Soil-plant hydrology of indigenous and exotic trees in an Ethiopian montane forest

Fast-growing exotic trees are widely planted in the tropics to counteract deforestation; however, their patterns of water use could be detrimental to overall ecosystem productivity through their impact on ecosystem water budget. In a comparative field study on seasonal soil-plant water dynamics of two exotic species (Cupressus lusitanica Mill. and Eucalyptus globulus Labill.) and the indigenous Podocarpus falcatus (Thunb.) Mirb. in south Ethiopia, we combined a 2.5-year record for climate and soil water availability, natural-abundance oxygen isotope ratios (delta(18)O) of soil and xylem water, destructive root sampling and transpiration measurements. Soil was generally driest under C. lusitanica with its dense canopy and shallow root system, particularly following a relatively low-rainfall wet season, with the wettest soil under E. globulus. Wet season transpiration of C. lusitanica was twice that of the other species. In the dry season, P. falcatus and C. lusitanica reduced transpiration by a factor of six and two, respectively, whereas E. globulus showed a fivefold increase. In all species, there was a shift in water uptake to deeper soil layers as the dry season progressed, accompanied by relocation of live fine root biomass (LFR) of C. lusitanica and P. falcatus to deeper layers. Under P. falcatus, variability in soil matric potential, narrow delta(18)O depth gradients and high LFR indicated fast water redistribution. Subsoil water uptake was important only for E. globulus, which had low topsoil LFR and tap roots exploiting deep water. Although P. falcatus appeared better adapted to varying soil water availability than the exotic species, both conifers decreased growth substantially during dry weather. Growth of E. globulus was largely independent of topsoil water content, giving it the potential to cause substantial dry-season groundwater depletion.     

Vitality variation and population structure of a riparian forest in the lower reaches of the Tarim River,NW China

Since 2000, the Chinese government has implemented emergency water diversion measures to restore the damaged riparian forest ecosystem with dominant tree species Euphrat poplar(Populus euphratica Oliv.)at the lower reaches of the Tarim River. In the present study, comparative analysis of variations in the vitality of P. euphratica trees were made using 2005 and 2010 data to illustrate the revitalization process of riparian forest. Poplar trees within 300 m of the riverbed were positively revitalized, while the vitality of trees farther than 300 m from the river decreased. Population structure was studied to demonstrate the development of poplar community. In the first belt, the class structure for the diameter at breast height(DBH) of P. euphratica fit a logistic model, and the 2nd, 3rd and 4th belt curve fittings were close to a Gaussian model; in other plots they were bimodal. Cluster analysis of the composition of the DBH class of poplar trees demonstrated that those within 16–36 cm DBH were the most abundant(58.49% of total) in study area, under 16 cm of DBH were second(31.36%), and trees 40 cm DBH were the least abundant(10.15%). More than 80% of the trees were young and medium-sized, which means that the poplar forest community in the vicinity of the lower Tarim River is at a stable developmental stage. The abundance of juvenile trees of P. euphratica in the first and second measuring belts was 12.13% in 2005 and increased to 25.52% in 2010, which means that the emergency water transfer had a positive impact on the generation of young P. euphratica trees in the vicinity of the river.     

Analysis of Accumulation Patterns of <Emphasis Type="Italic">Barley yellow dwarf virus-PAV</Emphasis> (BYDV-PAV) in Two Resistant Wheat Lines

Barley yellow dwarf (BYD) is one of the main viral diseases of small-grain cereals. This disease, reported on numerous plant species of the Poaceae family, is caused by a complex of eight viral species including the species Barley Yellow Dwarf Virus-PAV (BYDV-PAV), frequently found in western Europe. Resistance sources against BYDV-PAV are scarce and only identified in perennial Triticineae. Some BYDV-resistant wheat lines have been obtained by introgressing these resistances into bread wheat germplasms. Genetic and biological characterization of the resulting lines has been undertaken. However, little information on the resistant behaviour of these lines during the early stages of the infection process is available. To evaluate the resistance of two genetically distinct resistant lines (Zhong ZH and TC14), 1740 young plantlets, belonging to susceptible reference hosts (barley cv. Express and wheat cv. Sunstar), Zhong ZH or TC14 wheat lines, were inoculated in controlled conditions with French BYDV-PAV isolates. The infection process was monitored during the first 21 days after inoculation (DAI) using a semi-quantitative ELISA. A standardized protocol including five successive samplings of leaves from all inoculated plants and the collection of plant roots at the end of the monitored period was carried out. This protocol enabled an assessment of the infection percentage and the evolution of the viral load in plants from the 7th DAI to the 21st DAI. Statistical analyses of the BYDV infection kinetics using raw ELISA data, a model of the time-dependent variation of the percentage of infected plants and the area under concentration progress curves (AUCPC) demonstrated that Zhong ZH and TC14 lines (1) reduce the development rate of the BYD disease during the first days of infection, (2) decrease the infection efficiency of BYDV-PAV isolates, in the leaves, from 98.7% for susceptible plant genotypes to 81.9% and 71.7% for Zhong ZH and TC14, respectively, (3) reduce the virus load in the leaves of infected plants and (4) are not spared from BYDV infection, as 95.1% of Zhong ZH and 90.2% of TC14 inoculated plants accumulated viral particles in roots and/or in leaves at 21 DAI. These results confirm the BYDV-partial resistant behaviour of both Zhong ZH and TC14 lines. The development rate of the disease was the single parameter that allowed the distinction between the two resistant sources present in the tested lines.     

Tubers from leaf-bud cuttings: A tool for potato seed certification and breeding programs

The use of leaf-bud cuttings as a tool for rapid clonal increase was studied in 6 cultivars. Small tubers were obtained directly from leaf-bud cuttings maintained for 7 weeks in sand-filled pots or benches. The tubers ranged in size up to 1 1/4 inches (3cm) in diameter. The number of leaf-bud cuttings ranged from 37 to 288, depending on size of mother plant. They averaged 114 cuttings. Almost all of the leaf-bud cuttings produced tubers. The procedure is fast, simple, and provides for rapid increase of selected stocks.     

Chimpanzee reservoirs of pandemic and nonpandemic HIV-1

Human immunodeficiency virus type 1 (HIV-1), the cause of human acquired immunodeficiency syndrome (AIDS), is a zoonotic infection of staggering proportions and social impact. Yet uncertainty persists regarding its natural reservoir. The virus most closely related to HIV-1 is a simian immunodeficiency virus (SIV) thus far identified only in captive members of the chimpanzee subspecies Pan troglodytes troglodytes. Here we report the detection of SIVcpz antibodies and nucleic acids in fecal samples from wild-living P. t. troglodytes apes in southern Cameroon, where prevalence rates in some communities reached 29 to 35%. By sequence analysis of endemic SIVcpz strains, we could trace the origins of pandemic (group M) and nonpandemic (group N) HIV-1 to distinct, geographically isolated chimpanzee communities. These findings establish P. t. troglodytes as a natural reservoir of HIV-1.     

Cytological description of testicular cell populations in sexually mature cats with normal spermatogenesis

In cats, assessment of the testicular function is mainly based on sperm evaluation. Whatever the technique used, the volume of collected sperm is often small, which may lead to technical difficulties to achieve the semen evaluation in routine practice. Fine-needle aspiration (FNA) biopsy of the testicular parenchyma is one of the other methods used to assess testicular function. The aim of this study was to explore the relevance of FNA in the assessment of testicular cells in sexually mature cats. Eighteen cats over one year of age were recruited among animals presented for surgical neutering. Semen was collected by electroejaculation before it was evaluated. FNA biopsies of the testicles were taken using a 21-gauge needle. After castration, histological analysis of the testes was performed. Semen evaluation and histological analysis showed no anomalies, which confirmed normal spermatogenesis in all the cats and allowed a proper interpretation of the cytological findings. The cells identified through cytological examination were spermatogonia (1.99 ± 0.17%), primary spermatocytes (10.49 ± 0.74%), round spermatids (34.80 ± 1.57%), elongated spermatids (23.59 ± 2.02%), spermatozoa (21.56 ± 1.86%), Sertoli cells (7.53 ± 1.23%) and Leydig cells (0.04 ± 0.03%). However, spermatocytes II were not identified. This is due to the low proportions of these cells, related to their very short lifespan. Likewise, the very low number of Leydig cells observed is probably due to the damage caused during the aspiration stage. This study showed that fine-needle aspiration is an efficient method to describe cytologically normal testicular populations, a cornerstone for future research aimed to study abnormal spermatogenesis and to correlate it to cytological proportion of germ cells.     

Alterations of epidermal proliferation and cytokeratin expression in skin biopsies from heavy draught horses with chronic pastern dermatitis

We report the historical, clinical and histopathological characteristics of skin lesions in biopsies from 37 heavy draught horses with chronic pastern dermatitis. The skin lesions were divided into four macroscopic groups: scaling (group I, n=5), hyperkeratotic and hyperplastic plaque-like lesions (group II, n=14), nodular skin masses (group III, n=16) and verrucous skin lesions (group IV, n=2). The principal histological findings were hyperkeratosis and epidermal hyperplasia. There was a gradual increase in epidermal hyperplasia from groups I to IV, suggesting that the lesions represent different stages of disease. In all cases, there was perivascular dermatitis dominated by T lymphocytes with an increase in MHC class II-positive dendritic-like cells. Immunohistochemical labelling for cytokeratins CK5/6(4), CK10 and CK14 indicated a change in their expression pattern. This correlated with the degree of epidermal hyperplasia, indicating abnormal differentiation of keratinocytes. There was a statistically significant correlation between the severity of skin lesions and several other factors including increasing age, increasing cannon circumference, prominence of anatomical structures such as fetlock tufts of hairs, ergots and chestnuts, and bulges in the fetlock region.     

Detection of vascular endothelial growth factor (VEGF) and VEGF receptors Flt-1 and KDR in canine mastocytoma cells

Vascular endothelial growth factor (VEGF) is a major regulator of angiogenesis and a potential autocrine growth factor for neoplastic cells in various malignancies. In the present study, we have investigated expression of VEGF and VEGF receptors in canine mastocytomas and the canine mastocytoma cell line C2. As assessed by immunostaining of tissue sections and cytospin slides, primary neoplastic mast cells (MC) and C2 cells were found to express the VEGF protein. In Northern blot and RT-PCR experiments, C2 cells expressed VEGF mRNA in a constitutive manner. VEGF mRNA expression in C2 cells was counteracted by LY294002 and rapamycin, suggesting involvement of the PI3-kinase/mTOR pathway. Moreover, C2 cells were found to express VEGF receptor-1 (Flt-1) and VEGF receptor-2 (KDR). However, recombinant VEGF failed to promote (3)H-thymidine uptake in C2 cells, and a neutralizing anti-VEGF antibody (bevacizumab) failed to downregulate spontaneous proliferation in these cells. In addition, rapamycin decreased the expression of VEGF in C2 cells at the mRNA and protein level without suppressing their proliferation. Together, canine mastocytoma cells express VEGF as well as VEGF receptors. However, despite co-expression of VEGF and its receptors, VEGF is not utilized as an autocrine growth regulator by canine mastocytoma cells.     

Cardiac‐gated,phase contrast magnetic resonance angiography is a reliable and reproducible technique for quantifying blood flow in canine major cranial abdominal vessels

Blood flow changes in cranial abdominal vessels are important contributing factors for canine hepatic disease. This prospective, experimental, pilot study aimed to evaluate cardiac‐gated, phase contrast magnetic resonance angiography (PCMRA) as a method for characterizing blood flow in canine major cranial abdominal vessels. Eleven, healthy, adult beagle dogs were sampled. Cardiac‐gated, phase contrast magnetic resonance angiography of the cranial abdomen was performed in each dog and blood flow was independently measured in each of the major cranial abdominal vessels by three observers, with two observers recording blood flow values once and one observer recording blood flow values three times. Each dog then underwent ultrasonographic examination of the liver with fine needle aspirations and biopsies submitted to cytologic and histologic examination. The mean absolute stroke volume and velocity were respectively 9.6 ± 1.9 ml and –11.1 ± 1.1 cm/s for the cranial abdominal aorta, 2.1 ± 0.6 ml and –6.6 ± 1.9 cm/s for the celiac artery, and 2.3 ± 1.0 ml and –7.9 ± 3.1 cm/s for the cranial mesenteric artery. The mean absolute stroke volume and velocity were respectively 6.7 ± 1.3 ml and 3.9 ± 0.9 cm/s for the caudal vena cava and 2.6 ± 0.9 ml and 3.2 ± 1.2 cm/s for the portal vein. Intraobserver reliability was excellent (intraclass correlation coefficient > 0.9). Interobserver reproducibility was also excellent (intraclass correlation coefficient 0.89–0.99). Results of liver ultrasonography, cytology, and histopathology were unremarkable. Findings indicated that cardiac‐gated, phase contrast magnetic resonance angiography is a feasible technique for quantifying blood blow in canine major cranial abdominal vessels. Blood flow values from this sample of healthy beagles can be used as background for future studies on canine hepatic disease.