Stimulation of Nonspecific Host Resistance to Infection Induced by Muramyldipeptides

The effect of muramyldipeptide (MDP), N-acetylmuramyl-l-alanyl-d-isoglutamine [MDP(Ala)], and its analogs on bacterial infection was studied using the experimental model of sepsis infection in mice. Injection of MDP(Ala) gave mice definitive protection against E. coli infection, but only partial protection against P. aeruginosa or K. pneumoniae infection. Several factors influencing the protective activity of MDP (Ala) on E. coli infection were studied, and it was demonstrated that the activity was induced by various routes of administration of MDP(Ala), including the oral route, and was markedly influenced by the bacterial inoculum size. It was also shown that the effective dose of MDP(Ala) was 100 μg per mouse for intraperitoneal, intravenous or subcutaneous injections and 1,000 μg per mouse when administered orally. Furthermore, the optimal interval between MDP-treatment and infection was 24 hr when the treatment was carried out before infection. Clearance of bacterial cells in blood was observed after E. coli infection in mice treated with MDP(Ala). The efficacy of MDP(Ala) and two analogs, N-acetylmuramyl-l-valyl-d-isoglutamine [MDP(Val)] and N-acetylmuramyl-l-seryl-d-isoglutamine [MDP (Ser)], was evaluated for the E. coli infection; MDP(Val) was proven to be slightly less active than MDP(Ala), and MDP(Ser) to be the least effective, although MDP(Val) or MDP(Ser) was reported to have higher adjuvanticity than MDP (Ala) for the development of delayed-type hypersensitivity.     

Genomic regions affecting backfat thickness and cannon bone circumference identified by genome‐wide association study in a Duroc pig population

We performed a genome‐wide association study using the porcine 60K SNP array to detect QTL regions for nine traits in a three‐generational Duroc samples (n = 651), viz. generations 1, 2 and 3 from a population selected over five generations using a closed nucleus breeding scheme. We applied a linear mixed model for association mapping to detect SNP effects, adjusting for fixed effects (sex and season) and random polygenic effects (reflecting genetic relatedness), and derived a likelihood ratio statistic for each SNP using the efficient mixed‐model association method. We detected a region on SSC6 for backfat thickness (BFT) and on SSC7 for cannon bone circumference (CANNON), with a genome‐wide significance of P < 0.01 after Bonferroni correction. These regions had been detected previously in other pig populations. Six genes are located in the BFT‐associated region, while the CANNON‐associated region includes 66 genes. In the future, significantly associated SNPs, derived by sequencing the coding regions of the six genes in the BFT region, can be used in marker‐assisted selection of BFT, whereas haplotypes constructed from the SSC7 region with strong LD can be used to select for the CANNON trait in our resource family.     

Vital labelling of somite-derived myogenic cells in the chicken limb bud

Summary In order to understand how myogenic cells migrate in the limb bud, it is indispensable to distinguish undifferentiated myogenic cells from other mesenchymal cells. Thus, a suitable method for this purpose has been sought. A method to exchange the somites of a chicken and a quail microsurgically has widely been used, since the nuclei of the two species are morphologically distinguishable. However, microsurgery is accompanied by disturbances at the operated locus, and introducing cells of different species might induce unexpected effects. We report a new method for labelling chicken myogenic cells without transplantational operations, and describe their migration pattern in limb buds. Injection of a fluorescent carbocyanine dye into the somite lumen intensely labelled the somitic cells. Myogenic cells derived from the somite were clearly detected in limb buds. Before stage 20, the labelled cells were diffusely distributed in the proximal region of the limb bud. At about stage 21 in both wing and leg buds, labelled cells began to form dorsal and ventral masses. The label was followed until the cells differentiated and expressed myosin. This vital labelling method has advantages over the somite transplantation method: it does not include surgical operations that may disturb the normal development, and the cells are labelled intensely enough to be detected in a whole mount preparation. Offprint requests to: K. Hayashi     

Activities of auxin polar transport in inflorescence axes of flower mutants ofArabidopsis thaliana: Relevance to flower formation and growth

Relationships between the activity of auxin polar transport and flower formation were studied using several flower mutants ofArabidopsis thaliana. The activity of auxin polar transport in the upper portion of inflorescence axis of wildtype plants ofArabidopsis thaliana was significantly lower than that of the basal part. The activities of auxin polar transport in the upper portion of inflorescence axes ofap1 andclv1 mutants were significantly higher than that of wild-type plant. However, those of other flower mutants tested,ap3-1, ag, pi, Fl-40, Fl-54, Fl-89 andpin-formed, were extremely low as compared with that of wild one. We got some evidence that the reduction of the activity of auxin polar transport is concerned with the growth and development of plants. We could mimic it by the removal of all flowers and pods including mature or immature seeds. Moreover, artificial pollination inap3-1 andpi mutants, in which no seeds are found naturally, resulted in the partial recovery of the activity of auxin polar transport in inflorescence axis. Considering these results in this study together with the fact that inhibitors of auxin polar transport generated almost same disruptions ofpin-formed orpinoid mutants which normally had no flowers in inflorescence axis (Okadaet al. 1991, Uedaet al. 1992, Bennettet al. 1995), the systern of auxin polar transport and its activity in inflorescence axis seems to be essential for the development of flower bud in early stage ofArabidopsis thaliana, and the activity of auxin polar transport is also regulated by the formation of flowers and seeds in inflorescence axis.     

Cloning and characterization of an allene oxide cyclase,PpAOC3, in <Emphasis Type="Italic">Physcomitrella patens</Emphasis>

Allene oxide cyclase (AOC) is a key enzyme in the octadecanoid pathway of flowering plants that synthesizes 12-oxo-phytodienoic acid (OPDA), which is a biosynthetic precursor of the signal molecule jasmonic acid (JA). A database search of the Physcomitrella patens genome revealed the presence of an AOC gene unique from the two previously reported AOC genes, PpAOC1 and PpAOC2. After cloning the identified AOC gene, designated PpAOC3, the obtained cDNA sequence (897 bp) was larger than the predicted AOC gene (765 bp) in the database because a speculated intron was not fully deleted. Although PpAOC3 did not display high similarity with AOC proteins from other species, recombinant PpAOC3 exhibited AOC activity and translocated to chloroplasts, as is observed for other AOC proteins. Notably, the expression profile of PpAOC3 differed from the other PpAOCs, as its expression in protonemata was higher than that in gametophores. Although the function of oxylipins such as OPDA and JA remains elusive in P. patens, further characterization of the enzymes in the octadecanoid pathway and the role of oxylipin will aid in the elucidation of physiological processes in this model bryophyte.     

On some basic laws in physiological systems

Summary By the application of a new concept of activity, which is an extension of excitability in physiology, it was possible to establish the activity cycle in relation to the interstimulus interval as an extension of excitability cycle. It was proved also that the response area and audiogram in the auditory system, as well as the spectral response curve in the visual system can be described in uniform fashion as a special situation of activity.It was further found that Fechner's law and Stevens' power function are none other than one of the laws of activity in the semi-logarithmic and in the double logarithmic domains, respectively.     

Replication origin of bacteriophage f1: Two signals required for its function

Plus strand synthesis in bacteriophage f1 initiates in a region of dyad symmetry at a specific site (plus origin) recognized and nicked by the viral gene II protein. In this paper we describe several small deletions on the 5′ side of the f1 plus origin which disrupt the region of dyad symmetry and extend up to only four nucleotides from the gene II protein nicking site. These deletions do not impair the ability of gene II protein in vitro to nick this site. However, they do inhibit in vivo plus strand synthesis. We conclude that the nucleotide sequence at the f1 plus origin contains at least two specific signals that are required for efficient plus strand synthesis.     

Vimentin Expression Pattern is Different between the Flank Region and Limb Regions of Somatopleural Mesoderm in the Chicken Embryo

It is known that the chicken flank somatopleure also has a limb-forming potential at early stages of development, but loses this potential later. Molecular changes during this process is, however, not well known. We obtained a monoclonal antibody which reacts to the flank somatopleure, but not to the wing bud, the leg bud and the neck somatopleure in the stage 22 chicken embryo. Further study revealed that this antibody is specific to vimentin. Time course of vimentin expression in the somatopleural mesoderm during the development was studied. It was revealed to be biphasic. Somatopleural mesoderm expressed vimentin at stage 10, but not at stage 16. Flank somatopleural mesoderm began to express vimentin again at stage 18, whereas limb bud mesenchymal cells did not until stage 27. The earlier re-expression of vimentin at the flank somatopleure suggests that certain physiological changes take place in cells at this region.