Are natural lipids UV-screening agents?

Summary Isolated lipids from Deinococcus radiodurans were reconstituted at final concentrations of 1 mg/ml into dioleoyl phosphatidyl choline (DOPC) vesicles and assayed for the ability to protect cells of Escherichia coli against killing by UV light (254 nm). Values of D₃₇ (UV dose required to reduce the number of surviving cells to 37% of the original number) were calculated from killing curves. E. coli was afforded the greatest protection with an individual lipid, identified as vitamin MK8 (D₃₇=310 J//m², compared to D₃₇=67 J/m² for E. coli irradiated in the presence of DOPC alone). Liposome-mediated protection was dependent on UV₂₅₄ absorbance and not on turbidity-related light-scattering. BOth vitamin MK8 from D. radiodurans and vitamin K₁, which is available commercially, showed a similar degree of UV₂₅₄-protection for E. coli. The UV-protective properties of vitamin K₁ were also investigated on mammalian cells in comparison with other natural lipids and known sunscreens. Survival curves were obtained for mouse fibroblast (L) cells irradiated at UV₂₅₄ in the absence or presence of DOPC liposomes into which were incorporated various natural lipids or standard sunscreen ingredients, all at final concentrations of 1 mg/ml. Experimentally determined values of D₃₇ were as follows: Vitamin K₁, 73 J/m²; \-carotene, 44 J/m₂; -tocopherol, 20 J/m₂; sulisobenzone, 156 J/m²; p-aminobenzoic acid (PABA), 113 J/m²; benzophenone, 80 J/m²; oxybenzone, 61 J/m² and DOPC alone. 23 J/m². Vitamin K₁, the most protective lipid tested, was also compared with PABA and oxybenzone (all at concentrations of 20 mg/ml; applied topicall) for its ability to protec Skh-hairless mice from UV₂₅₄-induced erythema, yielding a UV₂₅₄ protection factor of 3.5. In addition, vitamin K₁ (at 100 mg/ml) was able to provide hairless mice with a small degree of UVB protection, as indicated by an experimentally determined Solar Protection Factor of 1.5–2.0. Although it is concluded that vitamin K is not likely to account for the extraordinarily high degree of UV-resistance of D. radiodurans, vitamin K does show characteristics worthy of its consideration as a UV-screening agent. Offprint requests to: R. Anderson     

How strong is natural selection?

The strength of selection in nature has long been a controversial subject, partly because there were few quantitative measurements of phenotypic selection available until recently. In a new paper, Kingsolver and colleagues reviewed 63 studies and found that the median standardized directional selection gradient (a measure of the strength of phenotypic selection) was 0.16. Whether this means selection in nature is strong or weak depends both on one's point of view and on the error in selection estimates.     

Protein reactivity of natural product-derived γ-butyrolactones

The discovery of novel and unique target-drug pairs for the treatment of human diseases such as cancer and bacterial infections is an urgent goal of chemical and pharmaceutical sciences. Natural products represent an inspiring source of compounds for designing chemical biology methods with applications in target identification and characterization. Inspired by the huge structural diversity of γ-butyrolactones, which constitute up to 10% of all known compounds of natural origin, we extended the "activity-based protein profiling" (ABPP) target identification technology to this promising and so far unexplored natural compound class. We designed and synthesized a comprehensive set of natural product-derived γ-lactones and thiolactones that varied in protein reactivity. Several important bacterial enzymes that are involved in diverse cellular functions such as metabolism (dihydrolipoyl dehydrogenase and 6-phosphofructokinase), cell wall biosynthesis (MurA1 and MurA2), and protein folding (trigger factors) were obtained. Especially protein folding in bacteria could represent a novel strategy for antibiotic intervention and requires chemical tools for characterization and inhibition. Future studies that extend structural modifications to protein reactive α-methylene-γ-butyrolactone as well as to reversible binding γ-lactones and thiolactones will reveal if this premise holds true.     

Do national parks protect natural landscapes?

Establishing national parks should result from a desire to protect natural or near natural landscapes with the lowest degree of anthropogenic transformation. This paper tries to ascertain whether national parks in Poland protect the most natural landscapes and how far they have been affected by humans. The level of anthropogenic transformation of natural landscapes was assessed based on an analysis of the percentage of natural, semi-natural and anthropogenic land cover. The vast majority of national parks in Poland (21 out of 23) protect landscapes which have been minimally transformed by humans (RAT_TNP ranges from 1.01 to 1.16). Only two kinds of natural landscapes, those that are the most transformed by humans, are not represented within the set of the Polish national parks. Hence, the distribution of national parks reflects the degree of anthropogenic landscape transformation. The proposed method could be applied to any type of spatial unit and thus be the basis for designating areas that should be protected.     

Haldane’s view of natural selection

Among many things, J. B. S. Haldane is known for demonstrating how the principle of natural selection can be used to build a mathematical, and in particular quantitative, theory of evolution. However, to the end, he remained open to the idea of other evolutionary mechanisms. In his late writings, he repeatedly drew attention to situations in which natural selection did not operate, was hemmed in by constraints, or worked in a surprising manner. In this respect Haldane stands out among the architects of the Modern Synthesis.     

Can natural enemies enforce geographical range limits?

We develop a simple mathematical model to investigate the question as to whether a specialised consumer can be responsible for creating a range limit in the population of its dynamic resource. The model is most attuned for parasitoid-host relationships, but the central results should apply to a broad range of systems. Specifically, at the beginning of each simulation host and parasitoid populations are distributed at random along a string of patches. In each discrete generation and for each patch, host and parasitoid populations grow and interact, and then a constant fraction of those remaining disperses one or more patch distances in either direction according to a geometric distribution. We iterate the model 200 generations, and in any generation for any patch, either host and/or parasitoid can go locally extinct if its population falls below a threshold density. We find that a specialised parasitoid can enforce a limit, and it is even more likely to fragment its host population. The two most important conditions for parasitoid-enforced range limits are: 1) the theoretical host equilibrium density in the presence of the parasitoid be very small at sites eliminated from the host's range, and 2) the parasitoid disperses at high rates. We close by discussing our findings for specialist and generalist natural enemies, and the relevance of our study to the wealth of investigations on the causes of geographical range limits.     

Isolated γδ T cells express natural cytotoxicity receptors

BACKGROUND: The aim of this work was to investigate in vitro the putative role of EGR-1 in the growth of glioma cells. EGR-1 expression was examined during the early passages in vitro of 17 primary cell lines grown from 3 grade III and from 14 grade IV malignant astrocytoma explants. The explanted tumors were genetically characterized at the p53, MDM2 and INK4a/ARF loci, and fibronectin expression and growth characteristics were examined. A recombinant adenovirus overexpressing EGR-1 was tested in the primary cell lines. RESULTS: Low levels of EGR-1 protein were found in all primary cultures examined, with lower values present in grade IV tumors and in cultures carrying wild-type copies of p53 gene. The levels of EGR-1 protein were significantly correlated to the amount of intracellular fibronectin, but only in tumors carrying wild-type copies of the p53 gene (R = 0,78, p = 0.0082). Duplication time, plating efficiency, colony formation in agarose, and contact inhibition were also altered in the p53 mutated tumor cultures compared to those carrying wild-type p53. Growth arrest was achieved in both types of tumor within 1-2 weeks following infection with a recombinant adenovirus overexpressing EGR-1 but not with the control adenovirus. CONCLUSIONS: Suppression of EGR-1 is a common event in gliomas and in most cases this is achieved through down-regulation of gene expression. Expression of EGR-1 by recombinant adenovirus infection almost completely abolishes the growth of tumor cells in vitro, regardless of the mutational status of the p53 gene.     

Neobetanin: A new natural plant constituent?

Neobetanin, recently reported as a natural constituent of beetroot, is not present in fresh beet juice and hence appears to be an artifact of the isolation process.     

Obolinga (Mimosaceae)—its natural history

Obolinga zanonii is endemic to the mountain chain of the Sierra de Bahoruco (Dominican Republic)-Massif de la Selle (Haiti) in southern Hispaniola. Its habitat is the humid broadleaf forest (“cloud forest”) at approximately 1500 m. Little is known about the dispersal of the seeds, but many fall and germinate below the parent tree. Germination in a nursery occurs in about 30 days.     

Microbiological changes in mawè during natural fermentation

Lactic acid bacteria increased from 3.2 × 10⁶ and 1.6 × 10⁷ c.f.u./g (wet wt) to 2 × 10⁹ and 1.6 × 10⁹ c.f.u./g after 12 to 24 h of fermentation of home-produced mawè (a dough produced from dehulled maize) and commercial mawè, respectively. In commercial mawè, the yeast count increased from 1.3 × 10⁵ to 2.5 × 10⁷ c.f.u./g after 48 h of fermentation before decreasing, whereas in the home-produced mawè it increased from 2.5 × 10⁴ to 3.2 × 10⁷ c.f.u./g after 72 h of fermentation; the dominant yeasts were mainly Candida krusei, although C. kefyr, C. glabrata and Saccharomyces cerevisiae were also present. Enterobacteriaceae counts increased slightly during the initial stage ofthe fermentation, but decreased below the detection level after 24 to 48 h. Enterobacter cloacae was mostly found in commercial mawè and Escherichia coli mostly in homeproduced mawè.D.J. Hounhouigan and C.M. Nago are with the Université Nationale du Bénin, Faculté des Sciences Agronomiques, Département de Nutrition et de Sciences Alimentaires, BP 526, Cotonou, Benin; M.J.R. Nout and F.M. Rombouts are with the Agricultural University, Department of Food Science, Bomenweg 2, 6703 HD Wageningen, The Netherlands. J.H. Houben is with Utrecht University, Department of the Science of Foods of Animal Origin, Yalelaan 2, 3508 TD Utrecht, The Netherlands.     

“Complement fractionation” in natural diploid orchid species

Summary Four out of 10 diploid orchid species showed complement fractionation a complex cytological phenomenon, hitherto reported only in polyploid plants. The manifestation of this phenomenon during meiosis is the formation of chromosome subgroups resulting eventually in cells with more than the usual four sporads; five or six being the optimum number in the investigated orchid species. No implications whatsoever can be deduced as to the genetic or genomic constitution of the end products. The presence of the phenomenon in these orchid species could perhaps indicate a polyploid ancestry or concealed hybridity. The operation of complement fractionation, however, could be interpreted as an alternative evolutionary pathway opposed to polyploidy.     

Are natural microcosms useful model systems for ecology?

Several recent, high-impact ecological studies feature natural microcosms as tools for testing effects of fragmentation, metacommunity theory or links between biodiversity and ecosystem processes. These studies combine the microcosm advantages of small size, short generation times, contained structure and hierarchical spatial arrangement with advantages of field studies: natural environmental variance, 'openness' and realistic species combinations with shared evolutionary histories. This enables tests of theory pertaining to spatial and temporal dynamics, for example, the effects of neighboring communities on local diversity, or the effects of biodiversity on ecosystem function. Using examples, we comment on the position of natural microcosms in the roster of ecological research strategies and tools. We conclude that natural microcosms are as versatile as artificial microcosms, but as complex and biologically realistic as other natural systems. Research to date combined with inherent attributes of natural microcosms make them strong candidate model systems for ecology.     

Waldenstr?m macroglobulinemia – immunophenotype and natural history

Despite encouraging progress in recent years, our knowledge of the natural history of Waldenstr?m macroglobulinemia (WM), a low-grade LPL (lymphoplasmacytic lymphoma) of mature IgM⁺ B-lymphocytes, remains superficial. This is particularly true of the etiology of WM (tumor causation and initiation) and the sequence of events that underlie the malignant transformation of precursor B cells (tumor progression). Here we briefly review the epidemiology of and genetic predisposition to WM and consider the role of autoimmunity and chronic inflammation in related tumor development. We discuss the immunophenotypic features of WM, including the immunological specificity of WM-associated IgM paraproteins. The proclivity of patients with WM to develop the rare immunoglobulin autoantibody syndromes mixed IgM-IgG cryoglobulinemia, chronic cold agglutinin disease, and IgM neuropathy will also be discussed. We conclude with a call for additional research to elucidate outstanding questions, such as the role of T cell-dependent vs. –independent immune responses in the pathophysiology of WM.     

Is canavanine a natural component of mammalian metabolism?

A group of non-protein amino acids of higher plants, namely l-canavanine, l-canaline, 0-ureido-l-homoserine, and l-canavaninosuccinic acid, have been implicated in mammalian intermediary metabolism. The clinical observations and biochemical basis for this hypothesis as well as conflicting experimental evidence are presented. A possible explanation for the apparent role of these non-protein amino acids in mammalian metabolism is offered.