Structural analysis of a non-contiguous second-site revertant in T4 lysozyme shows that increasing the rigidity of a protein can enhance its stability.

The mutation Glu108-->Val (E108V) in T4 lysozyme was previously isolated as a second-site revertant that specifically compensated for the loss of function associated with the destabilizing substitution Leu99-->Gly (L99G). Surprisingly, the two sites are 11 A apart, with Leu99 in the core and Glu108 on the surface of the protein. In order to better understand this result we have carried out a detailed thermodynamic, enzymatic and structural analysis of these mutant lysozymes as well as a related variant with the substitution Leu99-->Ala. It was found that E108V does increase the stability of L99G, but it also increases the stability of both the wild-type protein and L99A by essentially equal amounts. The effects of E108V on enzymatic activity are more complicated. The mutation slightly reduces the maximal rate of cell wall hydrolysis of wild-type, L99G and L99A. At the same time, L99G is an unstable protein and rapidly loses activity during the course of the assay, especially at temperatures above 20 degrees C. Thus, even though the double mutant L99G/E108V has a slightly lower maximal rate than L99G, over a period of 20-30 minutes it hydrolyzes more substrate. This decrease in the rate of thermal inactivation appears to be the basis of the action of E108V as a second-site revertant of L99G. Mutant L99A creates a cavity of volume 149 A(3). Instead of enlarging this cavity, mutant L99G results in a 4-5 A displacement of part of helix F (residues 108-113), creating a solvent-accessible declivity. In the double mutant, L99G/E108V, this helix returns to a position akin to wild-type, resulting in a cavity of volume 203 A(3). Whether the mutation Glu108-->Val is incorporated into either wild-type lysozyme, or L99A or L99G, it results in a decrease in crystallographic thermal factors, especially in the helices that include residues 99 and 108. This increase in rigidity, which appears to be due to a combination of increased hydrophobic stabilization plus a restriction of conformational fluctuation, provides a structural basis for the increase in thermostability.     

The evolution of developmental strategy in marine invertebrates

Developmental mode varies widely in most animal phyla. These differences in developmental strategy exert a profound influence on the ecology and evolution of closely related species. The mechanistic alterations in ontogeny that lead to switches in developmental mode are coming under increasing scrutiny. Echinoids are one of the best-understood groups in this regard. Parallel modifications in direct-developing echinoids point to some of the key changes in oogenesis and embryogenesis that produce switches in developmental mode.     

Use of the rectus abdominis muscle flap to reconstruct an elbow defect

A superiorly based rectus abdominis muscle flap was successfully used to reconstruct an infected elbow wound with exposed bone and metal screws. We could find no previous report describing the use of this muscle to cover elbow defects.     

Identification of repressor binding sites controlling expression of tetracycline resistance encoded by Tn10

The regulatory region controlling the expression of tetracycline resistance and repressor genes contains two nearly identical regions of dyad symmetry. Deletions of this control region were isolated by digestion with S1 nuclease. The ability of these deletions to bind the tet repressor was determined by an in vivo repressor titration assay. The results indicate that repressor specifically binds both regions of dyad symmetry.     

MOLECULAR HETEROCHRONIES AND HETEROTOPIES IN EARLY ECHINOID DEVELOPMENT

By comparing the spatial and temporal distribution of three proteins during early development in seven echinoid species, we demonstrate that both heterochronies and heterotopies in gene-product expression have accompanied the radiation of post-Paleozoic echinoids. All three proteins examined showed significant alterations in time of expression, site of expression, or both. These molecular heterochronies and heterotopies indicate that early development is not necessarily as evolutionarily conservative as morphology of embryos alone would suggest. Evolutionary alterations in early development may be more common than is generally assumed.     

Regional levels of cyclic AMP in rat brain: pitfalls of microwave inactivation.

Techniques of in-vivo microwave irradiation to inactivate brain enzymes in rats were varied as to exposure configuration and output power. The rate at which metabolism was stopped was studied in various regions of the rat brain, using changes in levels of cyclic AMP and phosphodiesterase activity. Exposure times required to obtain stabilized levels of cyclic AMP varied in different brain regions, i.e., hypothalamus, cortex and cerebellum. Levels of cyclic AMP in selective regions of the brain decreased as more rapid inactivation was achieved. The authors identify important sources of variability of present microwave inactivation systems and the need for improved control of signficant microwave parameters.     

Marine biosurfactants. IV. Production,characterization and biosynthesis of an anionic glucose lipid from the marine bacterial strain MM1

Summary During screening for biosurfactants among marine, n-alkane-utilizing bacteria, low- and high-molecular surface-active substances were detected. The marine bacterial strain MM1 was found to synthesize a novel glycolipid that has not so far been cited in the literature. Both ¹H, ¹³C-nuclear magnetic resonance spectroscopic and positive ion fast atom bombardment mass spectrometer studies led to the identification of a glucose lipid consisting of four 3-OH-decanoic acids, which are linked together by ester bonds. The lipophilic moiety is coupled glycosidically with C-1 of glucose. The glucolipid reduced the surface tension from 72 mN/m to 30 mN/m while the minimum interfacial tension towards n-hexadecane was lowered to values smaller than 5 mN/m. Correspondence to: S. Lang     

Spontaneous regression of the primary lesion of a metastatic maligvant melanoma.

An atypical elderly patient with spontaneous regression of a primary lesion of malignant melanoma is presented. The 12 previously reported cases are also reviewed. The histological diagnosis of spontaneous regression of a melanoma can still be made after the regression appears to be grossly complete. All localized areas of depigmentation, or of scarring, should be biopsied when searching for an "occult" primary.     

Unraveling the Genetic Etiology of Adult Antisocial Behavior: A Genome-Wide Association Study

Crime poses a major burden for society. The heterogeneous nature of criminal behavior makes it difficult to unravel its causes. Relatively little research has been conducted on the genetic influences of criminal behavior. The few twin and adoption studies that have been undertaken suggest that about half of the variance in antisocial behavior can be explained by genetic factors. In order to identify the specific common genetic variants underlying this behavior, we conduct the first genome-wide association study (GWAS) on adult antisocial behavior. Our sample comprised a community sample of 4816 individuals who had completed a self-report questionnaire. No genetic polymorphisms reached genome-wide significance for association with adult antisocial behavior. In addition, none of the traditional candidate genes can be confirmed in our study. While not genome-wide significant, the gene with the strongest association (p-value = 8.7×10⁻⁵) was DYRK1A, a gene previously related to abnormal brain development and mental retardation. Future studies should use larger, more homogeneous samples to disentangle the etiology of antisocial behavior. Biosocial criminological research allows a more empirically grounded understanding of criminal behavior, which could ultimately inform and improve current treatment strategies.