The Cell Cycle and Cell Population Kinetics in the Programmed Cell Death in the Limb-Buds of Normal and 5-Bromodeoxyuridine- Treated Chick Embryos

The cell cycle and cell population kinetics have been analyzed in the interdigital regions of chick limb-buds during the course of programmed cell death both in normal and the 5-bromodeoxyuridine (BrdU)-treated embryos. Our previous study has shown that a single administration of BrdU at day 6 1/3 inhibited the programmed cell death occurring in normal development of limb-buds.
Pulse- as well as continuous labelings with tritiated thymidine (³H-TdR) were used. The results obtained from the analyses made on both normal and experimental embryos have demonstrated the presence of a particular DNA-synthetic period, around day 6 1/3, closely related to the programmed death occurring on day 7 1/3. In normal embryos, new cell populations, which did not belong to any phases of normal cell cycle, made their appearances in the process of programmed cell death. A possible correlation between programmed cell death and the cell cycle has been discussed in relation to the morphogenesis of limbs in both normal and BrdU-treated embryos.     

Group composition and contributions to breeding by Rufous Vangas Schetba rufa in Madagascar

The social system of the Rufous Vanga Schetba rufa was studied in a deciduous dry forest in Ampijoroa, western Madagascar. The species lived in groups of two to four individuals. Groups typically contained one adult female, one or two adult males and sometimes a (presumed) immature. All group members appeared to defend the territory. The presumed immatures had spotted throats and were smaller than adults in body size. They helped feed young and guard the nest but did not incubate or brood.     

Bombyx acid cysteine proteinase

Summary

Three kinds of yolk proteins (vitellin, egg-specific protein and 30 k-proteins) are found in silkmoth eggs and have been well characterized. Essentially these proteins are considered to be amino acid reserves for developing embryos. Since at an early stage of egg development the cysteine proteinase accounts for the majority of the total proteinase activity, it may be involved in the degradation of yolk proteins. The enzyme is stored in the eggs as an inactive pro-form, indicating that the activation of the enzyme might be one of the key steps in yolk protein degradation. To investigate at the molecular level how yolk proteins degradation takes place, we have studied Bombyx acid cysteine proteinase (BCP) during an early period of embryonic development. We summarize how proteinases are regulated and are involved in the degradation of Bombyx yolk proteins during embryogenesis. These will be discussed mainly in light of recent results obtained from eggs of the silkmoth, Bombyx mori.     

Development of microsatellite markers in the grey‐crowned babbler (Pomatostomus temporalis)

The grey‐crowned babbler (Pomatostomus temporalis) is a cooperative breeding bird species in which nonbreeding helpers of both sexes care for the young of breeding individuals. To measure the genetic relatedness between breeders and their offspring and helpers, we developed nine microsatellite markers. Most of the loci were highly polymorphic. These loci will be useful in understanding the evolution and maintenance of cooperative breeding and helping behaviour in this species.     

Ontogenetic histology of Stegosaurus plates and spikes

Abstract: The dinosaur Stegosaurus is characterized by osteoderms of alternating plates and terminal paired spikes. Previous studies have described the histological features and possible functions of these osteoderms. However, ontogenetic changes are poorly documented. In this study, the ontogenetic changes of the osteoderms are examined using eight different ontogenetic skeletons (a juvenile, a subadult, a young adult, and five old adults based on the cortical histology of their body skeletons). The juvenile plate and subadult spike show thin cortex and thick cancellous bone. The young adult plates have an extensive vascular network, which is also seen in old adults. Old adult spikes are different from old adult plates in having a thick cortex and a large axial channel. The cortical histology, in both plates and spikes, show well‐vascularized bone tissue consisting of dense mineralized fibres in young adult forms. In old adult forms, the bone tissues in the spikes become more compact and are extensively remodelled. This might contribute to the structural reinforcement of the spikes. The plates in old adult forms also show extensive remodelling and lines of arrested growth, but only limited signs of compaction. The timing for acquisition of features seen in old adults is different between plates (an extensive vascular network in the young adult) and spikes (a thick cortex with a large axial channel in old adults). The result suggests that the timing for plate and spike functions is different. The extensive vascular networks seen in large plates suggest their function is for display and/or thermoregulation. The thick cortical bone of spikes of old adults suggests that spikes acquire a weapon function for defence ontogenetically late.     

Comparative foraging ecology of Madagascar vangids (Vangidae)

The Vangidae, an endemic family in Madagascar, contains 14 species in 11 genera. The foraging behaviour of 13 species of vangids was investigated during the periods August-November 1989 and September-November 1990. These vangids are grouped into six bill types according to their bill shape, using the analogy of gripping tools: (1) forceps. (2) radio pliers, (3) strong pinchers, (4) pliers, (5) standard and (6) flat forceps types. We recognized seven foraging niches: (A) canopy-gleaning, (B) general, (C) ground-snatching, (D) trunk/ branch-probing, (E) leaf and twig/branch-gleaning/probing, (F) leaf and twig/branch-gleaning and (G) trunk-gleaning niches. Two or more coexisting species with the same foraging niche differed in their bill types. Those vangids that exploited similar resources segregated in their bill types, geographic ranges and/or foraging niches, presumably to avoid severe competition. Several vangid species partially occupied the ecological niche that would be filled by woodpeckers elsewhere.     

Suppression of Cdc27B expression induces plant defence responses

Non-host resistance is the most general form of disease resistance in plants because it is effective against most phytopathogens. The importance of hypersensitive responses (HRs) in non-host resistance of Nicotiana species to the oomycete Phytophthora is clear. INF1 elicitin, an elicitor obtained from the late-blight pathogen Phytophthora infestans , is sufficient to induce a typical HR in Nicotiana species. The molecular mechanisms that underlie the non-host resistance component of plant defence responses have been investigated using differential-display polymerase chain reaction (PCR) in a model HR system between INF1 elicitin and tobacco BY-2 cells. Differential-display PCR has revealed that Cdc27B is down-regulated in tobacco BY-2 cells after treatment with INF1 elicitin. Cdc27B is one of 13 essential components of the anaphase-promoting complex or cyclosome (APC/C)-type E3 ubiquitin ligase complex in yeast. This APC/C-type E3 ubiquitin ligase complex regulates G2-to-M phase transition of the cell cycle by proteolytic degradation. In this study, we investigated the roles of this gene, NbCdc27B , in plant defence responses using virus-induced gene silencing. Suppression of NbCdc27B in Nicotiana benthamiana plants induced defence responses and a gain of resistance to Colletotrichum lagenarium fungus. Elicitin-induced hypersensitive cell death (HCD) was inhibited mildly in plants silenced with tobacco rattle virus::Cdc27B. Cdc27B could manage the signalling pathways of plant defence responses as a negative regulator without HCD.     

The Inhibitory Effect of 5-Bromodeoxyuridine on the Programmed Cell Death in the Chick Limb

The inhibitory effect of 5-bromodeoxyuridine (BrdU) on the programmed cell death in interdigital mesenchyme of a chick leg bud was studied using vital staining and histological methods. A single administration of BrdU at day 6 1/3 specifically inhibited the programmed cell death in the mesenchyme of interdigital areas of a leg bud, resulting in the formation of a web-like structure. No inhibitory effect was observed on general development of limb buds. Hoechst 33258 staining revealed that many cells of interdigits incorporated BrdU into their nuclei. The simultaneous administration of thymidine blocked the BrdU effect.