Misconceptions About the Evolution of Complexity

Despite data and theory from comparative anatomy, embryology, molecular biology, genomics, and evolutionary developmental biology, antievolutionists continue to present the eye as an example of a structure too complex to have evolved. They stress what we have yet to explain about the development and evolution of eyes and present incomplete information as evidence that evolution is a “theory in crisis.” An examination of the evidence, however, particularly evidence that has accumulated in the twentieth and twenty-first centuries, refutes antievolutionists’ claims. The distribution of eyes in extant organisms, combined with what we now know about the control of eye development across diverse groups of organisms, provides significant evidence for the evolution of all major components of the eye, from molecular to morphological, and provides an excellent test of predictions based on common ancestry.     

Reproducibility of vegetation cover estimates in south‐central Alaska forests

Abstract. Reproducibility of vegetation measurements is critical for large‐scale or long‐term studies, where numerous observers collect data, but past studies have questioned repro‐ducibility of some techniques. Five methods of evaluating understory composition were appraised for reproducibility among six observers in two forest types in south‐central Alaska: ocular estimates in quadrats, overall community species rank and cover estimates, nested rooted frequency, horizontal‐vertical profiles, and pin drop (systematic points). One forest type was selected to represent structure of coastal communities, another to represent structure of interior Alaska communities. Three general methods of evaluating reproducibility were considered: standard deviations (precision among observers), components of variance (percentage of total variance attributable to observers), and analysis of variance (significance of observer variance). Observer variances were generally similar among techniques and significant in most cases. No technique stood out as being more reproducible than others. Features of techniques other than reproducibility may be more important when selecting a technique. Management decisions based on vegetation cover data should consider the observer errors involved as well as biological significance.     

Immunoprophylaxis of respiratory syncytial virus: global experience

In sarcoidosis, host genetic factors are discussed as contributing to disease susceptibility and course. Since tumor necrosis factor (TNF)-α is a central mediator of granuloma formation and since elevated TNF-α levels are found during active phases of sarcoidosis, genetic polymorphisms correlating with influences on TNF-α levels are of special interest. The complete sequencing of the MHC region and the increase in the number of identified gene polymorphisms in this locus associated with TNF-α production offer the opportunity of detecting new genes associated with sarcoidosis and perhaps of defining disease-associated haplotypes that bear the potential of serving as predictive markers for this disease.     

Production of the Streptomyces scabies coronafacoyl phytotoxins involves a novel biosynthetic pathway with an F420‐dependent oxidoreductase and a short‐chain dehydrogenase/reductase

Coronafacoyl phytotoxins are secondary metabolites that are produced by various phytopathogenic bacteria, including several pathovars of the Gram‐negative bacterium Pseudomonas syringae as well as the Gram‐positive potato scab pathogen Streptomyces scabies. The phytotoxins are composed of the polyketide coronafacic acid (CFA) linked via an amide bond to amino acids or amino acid derivatives, and their biosynthesis involves the cfa and cfa‐like gene clusters that are found in P. syringae and S. scabies, respectively. The S. scabies cfa‐like gene cluster was previously reported to contain several genes that are absent from the P. syringae cfa gene cluster, including one (oxr) encoding a putative F₄₂₀—dependent oxidoreductase, and another (sdr) encoding a predicted short‐chain dehydrogenase/reductase. Using gene deletion analysis, we demonstrated that both oxr and sdr are required for normal production of the S. scabies coronafacoyl phytotoxins, and structural analysis of metabolites that accumulated in the Δsdr mutant cultures revealed that Sdr is directly involved in the biosynthesis of the CFA moiety. Our results suggest that S. scabies and P. syringae use distinct biosynthetic pathways for producing coronafacoyl phytotoxins, which are important mediators of host‐pathogen interactions in various plant pathosystems.     

Book Reviews: General, Applied and Theoretical

Polynesian Seafaring . EDWARD DODD.
The Settlement of Polynesia: A Computer Simulation . MICHAEL LEVISON, R. GERARD WARD, and JOHN W. WEBB.     

Uses of barium meal examination in dyspeptic patients under 50.

No abnormality was found in 76 of 100 dyspeptic out-patients under the age of 50 who underwent barium meal examination, while various non-malignant lesions were found in the remaining 24. Only 10% of those under 30, and 10% of those with symptoms for less than a year proved to have any abnormality. Because of the radiographic results treatment was altered in only 11 patients, and most of these changes were small.