Application of Crustacean Chitin as a Co-diluent in Direct Compression of Tablets

A “simplex-centroid mixture design” was used to study the direct-compression properties of binary and ternary mixtures of chitin and two cellulosic direct-compression diluents. Native milled and fractioned (125–250 μm) crustacean chitin of lobster origin was blended with microcrystalline cellulose, MCC (Avicel® PH 102) and spray-dried lactose–cellulose, SDLC Cellactose® (composed of a spray-dried mixture of alpha-lactose monohydrate 75% and cellulose powder 25%). An instrumented single-punch tablet machine was used for tablet compactions. The flowability of the powder mixtures composed of a high percentage of chitin and SDLC was clearly improved. The fractioned pure chitin powder was easily compressed into tablets by using a magnesium stearate level of 0.1% (w/w) but, as the die lubricant level was 0.5% (w/w), the tablet strength collapsed dramatically. The tablets compressed from the binary mixtures of MCC and SDLC exhibited elevated mechanical strengths (>100 N) independent of the die lubricant level applied. In conclusion, fractioned chitin of crustacean origin can be used as an abundant direct-compression co-diluent with the established cellulosic excipients to modify the mechanical strength and, consequently, the disintegration of the tablets. Chitin of crustacean origin, however, is a lubrication-sensitive material, and this should be taken into account in formulating direct-compression tablets of it.     

EVIDENCE FOR XYLEM CONSTRICTIONS IN THE PRIMARY VASCULATURE OF PSILOPHYTON DAWSONII,AN EMSIAN TRIMEROPHYTE

Serial peels through the branch junctions of Psilophyton dawsonii were examined in an attempt to determine if “hydraulic constrictions” (i.e., a localized decrease in mean diameter of xylem elements) sensu Zimmermann (1983) had occurred during bifurcation. Based on the mean diameters of primary xylem tracheids measured acropetally and basipetally to branch junctions, evidence for xylem constrictions (= localized decrease in mean tracheid diameter) was found within the basalmost portions of four out of six minor axes examined near their attachment to major axes (anisotomous junctions). Xylem constrictions were not detected in branch junctions between axes of equal girth (isotomous junctions). Xylem constrictions were detected within the base of five out of seven junctions between fertile and main axes. The mean diameters of tracheids of the branch trace near its origin are larger both basipetally and acropetally from the constriction. There is no evidence for a localized decrease in the mean diameter of the xylem strand in the region of a constriction. Therefore, xylem constrictions are not the result of epidogenesis. Based on the production of “hydraulic constrictions” in extant plants, which serve to localize the formation of embolisms in lateral branches during water stress, it is speculated that P. dawsonii could protect the vasculature of major axes by a similar anatomical feature.     

Glycogen-enzymes containing bodies in type 2 fibres of tenotomized muscles in the rat

Inclusion bodies containing glycogen-enzymes were found in 30 to 60% of type 2 fibres of tenotomized calf muscles (m. gastrocnemius, m. soleus, m. plantaris) in rats, using histochemical reactions. The bodies appeared within 1 week after the tenotomy and were localized both in the central and the subsarcolemmal regions and rarely extruded into the extracellular space. These aggregates are 3 to 15 microns in length and 2 to 11 microns in diameter. In addition to glycogen, these bodies also contained various enzymes of the glycogen metabolism such as phosphorylase, a branching enzyme, and glucose-6-phosphatase, but showed no NADH-reductase, lactate dehydrogenase, or myofibrillar ATP-ase activity. The results indicate that glycogen-enzymes containing bodies are a degenerative phenomenon, which occurs only in type 2 fibres of the tenotomized muscles.     

Adenoviruses use lactoferrin as a bridge for CAR-independent binding to and infection of epithelial cells

Most adenoviruses bind to the coxsackie- and adenovirus receptor (CAR). Surprisingly, CAR is not expressed apically on polarized cells and is thus not easily available to viruses. Consequently, alternative mechanisms for entry of coxsackievirus and adenovirus into cells have been suggested. We have found that tear fluid promotes adenovirus infection, and we have identified human lactoferrin (HLf) as the tear fluid component responsible for this effect. HLf alone was found to promote binding of adenovirus to epithelial cells in a dose-dependent manner and also infection of epithelial cells by adenovirus. HLf was also found to promote gene delivery from an adenovirus-based vector. The mechanism takes place at the binding stage and functions independently of CAR. Thus, we have identified a novel binding mechanism whereby adenovirus hijacks HLf, a component of the innate immune system, and uses it as a bridge for attachment to host cells.     

Small heat shock proteins prevent aggregation of citrate synthase and bind to the N-terminal region which is absent in thermostable forms of citrate synthase

Citrate synthase (CS) is often used in chaperone assays since this thermosensitive enzyme aggregates at moderately increased temperatures. Small heat shock proteins (sHsps) are molecular chaperones specialized in preventing the aggregation of other proteins, termed substrate proteins, under conditions of transient heat stress. To investigate the mechanism whereby sHsps bind to and stabilize a substrate protein, we here used peptide array screening covering the sequence of porcine CS (P00889). Strong binding of sHsps was detected to a peptide corresponding to the most N-terminal α-helix in CS (amino acids Leu₁₃ to Gln₂₇). The N-terminal α-helices in the CS dimer intertwine with the C-terminus in the other subunit and together form a stem-like structure which is protruding from the CS dimer. This stem-like structure is absent in thermostable forms of CS from thermophilic archaebacteria like Pyrococcus furiosus and Sulfolobus solfatacarium. These data therefore suggest that thermostabilization of thermosensitive CS by sHsps is achieved by stabilization of the C- and N-terminae in the protruding thermosensitive softspot, which is absent in thermostable forms of the CS dimer.     

Artificial asymmetric warming reduces nectar yield in a Tibetan alpine species of Asteraceae

Background and Aims Asymmetric warming is one of the distinguishing features of global climate change, in which winter and night-time temperatures are predicted to increase more than summer and diurnal temperatures. Winter warming weakens vernalization and hence decreases the potential to flower for some perennial herbs, and night warming can reduce carbohydrate concentrations in storage organs. This study therefore hypothesized that asymmetric warming should act to reduce flower number and nectar production per flower in a perennial herb, Saussurea nigrescens, a key nectar plant for pollinators in Tibetan alpine meadows.Methods A long-term (6 years) warming experiment was conducted using open-top chambers placed in a natural meadow and manipulated to achieve asymmetric increases in temperature, as follows: a mean annual increase of 0·7 and 2·7 °C during the growing and non-growing seasons, respectively, combined with an increase of 1·6 and 2·8 °C in the daytime and night-time, respectively, from June to August. Measurements were taken of nectar volume and concentration (sucrose content), and also of leaf non-structural carbohydrate content and plant morphology.Key Results Six years of experimental warming resulted in reductions in nectar volume per floret (64·7 % of control), floret number per capitulum (8·7 %) and capitulum number per plant (32·5 %), whereas nectar concentration remained unchanged. Depletion of leaf non-structural carbohydrates was significantly higher in the warmed than in the ambient condition. Overall plant density was also reduced by warming, which, when combined with reductions in flower development and nectar volumes, led to a reduction of ∼90 % in nectar production per unit area.Conclusions The negative effect of asymmetric warming on nectar yields in S. nigrescens may be explained by a concomitant depletion of leaf non-structural carbohydrates. The results thus highlight a novel aspect of how climate change might affect plant–pollinator interactions and plant reproduction via induction of allocation shifts for plants growing in communities subject to asymmetric warming.     

The structure of feeding behavior in a phytophagous insect (Hylobius abietis)

Analysis of the feeding behavior of animals using such a high temporal resolution that meals can be defined may improve our understanding of the mechanisms regulating feeding. Meals can be distinguished in an ethologically meaningful manner by using the ‘meal criterion’, the shortest non‐feeding interval between feeding bouts recognized as meals. However, such a criterion has only been determined for a few insect species. Applying a recent method developed for assessing meal criteria for vertebrates, we determined the meal criterion for Hylobius abietis (L.) (Coleoptera: Curculionidae) based on data from video recordings of single individuals feeding on seedlings of Norway spruce, Picea abies (L.) Karst. (Pinaceae). The pine weevil is an economically important pest insect, because it feeds on the stem bark of planted conifer seedlings. Weevils had 4–5 meals per day. Each meal lasted about 24 min during which about 13 mm² of bark per meal were removed. Females had longer total meal durations and longer non‐feeding intervals within meals than males. Girdling seedlings did not affect the weevils' feeding properties. The size of meals was significantly correlated with the duration of non‐feeding intervals before and after them. This study is one of few describing the feeding behavior of an insect at a temporal resolution that allows individual meals to be distinguished. With more meal‐related data from insects available, differences in meal properties may be interpreted based on phylogeny, ecology, and physiology. Our results may also assist in the setup and interpretation of studies of plant‐insect interactions, and facilitate the evaluation and development of methods to protect plants against herbivores.     

Adaptive radiations in butterflies: evolutionary history of the genus Erebia (Nymphalidae: Satyrinae)

We studied the speciose butterfly genus Erebia by reconstructing its phylogenetic relationships using parsimony and Bayesian approaches. We estimated times and rates of diversification for its lineages and employed a biogeographical analysis in order to reconstruct its evolutionary history. DNA sequence data from one mitochondrial gene and three nuclear genes were analyzed for a total of 74 species in Erebia. The estimated dates of origin and diversification for clades, in combination with a biogeographical analysis, suggest that the genus originated in Asian Russia and started its diversification process around 23 Myr. An important event was the dispersal of a lineage from Asia to Western Europe between 23 and 17 Myr, which allowed the radiation of most of species in the genus. The diversification pattern is consistent with a model of diversity limited by clade richness, which implies an early rapid diversification followed by deceleration due to a decrease in speciation. We argue that these characteristics of the evolutionary history of Erebia are consistent with a density‐dependent scenario, with species radiation limited by filling of niche space and reduced resources. We found that the Boeberia parmenio appears strongly supported in the genus Erebia and therefore we place Boeberia Prout, 1901 as a junior synonym of Erebia Dalman, 1816 ( syn. nov. ).     

The effect of red wood ant abundance on feeding damage by the pine weevil Hylobius abietis

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