The tempo and mode of barnacle evolution

Previous phylogenetic attempts at resolving barnacle evolutionary relationships are few and have relied on limited taxon sampling. Here we combine DNA sequences from three nuclear genes (18S, 28S and H3) and 44 morphological characters collected from 76 thoracican (ingroup) and 15 rhizocephalan (outgroup) species representing almost all the Thoracica families to assess the tempo and mode of barnacle evolution. Using phylogenetic methods of maximum parsimony, maximum likelihood, and Bayesian inference and 14 fossil calibrations, we found that: (1) Iblomorpha form a monophyletic group; (2) pedunculated barnacles without shell plates (Heteralepadomorpha) are not ancestral, but have evolved, at least twice, from plated forms; (3) the ontogenetic pattern with 5-->6-->8-->12+ plates does not reflect Thoracica shell evolution; (4) the traditional asymmetric barnacles (Verrucidae) and the Balanomorpha are each monophyletic and together they form a monophyletic group; (5) asymmetry and loss of a peduncle have evolved twice in the Thoracica, resulting in neither the Verrucomorpha nor the Sessilia forming monophyletic groups in their present definitions; (6) the Scalpellomorpha are not monophyletic; (7) the Thoracica suborders evolved since the Early Carboniferous (340mya) with the final radiation of the Sessilia in the Upper Jurassic (147mya). These results, therefore, reject many of the underlying hypotheses about character evolution in the Cirripedia Thoracica, stimulate a variety of new thoughts on thoracican radiation, and suggest the need for a major rearrangement in thoracican classification based on estimated phylogenetic relationships.     

Estimating cell depth from somatic mutations

The depth of a cell of a multicellular organism is the number of cell divisions it underwent since the zygote, and knowing this basic cell property would help address fundamental problems in several areas of biology. At present, the depths of the vast majority of human and mouse cell types are unknown. Here, we show a method for estimating the depth of a cell by analyzing somatic mutations in its microsatellites, and provide to our knowledge for the first time reliable depth estimates for several cells types in mice. According to our estimates, the average depth of oocytes is 29, consistent with previous estimates. The average depth of B cells ranges from 34 to 79, linearly related to the mouse age, suggesting a rate of one cell division per day. In contrast, various types of adult stem cells underwent on average fewer cell divisions, supporting the notion that adult stem cells are relatively quiescent. Our method for depth estimation opens a window for revealing tissue turnover rates in animals, including humans, which has important implications for our knowledge of the body under physiological and pathological conditions.     

Herpes simplex virus type 1 preferentially targets human colon carcinoma: role of extracellular matrix

Viral therapy of cancer (viral oncolysis) is dependent on selective destruction of the tumor tissue compared with healthy tissues. Several factors, including receptor expression, extracellular components, and intracellular mechanisms, may influence viral oncolysis. In the present work, we studied the potential oncolytic activity of herpes simplex virus type 1 (HSV-1), using an organ culture system derived from colon carcinoma and healthy colon tissues of mouse and human origin. HSV-1 infected normal colons ex vivo at a very low efficiency, in contrast to high-efficiency infection of colon carcinoma tissue. In contrast, adenoviral and lentiviral vectors infected both tissues equally well. To investigate the mechanisms underlying the preferential affinity of HSV-1 for the carcinoma tissue, intracellular and extracellular factors were investigated. Two extracellular components, collagen and mucin molecules, were found to restrict HSV-1 infectivity in the healthy colon. The mucin layer of the healthy colon binds to HSV-1 and thereby blocks viral interaction with the epithelial cells of the tissue. In contrast, colon carcinomas express small amounts of collagen and mucin molecules and are thus permissive to HSV-1 infection. In agreement with the ex vivo system, HSV-1 injected into a mouse colon carcinoma in vivo significantly reduced the volume of the tumor. In conclusion, we describe a novel mechanism of viral selectivity for malignant tissues that is based on variance of the extracellular matrix between tumor and healthy tissues. These insights may facilitate new approaches to the application of HSV-1 as an oncolytic virus.     

Embryonic Porcine Skin Precursors Can Successfully Develop into Integrated Skin without Teratoma Formation Posttransplantation in Nude Mouse Model

How to improve the wound healing quality of severe burn patients is still a challenge due to lack of skin appendages and rete ridges, no matter how much progress has been made in the fields of either stem cell or tissue engineering. We thus systematically studied the growth potential and differentiation capacity of porcine embryonic skin precursors. Implantation of embryonic skin precursors (PESPs) of different gestational ages in nude mice can generate the integrity skin, including epidermis, dermis and skin appendages, such as sweat gland, hair follicle, sebaceous gland, etc.. PESPs of embryonic day 42 possess the maximal growth potential, while, the safe window time of PESPs transplantation for prevention of teratoma risk is E56 or later. In conclusion, PESPs can form the 3 dimensional structures of skin with all necessary skin appendages. Our data strongly indicate that porcine embryonic skin precursors harvested from E56 of minipig may provide new hope for high-quality healing of extensive burns and traumas.     

Speciation Versus Phenotypic Plasticity in Coral Inhabiting Barnacles: Darwin's Observations in an Ecological Context

Speciation and phenotypic plasticity are two extreme strategic modes enabling a given taxon to populate a broad ecological niche. One of the organismal models which stimulated Darwin's ideas on speciation was the Cirripedia (barnacles), to which he dedicated a large monograph. In several cases, including the coral-inhabiting barnacle genera Savignium and Cantellius (formerly Pyrgoma and Creusia, respectively), Darwin assigned barnacle specimens to morphological ``varieties' (as opposed to species) within a genus. Despite having been the subject of taxonomic investigations and revisions ever since, the significance of these varieties has never been examined with respect to host-associated speciation processes. Here we provide evidence from molecular (12S mt rDNA sequences) and micromorphological (SEM) studies, suggesting that these closely related barnacle genera utilize opposite strategies for populating a suite of live-coral substrates. Cantellius demonstrates a relatively low genetic variability, despite inhabiting a wide range of corals. The species C. pallidus alone was found on three coral families, belonging to distinct higher-order classification units. In contrast, Savignium barnacles exhibit large between- and within-species variations with respect to both micromorphology and DNA sequences, with S. dentatum ``varieties' clustering phylogenetically according to their coral host species (all of which are members of a single family). Thus, whereas Savignium seems to have undergone intense host-associated speciation over a relatively narrow taxonomic range of hosts, Cantellius shows phenotypic plasticity over a much larger range. This dichotomy correlates with differences in life-history parameters between these barnacle taxa, including host-infestation characteristics, reproductive strategies, and larval trophic type. Received: 18 January 1999 / Accepted: 9 May 1999     

From genome to function: the Arabidopsis aquaporins

Background

In the post-genomic era newly sequenced genomes can be used to deduce organismal functions from our knowledge of other systems. Here we apply this approach to analyzing the aquaporin gene family in Arabidopsis thaliana. The aquaporins are intrinsic membrane proteins that have been characterized as facilitators of water flux. Originally termed major intrinsic proteins (MIPs), they are now also known as water channels, glycerol facilitators and aqua-glyceroporins, yet recent data suggest that they facilitate the movement of other low-molecular-weight metabolites as well.

Results

The Arabidopsis genome contains 38 sequences with homology to aquaporin in four subfamilies, termed PIP, TIP, NIP and SIP. We have analyzed aquaporin family structure and expression using the A. thaliana genome sequence, and introduce a new NMR approach for the purpose of analyzing water movement in plant roots in vivo.

Conclusions

Our preliminary data indicate a strongly transcellular component for the flux of water in roots.     

Hand-operated box sampler for shallow water

The construction and operation of a hand-operated box sampler is described. The sampler covers an area of 25 × 25 cm and penetrates into the sediment to the depth of 15 cm. It was successfully operated on a sandy bottom, and on sand mixed with gravel up to a water depth of 1 meter.IAEC, Yavne 70600, Israel     

Studies in the biochemistry of cirripede eggs. V. Changes in the general biochemical composition during development of Chthamalus stellatus (Poli)

The biochemical composition of the eggs of Chthamulus stellatus (Poli) during their development has been investigated. The eggs are incubated within the mantle cavity of the adult but no substrates are contributed by the latter. Carbohydrates, protein, and lipid are all utilized. In contrast to two cold-water species, Balanus balanoides and B. balanus perviously investigated lipid rather than protein is consumed during the early stages. Possible explanations for this are considered.     

Thigmomorphogenesis: The Involvement of Auxin and Abscisic Acid in Growth Retardation Due to Mechanical Perturbation

When young bean plants are mechanically perturbed for up to10 days, they accumulate large amounts of an auxin-like substanceand increased amounts of ABA. Exogenous ethylene, applied inthe form of ethephon, produces the same result. Physiologicallymoderately high amounts of exogenously applied IAA or loweramounts of ABA cause the same sort of retardation of elongationthat is caused by either mechanical perturbation or exogenousethephon. Either mechanical perturbation or applied ethephonsignificantly retards the polar basipetal transport of ¹⁴C-IAAIt is proposed that mechanical perturbation of bean internodesinduces ethylene evolution which, in turn, induces the accumulationof high levels of IAA and the production of ABA, both of whichcontribute to the retardation of elongation of the internodes. (Received December 24, 1981; Accepted May 19, 1982)