of P for the biota and can contribute significantly to C oxidation in upland tropical forest soils.     

Mechanism of action of sodium channel blocker insecticides (SCBIs) on insect sodium channels

Sodium channel blocker insecticides (SCBIs) are a relatively new class of insecticides, with a mechanism of action different from those of other classes of insecticides that target voltage-gated sodium channels. These compounds have no effect at hyperpolarized membrane potentials, but cause a voltage-dependent, nearly irreversible block as the membrane potential is depolarized. The mechanism of action of SCBIs is similar to that of local anesthetics (LAs), class I anticonvulsants and class I antiarrhythmics. In this article, we review the physiological actions of these compounds on the whole animal, the nervous system and sodium channels, and also present the results from recent studies that elucidate the receptor site of SCBIs.     

Clinical signs associated with brain tumors in dogs: 97 cases (1992-1997).

OBJECTIVE: To determine the prevalence of various clinical signs in dogs with brain tumors. DESIGN: Retrospective study. ANIMALS: 97 dogs with brain tumors. PROCEDURE: Medical records were reviewed for signalment, tumor type and location, and clinical signs. RESULTS: 33 breeds were represented; Golden Retrievers were most commonly affected. Most dogs were older (median age, 9 years); 95% of dogs were > or = 5 years old. Seventy-six percent of dogs had tumors in the supratentorial region. Seizures were the most common clinical sign at initial examination, with lower prevalence for circling, ataxia, and head tilt. Meningioma was the most common tumor. CONCLUSIONS AND CLINICAL RELEVANCE: Brain tumors develop most often in dogs > or = 5 years old and are uncommon in dogs < 5 years old. Seizures are a common clinical sign, and a brain tumor should be considered in dogs that have their first seizure after they are 4 years old.     

规模化猪场猪支原体肺炎控制及净化技术研究

在四川蒲江某规模化８养猪场 ,对该场的猪支原体肺炎采用以监测、免疫为主,隔离、治 疗、淘汰、消毒等综合防制技术进行控制与净化,对全场有猪支原体肺炎症状的猪及可疑病猪进行隔治疗,治愈后的猪经与易感猪同居感染不发病,分离猪肺炎支原体为阴性,试验表明治愈后的猪不带菌。对全场种猪和后备健康猪群进行猪支原体肺炎疫苗的免疫接种,经抗体监测和攻毒试验,免疫后２４０天猪支原体肺炎的ＩＨＡ抗体仍可达到１：１０,保护率     

Physiological and pathological influences on sheep blood plasma amine oxidase: Effect of pregnancy and experimental alloxan-induced diabetes mellitus

A copper-containing amine oxidase is present in sheep blood plasma and has a high capacity to deaminate spermine and spermidine. The physiological function of this enzyme remains to be determined. Sheep blood plasma amine oxidase (SPAO) was measured by its ability to deaminate spermidine (700 microM) using a peroxidase-linked colorimetric assay developed for microtitre plates. SPAO activity has been studied in a group of Welsh Mountain sheep with experimental alloxan-induced diabetes. This resulted in an increase in SPAO activity which reached a peak of 70 days after alloxan treatment (60 per cent increase). This change could be seen in both pregnant and non-pregnant diabetic sheep. In normal pregnant ewes, SPAO activity remained stable for the first 100 days of pregnancy but declined by 50 per cent in the last month of pregnancy. Together, these findings suggest that SPAO activity is controlled by hormonal influences. This sensitive and convenient assay method could provide clues as to the physiological significance of SPAO and may be a useful clinical chemical indicator in the sheep.     

Characterisation of a novel Mannheimia sp from Australian feedlot cattle

OBJECTIVE: To characterise eight isolates of a Gram-negative organism obtained from the upper respiratory tract of cattle showing evidence of mild upper respiratory tract disease. DESIGN: The isolates were compared with the five recognised species within the genus Mannheimia - M haemolytica, M glucosida, M granulomatis, M ruminalis and M varigena--using a range of phenotypic and genotypic methods. RESULTS: Phenotypic characterisation indicated that the isolates belonged to the trehalose-negative [Pasteurella] haemolytica complex. This complex has recently been reorganised into five species within the new genus Mannheimia. Ribotyping performed using HindIII and a computerised analysis system indicated that the eight Australian isolates formed a distinct cluster that was related to, but different from, the five recognised species of Mannheimia. The 16S rRNA sequence of one isolate (BNO311) was determined and a phylogenetic analysis performed. Isolate BNO311 was distinct from the five named Mannheimia spp but did join a larger cluster consisting of rRNA cluster IV (M varigena) and the unnamed rRNA cluster V of Mannheimia. DNA:DNA hybridisation between isolate BNO311 and M haemolytica NCTC 9380T, M granulomatis P411 and Actinobacillus ligniersii NCTC 4189T all suggested similarities of approximately 30%. CONCLUSIONS: These phenotypic and genotypic characterisation studies suggest that the eight Australian isolates represent a new species of Mannheimia. Until further characterisation studies are performed, we are unwilling to propose a name for this taxon, preferring to refer to this possible new species as Bisgaard taxon 39 of cluster V of Mannheimia.