Composition of the cell walls of different asparagus (Asparagus officinalis) tissues

Portions of stems from the base of asparagus spears (Asparagus officinalis L. cv. Connovor Collossus) were dissected to give the following tissues: (1) pith, which was free of vascular bundles, (2) two surrounding layers, parenchyma and fibre I and II (PFI and PFII), containing parenchyma and vascular bundles, (3) sclerenchyma sheath, (4) epidermis and sub-epidermal layers and (5) asparagus vascular fibre (AVF). The alcohol-insoluble residues (AIRs) from these tissues were shown to be free of starch. They were analysed for moisture and protein, and the component sugars were released by two hydrolytic procedures, which helped to distinguish the sugars from non-cellulosic polysaccharides and cellulose. The AIRs from pith and epidermal tissues were relatively low in xylose, but were rich in cellulosic glucose, and sugars associated with pectic polysaccharides such as galacturonic acid, galactose and arabinose. Their major component polysaccharides (in decreasing amounts) were inferred to be pectic polysaccharides, cellulose, and hemicelluloses. AIR from sclerenchyma was rich in glucose and xylose, suggesting the presence of much cellulose and (acidic) xylans. The AIRs of PFI, PFII and AVF contained significant amounts of xylose in addition tn other sugars, and the major polysaccharides inferred to be present were pectic polysaccharides, cellulose and hemicelluloses, a significant proportion of which may be acidic xylans. Methylation analysis of the AIRs confirmed the above inferences. The bulk of the glucosyl residues were (1–4)-linked, and there were small but significant amounts of (1–4, 6)-linked glucosyl residues (the linkage characteristic of xyloglucans) in all the preparations. The presence of (1–4)-linked galactosyl, (1–5)-linked arabinosyl, terminal galactosyl, terminal arabinosyl, (1–2)- and (1–2, 4)-linked rhamnosyl residues in all the AIRs except that from sclerenchyma, confirmed the presence of significant levels of pectic polysaccharides in all the parenchyma tissues. All the preparations containing vascular tissues contained significant amounts of (1–4)-linked xylosyl residues, probably derived from acidic xylans. Even in the AIR of pith, a significant amount of (1–4)-linked xylosyl residues were detected. This may be due to the ability of these cells and the parenchyma cells associated with the vascular bundles, to undergo lignification in mature asparagus plants.     

Effect of maturation and storage on asparagus (Asparagus officinalis) cell wall composition

Changes in the cell wall composition of stems of asparagus ( Asparagus officinalis L. cv. Connovor Collossus) during maturation and during storage in modified atmospheres were investigated. Alcohol-insoluble residues from portions of stems were analysed for changes in alkali-soluble phenolics and in the constituent sugars and their glycosidic linkages. Maturation-related changes down the stem involved increased levels of (l–4)-linked xylosyl residues from xylans, cellulose and phenolics, which arise from the lignified vascular and sclerenchyma tissues, and a decrease in the levels of (l–5)-linked arabinosyl residues from pectic arabinans from the parenchy-matous tissues. Storage under aerobic conditions permitted stem elongation in the apical sections and secondary thickening in the basal sections. This was due to continued tissue maturation. Storage under anaerobic conditions inhibited such changes. In accordance with these effects of storage on stem physiology, maturation-related changes in cell wall components were enhanced by storage only under aerobic conditions. However, levels of (1–4)-linked galactosyl residues which remained relatively constant during maturation, decreased substantially (ca 50%) in all stem sections during both aerobic and anaerobic storage.     

Hodgkin's disease and anaplastic large cell lymphoma revisited

In cultures, and in tissues as well, Hodgkin's and Reed-Sternberg (H-RS) cells and anaplastic large cell lymphoma (ALCL) cells are known to express a variety of cytokines, including IL-1, -5, -6, -8, -9, TNF-, GM-CSF, M-CSF, TGF-, CD70, CD80, and CD86. Various numbers of H-RS/ALCL cells may express cytokine receptors (R), such as CD30, CD40, IL-2R (CD25/CD122), IL-6R (CD126), IL-7R (CD127), TNF-R (CD120), TGF--R (CD105/endoglin), M-CSF-R (CD115), and SCF-R (CD117/c-kit receptor). All of these cytokines and cytokine receptors are implicated in the growth regulation of H-RS/ALCL cells, the histopathologic alterations in tissues, and the clinical manifestations in patients with Hodgkin's disease (HD) or ALCL. Many of these cytokines or cytokine receptors also play an important role in the pathogenesis of other types of lymphomas. In this review, we describe the cytokine or cytokine-receptor expression that is diacritic for H-RS/ALCL cells. The identification of such unique cytokine-cytokine receptor interactions is likely to explain the biologic property that distinguishes HD/ALCL from other types of lymphomas. These interactions include those of CD30L-CD30, CD40L-CD40, CD70-CD27, CD80/CD86-CD28, SCF-CD117, IL-9-IL9R, and IL-7-IL-7R. The H-RS/ALCL cells express IL-9 and two cytokine receptors, CD30 and CD117, which are observed infrequently in NHLs. Although IL-7 expression is not restricted to H-RS/ALCL cells, the expression of IL-7 in conjunction with IL-9 and/or CD117 may be regarded as unique for HD/ALCL because of an unusual combination and a synergistic activity among these cytokines. The expression of CD70 and CD80/CD86 (as cytokines) may exert a unique effect in HD because of intimate contact between H-RS cells and CD27/CD28-positive T cells. The expression of these costimulators (CD70 and CD80/CD86) and other adhesion/constimulator molecules such as CD54 and CD58, along with the secretion of soluble cytokines such as Il-1, IL-6, IL-7, or TNFs by H-RS/ALCL cells, could result in the profound T-cell proliferation often seen in lymph nodes involved by HD and some ALCL. On the other hand, the expression of CD30L and CD40L by surrounding T cells may affect the proliferation of H-RS/ALCL cells. The cytokine-cytokine receptor interaction between H-RS cells and T cells via direct cell-cell contact is bidirectional, a situation not commonly seen in NHLs.     

The interaction of xylosyltransferase and glucuronyltransferase involved in glucuronoxylan synthesis in pea (Pisum sativum) epicotyls.

A particulate enzyme preparation from etiolated pea (Pisum sativum) epicotyls was found to incorporate xylose from UDP-D-xylose into beta-(1----4)-xylan. The ability of this xylan to act as an acceptor for incorporation of [14C]glucuronic acid from UDP-D-[14C]glucuronic acid in a subsequent incubation was very limited, even though glucuronic acid incorporation was greatly prolonged when UDP-D-xylose was present in the same incubation as UDP-D-[14C]glucuronic acid. This indicated that glucuronic acid could not be added to preformed xylan. However, the presence of UDP-D-glucuronic acid inhibited incorporation of [14C]xylose from UDP-D-[14C]xylose into beta-(1----4)-xylan, and neither S-adenosylmethionine nor acetyl-CoA stimulated either the xylosyltransferase or the glucuronyltransferase.     

The energetic costs of egg heating constrain incubation attendance but do not determine daily energy expenditure in the pectoral sandpiper

Heating eggs during incubation may be relatively energeticallycostly, affecting the outcome or number of breeding attempts.We determined the effect of reduced egg heating costs on nestattendance, change in body mass, and daily energy expenditure(DEE using the doubly labeled water technique) by heating nestsof pectoral sandpipers. We also considered ground temperature,which may influence overall incubation costs, and mass reservesand stage of incubation, which may influence an individual'sability to respond to changes in overall incubation cost. Thetotal proportion of time spent in attending the eggs was significantlygreater in nests that were experimentally heated (3.6% or 52min daily), and this effect was significantly greater at lowground temperatures (14.7% or 211.7 min daily). Mass changewas independent of experimental heating when controlling forattendance, although mass loss rate was greater for birds thatattended more (for every 10% increase in daily proportion ofattendance 0.12 extra grams of body mass were lost per hour),and overall daily attendance increased by 0.5% for every extra1 g of body mass. DEE was greater for birds that had the higherrates of mass gain (for every 0.1 g of mass gained per hour,DEE increased by 20.5 kJ per day) but was independent of experimentalheating when controlling for attendance. Overall, the resultssuggest that females are constrained from attending more bytheir energy reserve levels being depleted at least partly bythe costs of egg heating, but these costs probably do not determineDEE, as costs off the nest may far exceed those incurred whilesitting. Breeding in the arctic is clearly energetically demanding:pectoral sandpipers had an average DEE of 361.1 ± 8.9kjd^–1, a mean power output of 4.1 W, equivalent to 6.1times basal metabolic rate (n = 24 birds).     

Altered cell cycle progression and aberrant mitosis in adenovirus-infected rodent cells

Actively growing mouse or rat embryo cells suffered structural chromosome damage, mitotic anomalies, and polyploidy after infection by human adenovirus type 5. Chromosome damage required expression of one or more early viral genes and showed regular periodicity in its frequency. The growth cycle time of some of the infected cells was reduced by about 5 hours due to a decrease in G₁, and the interval between successive waves of chromosome damage corresponded to this reduced cycle time. After infection there was a decrease in cells with G₁ DNA content and an increase in cells with G₂ diploid, aneuploid, and polyploid DNA contents. We suggest these effects are due to the expression in semipermissive cells of early viral gene(s), whose function in productive infection in vivo is to alter cell cycle controls in order to maximize the number of cells able to replicate viral DNA and the time such cells spend in DNA replication.     

Avoiding the pitfalls of sponsored multicentre research in general practice.

Research in general practice is becoming increasingly popular, and most general practitioners will sooner or later have to decide whether to become involved with clinical trials sponsored by drug companies. This paper outlines the advantages and disadvantages of multicentre research--based on experience of running a research group since the early 1980s--to enable doctors to reach the appropriate decision and to avoid involvement in trials which are either unethical or ineffective.