Anthocyanins of the Sterculiaceae: Flavonoid scores and Hennigian phylogenetic systematics

Published results of the distribution of anthocyanins in the Sterculiaceae have been re-interpreted on the basis of the phylogenetic status of the compounds present. A flavonoid score system was less useful than a cladistic interpretation based on Hennigian arguments.     

Type VI collagen of the intervertebral disc. Biochemical and electron-microscopic characterization of the native protein.

The collagen framework of the intervertebral disc contains two major fibril-forming collagens, types I and II. Smaller amounts of other types of collagen are also present. On examination of the nature and distribution of these minor collagens within bovine disc tissue, type VI collagen was found to be unusually abundant. It accounted for about 20% of the total collagen in calf nucleus pulposus, and about 5% in the annulus fibrosus. It was discovered by serially digesting disc tissue with chondroitin ABC lyase and Streptomyces hyaluronidase that native covalent polymers of type VI collagen could be extracted. Electron micrographs of this material prepared by rotary shadowing revealed the characteristic dimensions of tetramers and double tetramers of type VI molecules, with their central rods and terminal globular domains. Molecular-sieve column chromatography on agarose under non-reducing non-denaturing conditions gave a series of protein peaks with molecular sizes equivalent to the tetramer, double tetramer and higher multimers. On SDS/polyacrylamide-gel electrophoresis after disulphide cleavage, these fractions of type VI collagen all showed a main band at Mr 140,000 and four lesser bands between Mr 180,000 and 240,000. On electrophoresis without disulphide cleavage in agarose/2.4% polyacrylamide only dimeric (six chains) and tetrameric (12 chains) forms of type VI molecules were present. The ability to extract all the type VI collagen of the tissue in 4 M-guanidinium chloride, and absence of aldehyde-mediated cross-linking residues on direct analysis, showed that, in contrast with most matrix collagens, type VI collagen does not function as a covalently cross-linked structural polymer.     

Susceptibility of cartilage collagens type II, IX, X, and XI to human synovial collagenase and neutrophil elastase

The action of purified rheumatoid synovial collagenase and human neutrophil elastase on the cartilage collagen types II, IX, X and XI was examined. At 25 degrees C, collagenase attacked type II and type X (45-kDa pepsin-solubilized) collagens to produce specific products reflecting one and at least two cleavages respectively. At 35 degrees C, collagenase completely degraded the type II collagen molecule to small peptides whereas a large fragment of the type X molecule was resistant to further degradation. In contrast, collagen type IX (native, intact and pepsin-solubilized type M) and collagen type XI were resistant to collagenase attack at both 25 degrees C and 35 degrees C even in the presence of excess enzyme. Mixtures of type II collagen with equimolar amounts of either type IX or XI did not affect the rate at which the former was degraded by collagenase at 25 degrees C. Purified neutrophil elastase, shown to be functionally active against soluble type III collagen, had no effect on collagen type II at 25 degrees C or 35 degrees C. At 25 degrees C collagen types IX (pepsin-solubilized type M) and XI were also resistant to elastase, but at 35 degrees C both were susceptible to degradation with type IX being reduced to very small peptides. Collagen type X (45-kDa pepsin-solubilized) was susceptible to elastase attack at 25 degrees C and 35 degrees C as judged by the production of specific products that corresponded closely with those produced by collagenase. Although synovial collagenase failed to degrade collagen types IX and XI, all the cartilage collagen species examined were degraded at 35 degrees C by conditioned culture medium from IL1-activated human articular chondrocytes. Thus chondrocytes have the potential to catabolise each cartilage collagen species, but the specificity and number of the chondrocyte-derived collagenase(s) has yet to be resolved.     

Induction of eIF-4E phosphorylation by the addition of L-pyrroline-5-carboxylic acid to rabbit reticulocyte lysate

Addition of L-pyrroline-5-carboxylic acid to reticulocyte lysates inhibits protein synthesis and induced phosphoproteins of 25 and 14 kDa. The 25 kDa phosphoprotein had the same Mr and pI as phosphorylated eIF-4E. Incubation of lysates with L-pyrroline-5-carboxylic acid did not alter the crosslinking of eIF-4E to reovirus mRNA caps. These results suggest that modifications of the translational apparatus other than eIF-4E phosphorylation may mediate the inhibitory effect seen with L-pyrroline-5-carboxylic acid and/or that phosphorylation of eIF-4E may effect functions subsequent to its interaction with the mRNA cap such as protein-protein interactions with other cap-specific translation factors.     

A heterozygous collagen defect in a variant of the Ehlers-Danlos syndrome type VII. Evidence for a deleted amino-telopeptide domain in the pro-alpha 2(I) chain

A structural defect in the alpha 2(I) chain of type I collagen was characterized in a new case of the Ehlers-Danlos syndrome type VII. The patient's skin, fascia, and bone collagens all showed an abnormal additional chain, pN-alpha 2(I)s, running slower than the alpha 2(I) chain on electrophoresis. The extension was shown to be on the amino-terminal fragment of pN-alpha (I)s by cleavage with human collagenase, but pepsin was unable to convert pN-alpha 2(I)s to alpha 2(I). Skin collagen was 4-fold more extractable and contained fewer beta-dimers and a lower concentration of cross-linking amino acids than control skin collagen. Electron micrographs of both dermis and bone showed markedly irregular ragged outlines of the collagen fibrils in cross-section, although the patient had no clinical signs of bone disease. Procollagen secreted by her skin fibroblasts in culture showed equal amounts of the normal and abnormal alpha 2(I) chains on pepsin digestion. Before pepsin, the pN-alpha 2(I) component ran as a doublet on electrophoresis; pepsin removed only the normal slower chain. The suspected deletion in pN-alpha 2(I)s was traced by CNBr peptide analysis to the N-propeptide fragment, which behaved on electrophoresis about 15-20 residues smaller than that from the normal pN-alpha 2(I) chain. The simplest genetic explanation is a spontaneous heterozygote in which one normal and one abnormal allele for the pro-alpha 2(I) gene are expressed, the protein defect being a deletion of the junction domain that spans the N-propeptidase cleavage site and the N-telopeptide cross-linking sequence.     

Effects of histamine on bronchial artery blood flow and bronchomotor tone

The effects of aerosolized 5% histamine (10 breaths) on bronchial artery blood flow (Qbr), airflow resistance (RL), and pulmonary and systemic hemodynamics were studied in mechanically ventilated sheep anesthetized with pentobarbital sodium. Histamine increased mean Qbr and RL to 252 +/- 45 and 337 +/- 53% of base line, respectively. This effect was significantly different from base line for 30 min after challenge. The histamine-induced increase in RL was blocked by pretreatment with the histamine H1 receptor antagonist, chlorpheniramine, whereas the histamine-induced elevation in Qbr was prevented by the H2 antagonist, metiamide. Both responses were blocked only when both antagonists were present. Changes in Qbr were not directly associated with alterations in systemic and pulmonary hemodynamics or arterial blood gas composition. In vitro histamine caused a dose-dependent contraction of ovine bronchial artery strips that was prevented by H1 antagonist. The H2 agonist, impromidine, caused relaxation of precontracted arterial strips and was more potent and efficacious than histamine, whereas H1 agonists failed to elicit a relaxant response. Thus these findings indicate that histamine aerosol induces a vasodilation in the bronchial vascular bed; histamine has a direct effect on Qbr that is independent of alterations in RL, systemic and pulmonary hemodynamics, or arterial blood gas composition; and, histamine-induced bronchoconstriction is mediated predominantly by H1-receptors, whereas increased Qbr is controlled predominantly by H2-receptors, probably located in resistance vessels. This local effect of histamine on Qbr may have important implications in the pathophysiology of bronchial asthma and pulmonary edema.     

Evidence for constraint on species coexistence in vegetation of the Park Grass experiment

Repeated patterns, of a type that would be expected to result from limitations to species coexistence (i.e. assembly rules) were sought in the Park Grass experiment. This classical grassland experiment was sampled in two years, using replicated biomass samples. Variance in a number of measures was examined, and compared to the variance expected under appropriate null models, the latter based on assumptions of no interactions between species. In each case, an assembly rule would result in low variance. Examining variance in species richness between quadrats within a treatment, there was no indication of constraint on species co-occurrences; variance in richness was actually greater than expected under the null model, attributable to environmental variation or perhaps positive interactions between species. However, there was control on biomass, evidenced by variance in total biomass (i.e. over all species) within a treatment being significantly lower than expected under the null model. There was no indication of community structure based on guilds (i.e. functional types). Although there was in 1991 some, non-significant, indication of a constant proportion of species from the legume guild, there was no sign of such an effect in 1992. Searches for intrinsic guilds failed to converge. There was no indication at all of constancy in the proportional representation of guilds by biomass. Thus, there is good evidence for competitive control on plant growth, but none for control of species occurrences. There is no convincing evidence for guild structure in this community at the scale sampled. Possible conflict is discussed between the existence of evidence for temporal stability but the absence of evidence for spatial uniformity. It is concluded that most of the mechanisms proposed for temporal stability will not necessarily lead to control on spatial variation. For many mechanisms, this would depend on the spatial scale examined.