Characterization and identification of leaf morphology of <Emphasis Type="Italic">Populus deltoides</Emphasis> Bartr. clones

Leaves are of fundamental importance to plants, representing their facility to generate power and are the sensing units of plants towards the environment. An attempt was made to characterize and compare the variations of leaf morphology of various Populus deltoides Bartr. clones by studying the winter buds and other leaf parameters of fully developed leaves. To achieve these objectives, forty-three exotic and indigenous clones of P. deltoides Bartr. were evaluated for different parameters. On the basis of various morphological characteristics the results reveal that each clone has a distinct color pattern of leaves. Different colors observed in these clones varied from light green through green to dark green. Two distinct lengths of the leaf apex were found, i.e., short and long; as well both acuminate and acute apex types were found. Erratic distribution of serration of leaves was also found. In this study, the morphological traits of leaves provided discriminatory grounds for separating various populations of P. deltoides Bartr. clones. Winter bud studies indicate that different clones vary considerably with regard to shape, color, shape of leaf scars and exudation.     

Pathological Conditions of the Reproductive Organs of Male Stray Dogs in the Tropics: Prevalence, Risk Factors, Morphological Findings and Testosterone Concentrations

The objective of this study was to estimate the prevalence of and risk factors for pathological conditions of the reproductive organs in stray dogs under tropical conditions. Three hundred and eighteen dogs were examined post-mortem in the period from 1 July 2002 to 30 June 2003. Before killing, a blood sample (from the cephalic vein) for testosterone assay was taken. Pathological conditions of the reproductive organs were found in 135 of the dogs (42.5%) and in 175 of the testes (64.8%). The most frequent pathologies found were testicular degeneration, cryptorchidism, testicular hypoplasia and testicular tumours (in 15.1%, 6.6%, 6.6% and 5.4% of the dogs and 15.1, 4.6, 6.0 and 3.5 of the testes, respectively). Transmissible venereal tumour (TVT) was seen in 5.4% of the dogs. Testicular degeneration was more common in old dogs and underweight dogs (p < 0.05). Testicular tumours were 14.3 times more common in cryptorchid dogs. Age was another important factor for the development of testicular tumours (p < 0.05). Lower levels of testosterone concentration (p < 0.05) were observed in dogs with advanced testicular degeneration (0.7 +/- 0.8 nM), dogs with hypoplastic testicles (0.8 +/- 0.9 nM) and dogs with one degenerated and one retained testis or with bilateral cryptorchidism (1.2 +/- 0.9 nM) compared to dogs with one or two normal testes (7.0 +/- 5.5 nM). Testicular volume and weight were significantly lower in degenerated, hypoplastic and retained testes compared with the contralateral normal testis. Some spermatogenic activity was found in three of the retained testes, producing oligozoospermic smears with a high percentage of sperm abnormalities. No comparable epidemiological data about male pathological conditions of the reproductive organs in the dog is available. The prevalence found in this study, yet, appears high.     

The Effects of Isoflavones on Androgens and Glucocorticoids During Puberty on Male Wistar Rats

Isoflavones are the most common phytoestrogens found in human diets. However, it is still not clear whether isoflavones have effects on the reproductive and the endocrine systems under normal dietary intake and overdose. The aim of this study was to determine how the most important isoflavones, genistein and daidzein, affect androgen and glucorticoid levels on male prepuberal rats. A hundred and seventy‐five 30‐day‐old male Wistar rats were dosed orally by stomach tube every day for 35 days, with saline solution, low and high doses of genistein, daidzein and a mixture of both. Serum samples were analysed by an enzyme immunoassay for hormone determinations. In control group, there was a peak of testosterone (T) and dihydrotestosterone levels associated to the onset of puberty, at the third week. However, in low‐dose groups, the same peak was found at the fourth week (p < 0.05), indicating a delay in the onset of puberty in these groups. Moreover, high doses groups serum androgen levels were significantly lower (p < 0.05) than the control group from the first week until fifth week. This fact was supported by a epididymal histological analysis that indicate in low doses there were several content of spermatozoa at fourth week and in high doses there were few content of spermatozoa. Besides, corticosterone levels followed the same pattern of androgens in all groups. We can conclude that oral administration of isoflavones in male rats decreased the secretion of androgens and glucocorticoids causing a delay in the onset of puberty and may cause physiological and developmental problems.     

Functional genomic analysis of RNA interference in C. elegans

RNA interference (RNAi) of target genes is triggered by double-stranded RNAs (dsRNAs) processed by conserved nucleases and accessory factors. To identify the genetic components required for RNAi, we performed a genome-wide screen using an engineered RNAi sensor strain of Caenorhabditis elegans. The RNAi screen identified 90 genes. These included Piwi/PAZ proteins, DEAH helicases, RNA binding/processing factors, chromatin-associated factors, DNA recombination proteins, nuclear import/export factors, and 11 known components of the RNAi machinery. We demonstrate that some of these genes are also required for germline and somatic transgene silencing. Moreover, the physical interactions among these potential RNAi factors suggest links to other RNA-dependent gene regulatory pathways.     

Live attenuated malaria vaccine designed to protect through hepatic CD8⁺ T cell immunity

Our goal is to develop a vaccine that sustainably prevents Plasmodium falciparum (Pf) malaria in ≥80% of recipients. Pf sporozoites (PfSPZ) administered by mosquito bites are the only immunogens shown to induce such protection in humans. Such protection is thought to be mediated by CD8(+) T cells in the liver that secrete interferon-γ (IFN-γ). We report that purified irradiated PfSPZ administered to 80 volunteers by needle inoculation in the skin was safe, but suboptimally immunogenic and protective. Animal studies demonstrated that intravenous immunization was critical for inducing a high frequency of PfSPZ-specific CD8(+), IFN-γ-producing T cells in the liver (nonhuman primates, mice) and conferring protection (mice). Our results suggest that intravenous administration of this vaccine will lead to the prevention of infection with Pf malaria.     

Mycorrhizal and common root-rot infection,and nutrient accumulation in barley grown on breton loam using N from biological fixation or fertilizer

Summary This paper presents soil biological data from a study on the functioning of three soil-plant systems on a Gray Luvisol in Cryoboreal Subhumid central Alberta. The systems were (1) an agroecological 8-year rotation, (2) a continuous grain system, both established in 1981, and (3) a classical Breton 5-year rotation established in 1930. The objectives were to (1) determine whether changes in vesicular-arbuscular mycorrhizae (VAM) populations occurred in soil under these cropping systems, (2) discover whether these cropping systems and/or VAM infection influenced the incidence of common root rot (Bipolaris sorokiniana), and (3) use nutrient translocation indices to test the hypothesis that soil quality influences non-specific physiological conditions in barley (Hordeum vulgare L.). VAM fungal propagules in soil samples and VAM infection under controlled conditions were significantly affected by the cropping system. VAM infection accounted for more than 85% of the variability in grain yield, plant biomass yield, and plant uptake of K, S, Ca, Fe, and Zn under controlled conditions. Backward-elimination regression analyses showed that under these conditions of high available P, plant P uptake was governed by the quantity of extractable P in the soil (r ²=0.82); the VAM infection contributed practically nothing when combined with available P (R ²=0.84). Neither VAM infection nor the cropping system were related to the B. sorokiniana infection in the barley. The growth of B. sorokiniana was equal, and its sporulation superior, when grown on residues of the non-host fababean (Vicia faba L.), compared with growth on residues of barley. Higher translocation of plant nutrients to the grain in the agroecological compared with the continuous grain treatments suggested that VAM and/or the soil history affected plant physiology, possible through hormonal effects. Superior barley yields in the agroecological compared with the continuous grain treatments were partly due to increased VAM colonization, greater nutrient accumulation and translocation to the grain, but not to a reduced disease incidence. These results demonstrate the benefits of a holistic systems approach while studying biological interactions involving plants and groups of soil microorganisms.(ICRISAT journal article number 1161)     

Computer Simulation of Tractor Single-point Drawbar Performance

A computer algorithm has been developed to predict single-point drawbar performance of a tractor taking into account all the necessary variables during field operation. The performance of tractor–implement system with a single-point hitch involves the effect of a number of variables on the whole tractor–implement–soil system. Considering all these, the developed computer algorithm is able to predict the performance of whole operation. This model is capable of determining the maximum pull available in the given field condition and matches the performance of trailed implements, such as a disc harrow and two-axle trailer. The model was able to predict maximum load and slope climbing ability of tractor with single- and two-axle trailers under different conditions. It was predicted by the model that the maximum pull developed by a tractor is limited by gross traction in the soft soil whereas it was limited by the power available from the tractor in hard soil. The longitudinal stability of the tractor taken for analysis varied with hitch point position. Appropriate determination of disc harrow performance was possible using the developed model.