Within- and between-species patterns of allocation to pulp and seed in vertebrate dispersed plants

Non-uniform scaling of pulp and seed mass has been shown to alter dispersal probabilities in vertebrate dispersed species. Since dispersal in tropical forests is strongly linked to establishment success, processes determining allocation to pulp and seed are likely to impact on parental fitness, and therefore should be under the control of natural selection. In this study I examine size-dependent dry mass allocation pattern to pulp and seed mass both among and within 20 fruit-producing plant species of tropical rainforest in northeast Queensland, Australia. Reduced major axis analyses using mean values for each species showed significant isometry, indicating that at the community level, plant species that employ vertebrates as a means of seed dispersal tend to allocate an equivalent mean relative proportion of the overall dry weight investment in fruit to pulp. However, identical analyses conducted for each species separately revealed that relationships within individual species do not reflect the inter-specific relationship. These results imply two influences on dry mass allocation to fruit components; the first (within-species allometry) determines how fruits vary within each species. The second (between-species allometry) operates in a similar manner across species to produce equal ratios of mean pulp and seed mass independent of within-species allometries.     

What Can We Learn from the Evolution of Protein-Ligand Interactions to Aid the Design of New Therapeutics?

Efforts to increase affinity in the design of new therapeutic molecules have tended to lead to greater lipophilicity, a factor that is generally agreed to be contributing to the low success rate of new drug candidates. Our aim is to provide a structural perspective to the study of lipophilic efficiency and to compare molecular interactions created over evolutionary time with those designed by humans. We show that natural complexes typically engage in more polar contacts than synthetic molecules bound to proteins. The synthetic molecules also have a higher proportion of unmatched heteroatoms at the interface than the natural sets. These observations suggest that there are lessons to be learnt from Nature, which could help us to improve the characteristics of man-made molecules. In particular, it is possible to increase the density of polar contacts without increasing lipophilicity and this is best achieved early in discovery while molecules remain relatively small.     

Advances in alternative DNA delivery techniques

This review describes recent advances in alternative DNA-delivery techniques with particular emphasis on silicon carbide fibers, intact tissue electroporation, electrophoresis and microinjection. The advantages/disadvantages of each method along with a historical overview and theory of practice are discussed.     

Differential metabolism of sodium azide in maize callus and germinating embryos

Sodium azide is a potent mutagen of maize (Zea mays L.) kernels that may have potential as a point mutagen for inducing biochemical mutations in maize tissue cultures. Azide mutagenicity was evaluated in friable, embryogenic maize callus and a nonregenerable maize suspension culture by determining the number of resistant variant cell lines able to grow on media containing inhibitory concentrations of lysine plus threonine (LT). The number of LT-resistant variants selected from either culture type did not increase in response to azide treatment. In addition, there was no increase in somatic mutations in more than 100 plants regenerated from azide treated LT-resistant lines. The levels of mutagenic metabolite of azide (presumably azidoalanine), were determined by bioassay in the two azide-treated maize callus types and compared to levels of mutagenic metabolite in embryos isolated from azide-treated kernels. The two types of maize tissue cultures and isolated embryos contained similar levels of mutagenic metabolite 4 h after azide treatment indicating similar uptake and conversion of azide to mutagenic metabolite in the three tissues. Mutagenic metabolite in azide-treated embryos did not significantly decrease after 40 h. However, mutagenic metabolite levels in both azide-treated tissue cultures decreased to near background levels within 20 h providing evidence for rapid metabolism of the azide mutagenic metabolite. The lack of evidence for azide mutagenicity in maize callus and its known potent mutagenicity in kernels appears to be associated with specific differences in azide metabolism between callus tissues and kernel embryos.     

Characteristic chromosome abnormalities,including rearrangements of 6p,del(7q), +12, and t(12;14), in 44 uterine leiomyomas

Summary The cytogenetic analysis of 224 leiomyomas from 138 patients is presented. An insufficient number of mitoses was found in 35 tumors, normal karyotypes in 145, and clonal chromosome aberrations were detected in 44. The three previously identified cytogenetic subgroups were all represented in this series: del(7) (q21.2q31.2) was found in 11, trisomy 12 in five, and t(12;14)(q14-15;q23-24) in one leiomyoma. Rearrangements of 6p, including deletions, inversions, and various translocations, were found in eight tumors, thus delineating a new cytogenetic subgroup of uterine leiomyoma. The remaining 21 karyotypically abnormal tumors had nonrecurrent changes. One leiomyoma had two cytogenetically unrelated clones characterized by del(7)(q21.2 q31.2) and +12. Karyotypic changes in two separate leiomyomas from the same uterus were identified in five patients; in three of them, different anomalies were found in the two tumors, whereas cytogenetically identical aberrations – del(7q) and dic(21;22) – were detected in two macroscopically discrete tumors. These findings suggest that whereas some multiple leiomyomas originate independently, others may be derived from the same neoplastic clone.     

Inability of murine peritoneal macrophages to convert linoleic acid into arachidonic acid. Evidence of chain elongation

Various murine macrophage populations synthesize and secrete large amounts of arachidonic acid (20:4n-6) derived eicosanoids (cyclo-oxygenase and lipoxygenase products). These metabolites are known to possess a wide variety of functions with regard to the initiation and regulation of inflammation and tumorigenesis. Because the dietary intake of 20:4n-6 is usually low, tissues are largely dependent upon dietary linoleic acid (18:2n-6) as an initial unsaturated precursor for the biosynthesis of 20:4n-6. The purpose of these experiments was to determine whether resident or responsive murine macrophages possess desaturase and elongase activities capable of in vitro conversion of 18:2n-6 into 20:4n-6. Peritoneal exudate macrophages were purified by adherence and incubated in serum-free medium containing fatty acid-free BSA with [1-14C] 18:2n-6. Approximately 90 to 98% of the [14C]18:2n-6 at 4 and 16 h was recovered in phosphatidylcholine and phosphatidylethanolamine. The metabolism of [14C]18:2n-6 was determined after transesterification and separation of the 14C-fatty acid methyl esters by argentation TLC, reverse phase HPLC, and electron impact gas chromatography/mass spectrometry. Resident and responsive macrophages lacked the capacity to transform [14C]18:2n-6 into 20:4n-6. In addition, prelabeled macrophages incubated with soluble, calcium ionophore A23187 or phorbol myristate, or particulate, zymosan, membrane perturbing agents also lacked delta 6 desaturase activity. All macrophages tested were capable of elongating [14C]18:2n-6 into [14C]20:2n-6. These observations suggest that 20:4n-6, present in macrophage phospholipids, is biosynthesized elsewhere and transported to the macrophage for esterification into the phospholipids. In addition, these findings demonstrate that elongase activity is present in both the resident and responsive peritoneal macrophage.     

Epitope mapping with a recombinant human 68-kDa (U1) ribonucleoprotein antigen reveals heterogeneous autoantibody profiles in human autoimmune sera

Several cDNA fragments encoding parts of the (U1)RNP specific 68-kDa autoantigen were expressed in Escherichia coli and the fusion proteins were used as substrate for localization of the autoreactive epitopes. We have identified a region of approximately 30 amino acids reacting with more than 90% (16 of 17) of all human anti-p68 sera tested, regions which carry only a few and a region with no autoepitopes. Comparative analysis of epitopes recognized on partially degraded fusion proteins indicated that the anti-p68 autoimmune response is polyclonal. It involves generation of antibodies to several epitopes including one in a region with retroviral gag protein homology speculated to play a role in the initiation of the autoimmune response. Each of the 17 sera tested contained a different set of autoantibody specificities. These data are not consistent with random mutation as a sole mechanism of anti-p68 autoantibody induction and argue for an Ag-driven autoimmune response.