Context and connectivity in plant metapopulations and landscape mosaics: does the matrix matter?

Recent reviews of evidence for plant metapopulation prevalence in nature have concluded that most species appear not to be arranged as metapopulations – hence other frameworks may be necessary for understanding large‐scale, regional dynamics in plants. Separate but related paradigms from the disciplines of landscape ecology and metapopulation ecology exist for understanding patterns of regional population variation. The major models of both paradigms assume a binary landscape mosaic composed of “suitable habitat” and background “matrix.” An important distinction between the two approaches is that metapopulation models essentially ignore features of the matrix. A binary approach to the landscape seems inappropriate for plants for several reasons. First, plants probably do not have a binary perception of the landscape, but rather respond to gradients of resource quality. Thus properties of patches, or the matrix per se, may be less important than the nature of the landscape mosaic, in particular as this is reflected in terms of connectivity. Secondly, many plants rely on a range of other agents for dispersal of pollen and seed, all of which are also affected by their environment in terms of connectivity. Furthermore the various components of the mosaic, including physical, spatial and functional elements can significantly influence plant movements. We review important effects of the matrix – via composition and configuration of habitat patches, extent of edges, patterns of land use, etc., upon plant populations. We describe evidence supporting a general integration of metapopulation and landscape ecological approaches for understanding regional dynamics in plants, emphasizing notions of connectivity (traditionally measured in very different ways by metapopulation and landscape ecologists), and context, an emerging concept describing components of variability in the landscape from a species‐specific perspective. Finally, we describe a functional landscape mosaic approach that treats structural and functional features of the landscape and show how these interact to determine the fate of plant populations.     

Developmental ocular disease of raptors

Sixteen raptors, including one eagle, two falcons, five hawks and eight owls, were found to have developmental ocular lesions. The most common lesion was microphthalmia. Other findings included cataract, microphakia, retinal dysplasia, malformation of the ciliary body, choroid and pecten, and lentoid formation. Specific causes for these lesions could not be determined. It is hypothesized that developmental ocular disease probably is more common than available reports indicate.     

Effect of confluence on endocytosis by 3T3 fibroblasts: increased rate of pinocytosis and accumulation of residual bodies

We have compared lysosomal enzyme distributions on density gradients and rates of transport of endocytic markers for actively-growing and confluent cells. While it has been previously established that mammalian cells accumulate lysosomal enzymes during quiescence, we show that this accumulation is predominantly in residual bodies (p greater than 1.12 g/ml) rather than in dense lysosomes (p = 1.08-1.10 g/ml) and does not represent a change in the endosomal and lysosomal enzyme content. The accumulation is not caused by a change in the rate of production of dense lysosomes, since the rate of transfer of epidermal growth factor (EGF) from light to dense compartments is the same between confluent and subconfluent cells. Confluent cultures have a higher rate of initial pinocytosis, and a higher rate of retroendocytosis and/or recycling, causing a net lower rate of accumulation of fluid-phase material. The accumulation of residual bodies in confluent cultures may be caused by a lower rate of exocytosis of their contents and/or a lack of dilution by cell division. The data indicate that the impact of culture confluence must be carefully assessed in experiments designed to analyze endocytic pathways.     

Effects of fenfluramine, m-chlorophenylpiperazine, and other serotonin-related agonists and antagonists on penile erections in nonhuman primates

Fenfluramine, m-chlorophenylpiperazine (m-CPP), 1-phenylpiperazine, and the buspirone metabolite, 1-(2-pyrimidyl)piperazine given intravenously to adult rhesus monkeys regularly elicited penile erections. In contrast, serotonin (5-HT) agonists with 5-HT1A site specificity (8-OH-DPAT, buspirone) as well as trazodone, ritanserin, and metergoline were no different from saline in producing penile erections. Fenfluramine's effects were blocked by the 5-HT2 antagonists, ritanserin and metergoline, while m-CPP's effects were not blocked by the peripheral 5-HT antagonist, xylamidine, indicating that tumescence can be elicited by serotonergic agents which act at non-5-HT1A sites in the central nervous system.     

Regulation of transforming growth factor alpha and transforming growth factor beta messenger ribonucleic acid abundance in T-47D, human breast cancer cells

Both transforming growth factor beta (TGF beta) and TGF alpha mRNA are expressed in human breast cancer cell lines. We have investigated the relationship of mRNA abundance for these growth modulators to the proliferation rate of a number of human breast cancer cell lines. Furthermore, we have investigated the relationship of regulation of TGF beta and TGF alpha mRNA to growth inhibition caused by progestins and nonsteroidal antiestrogens in T-47D human breast cancer cells. The abundance of TGF beta and TGF alpha mRNA in human breast cancer cell lines was not related directly to proliferation rate of the cells in culture or estrogen receptor positivity or negativity. The relationship of TGF beta and TGF alpha mRNA to growth inhibition caused by antiestrogens and progestins was investigated in T-47D human breast cancer cells. We observed that in T-47D human breast cancer cells the abundance of TGF beta mRNA is decreased in a time- and dose-dependent fashion by progestins but remains unaltered by nonsteroidal antiestrogens. Treatment of T-47D cells for 24 h with 10 nM medroxyprogesterone acetate (MPA) reduced the level of TGF beta mRNA to one third that present in untreated cells. The same treatment increased TGF alpha mRNA 3-fold above untreated controls in a time- and dose-dependent fashion and nonsteroidal antiestrogens caused a small decrease. The regulation of both TGF alpha and TGF beta mRNA was not directly related to inhibition of growth by progestins and antiestrogens in T-47D cells.(ABSTRACT TRUNCATED AT 250 WORDS)