Effect of Temperature on the Formation of Microsclerotia of Verticillium dahliae

Microsclerotium formation by six isolates of Verticillium dahliae was studied at different temperatures both in vitro and in Arabidopsis thaliana . In vitro mycelial growth was optimal at 25°C, but microsclerotium formation was greatest at 20°C (two isolates) or 15–20°C (one isolate). Seedlings of A. thaliana were root-dipped in a conidial suspension, planted, and either placed at 5, 10, 15, or 25°C, or left at 20°C until the onset of senescence, after which some of the plants were placed at 5, 10, 15, or 25°C. The amount of microsclerotia per unit of shoot weight was assessed in relation to isolate and temperature. The optimal temperature for production of microsclerotia was 15–25°C. Two isolates each produced about 10 times more microsclerotia than each of the other four isolates. For these isolates, high R ²_adj.-values of 0.77 and 0.66 were obtained, with temperature and its square as highly significant (P   < 0.001) independent variables. R ²_adj.-values for the other isolates varied between 0.28 and 0.39. Moving plants to different temperatures at the onset of senescence led to microsclerotial densities that were intermediate between densities on plants that had grown at constantly 20°C and plants grown at other temperatures. This suggests that vascular colonization rate and rate of microsclerotium formation are similarly affected by temperature. The senescence rate of plants appeared unimportant except for plants grown at 25°C, which showed the highest amounts of microsclerotia per unit of plant weight in the most rapidly senescing plants.     

Den distribution and den use by the red foxVulpes vulpes japonica in Kyushu

The distribution of dens and den use by the red fox was studied in Kumamoto Prefecture between 1968 and 1982. A total of 80 dens were classified into natal, residential, and temporarily-visited dens. Natal dens comprised 12.4% of all dens. Relative proportions were quite stable for a long period. This indicates a constant number of reproducing females in the area for a considerable length of time. Seasonally the utilization of den showed three peaks in February, May and October. The peaks coincided well with the peaks of reproductive activity of female foxes. The results of multiple regression analysis of distribution of dens with respect to selected environmental parameters around densites indicated that the fox selectively utilize open land, rather than densely vegetated areas. The persistence of dens, the selective utilization by foxes of open land and the sizes of dens were all related to the breeding activities of female foxes inhabiting the area. Reproductive females usually used plural dens (“den group”) in one reproductive season. The numbers of those females occuring in the area were maintained at a steady level for fairy long periods. These indicate that the existence of a stable social relationship between females mediated through occupancy of “den groups.”     

Gametangial interaction and oogenesis in the phycomycete Ciliomyces spectabilis (Fungi,Lagenidiales)

Gametangial interaction and oospore formation were studied in Ciliomyces spectabilis, a Lagenidiaceous fungus which is parasitic on ciliate cysts. Electron dense and granular vesicles of the antheridium are engaged in formation of the copulation porus between adjacent thalli. The oosphere is delimited by Golgi-derived cisternae which give rise to the membranes of the oosphere and the periplasm. The contents of the antheridium and the periplasm degenerate. The outer oospore wall is formed by wall vesicles originating from the endoplasmic reticulum. No vesicles are involved in the development of the thick inner oospore wall. Vacuoles with electron dense spherical contents fuse and form the central reserve globule. Lipid bodies aggregate first and disintegrate later into numerous small ones. The number of cytoplasmic organelles decreases. The possibility of wall formation via secretion of soluble wall material is discussed.     

Deme formation in scale insects: a test with the pinyon needle scale and a review of other evidence

ABSTRACT. 1. Deme formation is the transformation of a generalist population into one which is adapted to its local conditions. This adaptation has been inferred from many things but should be inferred from higher survival or fecundity of scale insects on their natal tree compared to that of immigrant scales on the same tree.
2. Transfers of the scale insect Matsucoccus acalyptus Herbert within and between infested host trees ( Pinus monophylla (Torr. & Frem.) resulted in significant differences in scale survivorship among recipient trees. Survival on individual trees was correlated across years, indicating stable differences in tree susceptibility to scale.
3. A significant natal tree colonized tree interaction was observed for late stage scale survival in one experiment but the interaction was not caused by superior survivorship of scales transferred back to the natal tree. Hence, we found no evidence of deme formation in M.acalyptus.
4. Previous studies have concluded that deme formation occurs in the black pineleaf scale based on a significant natal tree by colonized tree interaction in scale survival. We question this conclusion because the experimental design employed did not include transfers back onto the natal tree. Other indirect evidence for deme formation in scale insects is critically discussed.     

Acquisition of a brief behavioral experience in the presence of neuron-specific and D2-CAM/N-CAM-specific antisera

The effect of intraventricular infusion of D2-CAM/N-CAM directed antibodies prior to the acquisition of a passive-avoidance paradigm is described. The antisera used in this study were the neuron specific anti-BPM and a D2-CAM/N-CAM specific serum, anti-D2. Anti-BPM reliably inhibited paradigm acquisition when recall was ascertained at 24 and 48 hours and no effect was noted with absorbed anti-BPM or in sham-operated animals. This effect was time-dependent and no inhibition of memory formation was noted when the antiserum was administered at 6 and 10 hours after training. In contrast, infusion of anti-D2 had no effect on paradigm acquisition. These findings are discussed in relation to the potential synaptogenic events associated with memory formation.     

The complete sequence of the rice (Oryza sativa) chloroplast genome: intermolecular recombination between distinct tRNA genes accounts for a major plastid DNA inversion during the evolution of the cereals

Summary The entire chloroplast genome of the monocot rice (Oryza sativa) has been sequenced and comprises 134525 bp. Predicted genes have been identified along with open reading frames (ORFs) conserved between rice and the previously sequenced chloroplast genomes, a dicot, tobacco (Nicotiana tabacum), and a liverwort (Marchantia polymorpha). The same complement of 30 tRNA and 4 rRNA genes has been conserved between rice and tobacco. Most ORFs extensively conserved betweenN. tabacum andM. polymorpha are also conserved intact in rice. However, several such ORFs are entirely absent in rice, or present only in severely truncated form. Structural changes are also apparent in the genome relative to tobacco. The inverted repeats, characteristic of chloroplast genome structure, have expanded outward to include several genes present only once per genome in tobacco and liverwort and the large single copy region has undergone a series of inversions which predate the divergence of the cereals. A chimeric tRNA pseudogene overlaps an apparent endpoint of the largest inversion, and a model invoking illegitimate recombination between tRNA genes is proposed which accounts simultaneously for the origin of this pseudogene, the large inversion and the creation of repeated sequences near the inversion endpoints.     

The development of epidermal feet in preparation for metamorphosis in an insect

Insect epidermal cell surfaces can be seen by scanning electron microscopy after removal of the basal lamina. This let us study surface changes in the 5th larval stage of Calpodes ethlius (Lepidoptera, Hesperiidae) in preparation for metamorphosis at the end of the stadium, in particular changes in the basal cell processes or feet, intercellular lymph spaces, filopodia and hemidesmosomes. The feet develop in three phases, initiation, elongation and contraction. Initial growth begins immediately after ecdysis and continues until commitment to pupation 66 hr later. During this phase the feet are randomly oriented. Elongation and orientation begin after commitment to pupation. Orientation is probably achieved by selective survival and growth of those feet that are axially oriented rather than by reorientation. As the larva shortens to the pupal form late in the stadium, contraction of the feet occurs and the cells become columnar. The feet finally disappear as the cells rearrange themselves into new positions in the pupal epidermis. The lateral margins of the feet are united by adhesions even when their interdigitations are most complex. The adhesions separate an intercellular lymph space from the haemolymph. The lymph space remains small through most of the stadium, but enlarges with the loss of lateral junctions as the feet contract and eventually extends along most of the length of the columnar cells. Filopodia then form and span the gaps between the cells as though they have been induced by the separation and loss of lateral cell to cell contact. Scanning electron microscopy also shows that hemidesmosomes reflect the axial alignment of the cells even before the orientation of the feet. The hemidesmosome plaques are linear structures having a constant width of 0.15 - 0.2 mum and variable length. They arise in short sections and lengthen by the linear addition of more sections with the same width. Late in the stadium they lose their axial alignment and may become branched.     

Application of the Fröhlich theory to the modelling of rouleau formation in human erythrocytes

The details of Fröhlich's theory and some recent experiments on the rouleau formation of human erythrocytes which exhibit a strong interaction that appears to satisfy the prerequisites of the Fröhlich theory, are summarized. To verify whether the Fröhlich theory of long-range coherence in biological systems is applicable to the phenomenon of rouleau formation in human erythrocytes, the interactions between erythrocytes are modelled as those between two large, coupled oscillating dipoles. Relevant expressions for the resonant long-range and the van der Waals interaction are then derived. Using the available numerical data, the eigenfrequencies and the interaction energies corresponding to the experimental conditions are then derived. In the range of postulated frequencies (10¹¹–10¹² Hz) the effective interaction coefficient due to the resonant long-range forces is, indeed, found to agree with its experimental value of 3.0. However, the same value of can also be achieved through the ordinary van der Waals interactions between dipoles oscillating at lower frequencies. It is concluded that the resonant long-range interaction between erythrocytes may be responsible for the onset of rouleau formation. However, other mechanisms cannot be ruled out at this stage, especially since the Fröhlich mechanism requires a number of unconfirmed preconditions.     

Hyphal fusion during initial stages of trap formation in Arthrobotrys oligospora

Hyphal fusion during initial stages of trap formation by Arthrobotrys oligospora was studied by video-enhanced contrast and electron microscopy. Trap initials grew perpendicularly to the parent hypha, then curved around and anastomosed with a peg that developed on the hypha. Trap initials usually developed 40–140 m apart while the anastomosis occurred 20–25 m from the initial. Vigorous cytoplasmic movements in trap initials and developed traps corresponded to intense staining with fluorescein diacetate (FDA) of these cells. In addition, bundles of microfilaments were seen in developing loops of traps. On fusion organelle migration took place from the tip cell of the trap into the peg. Later on a septum was formed at the site of fusion.     

Synthesis of the herpes simplex virus type 1 trans-activator Vmw65 in insect cells using a baculovirus vector

Vmw65, the Herpes Simplex Virus trans-activator of immediate-early genes, was expressed in insect cells using a recombinant baculovirus expression vector and partially purified. Insect cell-derived Vmw65 was shown to be indistinguishable from authentic Vmw65 present in purified HSV-1 virions based on electrophoretic mobility, immunoreactivity with a monoclonal antibody, and ability to interact with cellular factors to form a protein/DNA complex with oligonucleotides containing a TAATGARAT element.Abbreviations AcNPV Autographica californica nuclear polyhedrosis virus - HSV Herpes Simplex Virus - IE Immediate Early - moi multiplicity of infection - Sf9 Spodoptera frugiperda cells