Stable annual pattern of water use by Acacia tortilis in Sahelian Africa

Water use by mature trees of Acacia tortilis (Forsk.) Hayne ssp. raddiana (Savi) Brenan var. raddiana growing in the northern Sahel was continuously recorded over 4 years. Water use was estimated from xylem sap flow measured by transient heat dissipation. Concurrently, cambial growth, canopy phenology, leaf water potential, climatic conditions and soil water availability (SWA) were monitored. In addition to the variation attributable to interannual variation in rainfall, SWA was increased by irrigation during one wet season. The wet season lasted from July to September, and annual rainfall ranged between 146 and 367 mm. The annual amount and pattern of tree water use were stable from year-to-year despite interannual and seasonal variations in SWA in the upper soil layers. Acacia tortilis transpired readily throughout the year, except for one month during the dry season when defoliation was at a maximum. Maximum water use of about 23 l (dm sapwood area)(-2) day(-1) was recorded at the end of the wet season. While trees retained foliage in the dry season, the decline in water use was modest at around 30%. Variation in predawn leaf water potential indicated that the trees were subject to soil water constraint. The rapid depletion of water in the uppermost soil layers after the wet season implies that there was extensive use of water from deep soil layers. The deep soil profile revealed (1) the existence of living roots at 25 m and (2) that the availability of soil water was low (-1.6 MPa) down to the water table at a depth of 31 m. However, transpiration was recorded at a predawn leaf water potential of -2.0 MPa, indicating that the trees used water from both intermediary soil layers and the water table. During the full canopy stage, mean values of whole-tree hydraulic conductance were similar in the wet and dry seasons. We propose that the stability of water use at the seasonal and annual scales resulted from a combination of features, including an extensive rooting habit related to deep water availability and an effective regulation of canopy conductance. Despite a limited effect on tree water use, irrigation during the wet season sharply increased predawn leaf water potential and cambial growth of trunks and branches.     

An analysis of elastic and plastic fruit growth of mango in response to various assimilate supplies

Changes in elastic and plastic components of mango (Mangifera indica L. cv 'Cogshall') fruit growth were analyzed with a model of fruit growth over time and in response to various assimilate supplies. The model is based on water relations (water potential and osmotic and turgor pressures) at the fruit level. Variation in elastic fruit growth was modeled as a function of the elastic modulus and variation in turgor pressure. Variation in plastic fruit growth was modeled using the Lockhart (1965) equation. In this model, plastic growth parameters (yield threshold pressure and cell wall extensibility) varied during fruit growth. Outputs of the model were diurnal and seasonal fruit growth, and fruit turgor pressure. These variables were simulated with good accuracy by the model, particularly the observed increase in fruit size with increasing availability of assimilate supply. Shrinkage was sensitive to the surface conductance of fruit peel, the elasticity modulus and the hydraulic conductivity of fruit, whereas fruit growth rate was highly sensitive to parameters linked to changes in wall extensibility and yield threshold pressure, regardless of the assimilate supply. According to the model, plastic growth was generally zero during the day and shrinkage and swelling were linked to the elastic behavior of the fruit. During the night, plastic and elastic growths were positive, resulting in fruit expansion.     

Tissue Doppler imaging for detection of radial and longitudinal myocardial dysfunction in a family of cats affected by dystrophin-deficient hypertrophic muscular dystrophy

Diagnosis of feline hypertrophic cardiomyopathy currently is based on the presence of myocardial hypertrophy detected using conventional echocardiography. The accuracy of tissue Doppler imaging (TDI) for earlier detection of the disease has never been described. The objective of this sudy was to quantify left ventricular free wall (LVFW) velocities in cats with hypertrophic muscular dystrophy (HFMD) during preclinical cardiomyopathy using TDI. The study animals included 22 healthy controls and 7 cats belonging to a family of cats with HFMD (2 affected adult males, 2 heterozygous adult females, one 2.5-month-old affected male kitten, and 2 phenotypically normal female kittens from the same litter). All cats were examined via conventional echocardiography and 2-dimensional color TDI. No LVFW hypertrophy was detected in the 2 carriers or in the affected kitten when using conventional echocardiography and histologic examination, respectively. The LVFW also was normal for 1 affected male and at the upper limit of normal for the 2nd male. Conversely, LVFW dysfunction was detected in all affected and carrier cats with HFMD when using TDI. TDI consistently detects LVFW dysfunction in cats with HFMD despite the absence of myocardial hypertrophy. Therefore, TDI appears more sensitive than conventional echocardiography in detecting regional myocardial abnormalities.     

麦田间作对麦长管蚜的生态调控作用

[目的]探讨麦田间作对麦长管蚜种群的生态调控作用。[方法]田间调查小麦单作田、小麦与绿豆、小麦与豌豆以8:2行距间作田麦长管蚜种群数量及其时间动态变化;室内利用"Y"型嗅觉仪测定麦长管蚜对小麦、小麦与绿豆、小麦与豌豆不同组合气味的选择性。[结果]麦田间作不能影响麦蚜种群随时间动态变化曲线,但能在一定程度上降低麦长管蚜无翅蚜和有翅蚜的数量。室内麦长管蚜无翅蚜和有翅蚜显著选择寄主植物的气味。当小麦与绿豆或小麦与豌豆组合时对麦长管蚜没有吸引作用。[结论]非寄主植物的气味对寄主植物气味起掩盖作用,干扰蚜虫的寄主定位,这可能是间作低于单作蚜量的原因之一。     

Colorectal basidiobolomycosis in a dog

A 7-year-old castrated male French Bulldog was examined for chronic large intestinal enteropathy. A colonic mass and thickened rectal mucosa were identified, and histopathologic examination of endoscopic biopsy specimens disclosed eosinophilic proctitis with large (5-20 μm), irregularly shaped, pauciseptate hyphae that were Gomori methenamine silver and periodic acid-Schiff positive. Amplification and sequencing of ribosomal DNA extracted from paraffin-embedded tissues yielded a sequence with 97% identity to GenBank sequences for Basidiobolus ranarum. After itraconazole, terbinafine, and prednisone administration, clinical signs resolved rapidly, and sonographic lesions were largely absent after 6 weeks. Treatment was discontinued by the owner 15 weeks after diagnosis. Three weeks later, the dog collapsed acutely and was euthanized. Necropsy identified metastatic islet cell carcinoma and grossly unremarkable colorectal tissues. However, histopathology of the rectum disclosed multifocal submucosal granulomas with intralesional hyphae morphologically similar to those previously observed. This report is the first to describe medical treatment of gastrointestinal basidiobolomycosis in a dog.     

The genome of the African trypanosome Trypanosoma brucei

African trypanosomes cause human sleeping sickness and livestock trypanosomiasis in sub-Saharan Africa. We present the sequence and analysis of the 11 megabase-sized chromosomes of Trypanosoma brucei. The 26-megabase genome contains 9068 predicted genes, including approximately 900 pseudogenes and approximately 1700 T. brucei-specific genes. Large subtelomeric arrays contain an archive of 806 variant surface glycoprotein (VSG) genes used by the parasite to evade the mammalian immune system. Most VSG genes are pseudogenes, which may be used to generate expressed mosaic genes by ectopic recombination. Comparisons of the cytoskeleton and endocytic trafficking systems with those of humans and other eukaryotic organisms reveal major differences. A comparison of metabolic pathways encoded by the genomes of T. brucei, T. cruzi, and Leishmania major reveals the least overall metabolic capability in T. brucei and the greatest in L. major. Horizontal transfer of genes of bacterial origin has contributed to some of the metabolic differences in these parasites, and a number of novel potential drug targets have been identified.     

Genetic parameters of drinking and feeding traits of wean-to-finish pigs under a polymicrobial natural disease challenge

Background:The pork industry faces unprecedented challenges from disease,which increases cost of production and use of antibiotics,and reduces production efficiency,carcass quality,and animal wellbeing.One solution is to improve the overall resilience of pigs to a broad array of common diseases through genetic selection.Behavioral changes in feeding and drinking are usually the very first clinical signs when animals are exposed to stressors such as disease.Changes in feeding and drinking behaviors in diseased pigs may reflect the way they cope with the challenge and,thus,could be used as indicator traits to select for disease resilience.The objectives of this study were to estimate genetic parameters of feeding and drinking traits for wean-to-finish pigs in a natural polymicrobial disease challenge model,to estimate genetic correlations of feeding and drinking traits with growth rate and clinical disease traits,and to develop indicator traits to select for disease resilience.Results:In general,drinking traits had moderate to high estimates of heritability,especially average daily water dispensed,duration,and number of visits(0.44 to 0.58).Similar estimates were observed for corresponding feeding traits(0.35 to 0.51).Most genetic correlation estimates among drinking traits were moderate to high(0.30 to 0.92)and higher than among feeding traits(0 to 0.11).Compared to other drinking traits,water intake duration and number of visits had relatively stronger negative genetic correlation estimates with treatment rate and mortality,especially across the challenge nursery and finisher(?0.39 and?0.45 for treatment rate;?0.20 and?0.19 for mortality).Conclusion:Most of the recorded drinking and feeding traits under a severe disease challenge had moderate to high estimates of heritability,especially for feed or water intake duration and number of visits.Phenotypic and genetic correlations among the recorded feeding traits under disease were generally low but drinking traits showed high correlations with each other.Water intake duration and number of visits are potential indicator traits to select for disease resilience because of their high heritability and had moderate genetic correlations with treatment and mortality rates under severe disease.     

Envelope-constrained neutralization-sensitive HIV-1 after heterosexual transmission

Heterosexual transmission accounts for the majority of human immunodeficiency virus-1 (HIV-1) infections worldwide, yet the viral properties that determine transmission fitness or outgrowth have not been elucidated. Here we show, for eight heterosexual transmission pairs, that recipient viruses were monophyletic, encoding compact, glycan-restricted envelope glycoproteins. These viruses were also uniquely sensitive to neutralization by antibody from the transmitting partner. Thus, the exposure of neutralizing epitopes, which are lost in chronic infection because of immune escape, appears to be favored in the newly infected host. This reveals characteristics of the envelope glycoprotein that influence HIV-1 transmission and may have implications for vaccine design.