The spatial arrangement of germ line cells in ovarian follicles of the mutantdicephalic inDrosophila melanogaster

Summary The pattern of intercellular connections between germ line cells has been studied in follicles of the mutantdicephalic (dic), which possess nurse cell clusters at both poles. Staining of follicles with a fluorescent rhodamine conjugate of phalloidin reveals ring canals and cell membranes and thus allows us to reconstruct the spatial organization of the follicle. Each germ line cell can be identified by the pattern of cell-cell connections which reflect the mitotic history of individual cells in the 16-cell cluster. The results indicate that in both wild-type anddicephalic cystocyte clusters one of the two cells with four ring canals normally becomes the pro-oocyte. However, in some follicles (dicephalic and wild-type) oocytes were found with fewer or more than four ring canals. Indic follicles, one or several nurse cells may become disconnected from the other cells during oocyte growth at stage 9–10. Such disconnected cells cannot later on empty their cytoplasm into the oocyte. This, in turn, might be of consequence for the determination of axial polarity of the embryo.     

Osteoderm histology of the Pampatheriidae (Cingulata,Xenarthra, Mammalia): Implications for systematics,osteoderm growth,and biomechanical adaptation

Pampatheres are extinct, large‐bodied cingulates, which share morphological characters with both armadillos and glyptodonts but are considered to be more closely related to the latter. The osteoderm histology of six pampathere taxa was examined and compared to the histology of other cingulate osteoderms. This study investigates the development and functional adaptation of pampathere osteoderms as well as the phylogenetic relationships of the Pampatheriidae within the Cingulata. We found that pampathere osteoderms share a uniform histological organization based on a basic diploe‐like structure. After initial stages of intramembranous growth, metaplastic ossification, that is, the direct incorporation and mineralization of pre‐existing protein fibers, plays an important role in osteoderm development and provides information on various kinds of soft tissue otherwise not preserved. The latest stages of osteoderm growth are dominated by periosteal bone formation especially in the superficial cortex. Movable band osteoderms show regular arrangements of incorporated fibers that may increase the resistance of particularly weak areas against strain. The histological composition of pampathere osteoderms is plesiomorphic in its basic structure but shows a number of derived features. A unique array of Sharpey's fibers that are incorporated into the bone matrix at sutured osteoderm margins is interpreted as a synapomorphy of pampatheres. The arrangement of dermal fibers in the deep and superficial cortexes supports the close relationship between pampatheres and glyptodonts. J. Morphol., 2012. © 2011 Wiley Periodicals, Inc.     

Enzymatic amidation of recombinant (Leu27) growth hormone releasing hormone-Gly45

By chemoenzymatic synthesis the gene for a (Leu27) analogue of human growth hormone releasing hormone-Gly45 [(Leu27)GHRH-Gly45] was constructed, cloned and expressed in Escherichia coli as a fusion protein with beta-galactosidase under the control of the lac promoter and operator. Upon induction with isopropyl-D-thio-beta-galactopyranoside the fusion protein accumulated to a yield of 15-20% of the total cellular protein. After cyanogen bromide cleavage of the fusion protein the precursor peptide (Leu27)hGHRH-Gly45 was separated by extraction and purified by ion exchange and h.p.l.c.-RP18 chromatography. The purified peptide was analysed by sequencing, isoelectric focusing, amino acid analysis and amino acid analysis after V8 protease digestion. The carboxy-terminal glycine was subsequently amidated by PAM (peptidylglycine-alpha-amidating-monooxygenase), an enzyme which was isolated and characterized from fresh bovine pituitaries. Correct amidation of the penultimate amino acid, leucine, was verified by peptide sequencing with an authentic leucine amide reference.     

The origin of P elements in Drosophila melanogaster.

The P family of transposable genetic elements is thought to be a recent addition to the Drosophila melanogaster genome. New evidence suggests that the elements came from another Drosophila species, possibly carried by parasitic mites. The transposition mechanism of P elements involves DNA gap repair which may have facilitated their rapid spread through D. melanogaster worldwide. These results provide new insight into the process of a transposon's invasion into a new species and the potential risk of extinction such an invasion might entail.     

The role of bisulfite in the debromination of 5-bromouracil. The debromination of 5-bromo-5,6-dihydrouracil-6-sulfonate

5-Bromouracil is dehalogenated in the presence of bisulfite buffers to yield uracil which subsequently adds bisulfite to form 5,6-dihydrouracil-6-sulfonate. Presumably, 5-bromo-5,6-dihydrouracil-6-sulfonate is an intermediate in uracil formation. Kinetic data indicate that the disappearance of 5-bromouracil in the presence of bisulfite buffers is second order with respect to total bisulfite concentration, thus indicating the participation of 2 moles of either sulfite or bisulfite in the overall reaction, Iodometric titrations of total bisulfite combined with spectral analysis of the various pyrimidine and dihydropyrimidine species present indicate that, in addition to the total bisulfite required to form 5,6-dihydrouracil-6-sulfonate, an additional mole of sulfite is consumed per mole of 5-bromouracil dehalogenated. These data combined with the finding that sulfate is generated during dehalogenation are indicative of a pathway for the dehalogenation of the intermediate 5-bromo-5,6-dihydro-uracil-6-sulfonate which involves the attack of sulfite either directly or via an intervening molecule of water to yield uracil. Subsequent reactions of halogen-containing intermediates yield sulfate and bromide as final products of the reaction.     

Polarity as a criterion in protein design

Hypothetical proteins can be tested computationally by determining whether or not the designed sequence-structure pair has the characteristics of a typical globular protein. We have developed such a test by deriving quantities with approximately constant value for all globular proteins, based on empirical analysis of the exposed and buried surfaces of 128 structurally known proteins. The characteristic quantities that best appear to segregate badly designed or deliberately misfolded proteins from their properly folded natural relatives are the polar fraction of side chains on the protein surface and, independently, in the protein interior. Three of the seven hypothetical structures tested here can be rejected as having too many polar side-chain groups in the interior or too few on the protein surface. In addition, a recently designed nutritional protein is identified as being very much unlike globular proteins. These database-derived characteristic quantities are useful in screening designed proteins prior to experiment and may be useful in screening experimentally determined (X-ray, NMR) protein structures for possible errors.     

Significance of myocardial eicosanoid production

Summary The precise role of eicosanoids in the development of myocardial injury during ischemia and reperfusion is still a matter of debate. Enhanced local production of these bioactive compounds appears to be a common response to tissue injury. Most likely, the cardiac tissue has the capacity to generate prostaglandins, thromboxanes as well as leukotrienes. Prostacyclin (PGI,) is the major eicosanoid produced by the jeopardized myocardium. In addition, at sites of tissue injury activation of platelets and infiltrating leukocytes results in the formation of considerable amounts of thromboxanes and leukotrienes. The production of eicosanoids requires prior release of arachidonic acid (AA) from phospholipids. Both ischemia and reperfusion are associated with a rise in the tissue level of AA. The absence of a proportional relationship between the tissue level of AA and the amounts of PGI, produced suggests that the sites of AA accumulation and PGI₂ formation are different. It is conceivable that AA accumulation is mainly confined to myocytes, whereas the capacity to synthesize PGI, mainly resides in vascular cells. Both beneficial and detrimental effects of eicosanoids on cardiac tissue have been described. Prostaglandins act as vasodilators. Besides, some of the prostaglandins, especially PGI,, are thought to possess cyto-protective properties. Thromboxanes and leukotrienes may impede blood supply by increasing smooth muscle tone. Besides, leukotrienes augment vascular permeability. Experimental studies, designed to evaluate the effect of pharmacological agents, like PGI₂-analogues and lipoxygenase and cyclo-oxygenase inhibitors, indicat that eicosanoids influence the outcome of myocardial injury. However, the delineation of the physiological significance of the locally produced eicosanoids is complicated by such factors as the wide variety of AA derivatives produced and the dose-dependency of their effects.     

Modified P Elements That Mimic the P Cytotype in Drosophila Melanogaster

Activity of the P family of transposable elements in Drosophila melanogaster is regulated primarily by a cellular condition known as P cytotype. It has been hypothesized that P cytotype depends on a P element-encoded repressor of transposition and excision. We provide evidence in support of this idea by showing that two modified P elements, each with lesions affecting the fourth transposase exon, mimic most of the P cytotype effects. These elements were identified by means of two sensitive assays capable of detecting repression by a single P element. One assay makes use of cytotype-dependent gene expression of certain P element insertion mutations at the singed bristle locus. The other measures suppression of transposase activity from the unusually stable genomic P element, delta 2-3(99B), that normally produces transposase in both germinal and somatic tissues. The P cytotype-like effects include suppression of snw germline hypermutability, snw somatic mosaicism, pupal lethality, and gonadal dysgenic sterility. Unlike P cytotype, however, there was no reciprocal cross effect in the inheritance of repression.