Intercellular communication via the endo-lysosomal system: Translocation of granzymes through membrane barriers

Cytotoxic lymphocytes (CLs) are responsible for the clearance of virally infected or neoplastic cells. CLs possess specialised lysosome-related organelles called granules which contain the granzyme family of serine proteases and perforin. Granzymes may induce apoptosis in the target cell when delivered by the pore forming protein, perforin. Here we follow the perforin-granzyme pathway from synthesis and storage in the granule, to exocytosis and finally delivery into the target cell. This review focuses on the controversial subject of perforin-mediated translocation of granzymes into the target cell cytoplasm. It remains unclear whether this occurs at the cell surface with granzymes moving through a perforin pore in the plasma membrane, or if it involves internalisation of perforin and granzymes and subsequent release from an endocytic compartment. The latter mechanism would represent an example of cross talk between the endo-lysosomal pathways of individual cells. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.     

Structure and function of bordered pits: new discoveries and impacts on whole-plant hydraulic function

Bordered pits are cavities in the lignified cell walls of xylem conduits (vessels and tracheids) that are essential components in the water-transport system of higher plants. The pit membrane, which lies in the center of each pit, allows water to pass between xylem conduits but limits the spread of embolism and vascular pathogens in the xylem. Averaged across a wide range of species, pits account for > 50% of total xylem hydraulic resistance, indicating that they are an important factor in the overall hydraulic efficiency of plants. The structure of pits varies dramatically across species, with large differences evident in the porosity and thickness of pit membranes. Because greater porosity reduces hydraulic resistance but increases vulnerability to embolism, differences in pit structure are expected to correlate with trade-offs between efficiency and safety of water transport. However, trade-offs in hydraulic function are influenced both by pit-level differences in structure (e.g. average porosity of pit membranes) and by tissue-level changes in conduit allometry (average length, diameter) and the total surface area of pit membranes that connects vessels. In this review we address the impact of variation in pit structure on water transport in plants from the level of individual pits to the whole plant.     

尖吻蝮的人工繁育

In this article, we report our first experience of successful artificial propagation about the five paced pit viper ( Deinagkistrodon acutus ) and breeding to its second filial generation. In May, 1994, 18 adult snakes (8 males, 10 females) were captured in field, and were reared in man made environment. In July and August of the same year, 5 females laid 134 eggs in total (26 8±5 26), which were artificially incubated into 123 hatchlings. 100 hatchlings (average body weight 12 13±1 50 g)were selected to feed. Three years later, 58 snakes were alive (livability 58%). In September of 1997, April and May of 1998, some of the 58 snakes copulated. From July to August of 1998, 6 females laid 64 eggs in total, 58 of which were fertilized, and 54 were incubated into hatchlings in September of 1998. Therefore, we had successfully bred the second filial generation of the five paced pit viper in complete artificial environment.     

L'epoca Della Differenziazione Delle Gemme Fiorali Nell'olivo

Abstract

Calcium, as in general for all plants, is very important for fruit trees and a tight correlation between leaf content and cropping efficiency has been found.

The annual removal of calcium oxide of an orchard has been estimated in kg per hectare: pear 200, apple 180, peach 150, grape 60–130, olive 35–70, kiwi 55–60.

The rootstock affects the calcium uptake from the soil and content of the scion; frequently a higher calcium content is found in trees grafted an dwarfing rootstocks as pear on quince, apple on M9 and M26, peach on Damas.

By the horticultural point of view, calcium is responsible of two main problems: chlorosis due to high active Ca content in the soil and bitter pit, on the apposite, due to a low Ca level in the fruits.

From soil and leaf studies it seems clear that lime-induced Fe chlorosis results from two conditions: a) slow availability of Fe in the soil, and b) immobilization of Fe in the tree in forms that are not available for chlorophyll formation.

Breeding tolerant rootstocks has been the practical solution of chlorosis for most of the susceptible species.

Bitter pit is a physiological disorder of apple fruits, sometime already evident before picking, more frequently after harvesting, during the storage.

The prevention of the disorder is, essentially, a good horticultural practice (pruning, fertilization, irrigation, fruit thinning). Very effective are also Ca sprays as chloride or nitrate, or citrate, or phosphate, starting after setting, 4–5 times every 10–12 days.     

Ultrastructure of the early stages of carposporophyte development in the red algaChondria tenuissima (Rhodomelaceae,Ceramiales)

The ultrastructure of the early stages of carposporophyte development in the marine red algaChondria tenuissima has been studied. The diploid carposporophyte grows on the gametophyte. Apical gonimoblast cells develop into diploid carpospores. The basal gonimoblast cells cease to divide and undergo considerable cytoplasmic changes before they become incorporated into the expanding fusion cell. Nucleus and plastids degenerate gradually, while mitochondria remain intact. The smooth endoplasmic reticulum becomes prominent, it seems to produce small vesicles with electron dense contents. Simultaneously, numerous mucilage sacs are formed, presumably from dilating ER cisternae. The contents of the mucilage sacs are secreted by exocytosis. The pit connections between gonimoblast cells flare out. They remain as isolated bodies without connection to a wall after fusion. Secondary pit connections occur between vegetative gametophyte cells and sterile carposporophyte cells. There are three different morphological types of pit connections.     

Electron microscopical studies ofThorea ramosissima (Thoreaceae,Rhodophyta): Taxonomic implications ofThorea pit plug ultrastructure

The thallus ofThorea ramosissima was studied electron microscopically. The cells of the medulla, the cortex and the assimilatory hairs differ not only in size and number of plastids and their equipment with thylakoids but also in cell wall structure, the number of mitochondria and the activity of the Golgi apparatus, with dictyosomes transforming complete cisternae into Golgi vesicles with mucilaginous contents in the outer region of the cortex. The pit connections have plugs with a distinct plate—like (not dome-like) outer cap layer. BecauseT. riekei was reported to have dome-like outer cap layers and because this character was the main reason to place theThoreaceae into theBatrachospermales (Pueschel & Cole 1982),T. riekei was reinvestigated, too. A distinct outer cap could not be detected. The reliability of pit plug structure as a taxonomic character and the taxonomic position ofThorea is discussed.     

Temperature-Induced Changes in the Number of Vesicles in the Free Nerve Endings of Temperature Neurons of the Snake

By observing ultrastructural changes under the electron microscope, we illustrated exocytosis and recycling of vesicles in the infrared receptor, a kind of free nerve ending in the pit organ of the crotaline snake, Trimeresurus flavoviridis. While maintaining the snake pit organs at stable temperatures of 15°C, 25°C, and 30°C, we fixed them by perfusion and then processed them for transmission electron microscopy. The largest number of clear and coated vesicles appeared in the terminals at the lowest temperature. The perimeter and area of a terminal were enlarged at 30°C, and “opening waves” on the plasma were prominently found at the highest temperature. We also observed coated vesicles that budded from the plasma membrane in the terminals. The configuration of mitochondria in the terminals was quantitatively different between lower and higher temperatures. The data suggest that exocytosis and endocytosis in these terminals operate in a manner similar to that observed in other cell types.     

Foraging in the ant-lionMyrmeleon mobilis hagen 1888 (neuroptera: Myrmeleontidae): Behavioral flexibility of a sit-and-wait predator

The relative effects of foraging benefits (food intake) and costs (disturbance = pit destruction) on growth rate and foraging behavior of larvae of the ant-lionMyrmeleon mobilis were investigated. In a laboratory experiment second-instar larvae were subjected to combinations of three rates of feeding and three rates of disturbance. Pit relocations were generally rare but occurred more often in starved larvae. Disturbance rate had no significant effect on pit relocation rate. Feeding rate was a major determinant of the energy allocated in pit construction and maintenance (positive relationship). In a second experiment third-instar larvae encountered changing rates of disturbance. Pit size was reduced as a response to increased rates of disturbance. Disturbance had no detectable effect on growth. In general,M. mobilis larvae were cost-conservative, foragers.     

An Experimental Evaluation of Different Methods of Restoring Phyllospadix torreyi (Surfgrass)

The surfgrass Phyllospadix torreyi is an abundant seagrass found on rocky exposed shores of the Pacific coast of North America. In southern California surfgrass populations are adversely affected by a range of natural events and anthropogenic activities. Few attempts have been made to develop restoration methods for surfgrass, and none have investigated the efficacy of using different life stages. We evaluated several techniques for restoration in intertidal and subtidal habitats using: (1) laboratory‐reared seedlings transplanted to the field (2) sprigs (short lengths of rhizome containing a few shoots) transplanted from undisturbed populations, and (3) plugs (a cohesive clump of shoots and rhizomes) transplanted from undisturbed populations. We calculated the net change in the aerial coverage of surfgrass after 6 months, taking into account the recovery or additional losses from the donor population, and amount of effort involved in transplanting. Transplanted seedlings survived poorly and had minimal rhizome growth at both the intertidal and the subtidal sites, yet the individuals that did survive showed a 275% increase in leaf number. Survivorship of transplanted plugs was high in both habitats; however, physical disturbances to the donor populations exacerbated damage sustained at the time of collecting, yielding a substantial net loss in surfgrass. Sprigs transplanted to the subtidal had higher survivorship (71 versus 48%) and a greater increase in the aerial coverage of rhizome (86 versus 42%) than those transplanted to the intertidal. Of the three techniques, transplanted sprigs had the greatest overall increase in aerial coverage per unit effort, suggesting that this method may be the most effective approach for restoring P. torreyi.     

THE MORPHOLOGY AND DEVELOPMENT OF SOME PROMINENTLY STALKED SOUTHERN AUSTRALIAN HALYMENIACEAE (CRYPTONEMIALES,RHODOPHYTA). II. THE SPONGE-ASSOCIATED GENERA THAMNOCLONIUM KUETZING AND CODIOPHYLLUM GRAY1

Three members of the red algal family Halymeniaceae (Thamnoclonium dichotomum (J. Ag.) J. Ag., Codiophyllum flabelliforme (Sond.) Schmitz, and C. decipiens (J. Ag.) Schmitz) are investigated. All are endemic to southern and southwestern Australia, possess basal stalks of substantial size and firmness, and are consistently associated with specific sponge taxa. In each case, the sponges are bonded by collagen-like fibrils to the host cuticle without modifying the algal tissue at the ultrastructural level. Secondary cortication and prominent growth rings occur in the stalks of all three species, and in each the pit plugs between cells become wider, more convoluted and less electron dense with increasing distance from the surface. Such pit plugs are apparently a unique attribute of the stalked Halymeniaceae. The three species share pit plug, sponge association and stalk morphological features but are not otherwise closely related, as they actually represent three distinct genera.