Karyology and reproductive biology of Muscari matritensis M. Ruíz Rejón et al. (Liliaceae)

VALDÉS, B. & DÍAZ LIFANTE, Z., 1992. Karyology and reproductive biology of Muscari matritensis M. Ruíz Rejón et al. (Liliaceae). Muscari matritensis M. Ruíz Rejón et al. , previously known from only five localities, has been recorded for S.W. Spain. The plants have a karyotype composition which differs from the other four karyotypes described for this species, and experimental studies of the breeding system provide evidence that they are moderately autogamous.     

Reproductive performance changes with age and laying experience in the Red-legged Partridge Alectoris rufa

Most studies of birds have reported positive effects of ageing on reproductive traits during the first years of life followed by a decline. We examined the effects of age and laying experience, controlling for confounding factors such as food availability/quality and timing of pair formation in a captive population of Red-legged Partridge Alectoris rufa . We found that all reproductive traits, except for the period between eggs, were highly repeatable within females both within and between years. The repeatability of egg mass was lower than that of clutch size, laying onset or chick traits other than the mass and size increase rates, perhaps suggesting a lower heritability value. As females aged, they showed a tendency to produce marginally lighter eggs (1.3%) and larger clutches, although this latter trend was not significant. We suggest that the senescence process implies the involvement of hormonal changes that could affect the reduction of egg mass (e.g. low levels of oestradiol). Younger females tended to start laying later than older females, which could be due to a low responsiveness to photoperiodic stimulation of the reproductive system, which would indicate a delay in gametogenesis and steroidogenesis. The mass of last-laid eggs decreased with age of the female. We suggest that physiological changes through the laying sequence could vary with age. Experienced breeders laid larger clutches linked with the advancement of laying onset. For a given age, females with more experience fared better than those with less experience.     

Plant trait responses to grazing – a global synthesis

Herbivory by domestic and wild ungulates is a major driver of global vegetation dynamics. However, grazing is not considered in dynamic global vegetation models, or more generally in studies of the effects of environmental change on ecosystems at regional to global scale. An obstacle to this is a lack of empirical tests of several hypotheses linking plant traits with grazing. We, therefore, set out to test whether some widely recognized trait responses to grazing are consistent at the global level. We conducted a meta‐analysis of plant trait responses to grazing, based on 197 studies from all major regions of the world, and using six major conceptual models of trait response to grazing as a framework. Data were available for seven plant traits: life history, canopy height, habit, architecture, growth form (forb, graminoid, herbaceous legume, woody), palatability, and geographic origin. Covariates were precipitation and evolutionary history of herbivory. Overall, grazing favoured annual over perennial plants, short plants over tall plants, prostrate over erect plants, and stoloniferous and rosette architecture over tussock architecture. There was no consistent effect of grazing on growth form. Some response patterns were modified by particular combinations of precipitation and history of herbivory. Climatic and historical contexts are therefore essential for understanding plant trait responses to grazing. Our study identifies some key traits to be incorporated into plant functional classifications for the explicit consideration of grazing into global vegetation models used in global change research. Importantly, our results suggest that plant functional type classifications and response rules need to be specific to regions with different climate and herbivory history.     

棉花和香瓜的甘薯粉虱Bemisia tabaci (同翅目 ,粉虱科 )B生态型虫体大小和重量的田间调查(英文)

20 0 0和 2 0 0 1年在美国凤凰城和北达科塔州法哥城田间 ,调查棉花和香瓜上甘薯粉虱BemisiatabaciB生态型所有虫期虫体大小和重量。从若虫大小计算出若虫的体积。第一到第四龄晚期 ,若虫平均体积以指数方式增加。体积增加最快的是第三到第四龄早期。棉花上的若虫比香瓜上的宽 ,但是并不比较长。香瓜上第一到第四龄早期的若虫 ,最厚部位的腹部和背部厚度比例显著比棉花上的要高。两种寄主作物上的若虫从第一到第四龄发育期 ,腹部厚度平均增加将近 5 1倍 ,而背部厚度只增加 2 8倍。雌虫和雄虫从头顶到翅尖平均长度分别为 112 6和 95 3微米 ,重量为 39和 17微克。棉花和香瓜上的虫卵平均长 ,宽 ,重分别为 197微米 ,99微米 ,和0 8微克。未被寄生的蛹壳长 ,宽 ,重分别为 6 73微米 ,4 92微米和 1 2微克 ;被寄生的蛹壳为 6 6 5微米 ,4 5 2微米 ,和 3 6微克。棉花上未被寄生和被寄生的蛹壳比香瓜上的长 ,宽 ,和更重。     

Modulatory effects of interferon‐γ and interleukin‐4 on cellular immune responses against Hypoderma lineatum antigens

This study investigates the in vitro modulatory effects of interferon‐γ (IFN‐γ) and interleukin‐4 (IL‐4) on both proliferative bovine T cell responses and IL‐10 production induced by different antigens [crude larval extract and the purified fractions hypodermin A, B and C (HyA, HyB, HyC)] obtained from first instars of Hypoderma lineatum (Diptera: Oestridae), alone or in the presence of the mitogen concanavalin A. Incubation with the different parasitic antigens resulted in significant inhibition of T cell proliferation and IL‐10 production, which, in general, did not revert after the addition of IFN‐γ and IL‐4. In the absence of antigens, IL‐4 induced significant inhibition of mitogen‐induced T cell responses. Exogenous IFN‐γ exhibited an inhibitory effect on cell proliferation in the presence of the purified fractions HyB and HyC. These in vitro data suggest that far from neutralizing the effects of larval antigens, the addition of IFN‐γ potentiates their anti‐proliferative activity; by contrast, IL‐4 had no consistent effects on proliferative responses to Hypoderma. IL‐4 provoked an increment of IL‐10 levels in supernatants of HyB‐stimulated cells. In conclusion, exogenous IFN‐γ and IL‐4 were unable to counteract the suppressor effects of H. lineatum antigens.     

Isokinetic Identification of Knee Joint Torques before and after Anterior Cruciate Ligament Reconstruction

The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knees before and after anterior cruciate ligament reconstruction (ACLR) in physically active males and to estimate the time of return to full physical fitness. Extension and flexion torques were measured for the injured and healthy limbs at two angular velocities approximately 1.5 months before the surgery and 3, 6, and 12 months after ACLR. Significant differences (p ≤ 0.05) in peak knee extension and flexion torques, hamstring/quadriceps (H/Q) strength ratios, uninvolved/involved limb peak torque ratios, and the normalized work of these muscles between the four stages of rehabilitation were identified. Significant differences between extension peak torques for the injured and healthy limbs were also detected at all stages. The obtained results showed that 12 months of rehabilitation were insufficient for the involved knee joint to recover its strength to the level of strength of the uninvolved knee joint. The results helped to evaluate the progress of the rehabilitation and to implement necessary modifications optimizing the rehabilitation training program. The results of the study may also be used as referential data for physically active males of similar age.     

Segmental differences in the stability of thetrp-repressor peptide backbone

Summary Exchange lifetimes of amide protons intrp-repressor with and without the corepressor,l-tryptophan, were studied by heteronuclear 2D NMR spectroscopy. The amide proton exchange times revealed pronounced differences in the stability of different regions of thetrp-repressor. The dimeric core of the molecule is relatively compact and homogeneous in terms of the measured parameters in both apo- and holorepressors. On the other hand the DNA-binding region appears less stable and more susceptible to the exchange of its backbone protons with the solvent. The NMR findings reported here are consistent with and amplify information on the stability of thetrp-repressor obtained by other methods.Dedicated to the memory of Professor V.F. Bystrov