Rupicolin-A and -B,rupin-A and -B,and cumambrin-B oxide from Artemisia tripartita ssp. Rupicola

Five new sesquiterpene Iactones have been isolated from Artemisia tripartita Rydb. ssp. rupicola Beetle. The compounds, all guaianolides, are structurally related in what appears to be a sequence in which epoxidation plays the principal role.     

7-Demethylsuberosin and osthenol as intermediates in furanocoumarin biosynthesis

¹⁴C-Labelled 7-demethylsuberosin (DMS) was a precursor of linear furanocoumarins in Conium maculatum and Heracleum lanatum (Umbelliferae), and in Ruta graveolens (Rutaceae), but not in Coronilla glauca (Leguminosae). Trapping experiments with ¹⁴C-umbelliferone over 3- to 24-hr periods revealed that DMS is rapidly metabolized, and that in short experiments its specific activity relative to the linear furano- coumarins′ is that of an intermediate. The specific activity of umbelliferone exhibited anomalies attributed to pool compartmentation. Analogous but less extensive experiments established that osthenol is an intermediate in angular furanocoumarin biosynthesis, but is much less rapidly metabolized than DMS. No significant incorporation into furanocoumarins of ¹⁴C from labelled l-valine, l-leucine, acetate, 2,3-di-hydroxyisovaleric acid, senecioic acid, isopentenylpyrophosphate, or mevalonate could be demonstrated. A synthesis of [1-¹⁴C]2,3-dihydroxyisovaleric acid is described.     

Incorporation of 14CO2, into cardenolide and sapogenin steroids of Digitalis purpurea

The relative rates of biosynthesis of cardenolide and sapogenin steroids of Digitalis purpurea were estimated by their uptake of ¹⁴CO₂. The incorporation of label into both groups, although initially slow, indicated that biosynthesis occurs even at the end of the growing season. The sapogenins were produced more rapidly than the cardenolides at this stage of plant development. Within the group of sapogenins, digitogenin, the trihydroxy compound, was produced at a greater rate than the dihydroxy steroid gitogenin. In the case of the cardenolides, the trihydroxy gitoxigenin was produced at a slower rate than the dihydroxy digitoxigenin.     

The p24 family and selective transport processes at the ER—Golgi interface

The secretory pathway is of vital importance for eukaryotic cells and has a pivotal role in the synthesis, sorting, processing and secretion of a large variety of bioactive molecules involved in intercellular communication. One of the key processes in the secretory pathway concerns the transport of cargo proteins from the ER (endoplasmic reticulum) to the Golgi. Type‐I transmembrane proteins of ～24 kDa are abundantly present in the membranes of the early secretory pathway, and bind the COPI and COPII coat complexes that cover vesicles travelling between the membranes. These p24 proteins are thought to play an important role in the selective transport processes at the ER—Golgi interface, although their exact functioning is still obscure. One model proposes that p24 proteins couple cargo selection in the lumen with vesicle coat recruitment in the cytosol. Alternatively, p24 proteins may furnish subcompartments of the secretory pathway with the correct subsets of machinery proteins. Here we review the current knowledge of the p24 proteins and the various roles proposed for the p24 family members.     

A chemosystematic study of some geraniaceae

The flavonoids of five Geranium, fourteen Erodium and four Monsonia species were studied. Quercetin was the most common aglycone with lesse     

The transepithelial shunt pathway in the renal proximal tubule of newt kidney

The transepithelial shunt pathway of newt proximal tubule was examined with glass micro-electrode and electron microscopic methods. The input resistance of the peritubular (basal) membrane and tubular wall were found to be $\text{4.2 ± 0.1 · 10}{}^6$ ($\text{mean ± S.E.}\text{, n = 16}$) and $\text{11.4 ± 0.2 · 10}{}^4\text{(n = 11)}$, respectively. The input resistance of the peritubular membrane was approximately 40-times larger than that of the tubular wall. When the kidneys were perfused in a lanthanum solution, the lanthanum ions were then observed in the junctional complexes and in the intercellular spaces on both the basal and apical sides. The results indicate that the electrical shunt pathway corresponds to the apical junctional complexes and the intercellular spaces, and that the tight junctions are not truly ‘tight’ for the transepithelial movement of small ions in the proximal tubule of the newt kidney.     

Biosynthesis of (−)-ent-kaurenoic acid in Smallanthus sonchifolius and its effect against microbial biofilms

The biosynthetic pathway of (–)-ent-kaurenoic acid (1) was investigated by incorporation of 1-d-¹³C-glucose in Smallanthus sonchifolius (Asteraceae) plantlets. The ¹³C-enrichment pattern indicated that methylerythritol-4-phosphate (MEP) pathway is the biosynthetic pathway involved in diterpenoid biosynthesis. Our studies in S. sonchifolius reinforce that the biosynthesis of different classes of terpenes should not be compartmentalized into cytosol and plastids. Additionally, (–)-ent-kaurenoic acid showed antimicrobial activity against Staphylococcus aureus biofilm.     

Chitin biosynthesis during pupal development of Drosophila melanogaster and the effect of the lethalcryptocephal mutation

Estimation of chitin deposition in the pupal and adult cuticles of adult Drosophila melanogaster during the pupal period is described. The timing of the periods of chitin deposition is compared with that deduced by previous workers using electron microscopy. The hypothesis that lethalcryptocephal mutant homozygotes are unable to evert their cephalic complexes at pupation because of excess chitin deposition is examined. The data obtained show no evidence that the mutation has any effect on chitin deposition.     

Testing the Metabolic Scaling Theory of tree growth

1.  Metabolic Scaling Theory (MST) predicts a 'universal scaling law' of tree growth. Proponents claim that MST has strong empirical support: the size-dependent growth curves of 40 out of 45 species in a Costa Rican forest have scaling exponents indistinguishable from the MST prediction.
2.  Here, we show that the Costa Rican study has been misinterpreted. Using Standardized Major Axis (SMA) line-fitting to estimate scaling exponents, we find that four out of five species represented by more than 100 stems have scaling exponents that deviate significantly from the MST prediction. On the other hand, sample sizes were too small to make strong inferences in the cases of 33 species represented by fewer than 50 stems.
3.  Recently, it has been argued that MST is useful for predicting average scaling exponents, even if individual species do not conform to the theory. We find that the mean scaling exponent of the Costa Rican trees is greater than predicted (across-species mean  =  0.44), and hypothesize that scaling exponents in natural forests will generally be greater than predicted, because the theory fails to model asymmetric competition for light.
4.   Synthesis . We highlight shortcomings in the interpretation of data used in support of a key MST prediction. We recommend that future research into biological scaling should compare the merits of alternative models rather than focusing attention on tests of a single theory.