Fusion between incompatible colonies of a viviparous ascidian, Botrylloides lentus

Abstract. The mode of allo-recognition among colonies was investigated in a viviparous ascidian, Botrylloides lentus . Each embryo is enveloped by a pouch of epithelial cells (brood pouch), and is brooded in the vascular lumen of the parental colony. That is, the parental colony tolerates the presence of semi-allogeneic conspecifics (embryos) in the vascular system. A rejection reaction occurs when incompatible colonies are brought into contact at their growing edges. The inflammatory rejection reaction is limited to a small area where the tunic of two colonies has partially fused. On the contrary, incompatible colonies fuse and their blood vessels become interconnected with one another, when they are brought into contact at artificially cut surfaces. This mode is the same as those of other viviparous species of Botrylloides, B. fuscus and B. violaceus . A relationship between viviparity and the loss of allo-recognition in the vascular system is suggested.     

Sarcoplasmic calcium-binding proteins in protochordate and cyclostome muscle

Summary A sarcoplasmic calcium-binding protein (SCP) has been purified from the muscle of the protochordate Amphioxus and shown to be more similar to invertebrate SCP's than to their counterpart found in vertebrates, i.e. parvalbumins. The Amphioxus protein has a pI of 4.9, is rich in tyrosine and tryptophan, has a molecular weight of 22,000 and binds strongly 2Ca²⁺ with a pK of 7.88. Magnesium competes with calcium for only one of the two metal-binding sites and induces positive cooperativity in Ca²⁺ binding.In cyclostome muscle (lamprey and hagfish), no protein with high affinity for Ca²⁺ or Mg²⁺ could be found, irrespective of molecular weight. Instead, a protein with moderate affinity for Ca²⁺ (10⁵ m ^–1) was detected: it has a molecular weight of 60,000 and might be quite ubiquitous, as the presence of a similar protein has been reported both in red and white muscle of vertebrates such as chicken and rabbit.     

Recovery of activated cytotoxic T cells from minor H incompatible tumor graft rejection sites

In this study we determined whether minor H-specific cytotoxic T cells and their precursors (pTc) are present at the site of rejection of minor H disparate tumor allografts. Lymphocytes were retrieved from eyes of BALB/c mice that received subconjunctival injections of minor H-incompatible P815 tumor cells. The lymphocytes were then assayed for direct cytotoxic activity as well as precursor frequency by limiting dilution. Similar assays were conducted on cells obtained from the draining lymph nodes and from the spleen. As expected, tumor rejection was accompanied by significant clonal expansion of minor H-specific pTc within the draining lymph node and the spleen. A correspondingly high frequency of pTc was also detected at the graft site. More importantly, fully functional cytotoxic T cells were recovered from the tumor graft site during rejection, but no similarly active cells were found in either the draining nodes or spleen. We conclude that, after Ag stimulation, pTc are generated in draining central lymphoid compartments. From this generative site, the precursor cells then disseminate systemically, gradually reaching and infiltrating the tumor graft site. A further activation step, dependent upon Ag and T cell help, permits these cells to mature into fully active cytotoxic cells which can then effect tumor rejection. We propose that the terminal stage(s) of pTc activation is promoted by lymphokines released locally from TDH cells that are also generated during the alloimmune response and simultaneously infiltrate the site.     

Electron microscopic study of bacterial development in colonies. The morphology of bacterial colonies

The morphology of colonies of some pathogenic Gram-negative and Gram-positive bacteria has been studied by scanning and transmitted electron microscopy. The presence of covers on the surface of cells in colonies has been revealed. The examination of colony fragments in ultrathin section has revealed that cells exist in associations and the elements of cell covers are differentiated in the form of fibrillar structures in the intracellular space. This investigation has shown that covers in the colonies of the bacteria under study should be regarded as their morphological feature playing an important role in the development of the infectious process.     

Intercellular matrix in colonies of Candida.

The histochemistry and fine structure of typical colonies of six species of Candida were studied, using a total of 31 clinical isolates. The colonies consisted of viable and degenerate cells which lay in an intercellular matrix. This matrix was made up of amorphous, granular, and fibrillar components, the relative proportions and total amount of which varied from species to species. The cells of all species were surrounded by a zone of homogeneous amorphus material, which may be a highly cross-linked carbohydrate. This separated intact cells from irregularly distributed granular debris derived from the cytoplasm of degenerate cells. Focal cellular degeneration and associated granular debris were present within the colonies of all species and were most common in the surface layers of cells of colonies of C. albicans and C. tropicalis. The large amounts of intercellular matrix in this region formed a surface coat on colonies of these two species. Intercellular strands of cell wall material, and to a lesser extent other membranous elements from degenerate cells, formed a prominent fibrillar meshwork in the colonies of C. albicans and C. tropicalis, but were less common in those of C. pseudotropicalis and C. guilliermondii and seldom seen in those of C. parapsilosis and C. krusei.     

Growth and carbon partitioning in compatible and incompatible peach/plum grafts

The shoot growth of compatible ( Prunus persica L. Batsch cv. Springtime grafted on Prunus cerasifera L. Ehrh cv. Myrobolan P2032) and incompatible ( Prunus persica L. Batsch cv. Springtime grafted on Prunus cerasifera L. Ehrh cv. Myrobolan P18) peach/plum grafts was observed over a period of 100 days after grafting under controlled conditions. Leaf and root activities were determined by studying carbon assimilation and partitioning, leaf mineral contents and water relations. Shoot length and leaf number were not significantly affected in the incompatible combination during the first 55 days after grafting, but then, shoot growth rate was significantly reduced. Final total dry weights of the shoot were similar in both graft combinations. The incompatible combination did not show any water stress. Soluble sugar and starch contents increased in the leaves of the incompatible combination, accounting for about 36% of the increase of leaf dry weight per unit area. Photosynthesis was affected by the compatibility of the grafts. Leaf nitrogen content (% dry weight) fell in the incompatible graft combination 65 days after grafting. However, nitrogen content on an area basis was not affected. The possibility of nitrogen stress is discussed.     

The Mre11/Rad50/Xrs2 complex and non-homologous end-joining of incompatible ends in S. cerevisiae

In Saccharomyces cerevisiae, the Mre11/Rad50/Xrs2 (MRX) complex plays important roles in both homologous and non-homologous pathways of DNA repair. In this study, we investigated the role of the MRX complex and its enzymatic functions in non-homologous repair of DNA ends containing incompatible end structures. Using a plasmid transformation assay, we found that mre11 and rad50 null strains are extremely deficient in joining of incompatible DNA ends. Expression of the nuclease-deficient Mre11 mutant H125N fully complemented the mre11 strain for joining of mismatched ends in the absence of homology, while a mutant of Rad50 deficient in ATP-dependent activities exhibited levels of end-joining similar to a rad50 deletion strain. Although the majority of non-homologous end-joining (NHEJ) products isolated did not contain microhomologies, introduction of an 8bp microhomology at mismatched ends resulted in microhomology-mediated joining in all of the products recovered, demonstrating that a microhomology exerts a dominant effect on processing events that occur during NHEJ. Nuclease-deficient Mre11p was less efficient in promoting microhomology-mediated end-joining in comparison to its ability to stimulate non-microhomology-mediated events, suggesting that Mre11p influences, but is not essential for, microhomology-mediated repair. When the linearized DNA was transformed in the presence of an intact homologous plasmid to facilitate gap repair, there was no decrease in NHEJ products obtained, suggesting that NHEJ and homologous repair do not compete for DNA ends in vivo. These results suggest that the MRX complex is essential for joining of incompatible ends by NHEJ, and the ATP-dependent activities of Rad50 are critical for this process.     

Resistance of W/Fu rats to adrenal regeneration hypertension.

The procedure for producing adrenal regeneration hypertension did not cause an increase in the systolic blood pressure of W/Fu animals. The regenerating adrenal gland in W/Fu animals was not restored to normal; reduced numbers of mitochondrial cristae were seen and the mitochondria were smaller in size; regeneration was complete in Sprague-Dawley rats of the Holtzman strain and there was a severe form of hypertensive, cardiovascular disease.     

Immunofluorescent localisation of somatostatin-like cells in the esophagus of a protochordate

By means of the indirect immunofluorescence method, somatostatin-like immunoreactive (SLI) cells are detected in the esophagus of the ascidian Styela plicata. They are of the "open" type; they act probably by a paracrine mechanism on the esophageal secretin-like cells. The ascidian SLI cells are negative to all the specific cytochemical methods characteristic of vertebrate somatostatin (D) cells, which were applied in this work. In consequence, special SLI cells are probably present in ascidians.     

The growth and form of bacterial colonies.

A simple method is described for measuring the profile of bacterial colonies. Profiles were determined for colonies of Bacillus cereus, Escherichia coli and Staphylococcus albus of different ages. In spite of differences in cell morphology, the colony profiles had a common basic structure consisting of steeply rising leading edge connected by a ridge to an interior region where height also rose, though less steeply, to a flat or domed centre. The colony mass increased exponentially through part of the growth phase. It is suggested that net colony growth consists of a combination of leading edge growth, which is unrestricted and approaches the maximum specific growth rate of the organism, and diffusion-limited growth in the colony interior. Common elements of profiles from each species may be a consequence of such differences in growth rate.     

Evolution of heterogeneous perceptual limits and indifference in competitive foraging

The collective behaviour of animal and human groups emerges from the individual decisions and actions of their constituent members. Recent research has revealed many ways in which the behaviour of groups can be influenced by differences amongst their constituent individuals. The existence of individual differences that have implications for collective behaviour raises important questions. How are these differences generated and maintained? Are individual differences driven by exogenous factors, or are they a response to the social dilemmas these groups face? Here I consider the classic case of patch selection by foraging agents under conditions of social competition. I introduce a multilevel model wherein the perceptual sensitivities of agents evolve in response to their foraging success or failure over repeated patch selections. This model reveals a bifurcation in the population, creating a class of agents with no perceptual sensitivity. These agents exploit the social environment to avoid the costs of accurate perception, relying on other agents to make fitness rewards insensitive to the choice of foraging patch. This provides a individual-based evolutionary basis for models incorporating perceptual limits that have been proposed to explain observed deviations from the Ideal Free Distribution (IFD) in empirical studies, while showing that the common assumption in such models that agents share identical sensory limits is likely false. Further analysis of the model shows how agents develop perceptual strategic niches in response to environmental variability. The emergence of agents insensitive to reward differences also has implications for societal resource allocation problems, including the use of financial and prediction markets as mechanisms for aggregating collective wisdom.     

2009-2013年中国西方蜜蜂蜂群损失情况调查分析

近年,欧洲和北美地区相继出现蜜蜂蜂群崩溃(Colony Collapse Disorder, CCD)现象,蜂业科学家在世界范围内开展蜜蜂蜂群损失情况调查与分析。基于此,探讨近4年我国主要西方蜜蜂饲养省份蜂群损失情况,并对损失量、损失原因进行分析。研究采用欧盟政府间合作框架(COST)下项目- CoLoss (Prevention of honey bee COlony LOSSes)项目组提供的国际统一的标准调查表格,利用R语言在RStudio环境下开展全部的统计分析工作,采用广义线性混合模型分析调查数据的相关性及因变量为非正态分布的非独立数据。调查我国12 个主要西方蜜蜂饲养省份的蜂群越冬死亡损失情况。2009-2013 年蜂群平均损失率为8.9%,损失比例同比低于欧洲和北美国家和地区的蜂群损失率,在可接受范围内。利用广义线性混合模型分析,显著影响蜜蜂蜂群损失的因素有:巢脾使用时间及蜂王因素。我国蜂群损失率较低,大部分损失症状不属于CCD。CCD现象在我国尚未确认发生。加强蜂螨及其他病害的防治工作,增加更新巢脾频率,监控蜂王在蜂群中的表现及增加换王次数等可以有效控制蜂群越冬损失率。结果对明确我国蜂群是否受蜜蜂蜂群崩溃症状现象影响提出了明确的解释,对蜂群损失的防控提供重要的指导建议。     

Mutagenicity evaluation of HC Blue No. 1 and HC Blue No. 2, I. Effect on the induction of micronuclei in mouse bone marrow cells

Two hair-dye chemicals, HC Blue No. 1 and HC Blue No. 2, were assessed for the ability to produce chromosome breakage and/or spindle malformation in vivo by evaluating the capacity of these compounds to induce micronuclei in polychromatic erythrocytes of mouse bone marrow. Initial studies were conducted in ICR male and female mice given a single intraperitoneal dose of 1000, 500 or 250 mg/kg body weight and examined for micronucleus induction 24 or 48 h later. Activity was observed in female mice given 1000 mg/kg of HC Blue No. 1 at the 24-h harvest time. A questionable response was noted with HC Blue No. 2 in males at the 1000 mg/kg, 24-h time point. No activity was observed in either sex at the 48-h harvest time. In a second set of studies, mice from two strains, ICR and CD-1, were administered a single intraperitoneal dose of 1000 mg/kg of each chemical and the bone marrow was extracted 24 h later. In these experiments, HC Blue No. 1 again produced a statistically significant elevation of micronuclei in female ICR mice. No significant effect was observed in CD-1 mice of either sex. HC Blue No. 2 did not produce any significant elevation of micronuclei in either sex of ICR or CD-1 mice.