Peter G. Waterman

Myocardial infarction accelerates atherosclerosis

During progression of atherosclerosis, myeloid cells destabilize lipid-rich plaques in the arterial wall and cause their rupture, thus triggering myocardial infarction and stroke. Survivors of acute coronary syndromes have a high risk of recurrent events for unknown reasons. Here we show that the systemic response to ischaemic injury aggravates chronic atherosclerosis. After myocardial infarction or stroke, Apoe−/− mice developed larger atherosclerotic lesions with a more advanced morphology. This disease acceleration persisted over many weeks and was associated with markedly increased monocyte recruitment. Seeking the source of surplus monocytes in plaques, we found that myocardial infarction liberated haematopoietic stem and progenitor cells from bone marrow niches via sympathetic nervous system signalling. The progenitors then seeded the spleen, yielding a sustained boost in monocyte production. These observations provide new mechanistic insight into atherogenesis and provide a novel therapeutic opportunity to mitigate disease progression.

DETERMINANTS OF VARIATION IN TROPICAL FOREST PRIMATE BIOMASS: NEW EVIDENCE FROM WEST AFRICA'

To explore sources of variation in tropical forest primate biomass, and, in particular, to test the hypothesis that soil conditions are a major ultimate determinant of the biomass of colobine monkeys and other primates, we compared data on the soils, vegetation, and primate community at a site in West Africa (Tiwai Island, Sierra Leone) with information from other sites, especially two other African sites (Douala-Edea in Cameroon, and Kibale Forest in Uganda). The biomass of eight anthropoid primate species in old secondary high forest on Tiwai was estimated from data on population densities assessed by transect samples combined with data on social group densities and individual body masses. Samples of soil and tree foliage were collected at the same site, and subjected to a variety of chemical and mechanical analyses. Our estimate of anthropoid biomass at Tiwai is 1229-1529 kg/kM2, including 682-889 kg/km2 of colobines. This is one of the highest primate biomasses recorded anywhere. The soils at Tiwai were found to be relatively high in sand content and low in pH, and to have low levels of mineral nutrients. Levels of condensed tannins in the mature foliage of the trees comprising a major part of the forest canopy were higher than at other sites, but the ratio of protein to fiber in this foliage was also higher than at any other site except Kibale. It is argued that a wide range of environmental factors affect primate population densities, and that nutrient-poor soils and high tannin levels in tree foliage do not necessarily produce a low primate (or colobine) biomass, as some earlier studies had suggested. Fur-

Food selection by the South Indian leaf-monkey, Presbytis johnii, in relation to leaf chemistry

SummaryThe leaf-monkey Presbytis johnii has been found to exhibit considerable selectivity in its dietary utilization of mature foliage in a rain-forest habitat. To investigate the basis of this selectivity and to examine the hypothesis that the observed selection is related to the digestibility and toxicity of the available foliage, chemical analyses have been made on 16 of the most important tree species in the monkeys habitat. It has been found that the most heavily used items, which form a staple part of the diet of P. johnii, are characterized by a low fibre content and a very low condensed tannin content. However, neither class of compound is an absolute feeding deterrent as minor, but still significant, mature leaf food items contain considerable amounts of both. It is suggested that the feeding deterrents in these minor items, which may be ingested to supply specific dietary requirements, can perhaps be tolerated because of their dilution in the gut by the dietary staples. An examination of the pepsin/cellulase digestibility of available mature foliage showed that the staple food items tended to be highly digestible. Little correlation has been found between alkaloid content and food selection and it is suggested that the colobine forestomach microflora has the ability to detoxify at least some alkaloids. Additional data on mature leaf petioles and young leaves suggest that the high ratio of cell-sap to cell-wall in these items, and their related high digestibility, explain the high relative abundance of these items in the P. johnii diet.

A critical analysis of techniques for measuring tannins in ecological studies

SummaryA series of seventeen taxonomically diverse plant extracts rich in phenolic materials, including condensed and hydrolysable tannins, have been subjected to a series of biochemical analyses in an attempt to gather ecologically significant information about their interaction with proteins and amino acids. Methods employed were (i) protein-precipitation, using bovine serum albumin as substrate, followed by computation of specific activities of the tannins present in the extracts, and (ii) the inhibition of cellulase activity by tannin extracts bound to the cellulose substrate and free in solution. Both techniques revealed that all extracts contained tannin material. However, attempts to relate the results of the two procedures and in turn to relate them to information reported previously on the chemical properties of these extracts revealed that there was little correlation between any of the chemical or biochemical properties examined. From this analysis it would seem that whilst the analytical procedures available for studying tannins may generate ecologically useful information it is at present impossible, at least where plant material that is taxonomically diverse is being examined, to extrapolate from one type of measure to anticipate what would be observed from another type of measure. In addition to the above three other observations arose from this study. First, it appears to be generally true that there is not an absolute positive correlation between the level of protein precipitation and the incorporation of tannin in the tannin-protein precipitate. As relative protein concentration increases the proportion of tannin bound in the precipitate decreases, leading to less stable precipitates. Second, it is confirmed that some basic amino acids will precipitate with tannins, a phenomenon that could potentially influence amino acid balance in the diet. Third, complexation between tannin and protein absorbed on a cellulose substrate is able to interfere with the digestion of that cellulose by cellulase enzymes. Cellulose masking of this type may potentially effect the efficiency of cellulolytic activity in the rumen and if so suggests another subtle variation in the potential antifeedant properties of tannins.

A review of the pharmacology and toxicology of Astragalus

Some Astragalus species are used as forage for livestock and wild animals. Many species are used in folk medicine for their hepatoprotective, antioxidative, immunostimulant, and antiviral properties, whereas others are toxic, and in many cases the toxic principles can pass to humans through milk and meat. Three groups of chemicals have been described as pharmacologically active principles: polysaccharides, saponins and phenolics. In addition, three kinds of toxic principles have been reported: indolizidine alkaloids, aliphatic nitro compounds and selenium.

A comparative study of the phytochemistry of two African Rain Forests

Abstract A comparative analysis of aspects of the secondary chemistry of plants from the Kibale Forest, Uganda, and the Douala-Edea Forest Reserve, Cameroon (93 species in all) has shown mean concentrations of tannins and other phenolics to be significantly greater in both young and mature foliage from Douala-Edea than in comparable taxa from Kibale. The differences remain significant when analysis was restricted to common species only. Chromatographic analysis confirmed that the proportion of species from Douala-Edea yielding tannin breakdown products was significantly greater than that from Kibale. In contrast, the proportion of species whose leaves gave definite alkaloid-positive Dragendorff reactions was significantly higher in the Kibale site. Within each site, mature leaves of the great majority of species yielded either tannins or alkaloids but the presence of detectable quantities of both types of compound was rare. In each site distributions of the two classes relative to one another departed significantly from independence at the O

The influence of topography and soil phosphorus on the vegetation of Korup Forest Reserve, Cameroun***

All living trees (≥30 cm gbh) were enumerated in 135 80×80 m plots, each subdivided into four 40×40 m subplots, and arranged along four 5 km transect lines in the Korup Forest Reserve, Cameroun. For each plot altitude, slope and the extent of permanent and seasonal swamps were recorded. Four hundred and eleven taxa were recognized of which 66% were identified to species. Mean tree density was 471 ha−1, basal area 27.6 m2 ha−1 and number of species per plot 75. The subfamily Caesalpinioideae (Leguminosae) was the most abundant family/subfamily in terms of basal area, but the Scytopetalaceae the most frequently represented, mainly on account ofOubanguia alata. Ten plots had at least three quarters of their area permanently swamped, and three, to a similar extent, were seasonally swamped. The ranges in sand, silt and clay content were 60–91, 0–24 and 4–20% respectively. The pH value, organic carbon content and nitrate-nitrogen concentration ranged between 4.0–5.8, 1.3–5.7% and 0–35 ppm respectively. The largest soil variations were in available phosphorus, range 2–29 ppm, and potassium, 38–375 ppm. Correspondence analysis ordination of all plots showed a major indirect floristic gradient correlated with increasing altitude, slope and soil phosphorus and potassium. Removal of the topographic effect by separate re-ordinations of four groups of plots at low, middle (2) and high altitude/slopes highlighted a strong correlation of the main floristic gradients of the middle altitude/slope groups with the concentration of available soil phosphorus. Direct gradient analysis using all plots with respect to available soil phosphorus concentration confirmed the indirect analyses. Individual species response to phosphorus were also shown by direct comparisons in the vegetation on plots of high and low available soil phosphorus concentration. Low available phosphorus soils (≤5 ppm) are strongly associated with species of the subfamily Caesalpinioideae, especially of the tribes Amherstieae and Detarieae. It is suggested that this result is probably due to the ability of these particular legume tribes to form associations with ectotrophic mycorrhizae.

Coumarins in the Rutaceae

Abstract The biogenesis, structural diversity and distribution of simple, furano- and pyranocoumarins in the Rutaceae is reviewed. The potential value of these compounds as taxonomic markers and their possible functions are discussed. The distribution of simple cinnamic acid precursors of coumarins in the family is also reviewed.

FOOD ACQUISITION AND PROCESSING AS A FUNCTION OF PLANT CHEMISTRY

Relatively little data exists concerning the energy and nutrient requirements of free-living primates. In the only comprehensive investigation published Nagy and Milton (1979a) recorded an average food intake of 53.5 g/kg/day of mixed fruit and immature leaves by six howler monkeys (Alouatta palliata). Of this about 35% was assimilated, representing a field energy budget of 355 kJ/ kg/day, almost twice the reported basal rate and markedly higher than the rate of 293 kJ/kg/day recorded for two caged howlers. Our knowledge of the minimum requirements of specific nutrients is similarly scant (Kerr, 1972). Protein demand can be assumed to be at least the 1 g/kg/day recommended for man, but could be appreciably higher. Most vitamin requirements are also probably comparable to those of man. Other nutrients required include Ca, Mg, Na, K, P, Cl, S, I, Fe, Cu, Se, Mo, B, Mn and V, and possibly Al, Si, Ni, Cr, Sn, Zn and Co (Kerr, 1972; Nagy and Milton, 1979b).

Light-induced variation in phenolic levels in foliage of rain-forest plants. I: Chemical changes

Levels of phenolic secondary metabolites in the leaves of four west African rain-forest plants,Acacia pennata, Cynometra leonensis, Diopyros thomasii, andTrema guineensis, were correlated with incident light intensity at both the inter- and intraindividual level. Enhanced phenolic levels under high light intensity appeared to be due to production of both polyphenolics (condensed and hydrolyzable tannins) and simple phenolics. InTrema guineensis, where it is possible to separate leaves in terms of both their age and the light incident upon them, condensed tannin production progressed differently during the development of “sun” and “shade” leaves, suggesting continuing production of new oligomers in the former but not in the latter. The results of this study suggest that the production of phenolics in relation to variation in incident light is a finely tuned process, which must be explained in terms of plant physiology and intermediate metabolism rather than in terms of resource allocation or a direct response to herbivory.