Can an individual bee ommatidium detect an image?

Summary Even if the dioptric apparatus of the worker bee provided a crisp image at the entrance to the rhabdom, the detection of this image is theoretically impossible due to a phenomenon of mode propagation analogous to acoustic beating or interference.Queen Elizabeth II Research Fellow.We thank Professor G. A. Horridge and Simon Laughlin for their assistance with this study.     

Irish moss—from an art to an industry

This red alga, harvested commercially along the shores of Prince Edward Island, Nova Scotia and New England, is today processed by five American companies into an extractive that finds a major market as a stabilizer in dairy products and enters also into the manufacture of a variety of other products ranging from beer to toothpaste.     

Bolboforma — an overview

A summary of the present knowledge ofBolboforma is presented in this paper. The genusBolboforma contains a diverse group of marine, mostly single-chambered enigmatic microfossils (phytoplankton, possibly Chrysophyta) which produced calcitic monocrystalline spheroidal tests with or without inner cysts and with various types of ornamentation. The genusBolboforma occurs in the time interval between late Early Eocene to Late Pliocene, at middle and higher latitudes, and thus, has not been recorded in Quaternary to Recent Sediments. The genus is represented globally, but the first and the last occurrence of the genus appear to be spatially diachronous in both hemispheres.Bolboforma started in the southern hemisphere at the Campbell Plateau (SW Pazific) during the Early Eocene approximately 53 Ma ago, and the genus lived there until latest Miocene times (5.3 Ma at the Kerguelen Plateau, Southern Indian Ocean). The first occurrence ofBolboforma in the northern hemisphere is observed in Upper Eocene Sediments (ca. 36.5 Ma) in the Labrador Sea (North Atlantic), and its youngest occurrence is observed in the Hatton-Rockall Basin (North Atlantic) in the Late Pliocene at 2.84 Ma. Well established and common species permit the definition of nineteenBolboforma zones/subzones. Not all of these are observed in both hemispheres. In the southern hemisphere all four Paleogene zones, but only eight Neogene zones are present, in the northern hemisphere only one Paleogene zone, but fourteen Neogene zones have been determined. Bolboforma distribution, which appears to be broadly bipolar in temperate to cool regions at middle to higher latitudes, aso seems to be linked to the evolution of surface watermasses and their boundaries.      

Non-canonical autophagy: an exception or an underestimated form of autophagy?

Macroautophagy (hereafter called autophagy) is a dynamic and evolutionarily conserved process used to sequester and degrade cytoplasm and entire organelles in a sequestering vesicle with a double membrane, known as the autophagosome, which ultimately fuses with a lysosome to degrade its autophagic cargo. Recently, we have unraveled two distinct forms of autophagy in cancer cells, which we term canonical and non-canonical autophagy. In contrast to classical or canonical autophagy, non-canonical autophagy is a process that does not require the entire set of autophagy-related (Atg) proteins in particular Beclin 1, to form the autophagosome. Non-canonical autophagy is therefore not blocked by the knockdown of Beclin 1 or of its binding partner hVps34. Moreover overexpression of Bcl-2, which is known to block canonical starvation-induced autophagy by binding to Beclin 1, is unable to reverse the non-canonical autophagy triggered by the polyphenol resveratrol in the breast cancer MCF-7 cell line. In MCF-7 cells, at least, non-canonical autophagy is involved in the caspase-independent cell death induced by resveratrol.     

Can an Engineer Fix an Immune System?–Rethinking theoretical biology

In an instant classic paper (Lazebnik, in Cancer Cell 2(3); 2002: 179–182) biologist Yuri Lazebnik deplores the poor effectiveness of the approach adopted by biologists to understand and “fix” biological systems. Lazebnik suggests that to remedy this state of things biologist should take inspiration from the approach used by engineers to design, understand, and troubleshoot technological systems. In the present paper I substantiate Lazebnik’s analysis by concretely showing how to apply the engineering approach to biological problems. I use an actual example of electronic circuit troubleshooting to ground the thesis that, in engineering, the crucial phases of any non-trivial troubleshooting process are aimed at generating a mechanistic explanation of the functioning of the system, which makes extensive recourse to problem-driven qualitative reasoning possibly based on cognitive artifacts applied to systems that are known to have been designed for function. To show how to translate these findings into biological practice I consider a concrete example of biological model building and “troubleshooting”, aimed at the identification of a “fix” for the human immune system in presence of progressing cancer, autoimmune disease, and transplant rejection. The result is a novel immune system model—the danger model with regulatory cells— and new, original hypotheses concerning the development, prophylaxis, and therapy of these unwanted biological processes. Based on the manifest efficacy of the proposed approach, I suggest a refocusing of the activity of theoretical biologists along the engineering-inspired lines illustrated in the paper.     

The mast cell: an active participant or an innocent bystander?

Mast cells (MC) are phylogenetically old cells which are distributed throughout the human organism and, on the whole, occupy roughly the volume of the spleen. MC have long been recognized as key cells of type I hypersensitivity reactions. Several lines of evidence, however, indicate that they not only express critical effector functions in classic IgE-associated allergic disorders, but also play important roles in host defence against parasites, bacteria and perhaps even viruses. Indeed, it is now clear that MC can contribute to host defence in the context of either acquired or innate immune responses through the release of a myriad of pro-inflammatory and immunoregulatory molecules and the expression of a wide spectrum of surface receptors for cytokines and chemokines. Moreover, there is growing evidence that MC exert distinct non-immunological functions, playing a relevant role in tissue homeostasis, remodeling and fibrosis as well as in the processes of tissue angiogenesis. In this review, we provide a small insight into the biology of human MC and their potential implications in clinical pathology.     

Adenosyltransferase: an enzyme and an escort for coenzyme B12?

Many organic cofactors are both rare and reactive. They are usually in low abundance, which poses problems for efficient collision-based targeting to dependent enzymes, whereas their reactivity is problematic for side reactions. Sequestration and escorted delivery presents one solution to this conundrum, but such porters, if they exist, are mostly unknown. In humans, the mitochondrial enzyme methylmalonyl-coenzyme A mutase uses coenzyme B(12) (adenosylcobalamin) but would be inactive if bound to the cofactor precursor that is delivered to the mitochondrion. Adenosyltransferase converts cob(II)alamin to coenzyme B(12). Based on kinetic evidence for interaction between the two enzymes, the 40-fold greater affinity for coenzyme B(12) and the higher coordination number for cobalt in the mutase, we propose that the adenosyltransferase is a dual-function protein: an enzyme that synthesizes coenzyme B(12) and a chaperone that delivers it.     

Microscopy: an art?

There can be no doubt that the finest creator of beauty is Mother Nature. And in many ways, science is the exploration of this beauty and of the mechanisms that have created it. Microscopy, as a technique in scientific investigation, has had a key role in uncovering nature's beauty, which has led some to propose that microscopy could be described as an art or even an art form. But is this claim justified?     

Polyamine analogues – an update

Summary. The polyamines are growth factors in both normal and cancer cells. As the intracellular polyamine content correlates positively with the growth potential of that cell, the idea that depletion of polyamine content will result in inhibition of cell growth and, particularly tumour cell growth, has been developed over the last 15 years. The polyamine pathway is therefore a target for development of rationally designed, antiproliferative agents. Following the lessons from the single enzyme inhibitors (α-difluoromethylornithine DFMO), three generations of polyamine analogues have been synthesised and tested in vitro and in vivo. The analogues are multi-site inhibitors affecting multiple reactions in the pathway and thus prevent the up-regulation of compensatory reactions that have been the downfall of DFMO in anticancer chemotherapy. Although the initial concept was that the analogues may provide novel anticancer drugs, it now seems likely that the analogues will have wider applications in diseases involving hyperplasia.     

Über Wuchsstoff-Mangelerscheinungen an Hefe-Riesenkolonien

Zusammenfassung Auf einem wuchsstoffkompletten synthetischen Nährboden (mit Gelatinezusatz) waren die Riesenkolonien aller untersuchten Stämme von Saccharomyces carlsbergensis einheitlich konvex und mit einem zentralen Krater versehen. Obwohl alle diese Hefen Inosit und Thiamin synthetisieren können, führt deren Fehlen im Nährboden zu deutlichen morphologischen Mangelerscheinungen an den Riesenkolonien:Bei Inosit-Mangel ist der Durchmesser aller Kolonien kleiner; sie zeigen die Form eines niedrigen Kegelstumpfes, dessen Oberseite häufig schwach konkav ist.Bei Thiamin-Mangel sind alle Riesenkolonien niedriger, aber in der Fläche größer als auf dem vollständigen Nährboden. Wenn das Inoculum nicht auf Würzeagar, sondern in Würze hergezüchtet wird, enthalten die Kolonien zudem noch einen konzentrischen Ring.     

Duftmale an Blüten

Ohne Zusammenfassung