Out of Africa and into an ice age: on the role of global climate change in the late Pleistocene migration of early modern humans out of Africa

The results from two climate model simulations are used to explore the relationship between North Atlantic sea surface temperatures and the development of African aridity around 100,000 years ago. Through the use of illustrative simulations with an Earth System Climate Model, it is shown that freshwater fluxes associated with ice sheet surges into the North Atlantic, known as Heinrich events, lead to the southward shift of the intertropical convergence zone over Africa. This, combined with the overall increased aridity in the cooler mean climate, leads to substantial changes in simulated African vegetation cover, particularly in the Sahel. We suggest that Heinrich events, which occurred episodically throughout the last glacial cycle, led to abrupt changes in climate that may have rendered large parts of North, East, and West Africa unsuitable for hominin occupation, thus compelling early Homo sapiens to migrate out of Africa.     

Stability of recombinant protein production by Penicillium chrysogenum in prolonged chemostat culture

Abstract A strain (WKW2) of Penicillium chrysogenum transformed with heterologous fungal acetamidase ( amd S) and bacterial β-galactosidase ( lac Z) was grown at a dilution rate of 0.17 h⁻¹ (doubling time of approx. 4.1 h) for 1600 h in a glucose-limited culture. By the end of the experiment the original strain had been almost completely replaced by spontaneous, morphological mutants, but the acetamidase and β-galactosidase activities of the culture were essentially unaltered. Furthermore, when WKW2 and the non-transformed parental strain (NRRL1951) were grown together in glucose- or NH₄⁺-limited chemostat cultures, neither strain had a selective advantage over the other. Thus, heterologous gene expression does not result in NRRL1951 having a selective advantage over WKW2. These results suggest that continuous flow culture systems could be used for efficient (and cost effective) production of recombinant proteins.     

Use of pH auxostats to grow filamentous fungi in continuous flow culture at maximum specific growth rate

Abstract The pH auxostat employs a pH-derived feedback control of biomass concentration and allows continuous flow cultures of organisms to be grown at their maximum specific growth rate. We examine three modifications of the pH auxostat system for the growth of filamentous fungi and discuss the suitability of each method according to the biomass concentration desired, the medium used and the equipment available. Fusarium graminearum and Geotrichum candidum were used for this work and it was possible to maintain steady state pH auxostats of these filamentous fungi for up to 20 days. pH auxostats have not previously been described for filamentous fungi.     

Genotype/phenotype correlation in autosomal recessive lamellar ichthyosis.

Autosomal recessive lamellar ichthyosis is a severe congenital disorder of keratinization, characterized by variable erythema of the whole body surface and by different scaling patterns. Recently, mutations have been identified in patients with lamellar ichthyosis in the TGM1 gene coding for keratinocyte transglutaminase, and a second locus has been mapped to chromosome 2. We have now analyzed the genotype/phenotype correlation in a total of 14 families with lamellar ichthyosis. Linkage analyses using microsatellites in the region of the TGM1 gene confirmed genetic heterogeneity. In patients not linked to the TGM1 gene, the second region identified on chromosome 2 and a further candidate region on chromosome 20 were excluded, confirming as well the existence of at least three loci for lamellar ichthyosis. Sequence analyses of the TGM1 gene in families compatible with linkage to this locus revealed seven different missense mutations, five of these unpublished so far, and one splice mutation. No genotype/phenotype correlation for mutations in the TGM1 gene was found in this group of patients, which included two unrelated patients homozygous for the same mutation. Similarly, no clear difference in the clinical picture was seen between patients with TGM1 mutations and those unlinked to the TGM1 locus. Comparison of genetic and clinical classifications for patients with lamellar ichthyosis shows no consistency and thus indicates that clinical criteria currently in use cannot discriminate between the molecularly different forms of the disease.     

Poxviral B1 kinase overcomes barrier to autointegration factor, a host defense against virus replication

Barrier to autointegration factor (BAF) is a DNA-binding protein found in the nucleus and cytoplasm of eukaryotic cells that functions to establish nuclear architecture during mitosis. Herein, we demonstrate a cytoplasmic role for BAF in host defense during poxviral infections. Vaccinia is the prototypic poxvirus, a family of DNA viruses that replicate exclusively in the cytoplasm of infected cells. Mutations in the vaccinia B1 kinase (B1) compromise viral DNA replication, but the mechanism by which B1 achieves this has remained elusive. We now show that BAF acts as a potent inhibitor of poxvirus replication unless its DNA-binding activity is blocked by B1-mediated phosphorylation. These data position BAF as the effector of an innate immune response that prevents replication of exogenous viral DNA in the cytoplasm. To enable the virus to evade this defense, the poxviral B1 has evolved to usurp a signaling pathway employed by the host cell.     

Acid phosphatase production by Aspergillus niger N402A in continuous flow culture

The production of acid phosphatases (E.C.3.1.3.2, ACPs) by Aspergillus niger N402A is regulated by specific growth rate, as well as phosphate availability and pH, as demonstrated by studies in continuous flow culture. Specific ACP activity was highest when A. niger was grown at pH 6.3 (64±8 U g⁻¹) or pH 2.8 (99±11 U g⁻¹), at a dilution rate of 0.07 h⁻¹ and phosphate concentrations below 0.46 mM. ACP production was growth correlated for specific growth rates between 0.07 and 0.13 h⁻¹. Four different ACPs, including two phytases, were produced by A. niger N402A. The ACP and the phytase with maximal activities at pH 5.5 were differentially expressed at different culture pH values, with greater production at low pH.     

Pollination strategies in Cretan Arum lilies

Flowers of the genus Arum are known to attract dung‐breeding flies and beetles through olfactory deceit. In addition to this strategy, the genus has evolved several other pollination mechanisms. The present study aimed to characterize the pollination strategies of the Cretan Arum species by investigating the flowering phenology, thermogeny, inflorescence odours, and the pollinating fauna. The results obtained show that Arum cyrenaicum and Arum concinnatum emit a strong dung smell and exhibit the distinctive features associated with this pollination syndrome. Both species are highly thermogenic, have a similar odour profile and attract small‐bodied Diptera. Although sharing the same habitat, these two plant species are never found growing sympatrically as a result of the early blooming period of A. cyrenaicum. By contrast, Arum creticum and Arum idaeum have evolved a more traditional and mutually beneficial pollination mechanism. The stinking smell has been replaced by a more flower‐like odour that attracts bees (Lasioglossum sp.) and, occasionally, bugs (Dionconotus cruentatus). Although attracting the same pollinator, the main compound present in the odour of A. creticum is different from that of A. idaeum. Principal component analysis (PCA), based on physiologically active components of the flower odours determined by testing on the antenna of the Lasioglossum bee, revealed two different clusters, indicating that pollinators can potentially discriminate between the odours of the two species. A further PCA on the main floral odour volatiles as identified by gas chroatography‐mass spectroscopy from all the Arum species under investigation displayed odour‐based similarities and differences among the species. The PCA‐gas chomotography‐electroantennographic detection active peaks analysis showed that the two species, A. creticum and A. idaeum, form two groups and are clearly separated from A. cyrenaicum and A. concinnatum, which, conversely, cluster together. The evolutionary forces and selective pressures leading to diversification of pollination mechanisms in the Cretan Arum spp. are discussed. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 991–1001.     

Opposing actions of the progesterone metabolites, 5α-dihydroprogesterone (5αP) and 3α-dihydroprogesterone (3αHP) on mitosis,apoptosis, and expression of Bcl-2, Bax and p21 in human breast cell lines

Previous studies have shown that breast tissues and breast cell lines convert progesterone (P) to 5α-dihydroprogesterone (5αP) and 3α-dihydroprogesterone (3αHP) and that 3αHP suppresses, whereas 5αP promotes, cell proliferation and detachment. The objectives of the current studies were to determine if the 5αP- and 3αHP-induced changes in cell numbers are due to altered rates of mitosis and/or apoptosis, and if 3αHP and 5αP act on tumorigenic and non-tumorigenic cells, regardless of estrogen (E) and P receptor status. The studies were conducted on tumorigenic (MCF-7, MDA-MB-231, T47D) and non-tumorigenic (MCF-10A) human breast cell lines, employing several methods to assess the effects of the hormones on cell proliferation, mitosis, apoptosis and expression of Bcl-2, Bax and p21. In all four cell lines, 5αP increased, whereas 3αHP decreased cell numbers, [³H]thymidine uptake and mitotic index. Apoptosis was stimulated by 3αHP and suppressed by 5αP. 5αP resulted in increases in Bcl-2/Bax ratio, indicating decreased apoptosis; 3αHP resulted in decreases in Bcl-2/Bax ratio, indicating increased apoptosis. The effects of either 3αHP or 5αP on cell numbers, [³H]thymidine uptake, mitosis, apoptosis, and Bcl-2/Bax ratio, were abrogated when cells were treated simultaneously with both hormones. The expression of p21 was increased by 3αHP, and was unaffected by 5αP. The results provide the first evidence that 5αP stimulates mitosis and suppresses apoptosis, whereas 3αHP inhibits mitosis and stimulates apoptosis. The opposing effects of 5αP and 3αHP were observed in all four breast cell lines examined and the data suggest that all breast cancers (estrogen-responsive and unresponsive) might be suppressed by blocking 5αP formation and/or increasing 3αHP. The findings further support the hypothesis that progesterone metabolites are key regulatory hormones and that changes in their relative concentrations in the breast microenvironment determine whether breast tissues remain normal or become cancerous.     

Bioconversion of D-galacturonate to keto-deoxy-L-galactonate (3-deoxy-L-<Emphasis Type="Italic">threo</Emphasis>-hex-2-ulosonate) using filamentous fungi

Background  

The D-galacturonic acid derived from plant pectin can be converted into a variety of other chemicals which have potential use as chelators, clarifiers, preservatives and plastic precursors. Among these is the deoxy-keto acid derived from L-galactonic acid, keto-deoxy-L-galactonic acid or 3-deoxy-L- threo -hex-2-ulosonic acid. The keto-deoxy sugars have been found to be useful precursors for producing further derivatives. Keto-deoxy-L-galactonate is a natural intermediate in the fungal D-galacturonate metabolic pathway, and thus keto-deoxy-L-galactonate can be produced in a simple biological conversion.