Effect of diet and feeding history on flight of Colorado potato beetle, Leptinotarsa decemlineata

We evaluated the hypothesis that Colorado potato beetle (Leptinotarsa decemlineata Say) (CPB) flight frequency is related to diet, and that it changes with duration of food unavailability or exposure to poor quality food by exposing adult overwintered and summer CPB populations to an acceptable host plant (conventional foliage), a poor host (insect resistant transgenic foliage expressing Bacillus thuringiensis tenebrionis[Btt] Cry3a toxin) and no host. Exposure to poor host and no host treatments (with or without water) decreased mean daily flight frequencies and the overall number of overwintered CPB flying, but increased the mean daily flight frequency and number of summer population CPB that flew. Overwintered CPB did not react to an absence of plants at emergence whereas summer CPB increased mean daily flight frequencies when plants and water were not available. The flight response to insect resistant foliage was similar to that for starvation treatments in both populations indicating that flight may not be triggered by Btt toxins but by starvation brought on by feeding on poor quality food. Flight was observed in all treatments for the duration of the test with two exceptions; overwintered beetles fed insect resistant foliage ceased flying after day 17 and summer beetles starved without water ceased after day 8 of a 29‐day study.     

Effect of Inhibition of Deoxyribonucleic Acid and Protein Synthesis on the Direction of Cell Wall Growth in Streptococcus faecalis

Selective inhibition of protein synthesis in Streptococcus faecalis (ATCC 9790) was accompanied by a rapid and severe inhibition of cell division and a reduction of enlargement of cellular surface area. Continued synthesis of cell wall polymers resulted in rapid thickening of the wall to an extent not seen in exponential-phase populations. Thus, the normal direction of wall growth was changed from a preferential feeding out of new wall surface to that of thickening existing cell surfaces. However, the overall manner in which the wall thickened, from nascent septa toward polar regions, was the same in both exponential-phase and inhibited populations. In contrast, selective inhibition of deoxyribonucleic acid (DNA) synthesis using mitomycin C was accompanied by an increase in cellular surface area and by division of about 80% of the cells in random populations. Little or no wall thickening was observed until the synthesis of macromolecules other than DNA was impaired and further cell division ceased. Concomitant inhibition of both DNA and protein synthesis inhibited cell division but permitted an increase in average cell volume. In such doubly inhibited cells, walls thickened less than in cells inhibited for protein synthesis only. On the basis of the results obtained, a model for cell surface enlargement and cell division is presented. The model proposes that: (i) each wall enlargement site is influenced by an individual chromosome replication cycle; (ii) during chromosome replication peripheral surface enlargement would be favored over thickening (or septation); (iii) a signal associated with chromosome termination would favor thickening (and septation) at the expense of surface enlargement; and (iv) a factor or signal related to protein synthesis would be required for one or more of the near terminal stages of cell division or cell separation, or both.     

Cryptococcal Cell Morphology Affects Host Cell Interactions and Pathogenicity

Cryptococcus neoformans is a common life-threatening human fungal pathogen. The size of cryptococcal cells is typically 5 to 10 µm. Cell enlargement was observed in vivo, producing cells up to 100 µm. These morphological changes in cell size affected pathogenicity via reducing phagocytosis by host mononuclear cells, increasing resistance to oxidative and nitrosative stress, and correlated with reduced penetration of the central nervous system. Cell enlargement was stimulated by coinfection with strains of opposite mating type, and ste3 a Δ pheromone receptor mutant strains had reduced cell enlargement. Finally, analysis of DNA content in this novel cell type revealed that these enlarged cells were polyploid, uninucleate, and produced daughter cells in vivo. These results describe a novel mechanism by which C. neoformans evades host phagocytosis to allow survival of a subset of the population at early stages of infection. Thus, morphological changes play unique and specialized roles during infection.     

Paramecium caudatum acquires heat-shock resistance in ciliary movement by infection with the endonuclear symbiotic bacterium Holospora obtusa

Holospora obtusa is a macronucleus-specific bacterium of the ciliate Paramecium caudatum. Three types of P. caudatum cells (H. obtusa-free cells, cells bearing the reproductive form of H. obtusa and cells bearing the predominantly infectious form of H. obtusa) cultured at 25 degrees C were transferred to 4, 10, 25, 35 and 40 degrees C and their swimming velocities were measured by taking photomicrographs with two-second exposures. The H. obtusa-free cells almost ceased swimming at both 4 and 40 degrees C, while cells bearing the reproductive form and those bearing the predominantly infectious form actively swam even at these temperatures. These results show that the host cell can acquire heat-shock resistance when infected by H. obtusa in the macronucleus. This is the first evidence to show that the endonuclear symbiont Holospora contributes to maintain the ciliary movement of the host even at temperatures unsuitable for the host growth.     

GROWTH AND ORGANIZED DEVELOPMENT OF CULTURED CELLS. VI. THE BEHAVIOR OF INDIVIDUAL CELLS ON NUTRIENT AGAR

Freely suspended cells of a long continuously cultured strain of carrot were dispersed in nutrient agar medium in Petri dishes. After inoculation, cells in randomly chosen fields were photographed at low magnification. The same cells were photographed at intervals over the next 23 days. The fate of 678 units, 24% of which grew visibly, was determined from the photographic record. Cells and units displayed a marked degree of individuality. In some units, there was a progressive increase in cell number; in others, after a few divisions, growth ceased; in still other units, cells enlarged without dividing. Although the evidence of cell division in free cells is conclusive, its incidence and maintenance increased with the size of the initial unit. In general, growth started after an “induction period” of about 5 days, but some cells remained apparently unchanged considerably longer after inoculation, before they started to grow. Although single cells of all sizes were observed to grow by one means or another, it was generally the shorter ones that continued to grow into viable colonies. Elongated cells predominated in the carrot strains used; these grew into colonies first by septation, with little or no over-all increase in size, followed by a stage of cell enlargement. Growth by both cell enlargement and division then ensued. During growth by septation within single cells, some derived cells were seen to burst and die. The most frequent divisions were observed during septation when the average cell generation time was 24 hr. Lacking the controls that normally operate in the intact plant body, there was much variation in the forms assumed during growth, a number of which are illustrated. The importance of epigenetic factors, or external controls, that determine the growth of cells in the plant body is stressed.     

Development of Stem Nodules in a Tropical Forage Legume, Aeschynomene afraspera

Rhizobial infection occurred on the stem of Aeschynomene afrasperaat the site of emergence of adventitious root primordia. Rhizobiainvaded cortical cells at the base of the root primordium. Thefirst infected cell enlarged and collapsed after rhizobia hadmultiplied in large numbers. At this time, a meristematic zonewas initiated some distance beneath the first infected cell.Rhizobial penetration into the deeper cortex was by progressivecollapse of infected cells towards the meristematic zone; rhizobiaentering the cortical cells by invagination of the host cellwall. At the entry point, rhizobia were embedded in digitatecell wall material. These infection structures were restricted,always originating from the cell wall of an adjacent infectedcell. Soon after infection, the cell collapsed progressivelyforming infection strand-like structures which developed upto the meristematic zone. When infection had reached the meristematiczone, invaded host cells ceased to collapse but divided repeatedlyto form the nodule. Key words: Aeschynomene afraspera, stem nodulation     

Transcriptional profiling identifies critical steps of cell cycle reprogramming necessary for Plasmodiophora brassicae‐driven gall formation in Arabidopsis

Plasmodiophora brassicae is a soil‐borne biotroph whose life cycle involves reprogramming host developmental processes leading to the formation of galls on its underground parts. Formation of such structures involves modification of the host cell cycle leading initially to hyperplasia, increasing the number of cells to be invaded, followed by overgrowth of cells colonised by the pathogen. Here we show that P. brassicae infection stimulates formation of the E2Fa/RBR1 complex and upregulation of MYB3R1, MYB3R4 and A‐ and B‐type cyclin expression. These factors were previously described as important regulators of the G2?M cell cycle checkpoint. As a consequence of this manipulation, a large population of host hypocotyl cells are delayed in cell cycle exit and maintained in the proliferative state. We also report that, during further maturation of galls, enlargement of host cells invaded by the pathogen involves endoreduplication leading to increased ploidy levels. This study characterises two aspects of the cell cycle reprogramming efforts of P. brassicae: systemic, related to the disturbance of host hypocotyl developmental programs by preventing cell cycle exit; and local, related to the stimulation of cell enlargement via increased endocycle activity.     

Water potentials induced by growth in soybean hypocotyls

Gradients in water potential form the driving force for the movement of water for cell enlargement. In stems, they are oriented radially around the vascular system but should also be present along the stem. To test this possibility, growth, water potential, osmotic potential, and turgor were determined at intervals along the length of dark-grown soybean (Glycine max L. Merr., cv. Wayne) hypocotyls. Transpiration was negligible in the dark, humid conditions, so that all water uptake was for growth. Elongation occurred in the terminal 1.5 centimeters of the hypocotyl. Water potential was −3.5 bars in the elongating region but −0.5 bar in the mature region, both in intact plants and detached tissue. There was a gradual transition between these values that was related to the growth profile along the hypocotyl. Tissue osmotic potentials generally paralleled tissue water potentials, so that turgor was the same throughout the length of the hypocotyl. If the elongating zone was excised, growth ceased immediately. If the elongating zone was excised along with mature tissue, however, growth continued, which confirmed the presence of a water-potential gradient that caused longitudinal water movement from the mature zone to the elongating zone. When the plants were grown in vermiculite having low water potentials, tissue water potentials and osmotic potentials both decreased, so that water potential gradients and turgor remained undiminished. It is concluded that growth-induced water potentials reflect the local activity for cell enlargement and are supported by appropriate osmotic potentials.     

The Roles of Cell Division and Cell Expansion in the Growth of Alfalfa Leaf Mesophyll

Leaf mesophyll of Medicago sativa (L.) was investigated to determinethe roles of cell division and cell expansion in tissue growth.Samples of leaf tissue were macerated, stained, and squashed.The slides were studied under a phase microscope to determinethe percentage of recently divided cells and the average celldiameter for leaflets of varying lengths. Cell division wasgreatest in young leaflets and virtually ceased as a leaf lengthof 12 mm was attained. For leaflets less than 12 mm in length,the rate of increase in cell size appeared to be inversely associatedto the degree of cell division. For alfalfa leaflets greaterthan 12 mm in length, the mean cell size increased in proportionto leaf length since cell division had virtually ceased.     

Mitogenic effect of muscle on the neuroepithelium of the developing spinal cord

A previous study revealed that segments of bowel grafted between the neural tube and somites of a younger chick host embryo would induce a unilateral increase in cellularity of the host's neural tube. The current experiments were done to test the hypotheses that muscle tissue in the wall of the gut is responsible for this growth-promoting effect and that the spinal cord enlargement is the result of a mitogenic action on the neuroepithelium. Fragments of skeletal (E8-15) or cardiac muscle (E4-14) were removed from quail embryos and grafted between the neural tube and somites of chick host embryos (E2). Both skeletal and cardiac muscle grafts mimicked the effect of bowel and induced an increase in cell number as well as a unilateral enlargement of the region of the host's neural tube immediately adjacent to the grafts. The growth-promoting effect of muscle-containing grafts was restricted to the neural tube itself and was not seen in proximate dorsal root or sympathetic ganglia. The action of the grafts of muscle was neither species- nor class-specific, since enlargement of the neural tube was observed following implantation of fetal mouse skeletal muscle into quail hosts. Grafts of skeletal muscle or gut increased the number of cells taking up [3H]thymidine in the host's neuroepithelium as early as 9 h following implantation of a graft. The increase in the number of cells entering the S phase of the cell cycle preceded the increase in cell number. These observations demonstrate that muscle-containing tissues can increase the rate of proliferation of neuroepithelial cells when these tissues are experimentally placed together.     

Altered ornithine metabolism in tumor-bearing mice

A flux of ornithine from the host tissues to the tumor was deduced from the concentrations of ornithine in plasma, ascitic liquid, liver and tumor cells during tumor growth. The activities of arginase and ornithine decarboxylase in both liver and tumor cells confirmed this proposed ornithine supply. Moreover, "in vitro" incubations of tumor cells showed that glutamine could be an additional source of ornithine for tumors. Finally, shortly before death, when tumor cell proliferation had ceased, altered hepatic ornithine metabolism was also detected.     

Erythrocyte membrane alterations induced by Plasmodium simium infection in Saimiri sciureus: relation to Schüffner's dots.

The nature of erythrocyte membrane alterations in Plasmodium simium infections was determined employing light microscopy, carbon replication and transmission electron microscopy. Light microscopy of Giemsa stained preparations shows that infected cells initially acquire a faint stippling (schuffnerization) which becomes pronouced with subsequent parasite development. Enlargement of the host cell usually accompanied stippling. Both phenomena appear to depend on host cell age since infected mature erythrocytes were neither stippled nor enlarged. Carbon replicas show numerous indentations over the outer membrane surface of most infected cells. Their distribution suggests that they account for Schuffner's granules. The surface indentations are manifest as small infundibular which open to the infected cell's surface. Cytoplasmic microvesciles in the infected cell's stroma frequently are observed adjacent or catenated to the surface infundibula. Images suggest their funsion with the surface infundibula thus adding membrane to the cell's surface and accounting for host cell enlargement.     

Regeneration of Tissues in Wounded Stems: A Quantitative Study

When a dicotyledonous stem is wounded by longitudinally splittinga young internode into halves, cells near the cut surface proliferateto form a callus within which vascular tissues differentiateand tend to restore a vascular cylinder in each half. Threephases of regeneration after wounding were identified and quantifiedin stems of three Solanaceous species. (1) In an initial ‘lag’phase, lasting about 2 d, neither cell division nor enlargementwere detected, but mitotic figures were observed within about300 µm of the cut surface. (2) Throughout a second, ‘division’phase, from about days 2–10, cell division and enlargementoccurred. Both were initiated mainly in the two cell layersnearest the surface. A mass of callus formed, with new cellwalls mostly parallel to the surface. Cell enlargement laggedbehind cell division for the first few days, so that mean radialcell diameter decreased until day 6, thereafter remaining almostconstant at 30–40 µm. Towards the end of this phase,mitoses ceased within the callus except in the positions ofthe future vascular and cork cambia, where radial cell diameterfell towards a constant 15–20 µm. (3) During a third,‘differentiation’ phase, cell division was restrictedto the cambial zones, and derivatives differentiated into cork,phloem or xylem according to position. The rate of increasein cell number per transect was 1.5–2.0 cells d^–1,of which more than half was xylem. Capsicum annuum L., sweet pepper, Lycopersicon esculentum Mill., tomato, cambium, cell division, differentiation, regeneration, wounding of stems, xylem     

Infection and Root-Nodule Development in Stylosanthes Species by Rhizobium

Root nodules of the tropical forage legume Stylosanthes occurredonly at lateral root junctions and resulted from direct invasionby rhizobia through spaces between epidermal cells. No infectionthreads were present in either the root hairs or nodules. Invasionof the host cortical cells was through structurally alteredcell walls. The bacteria reached the site of nodule initiationin the lateral root cortex by progressive collapse of the initiallyinvaded cells which were compressed by neighbouring cells toform intercellular thread-like infection zones. The bacteriamultiplied in the invaded cells of the nodule initial whichdivided repeatedly to form the nodule. Bacteroids formed onlywhen the host cells ceased to divide. Some abnormal associations occurred in S. capltata and S. hamata40264A. Division of invaded cells was restricted in S. capitataand the bacteria became enlarged and grossly deformed. In S.hamata restricted cell division was immediastely followed bythe brcakdown of the host cells and, although the bacteria multiplied,no bacteroids were formed. Bacteria isolated from these nodulesformed both effective and abnormal nodules when inoculated ontothe same host.     

HISTOLOGICAL AND HISTOCHEMICAL CHANGES IN DEVELOPING AND RIPENING PEACHES. II. THE CELL WALLS AND PECTINS

Reeve , R. M. (U.S.D.A., Albany, California.) Histological and histochemical changes in developing and ripening peaches. II. The cell walls and pectins. Amer. Jour. Bot. 46(4): 241–247. Illus. 1959.—Histological and histochemical observations on developing and ripening clingstone and freestone peaches have revealed that, after cell divisions have ceased in the mesocarp, cell wall thickening and cell enlargement in the mesocarp parenchyma increase until the fruit is nearly full cell size. The cell walls then decrease in thickness as the fruit ripens and softens. Degree of methyl esterification of the pectic substances, as estimated histochemically, remains at about 75–80% in immature fruits during their cell-enlargement phase of growth. Percent of methyl esterification apparently is much lower, or amounts of esterified pectates are very low during the meristematic phases of fruit growth. Just prior to ripening, degree of esterification increases and approaches 100% in hard, ripe fruit at about the same time that the parenchyma cell walls exhibit their greatest thickness or degree of hydration. The degree of esterification of the pectic substances then rapidly decreases and the cell walls become appreciably thinner as the ripening fruit softens. Further relation of these changes in wall thickness, in degree of esterification of the pectins, and in other cell wall carbohydrates to the textural qualities of ripening fruits is discussed. Interpretations concerning cell wall plasticity, cell growth and relation between auxin and changes in pectins also are presented.     

Human hepatocytes and aging: a cytophotometrical analysis in 35 sudden-death cases.

Alterations in the nuclear and cellular size of human hepatocytes occurring with age, and particularly in senescence, were studied by microphotometry. The material studied was obtained in 35 cases of sudden death, involving 17 males and 18 females ranging in age from 16 to 100 years. Cells of the peripheral zones of hepatic lobules were analyzed. The following results were obtained: 1. The mean nuclear area of hepatocytes remained relatively constant in subjects under 60 years of age but showed an increase in those over 60, this increase being associated with a greater standard deviation. 2. Volumetric analysis showed that the modal value included between 61 and 100% (mean 86%) of the cell nuclei examined and did not increase with age. This cell population was presumed to consist of diploid cells, the size of which remained constant. 3. An increase in mean nuclear area was due to the appearance of cells with larger nuclei which probably were the result of polyploidization. 4. Hepatocyte size increased with age. Analysis of the nucleus-to-cell sizes showed that the increase in cell size with age was more significant than the increase in nuclear size. 5. Cellular enlargement was more closely correlated with decrease in gross liver weight than with nuclear enlargement.     

Cryptococcus neoformans capsular enlargement and cellular gigantism during Galleria mellonella infection

We have studied infection of Cryptococcus neoformans in the non-vertebrate host Galleria mellonella with particular interest in the morphological response of the yeast. Inoculation of C. neoformans in caterpillars induced a capsule-independent increase in haemocyte density 2 h after infection. C. neoformans manifested a significant increase in capsule size after inoculation into the caterpillar. The magnitude of capsule increase depended on the temperature, being more pronounced at 37°C than at 30°C, which correlated with an increased virulence of the fungus and reduced phagocytosis at 37°C. Capsule enlargement impaired phagocytosis by haemocytes. Incubation of the yeast in G. mellonella extracts also resulted in capsule enlargement, with the polar lipidic fraction having a prominent role in this effect. During infection, the capsule decreased in permeability. A low proportion of the cells (<5%) recovered from caterpillars measured more than 30 μm and were considered giant cells. Giant cells recovered from mice were able to kill the caterpillars in a manner similar to regular cells obtained from in vivo or grown in vitro, establishing their capacity to cause disease. Our results indicate that the morphological transitions exhibited by C. neoformans in mammals also occur in a non-vertebrate host system. The similarities in morphological transitions observed in different animal hosts and in their triggers are consistent with the hypothesis that the cell body and capsular responses represent an adaptation of environmental survival strategies to pathogenesis.     

Response of xylem formation of Larix sibirica to climate change along the southern Altai Mountains,Central Asia

Under the ongoing warmer and wetter climate in the arid and semi-arid Altai Mountains, the key to understanding and predicting how forest growth responds to the changing climate in this area is to explore the dynamics of xylem formation and its climate drivers. However, such precise and high-time resolution knowledge is currently scarce. Here, we investigated the cambium activity and xylem formation of Siberian larch (Larix sibirica Ledeb.) in four sites along the southern Altai Mountains during the two consecutive growing seasons of 2018 and 2019. We found that the onset of xylem formation along the southern Altai Mountains started from mid-May to early June and ceased from late August to early September. The linear mixed model results showed that the onset of xylogenesis happened earlier when April was warmer and with lower precipitation. The cessation of xylem differentiation was closely related to the total number of xylem cells, regardless of temperature and precipitation. Therefore, a greater number of xylem cells resulted in delayed completion of cell enlargement and wall thickening. In addition, xylem cell production (total number of xylem cells) was negatively affected by May–July temperature and positively affected by May–July total precipitation. Our findings provide key data at the cellular level and high time resolution (weekly) and new insights into how forest ecosystems in the southern Altai Mountains respond to a warmer and wetter climate in the context of global warming.     

Cell Production and DNA Accumulation in the Wheat Endosperm, and their Association with Grain Weight

Nuclear DNA content was measured in developing endosperm cellsof two wheat varieties, Chinese Spring and Spica. 3C, 6C, 12Cand 24C nuclei were detected, indicating that some form of endoreduplicationand/or endopolyploidization was occurring. The total amountof DNA in the endosperm continued to increase until 24 dayspost anthesis. This accumulation of DNA resulted both from productionof new nuclei and also from increases in the DNA content ofexisting nuclei. Estimates of endosperm cell numbers were made from the totalDNA content per endosperm and the mean DNA content per endospermnucleus for a range of genotypes differing in mature grain weight.Endosperm DNA content and cell number were both positively associatedwith mature grain weight among the genotypes examined. However,not all of the variation in grain weight could be attributedto variation in cell number because of differences in mean dryweight per endosperm cell. The large-grained variety, Spica, had a greater mean weightper endosperm cell than Chinese Spring and this difference aroseafter cell production in the endosperm had ceased. Triticum aestivum, grain weight, cell size, cell number, DNA content     

Enhanced phosphorylation of endogenous membrane proteins during induction of B lymphocyte proliferation

Phosphorylation of endogenous proteins was assessed employing membrane preparations derived from splenocytes induced to proliferate in response to Sepharose linked anti-immunoglobulins. Time course studies revealed that enhanced protein phosphorylation was preceded by cell enlargement and was either followed by or closely related in time to the onset of DNA synthesis. Thus maximal enhancement of phosphorylation was initially observed at 24 h whereas cell enlargement was optimal at 16 h at a time when there was no enhancement in protein phosphorylation. Furthermore thymidine incorporation was maximal at 32 h and low at 24 h when phosphoprotein synthesis was maximally enhanced. Taken together, these results suggest that phosphorylation of endogenous membrane proteins may be involved in signalling entry of cells into S phase of the cell cycle.