Circadian clock adjustment to plant iron status depends on chloroplast and phytochrome function

Plant chloroplasts are not only the main cellular location for storage of elemental iron (Fe), but also the main site for Fe, which is incorporated into chlorophyll, haem and the photosynthetic machinery. How plants measure internal Fe levels is unknown. We describe here a new Fe‐dependent response, a change in the period of the circadian clock. In Arabidopsis, the period lengthens when Fe becomes limiting, and gradually shortens as external Fe levels increase. Etiolated seedlings or light‐grown plants treated with plastid translation inhibitors do not respond to changes in Fe supply, pointing to developed chloroplasts as central hubs for circadian Fe sensing. Phytochrome‐deficient mutants maintain a short period even under Fe deficiency, stressing the role of early light signalling in coupling the clock to Fe responses. Further mutant and pharmacological analyses suggest that known players in plastid‐to‐nucleus signalling do not directly participate in Fe sensing. We propose that the sensor governing circadian Fe responses defines a new retrograde pathway that involves a plastid‐encoded protein that depends on phytochromes and the functional state of chloroplasts.     

Establishment of cellulolytic bacteria in the digestive tract of conventionally reared young mice: effect of the dietary cellulose content in the adult

Cellulolytic bacteria became established 12 days after birth in the caecum and colon of conventionally-reared mice fed a diet containing 5 p. 100 crude cellulose (Weende). Their population reached a level between 10(6) and 10(7) bacteria per gram of digestive contents in 25-day-old animals. However, variations between animals were very large; 20 to 50% of the individuals were free of cellulolytic bacteria. A low cellulolytic population was observed in adult mice fed a cellulose-free diet. The amount of cellulose in the diet and its nature (crude or pure cellulose) affected the number of cellulolytic bacteria: the higher the percentage of cellulose in the diet, the higher the number of cellulolytic bacteria, in particular with crude cellulose-containing diet.     

First descriptions of Coelometopini pupae (Coleoptera: Tenebrionidae) from Australia,Southeast Asia and the Pacific region,with comments on phylogenetic relationships and antipredator adaptations

Abstract. The pupal stage of ten Coelometopini species occurring in Australia, New Guinea, Southeast Asia and the Pacific region are described and a key for their identification is provided. The species are Chrysopeplus expolitus Broun, Derosphaerus hirtipes Kaszab, Hypaulax crenata (Boisduval), Leprocaulus borneensis Kaszab, Metisopus purpureipennis Bates, Promethis carteri Kaszab, P. nigra (Blessig), P. quadraticollis (Gebien), P. quadricollis Pascoe and P. sulcigera (Boisduval). The gin trap structures of D. hirtipes and P. quadraticollis are described in detail using scanning electron micrographs. A summary of antipredator structures of all known Coelometopini pupae is given. The phylogenetic value of pupal characters is assessed at intra‐ and intergeneric levels within the tribe.     

Evidence for a dual mechanism of chick embryo fibroblast adhesion on fibronectin and laminin substrata

Eight-day-old chick embryo fibroblasts were shown to adhere specifically to fibronectin and laminin substrata. Moreover, the Scatchard analysis reveals 540,000 binding sites per cell for the fibronectin with a dissociation constant (Kd) of 1.35 microM and 5,500 binding sites per cell for laminin with a Kd of 1.5 nM. Furthermore, cell-fibronectin interactions are mediated by plasma membrane proteins of high molecular weight (HMW) (150K and 125K) insensitive to trypsin treatment and low molecular weight (LMW) proteins (95K, 80K, 65K and 45K) sensitive to trypsin treatment. Adhesion of 8-day-old chick embryo fibroblasts on laminin is mediated by plasma membrane proteins highly sensitive to trypsin treatment. Regarding the paucity of laminin-binding sites, the identification of laminin receptor could not be achieved. Nevertheless, this study provides quantitative and qualitative evidences for different mechanisms of 8-day-old chick embryo fibroblasts on laminin and fibronectin.     

Intestinal microflora of the newborn rat as related to mammary, faecal, and vaginal Staphylococci strains isolated from the dam

To determine the relative importance of maternal microflora (faeces, vagina, and teats) in the contamination of newborn rats, strains of staphylococci from six different families (dam + litter) were isolated. These strains were identified, and by means of numerical profiles analyzed for their degree of similarity for each litter and (or) biotope. The staphylococci strains found in the gut of the newborn rat originated first from the teats and thereafter from the faeces. Concomitant observation of some identical strains, however, suggested a certain degree of similarity between these two maternal biotopes in this animal.     

Establishment of ciliate protozoa in the rumen of conventional and conventionalized lambs: influence of diet and management conditions

The establishment of ciliate protozoa in the rumen was studied in conventional lambs reared under different conditions of management. The role of the microflora in the kinetics of this establishment was also investigated in conventionalized lambs. In lambs reared under farm conditions ciliate protozoa appeared in the following order: Entodinium (15-20 days), Polyplastron, Eudiplodinium, and Epidinium (20-25 days), and Isotricha (50 days). Entodinium was the most abundant (10(5)-10(6) ciliates mL-1). During the 3rd month, ciliates disappeared spontaneously in about 60% of the lambs during a period that varied from 1 to 4 weeks. In lambs fed only cow's milk Entodinium spp. and Polyplastron multivesiculatum became established at low levels. The results obtained with the conventionalized lambs demonstrate that the establishment of the ciliates in the rumen requires that the bacterial flora be well established beforehand.     

A yeast protein analogous to Escherichia coli RecA protein whose cellular level is enhanced after UV irradiation

Summary In Saccharomyces cerevisiae, a protein was recognized by polyclonal antibodies raised against homogeneous Escherichia coli K12 RecA protein. The cellular level of the yeast protein called RecAsc (molecular weight 44 kDa, pI 6.3), was transiently enhanced after UV irradiation. Protease inhibitors were required to minimize degradation of the RecAsc protein during cell lysis. The RecAsc protein exhibited similar basal levels and similar kinetics of increase after UV irradiation in DNA-repair proficient (RAD ⁺) strains carrying mitochondrial DNA or not (rho ⁰). This was also true for the following DNA-repair deficient (rad ^-) strains: rad2-6 rad6-1 rad52-1, a triple mutant blocked in three major repair pathways; rad6-, a mutant containing an integrative deletion in a gene playing a central role in mutagenesis; pso2-1, a mutant that exhibits a reduced rate of mutagenesis and recombination after exposure to DNA cross-linking agents.     

Thermography as a predictive tool for laser treatment of port-wine stains

The argon laser, which has been proven both useful and safe for port-wine stain therapy, interacts with the hemoglobin of the vessels. In a percentage of cases, this treatment is still inefficient, and there is a lack of correlation between these bad results and clinical or histologic criteria. Thermography, which explores the vascularization of the port-wine stain, leads us to consider port-wine stains from a physical point of view. This very simple test shows no correlation with the clinical parameters of port-wine stain but is closely related to the results obtained with laser therapy. It seems to be a good criterion to estimate the argon laser treatment prognosis.