Fibroblast-led collective invasion of carcinoma cells with differing roles for RhoGTPases in leading and following cells

Imaging of collectively invading cocultures of carcinoma cells and stromal fibroblasts reveals that the leading cell is always a fibroblast and that carcinoma cells move within tracks in the extracellular matrix behind the fibroblast. The generation of these tracks by fibroblasts is sufficient to enable the collective invasion of the squamous cell carcinoma (SCC) cells and requires both protease- and force-mediated matrix remodelling. Force-mediated matrix remodelling depends on integrins alpha3 and alpha5, and Rho-mediated regulation of myosin light chain (MLC) activity in fibroblasts, but these factors are not required in carcinoma cells. Instead, carcinoma cells use Cdc42 and MRCK (myotonic dystrophy kinase-related CDC42-binding protein kinases) mediated regulation of MLC to follow the tracks generated by fibroblasts.     

Overyielding among plant functional groups in a long-term experiment

A recent debate among ecologists has focused on mechanisms by which species diversity might affect net primary productivity. Communities with more species could use a greater variety of resource capture characteristics, leading to greater use of limiting resources (complementarity) and therefore greater productivity (overyielding). Recent experiments, however, have shown a variety of relationships between diversity and productivity. In an experiment on serpentine grassland communities spanning 8 years, we found that overyielding increased several years after plot establishment. Overyielding varied greatly depending on the functional characteristics of the species involved and the biotic and abiotic environment (particularly water availability). While functional differences among species led to strong complementarity and facilitation, these effects were not sufficient to cause significant transgressive overyielding or consistent increases in productivity with increased plant diversity. These results suggest that greater absolute production with greater diversity may be restricted to particular species combinations or environmental conditions.     

Profiles of hypoxanthine guanine phosphoribosyl transferase and adenine phosphoribosyl transferase activities measured in single preimplantation human embryos by high-performance liquid chromatography

The profiles of hypoxanthine guanine phosphoribosyl transferase (HGPRT) and adenine phosphoribosyl transferase (APRT) activities were examined in normally fertilized human embryos developing at the normal rate in vitro between the 2-4-cell stage on Day 2 and the blastocyst stage on Day 6 after insemination. The activities of both enzymes were assayed simultaneously in extracts of single embryos by measuring the rate of production of the reaction products, inosine monophosphate (IMP) and adenine monophosphate (AMP), separated by high-performance liquid chromatography (HPLC). The activity profiles of the two enzymes over this period showed marked differences. The activity of HGPRT, coded by the X chromosome, increased between Days 2 and 4 (P less than 0.01) but declined sharply by Day 6 (P less than 0.001), whereas autosome-coded APRT activity remained low between Days 2 and 5, but increased on Day 6 (P less than 0.05). The profile of HGPRT activity may reflect a combination of decreasing levels of maternal enzyme inherited from the oocyte and the initiation of embryonic gene expression followed by X inactivation at the blastocyst stage on Day 6.     

Enzymology of the oxidation of ammonia to nitrite by bacteria

The enzymes which catalyze the oxidation of ammonia to nitrite by autotrophic bacteria are reviewed. A comparison is made with enzymes which catalyze the same reactions in methylotrophs and organotrophic heterotrophic bacteria.     

GSMN-TB: a web-based genome-scale network model of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis>metabolism

Background  

An impediment to the rational development of novel drugs against tuberculosis (TB) is a general paucity of knowledge concerning the metabolism of Mycobacterium tuberculosis, particularly during infection. Constraint-based modeling provides a novel approach to investigating microbial metabolism but has not yet been applied to genome-scale modeling of M. tuberculosis.     

ACEH/ACE2 is a novel mammalian metallocarboxypeptidase and a homologue of angiotensin-converting enzyme insensitive to ACE inhibitors

A human zinc metalloprotease (termed ACEH or ACE2) with considerable homology to angiotensin-converting enzyme (ACE) (EC 3.4.15.1) has been identified and subsequently cloned and functionally expressed. The translated protein contains an N-terminal signal sequence, a single catalytic domain with zinc-binding motif (HEMGH), a transmembrane region, and a small C-terminal cytosolic domain. Unlike somatic ACE, ACEH functions as a carboxypeptidase when acting on angiotensin I and angiotensin II or other peptide substrates. ACEH may function in conjunction with ACE and neprilysin in novel pathways of angiotensin metabolism of physiological significance. In contrast with ACE, ACEH does not hydrolyse bradykinin and is not inhibited by typical ACE inhibitors. ACEH is unique among mammalian carboxypeptidases in containing an HEXXH zinc motif but, in this respect, resembles a bacterial enzyme, Thermus aquaticus (Taq) carboxypeptidase (EC 3.4.17.19). Collectrin, a developmentally regulated renal protein, is homologous with the C-terminal region of ACEH but has no similarity with ACE and no catalytic domain. Thus, the ACEH protein may have evolved as a chimera of a single ACE-like domain and a collectrin domain. The collectrin domain may regulate tissue response to injury whereas the catalytic domain is involved in peptide processing events.     

The effects of ovariectomy and injected oestradiol monobenzoate on polypeptide metabolism in the hypothalamus

1. The activities of two groups of peptidases separated from a homogenate of rabbit hypothalamus were determined (a) in adult female animals, (b) in ovariectomized animals and (c) in intact female animals after injection of oestradiol monobenzoate (15-120mug.). 2. Ovariectomy decreased the enzyme activity initially; the activity in the particulate group of enzymes subsequently returned to normal whereas the activity of the supernatant fraction was less than normal 8 months after operation. 3. Injection of oestradiol monobenzoate increased the enzyme activity in the supernatant fraction to that observed in pregnant animals and in suckled lactating animals. 4. There is a correlation between changes in enzyme activity of the supernatant fraction and conditions that are known to influence gonadotrophin secretion.     

Differential effects of albumin on microglia and macrophages; implications for neurodegeneration following blood–brain barrier damage

Microglial activation by blood-borne factors following blood–brain barrier damage may play a significant role in subsequent neuropathogenesis of several neurodegenerative diseases. Exposure of primary cultured rat brain microglia to pure, fatty acid- and lipid-deficient rat serum albumin or fraction V, (fatty acid and lipid-containing rat serum albumin), caused inducible nitric oxide synthase (iNOS) expression, glutamate release, tumour necrosis factor alpha (TNFα) and transforming growth factor-beta1 release. iNOS expression was attenuated by the MAPK/extracellular signal-regulated kinase pathway inhibitor U0126 and the phosphorylated forms of extracellular signal-regulated kinase 1 and 2 were detectable in microglia treated with albumin or fraction V. Glutamate release was prevented by l -α-aminoadipate and glutathione levels in microglia rose on exposure to albumin. Conditioned medium from microglia exposed to albumin or fraction V was neurotoxic. Peripheral macrophages were resistant to the effects of albumin but both microglia and macrophages responded to lipopolysaccharide, which induced interleukin-1 beta and tumour necrosis factor alpha release, cyclooxygenase-2 and iNOS expression in both cell types, indicating a discrete desensitised pathway in macrophages for albumin which was not desensitised in microglia. Thus, exposure of microglia in the brain to albumin may contribute to neuronal damage following blood–brain barrier breakdown and point to resident microglia rather than infiltrating macrophages as therapeutic targets.