Note on a combinatorial problem in topological biology

In connection with a previous paper, an expression is derived for the number of possibilities in whichn distinguishable elements can be distributed intom≤n classes, so that each class contains at least one element.     

Studies on an interesting Saccharomyces carlsbergensis mutant

The genetics of a spontaneous double mutant Hla, belonging toSaccharomyces carlsbergensis, has been studied. The two mutated loci, controlling the biosyntheses of lysine and uracil are either loosely linked or they are located on separate chromosomes. Spontaneous mutations in the two genes are therefore likely to have followed from two independent mutagenic events. The mating-type locus, the methionine, the lysine and the uracil synthesising loci are not linked. Segregations for mating-type locus are Mendelian where as segregations for lysine, uracil and methionine synthesising loci are both Mendelian and Non-Mendelian. The 4:0 class of Non-Mendelian segregation is not found. The apparently Non-Mendelian segregations for mehtionine synthesis can be explained on the basis of the presence of two complementary methionine synthesising genes in Hla.

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Zusammenfassung Die Genetik eines spontanen Doppelmutanten Hla, der zuSaccharomyces carlsbergensis gehört, wurde untersucht. Die zwei Loci, die die Biosynthese von Lysin und Uracil kontrollieren, sind entweder locker gebunden oder sind an verschiedene Chromosomen gebunden. Spontane Mutationen in beiden Genen sind deshalb wahrscheinlich das Ergebnis von zwei unabhängigen mutagenen Faktoren. Der Locus der Geschlechtstype, die Loci der Synthese von Methionine, Lysine und Uracil sind nicht gebunden. Die Absonderung des Locus für die Geschlechtstype ist gemäß Mendel, während die Absonderung für Lysine, Uracil und Methionine teils gemäß, teils nicht gemäß Mendel erfolgt. Die Klasse 4 : 0 der Absonderung nicht gemäß Mendel ist nicht gefunden worden. Die scheinbare Absonderung nicht gemäß Mendel für die Synthese von Methionine kann auf Grund der Gegenwart von zwei komplementären Genen in Hla für die Synthese von Methionine erklärt werden.

     

Studies on an interesting Saccharomyces carlsbergensis mutant

Summary 32 sputa from 29 patients known to have yeasts were emulsified and quantitatively plated on Sabouraud's glucose agar. Colony counts showed that the yeast flora varied from about 300 to about one million cells per ml of the specimen. Sputa collected at bed-side and plated within 2 hours gave lower counts than those received routinely. In the 28 specimens in which identification was carried outC. albicans was found in 23 as the only or the dominant species andC. tropicalis in 4; an unidentified species was present in one specimen.This work was supported by a Grant from the Medical Research Council, Ottawa, Canada.     

A comparison of set-theoretical and graph-theoretical approaches in topological biology

Two somewhat different approaches to topological biology have been developed in recent years. The latest, set-theoretical approach leads rather immediately to a number of conclusions which are verified experimentally. It also predicts a number of new biological relations. The older, graph-theoretical approach does not lead directly to those conclusions but suggests a number of combinatorial relations between number of organs and number of cell types. Such suggestions are absent from the set-theoretical approach. It is shown that the above-mentioned combinatorial relations are independent of the graph-theoretical method proper and can be introduced into the set-theoretical approach through the addition of an independent postulate. A possible addition to the principle of biotopological mapping is suggested, which brings into focus the relations between the organism and its individual organs and which has a predictive value.     

Assembly of hair bundles,an amazing problem for cell biology

The hair bundle—the sensory organelle of inner-ear hair cells of vertebrates—exemplifies the ability of a cell to assemble complex, elegant structures. Proper construction of the bundle is required for proper mechanotransduction in response to external forces and to transmit information about sound and movement. Bundles contain tightly controlled numbers of actin-filled stereocilia, which are arranged in defined rows of precise heights. Indeed, many deafness mutations that disable hair-cell cytoskeletal proteins also disrupt bundles. Bundle assembly is a tractable problem in molecular and cellular systems biology; the sequence of structural changes in stereocilia is known, and a modest number of proteins may be involved.     

Short stature and an interesting association

Untreated hypothyroidism in children usually results in delayed puberty, but juvenile hypothyroidism causes isosexual precocious puberty in a rare syndrome called Van Wyk Grumbach syndrome, with a complete reversal to the pre pubertal state following thyroid hormone replacement therapy. We report here, a 7-year-old girl who presented with short stature, constipation and isosexual precocious puberty due to the long standing untreated severe hypothyroidism with this syndrome.     

The problem of prediction in invasion biology

Invasion biology is a relatively young discipline which is important, interesting and currently in turmoil. Biological invaders can threaten native ecosystems and global biodiversity; they can incur massive economic costs and even introduce diseases. Invasion biologists generally agree that being able to predict when and where an invasion will occur is essential for progress in their field. However, successful predictions of this type remain elusive. This has caused a rift, as some researchers are pessimistic and believe that invasion biology has no future, whereas others are more optimistic and believe that the key to successful prediction is the creation of a general, unified theoretical framework which encompasses all invasion events. Although I agree that there is a future for invasion biology, extensive synthesis is not the way to better predictions. I argue that the causes of invasion phenomena are exceedingly complex and heterogeneous, hence it is impossible to make generalizations over particular events without sacrificing causal detail. However, this causal detail is just what is needed for the specific predictions which the scientists wish to produce. Instead, I show that a limited type of synthesis (integration of data and methods) is a more useful tool for generating successful predictions. An important implication of my view is that it points to a more pluralistic approach to invasion biology, where generalization and prediction are treated as important yet distinct research goals.     

The problem of teleology in biology as a problem of biology-teacher education

The paper sketches the ways ‘the problem of teleology’ appears in pupil-texts, teacher-guides, and college-level texts. Excerpts from the literature in the field of philosophy and history of science are then quoted, which illustrate that ‘the problem of teleology’ cannot be handled dogmatically, as if the issues were indisputable. It is pointed out, that teacher-education does not enable the prospective teacher to analyse the teacher and pupil texts objectively and critically as to their philosophical implications. Suggestions are made which might alter this situation.     

Formal thinking in biology: the woodlouse problem

Understanding biology increasingly depends upon the development of abstract, or formal thinking. Piaget, in describing formal, thought, illustrated its development in response to certain scientific problems. The ‘woodlouse problem’ described here, provides a biological example which can also be used to test the level of thinking reached by children. Sample data show that few pupils have begun to think at the formal level by the age of twelve years, but some progress is made by the time they are thirteen years old.     

Contributions to topological biology: Some considerations on the primordial graph and on some possible transformations

This paper is a continuation of some discussions published previously (Bull. Math. Biophysics,16, 317–347, 1954). A different example of a primordial graph is suggested and discussed. Then six different types of geometric transformations, similar in some respects to the one discussed in the previous paper are proposed. Another set of seven different transformations which emphasize the central role of the circulatory system is described. A theorem about the “lumping” of several points of a graph into one point is proved and possible biological aspects of it are discussed.     

Historical biology and the problem of design

Organisms are historical entities in that their past history plays an important role in shaping the properties they exhibit today. While this fact is widely acknowledged, little attempt has been made to develop a testable approach to the analysis of the historical factor in evolutionary morphology. The analysis of extrinsic environmental factors may reveal the limits imposed by the environment on biological design, but the intrinsic phylogenetic component of design may severely constrain the directions of structural modification that can occur. The importance of history can be assessed with (1) a phylogenetic hypothesis of genealogical relationship, (2) the use of emergent structural or functional attributes with general properties, and (3) the testing of historical hypotheses by the comparison of general properties between monophyletic lineages. The synthesis of a structural/phylogenetic approach to historical morphology with the analysis of extrinsic limits to form may provide the level of resolution needed to generate testable mechanistic hypotheses regarding the distribution of extant organismal forms in the hyperspace of possible morphologies.     

Biosynthesis of the thioquinolobactin siderophore: an interesting variation on sulfur transfer

The thioquinolobactin siderophore from Pseudomonas fluorescens ATCC 17400 utilizes a variation of the sulfur transfer chemistry found in thiamine and molydobterin biosynthesis. A JAMM motif protein cleaves the C-terminal amino acid residues following a diglycine moiety on a small sulfur carrier protein, and the modified C terminus is activated and sulfurylated, forming a thiocarboxylate.