Increased CDK1 activity determines the timing of kinetochore-microtubule attachments in meiosis I

Chromosome segregation during cell division depends on stable attachment of kinetochores to spindle microtubules. Mitotic spindle formation and kinetochore–microtubule (K-MT) capture typically occur within minutes of nuclear envelope breakdown. In contrast, during meiosis I in mouse oocytes, formation of the acentrosomal bipolar spindle takes 3–4 h, and stabilization of K-MT attachments is delayed an additional 3–4 h. The mechanism responsible for this delay, which likely prevents stabilization of erroneous attachments during spindle formation, is unknown. Here we show that during meiosis I, attachments are regulated by CDK1 activity, which gradually increases through prometaphase and metaphase I. Partial reduction of CDK1 activity delayed formation of stable attachments, whereas a premature increase in CDK1 activity led to precocious formation of stable attachments and eventually lagging chromosomes at anaphase I. These results indicate that the slow increase in CDK1 activity in meiosis I acts as a timing mechanism to allow stable K-MT attachments only after bipolar spindle formation, thus preventing attachment errors.     

Adaptive timing of detachment in a tick parasitizing hole-nesting birds

In non-permanent parasites with low intrinsic mobility such as ticks, dispersal is highly dependent on host movements as well as the timing of separation from the hosts. Optimal detachment behaviour is all the more crucial in nidicolous ticks as the risk of detaching in non-suitable habitat is high. In this study, we experimentally investigated the detachment behaviour of Ixodes arboricola, a nidicolous tick that primarily infests birds roosting in tree-holes. We infested great tits with I. arboricola larvae or nymphs, and submitted the birds to 2 experimental treatments, a control treatment in which birds had normal access to nest boxes and an experimental treatment, in which the birds were prevented access to their nest boxes for varying lengths of time. In the control group, most ticks detached within 5 days, whereas in the experimental group, ticks remained on the bird for as long as the bird was prevented access (up to 14 days). This prolonged attachment caused a decrease in survival and engorgement weight in nymphs, but not in larvae. The capacity of I. arboricola larvae to extend the duration of attachment in non-suitable environments with no apparent costs, may be an adaptation to unpredictable use of cavities by roosting hosts during winter, and at the same time may facilitate dispersal of the larval instars.     

The Food of Nestling Jays and Magpies

Half of the 4,000 Grey Plovers which reach the Wash in late summer remain there to moult; more than a quarter are already in arrested wing moult, having begun elsewhere. The authors discuss this condition and also the birds' movements in the light of ringing recoveries.     

Pubertal timing and the development of psychopathology in adolescence and beyond

This article is part of a Special Issue “Puberty and Adolescence”.     

Effects of temperature on development and growth in the tick,Haemaphysalis longicornis

As a part of ecological studies onHaemaphysalis longicornis, the effects of controlled temperatures (12, 15, 20, 25 and 30°C; 100% RH) on development and growth of the tick were investigated and the critical low temperature for each stage in the life cycle was estimated. As the temperature became low, the periods of preoviposition, oviposition, egg hatching (incubation) and moulting were prolonged. At 12°C, however, oviposition, egg hatching and moulting of the larva and nymph did not occur. The critical low temperatures for oviposition, egg hatching (developmental zero) and larval and nymphal moulting which were calculated theoretically from the regression equations, were 11.1, 12.2, 10.2 and 11.8°C, respectively. The temperature also affected the egg productivity and hatch-ratio. The number of deposited eggs per mg of body weight decreased markedly at 15°C, and the hatch-ratio was lowered with dropped temperatures.     

Vertebrate–arthropod communication dictates tick development and pathogen transmission

Cross-species communication drives the coordination of diverse biological processes in complex systems. Rana et al. discovered that Ixodes scapularis, the tick vector of Lyme disease, produces a receptor that binds host interferon-gamma (IFNγ) in the blood meal, which orchestrates tick development, immunity, and vector competence.     

Noelins modulate the timing of neuronal differentiation during development

Noelins comprise a family of extracellular proteins with proposed roles in neural and neural crest development. Here, we show that a previously uncharacterized family member, Noelin-4, functions to maintain neural precursors in an undifferentiated state and biases ectoderm toward a neural fate. We show that Noelin-4 is induced by the neurogenic genes X-ngnr-1 and XNeuroD. Over-expression of Noelin-4 causes expansion of the neural plate at the expense of neural crest and epidermis. Although there is an apparent increase in the neural precursor pool, no increase was noted in differentiated neurons. Later, derivatives such as the neural tube and retina appear enlarged. We show biochemically that Noelin-4 protein is glycosylated and secreted and that it interacts with Noelin-1, an isoform previously found to promote differentiation in neuralized animal caps. Accordingly, the neural precursor expansion activity of Noelin-4 is reversed by co-expression of Noelin-1. Our finding that Noelin isoforms can bind to and antagonize one another suggests that interacting Noelin isoforms may play a role in regulating timing of differentiation.     

Evolution of meiosis timing during floral development

Meiosis divides the haploid and diploid portions of the life cycle in all sexual organisms. In angiosperms meiosis occurs during flower development, the duration of which varies widely among species and is affected by environmental conditions within species. For 36 species representing 13 angiosperm families, we determined the time at which meiosis ceased in the anthers as a fraction of the total time from floral primordium initiation (beginning of development) to flower opening (end). It was found that this fraction, rather than being continuously distributed among species, occurred in three discrete classes despite wide variations within and among species in absolute developmental durations. Each species was characterized by a single timing class. For all species within a given timing class, therefore, the durations before and after the end of microsporocyte meiosis existed in constant ratio. Each timing class was found in phylogenetically distant species; conversely, a plant family often contained more than one class. Timing class was not related to ploidy level, inflorescence architecture, pollination syndrome or mating system. These findings show that either the durations before and after microsporocyte meiosis are regulated by the same exogenous process, or one duration determines the other. They further imply that the underlying developmental processes have evolved in a limited number of ways among flowering plants.     

荒漠伯劳的繁殖及雏鸟生长发育

2006～2007年对新疆石河子市荒漠伯劳(Lanius isabellinus phoenicuroides)的巢、卵及雏鸟的生长发育状况进行了研究.结果表明,荒漠伯劳窝卵数平均5.67枚,孵卵期17 d,育雏期15 d.育雏主要由雌鸟担任.采用Logistic方程对雏鸟发育过程中主要生长指标的生长方程进行了曲线拟合,相关指标生长方程的拟合度均在0.99以上.     

Identification of novel tick salivary gland proteins for vaccine development

Methods currently used to control Ixodes scapularis ticks rely principally on acaricidal applications which suffer from a number of limitations. Recently, host vaccination against ticks has been shown to be a promising alternative tick control method. In tick salivary glands, numerous genes are induced during the feeding process. Many of these newly expressed proteins are secreted in tick saliva and may play a role in modulating host immune responses and pathogen transmission. We have performed suppression subtraction hybridization to identify unique I. scapularis salary gland proteins specifically expressed during engorgement. We have cloned and sequenced ten unique salivary gland-associated cDNAs that are up-regulated during feeding. The protein products of these genes represent potential vaccine candidates for use in the control of ticks and to prevent transmission of tick-borne diseases.     

白骨顶雏鸟叫声回放实验

2008年4～6月在黑龙江省安邦河湿地自然保护区录制白骨顶(Fulica atra)雏鸟叫声后回放,分析回放时环境中的背景噪音对繁殖期白骨顶活动的影响.结果表明,游人、拖拉机产生的噪音及过往车辆均会干扰繁殖期白骨顶的正常活动.     

Changing patterns of vitellin-related peptides during development of the cattle tick Boophilus microplus

The major components of protein extracts from the cattle tick Boophilus microplus eggs and larvae of various ages were characterized by molecular sieving chromatography, ion exchange chromatography and SDS-PAGE. The fractions analysed showed a changing chromatographic pattern development. A serum raised against the components of a fraction showing characteristics of vitellin strongly reacted in Western blots with the major peptides of extracts from eggs, larvae, gut and ovary. Comparison of patterns obtained by electrophoresis in non-denaturing PAGE, stained with Coomassie blue or with benzidine/hydrogen peroxide, revealed that the major proteins of these extracts are haemoproteins, possibly in different aggregation states or heterogeneous in composition.     

Aspergillus fumigatus rasA and rasB regulate the timing and morphology of asexual development

Expression of rasA plays an important role in conidial germination in Aspergillus nidulans. Conidial germination is required to initiate both infection and asexual development in the opportunistic pathogen Aspergillus fumigatus. Therefore, we sought to determine the requirements for Ras proteins in conidial germination and asexual development of A. fumigatus. A second homolog, rasB, has been identified that characterizes a new subclass of Ras genes. Dominant active (DA) and dominant negative (DN) mutations of each gene were introduced into protoplasts as transgenes. DArasA expression led to reduced conidiation, malformed conidiophores, and altered mitotic progression, whereas expression of DNrasA caused a significant reduction in the rate of conidial germination. In contrast, expression of DNrasB slightly delayed the initiation of germination and caused the development of conidiophores in submerged culture. DArasB expression led to reduced conidiation. RasA and RasB appear to play different, but overlapping, roles in the vegetative growth and asexual development of A. fumigatus.