Life Sciences Commons^™

Following Form And Function: A Philosophical Archaeology Of Life Science, Stephen Asma

Stephen T Asma

No abstract provided.

The Epidermis Still In Control?, Winfried Peters, A. Tomos

Winfried S. Peters

Reversal Of Cell Fate Determination In Caenorhabditis Elegans Vulval Development, Susan Euling, Victor Ambros

Victor R. Ambros

In Caenorhabditis elegans, the fates of the multipotent vulval precursor cells (VPCs) are specified by intercellular signals. The VPCs divide in the third larval stage (L3) of the wild type, producing progeny of determined cell types. In lin-28 mutants, vulva development is similar to wild-type vulva development except that it occurs precociously, in the second larval stage (L2). Consequently, when lin-28 hermaphrodites temporarily arrest development at the end of L2 in the dauer larva stage, they have partially developed vulvae consisting of VPC progeny. During post-dauer development, these otherwise determined VPC progeny become reprogrammed back to the multipotent, signal-sensitive state …

Oxidized Low Density Lipoprotein And Lysophosphatidylcholine Stimulate Cell Cycle Entry In Vascular Smooth Muscle Cells - Evidence For Release Of Fibroblast Growth Factor-2., Yuh-Cherng Chai, Philip Howe, Paul Dicorletto, Guy Chisolm

Yuh-Cherng Chai

We have previously shown that oxidized low density lipoprotein (LDL) but not native LDL stimulated DNA synthesis in cultured smooth muscle cells (SMC) and that α-tocopherol (vitamin E) inhibited this proliferative response (Lafont, A., Chai, Y. C., Cornhill, J. F., Whitlow, P. L., Howe, P. H., and Chisolm, G. M. (1995) J. Clin. Invest. 95, 1018-1025). The moiety of oxidized LDL that stimulates DNA synthesis and the cellular mechanism for this potentially mitogenic effect are not known. We now report that lipid fractions containing lysophospholipids from oxidized LDL or phospholipase A2-treated native LDL stimulated SMC DNA synthesis as did palmitoyl …

Pseudomonas Aeruginosa And Epithelial Permeability: Role Of Virulence Factors Elastase And Exotoxin A., Ali Azghani

Ali Azghani

The History Of Tissue Tension, Winfried S. Peters, A. Deri Tomos

Winfried S. Peters

Heterochronic Genes Control Cell Cycle Progress And Developmental Competence Of C. Elegans Vulva Precursor Cells, Susan Euling, Victor Ambros

Victor R. Ambros

Heterochronic genes control the timing of vulval development in the C. elegans hermaphrodite. lin-14 or lin-28 loss-of-function mutations cause the vulval precursor cells (VPCs) to enter S phase and to divide one larval stage earlier than in the wild type. A precocious vulva is formed by essentially normal cell lineage patterns, governed by the same intercellular signals as in the wild type. Mutations that prevent the normal developmental down-regulation of lin-14, activity delay or block VPC division and prevent vulval differentiation. A genetic pathway that includes lin-4, lin-14, and lin-28 controls when VPCs complete G1 and also controls when VPCs …

Trees Of History In Systematics And Philology, Robert O’Hara

Robert J. O’Hara

«The Natural System» is the name given to the underlying arrangement present in the diversity of life. Unlike a classification, which is made up of classes and members, a system or arrangement is an integrated whole made up of connected parts. In the pre-evolutionary period a variety of forms were proposed for the Natural System, including maps, circles, stars, and abstract multidimensional objects. The trees sketched by Darwin in the 1830s should probably be considered the first genuine evolutionary diagrams of the Natural System—the first genuine evolutionary trees. Darwin refined his image of the Natural System in the well-known evolutionary …

Lion-Tailed Macaques (Macaca Silenus) In A Disturbed Forest Fragment: Activity Patterns And Time Budget, Shaily Menon, Frank Poirier

Shaily Menon

We describe the activity patterns and time budget of a feral group of lion-tailed macaques that were confined to a disturbed forest fragment of 65 ha and compare the results with those obtained for groups in protected forests. The degraded nature of the study site was reflected in low tree densities, low specific diversity, gaps in the girth distribution of trees, and frequent disturbance by humans. The study group of 43 subjects was twice as large as lion-tailed macaque groups in protected habitats. They spent the most time ranging (34.0%), followed by foraging (23.7%), feeding (17.9%), resting (16.0%), and other …

Effects Of The Ferritin Open Reading Frame On Translational Induction By Iron., David Mascotti, Lisa Goessling, Diane Rup, Robert Thach

David P. Mascotti

No abstract provided.

Features Of Roots Of Cam Plants, P. Nobel, Gretchen North

Gretchen North

No abstract provided.

Radial Hydraulic Conductivity Of Individual Root Tissues Of Opuntia Ficus-Indica (L.) Miller As Soil Moisture Varies, Gretchen North, P. Nobel

Gretchen North

The constraints on water uptake imposed by individual root tissues were examined for Opuntia ®cus-indica under wet, drying, and rewetted soil conditions. Root hydraulic conductivity (L P ) and axial conductance (K h ) were measured for intact root segments from the distal region with an endodermis and from midroot with a periderm; L P was then measured for each segment with successive tissues removed by dissection. Radial conductivity (L R ) was calculated from L P and K h for the intact segment and for the individual tissues by considering the tissue conductivities in series. Under wet conditions, L …

The Chlorophyll Biosynthetic Enzyme Mg-Protoporphyrin Ix Monomethyl Ester (Oxidative) Cyclase (Characterization And Partial Purification From Chlamydomonas Reinhardtii And Synechocystis Sp. Pcc 6803), David Bollivar

David Bollivar

A universal structural feature of chlorophyll molecules is the isocyclic ring. This ring is formed by the action of the enzyme Mg-protoporphyrin IX monomethyl ester (oxidative) cyclase, which catalyzes a complex reaction in which Mg-protoporphyrin IX monomethyl ester is converted to divinyl protochlorophyllide (also called Mg-2,4-divinylpheoporphyrin a5), with the participation of NADPH and O2. Cyclase activity was demonstrated in lysed Chlamydomonas reinhardtii chloroplasts and extracts of Synechocystis sp. PCC 6803. The yield of the reaction product was increased by the addition of catalase and ascorbate or isoascorbate to the incubation mixture. These compounds may act by preventing degradation of the …