A novel foam structure is presented, which exhibits a negative Poisson's ratio. Such a material expands laterally when stretched, in contrast to ordinary materials.

http://science.sciencemag.org/content/sci/235/4792/1038.full.pdf

Foam structures with a negative poisson's ratio

The Pharmacological Basis of Therapeutics A Textbook of Pharmacology, Toxicology and Therapeutics for Physicians and Medical Students. By Prof. Louis Goodman and Prof. Alfred Gilman. Pp. xiii + 1383. (New York: The Macmillan Company, 1941.) 50s. net.

The Pharmacological Basis of Therapeutics

Medicinal plants: Traditions of yesterday and drugs of tomorrow

The protein actin forms filaments that provide cells with mechanical support and driving forces for movement. Actin contributes to biological processes such as sensing environmental forces, internalizing membrane vesicles, moving over surfaces, and dividing the cell in two. These cellular activities are complex; they depend on interactions of actin monomers and filaments with numerous other proteins. Here, we present a summary of the key questions in the field and suggest how those questions might be answered. Understanding actin-based biological phenomena will depend on identifying the participating molecules and defining their molecular mechanisms. Comparisons of quantitative measurements of reactions in live cells with computer simulations of mathematical models will also help generate meaningful insights.

/pdf/actin-a-central-player-in-cell-shape-and-movement-23j2vhse9o.pdf

Actin, a Central Player in Cell Shape and Movement

Pathogenic bacteria that penetrate the intestinal epithelial barrier stimulate an inflammatory response in the adjacent intestinal mucosa. The present studies asked whether colon epithelial cells can provide signals that are important for the initiation and amplification of an acute mucosal inflammatory response. Infection of monolayers of human colon epithelial cell lines (T84, HT29, Caco-2) with invasive strains of bacteria (Salmonella dublin, Shigella dysenteriae, Yersinia enterocolitica, Listeria monocytogenes, enteroinvasive Escherichia coli) resulted in the coordinate expression and upregulation of a specific array of four proinflammatory cytokines, IL-8, monocyte chemotactic protein-1, GM-CSF, and TNF alpha, as assessed by mRNA levels and cytokine secretion. Expression of the same cytokines was upregulated after TNF alpha or IL-1 stimulation of these cells. In contrast, cytokine gene expression was not altered after infection of colon epithelial cells with noninvasive bacteria or the noninvasive protozoan parasite, G. lamblia. Notably, none of the cell lines expressed mRNA for IL-2, IL-4, IL-5, IL-6, IL-12p40, IFN-gamma, or significant levels of IL-1 or IL-10 in response to the identical stimuli. The coordinate expression of IL-8, MCP-1, GM-CSF and TNF alpha appears to be a general property of human colon epithelial cells since an identical array of cytokines, as well as IL-6, also was expressed by freshly isolated human colon epithelial cells. Since the cytokines expressed in response to bacterial invasion or other proinflammatory agonists have a well documented role in chemotaxis and activation of inflammatory cells, colon epithelial cells appear to be programmed to provide a set of signals for the activation of the mucosal inflammatory response in the earliest phases after microbial invasion.

/pdf/a-distinct-array-of-proinflammatory-cytokines-is-expressed-3khuhdbqhv.pdf

A distinct array of proinflammatory cytokines is expressed in human colon epithelial cells in response to bacterial invasion.

https://www.cell.com/parasitology/pdf/0169-4758(91)90169-O.pdf

Organelles of protein transport in Giardia lamblia.

An atypical proprotein convertase in Giardia lamblia differentiation

Giardia lamblia: absence of cyst antigens and reduced secretory vesicle formation and bile salt uptake in an encystation-deficient subline.

We found previously that the A6 clone of Giardia lamblia strain WB that did not encyst in vitro was blocked at an early stage in differentiation, as it did not form encystation secretory vesicles (ESV) efficiently or express cyst antigens, in comparison with the related clone C6. We now report that A6 formed ESV normally in the suckling mouse model. Therefore, we asked whether our serum-containing encystation media might lack a stimulus or component or contain an inhibitor of ESV formation to which A6 was especially sensitive. We found that replacing bovine serum with a lipoprotein-cholesterol solution and bovine serum albumin (LPC) in pre-encystation and encystation media increased ESV formation by both A6 and C6. The % of A6 cells with ESV increased from 8% in BS medium to 48% in LPC medium, compared with 64% and 98% for C6. Similarly, the average number of ESV/positive cell increased from 1.5 in BS medium to 7.7 in LPC medium for A6, and from 13.3 to 19.7 for C6. Moreover, in LPC encystation media, A6 expressed the cyst wall epitope recognized by monoclonal GCSA-1. Although formation of water-resistant cysts by A6 was increased > 60 fold in LPC media, the numbers of cysts remained only approximately 3-15% that of C6. This suggests that LPC may primarily affect early events in encystation and that A6 may require additional factors later in encystation.

A lipoprotein-cholesterol-albumin serum substitute stimulates Giardia lamblia encystation vesicle formation.

One of the major problems in studying Giardia cysts is separating this form of the parasite from faecal debris and bacteria. We approached this problem by passing filtered stool suspensions over a column of Sephadex G-50 followed by low speed centrifugations. The Sephadex retained most of the faecal debris and the centrifugation reduced the bacterial flora more than 10 5 -fold to 4 /ml. Cyst recovery was 61% (±28%). This new method of separating G. lamblia from faecal material is simple, rapid, and effective.

David S. Reiner

Papers

Organelles of protein transport in Giardia lamblia.

An atypical proprotein convertase in Giardia lamblia differentiation

Giardia lamblia: absence of cyst antigens and reduced secretory vesicle formation and bile salt uptake in an encystation-deficient subline.

A lipoprotein-cholesterol-albumin serum substitute stimulates Giardia lamblia encystation vesicle formation.

A new method for purification of Giardia lamblia cysts.