Mutation of the central nervous system neuroblast proliferation repressor ana leads to defects in larval olfactory behavior

In the developing nervous system, interactions between glia and immature neurons or neuroblasts regulate axon pathfinding, migration, and cell division, and therefore affect structure and function. Glial control of neuroblast cell division has been documented by studies of the anachronism (ana) gene of Drosophila melanogaster. ana encodes a glycoprotein which, in the developing larval central nervous system, is secreted by glia that neighbor regulated neuroblasts. Mutations in ana lead to premature neuroblast proliferation in the larval brain. Examination of lacZ expression from an ana enhancer trap line as well as detection of the ana protein show that ana is also expressed in the larval antennal-maxillary complex (AMC) at all larval stages. As previously reported for the central nervous system, ana expression in the AMC appears to be confined to glial cells. Larval olfactory system function in ana mutants was assayed in a behavioral paradigm. When tested with the three different chemoattractants, third instar ana⁹ mutant larvae showed diminished olfactory response compared to controls. Examination of a second ana allele revealed aberrant olfactory response to ethyl acetate, demonstrating that more than one mutation in ana can give rise to abnormal larval olfactory behavior. Assays of early first instar ana⁹ mutant larvae revealed defective olfactory behavior, implying that the olfactory phenotype stems from early larval AMC and/or embryonic origins. This is consistent with proliferation analysis in the early larval AMC region which uncovered a significantly higher number of S-phase cells in ana⁹ mutants. © 1997 John Wiley & Sons, Inc. J Neurobiol 33: 199–211, 1997     

Pyruvate metabolism by Anaplasma marginale in cell-free culture.

Partially purified Anaplasma marginale initial bodies were cultivated in a cell-free system in the presence of [3-14C]pyruvate for 24 or 48 h. Experiments showed that a significant portion of the pyruvate supplied to the cultures was incorporated into initial body components. Label incorporation was reduced by 72% in the presence of oxytetracycline. Fractionation and chromatography of the organisms revealed radioactive incorporation as alanine. This is the first report of de novo amino acid synthesis by A. marginale demonstrating that the rickettsia is capable of using pyruvate, an erythrocyte glycolytic product, in its metabolism.     

In situ localization of cholesterol in skeletal muscle by use of a monoclonal antibody.

A common perception is that cholesterol, the major structural lipid found in mammalian membranes, is localized nearly exclusively to the plasma membrane of living cells and that it is found in much smaller quantities in internal membranes. This perception is based almost exclusively on cell fractionation studies, in which density gradient centrifugation is used for purification of discrete subcellular membrane fractions. Here we describe a monoclonal antibody, MAb 2C5-6, previously reported to detect purified cholesterol in synthetic membranes (Swartz GM Jr, Gentry MK, Amende LM, Blanchette-Mackie EJ, and Alving CR. Proc Natl Acad Sci USA 85: 1902-1906, 1988), that is capable of detecting cholesterol in situ in the membranes of skeletal muscle sections. Localization of cholesterol, the dihydropyridine receptor of the T tubule, and the Ca(2+)-ATPase of the sarcoplasmic reticulum (SERCA2) by means of double and triple immunostaining protocols clearly demonstrates that cholesterol is primarily localized to the sarcoplasmic reticulum membranes of skeletal muscle rather than the sarcolemmal or T tubule membranes. The availability of this reagent and its ability to spatially localize cholesterol in situ may provide a greater understanding of the relationship between membrane cholesterol content and transmembrane signaling in skeletal muscle.     

Changes of sex hormone-binding globulin/SHBG expression in the hypothalamo-hypophyseal system of rats during pregnancy, parturition and lactation.

Sex hormone-binding globulin (SHBG) is expressed in hypothalamic magnocellular neurons. High co-localization rates of SHBG with oxytocin have been observed in the hypothalamus, indicating that SHBG plays a role in pregnancy, parturition and lactation. Further studies have shown that hypothalamic SHBG expression is malleable to changing steroid conditions. In this study, we have examined SHBG levels in the supraoptic and paraventricular hypothalamic nuclei and in the posterior pituitary lobe of late pregnant, parturient and early lactating rats by IN SITU hybridization, immunocytochemistry, and ELISA. Immunocytochemical and biochemical analysis showed that the SHBG levels increased during late pregnancy in hypothalamic nuclei. During parturition, SHBG levels fell in the magnocellular nuclei but increased in the posterior pituitary lobe. SHBG levels increase again during lactation. At day six of lactation, there was no significant difference in SHBG levels compared to normal cycling female rats, which served as control in this study. IN SITU hybridization showed increased SHBG mRNA signal during late pregnancy. The highest SHBG expression was observed during parturition. Our data indicate that hypothalamic SHBG expression changes during pregnancy, parturition and lactation, parallel to ovarian steroid and co-localized OT levels. This may in part be linked to known steroid actions on synthesis and secretion of magnocellular hypothalamic peptide hormones, important for the control of parturition and lactation.     

Environmental effects of ozone depletion and its interactions with climate change: progress report, 2004.

The complexity of the linkages between ozone depletion, UV-B radiation and climate change has become more apparent.     

d-arabinose metabolism byBacteroides fragilis strain 2044

During growth in the presence of 1-14C-d-arabinose,Bacteroides fragilis strain 2044 formed labeled succinic, acetic, and propionic acis. Degradation of the acids by the Schmidt reaction revealed that at least 89% of the succinate radioactivity was found in the methylene carbons and that 75% and 84% of the label in propionate and acetate were found in the noncarboxyl carbons of these molecules. No label was found in acetate, propionate, or succinate during growth of strain 2044 in the presence of 5-3H-d-arabinose. Strain 2044 converted radioactivity from 1- or 2-labeled glycolic acid and glycine to succinate by a mechanism involving cleavage of the glycine and glycolic acid carbon skeletons. Label from 1- or 2-labeled glycine and 2 but not 1-labeled glycolic acid was found in acetate. Uniformly labeled 14C-glyoxalate gave rise to labeled acetate, but not succinate.Bacteroides fragilis strain 2044 metabolizesd-arabinose by a mechanism involving a 32 cleavage of the molecule.     

Canopy structure,light microclimate and leaf gas exchange of Quercus coccifera L. in a Portuguese macchia: measurements in different canopy layers and simulations with a canopy model

Summary The structural characteristics of a diverse array of Quercus coccifera canopies were assessed and related to measured and computed light attenuation, proportion of sunlit foliage, foliage temperatures, and photosynthesis and diffusive conductance behavior in different canopy layers. A canopy model incorporating all components of shortwave and longwave radiation, and the energy balance, conductance, and CO₂ and H₂O exchanges of all leaf layers was developed and compared with measurements of microclimate and gas exchange in canopies in four seasons of the year. In the denser canopies with a leaf area index (LAI) greater than 5, there is little sunlit foliage and the diffuse radiation (400–700 nm) is attenuated to 5% or less of the global radiation (400–700 nm) incident on the top of the canopy. Foliage of this species is nonrandomly distributed with respect to azimuth angle, and within each canopy layer, foliage azimuth and inclination angles are correlated. A detailed version of the model which computed radiation interception and photosynthetic light harvesting according to these nonrandom distributions indicated little difference in whole-canopy gas exchange from calculations of the normal model, which assumes random azimuth orientation. The contributions of different leaf layers to canopy gas exchange are not only a function of the canopy microclimate, but also the degree to which leaves in the lower layers of the canopy exhibit more shade-leaf characteristics, such as low photosynthetic and respiratory capacity and maximal conductance. On cloudless days, the majority of the foliage in a canopy of 5.4 LAI is shaded —70%–90% depending on the time of year. Yet, the shaded foliage under these conditions is calculated to contribute only about one-third of the canopy carbon gain. This contribution is about the same as that of the upper 13% of the canopy foliage. Computed annual whole-canopy carbon gain and water use are, respectively, 60% and 100% greater for a canopy of 5 LAI than for one of 2 LAI. Canopy water-use efficiency is correspondingly less for the canopy of 5 LAI than for that of 2 LAI, but most of this difference is apparent during the cool months of the year, when moisture is more abundant.     

A quantitative study of intramembrane changes during cell junctional breakdown in the dystrophic rat retinal pigment epithelium

Previous electron microscope freeze-fracture and tracer studies have revealed that intercellular junctions in the retinal pigment epithelium (RPE) of Royal College of Surgeons (RCS) rats with inherited retinal dystrophy [5] break down between three and six postnatal weeks [6, 7]. In this study quantitative computer techniques were used to analyze the freeze-fracture changes in the dystrophic RPE. The following parameters were measured: length of tight junctional strands/micron2; number of tight junctional strand anastomoses/micron2; number of gap junctional aggregates/micron2; area of gap junctional aggregates/micron2; and density of background intramembrane particles/micron2. At three postnatal weeks, the dystrophic junctional complex membrane is similar to normal, but at 10 weeks and later there are dramatic decreases in tight junctional strand length/micron2 and number of anastomoses/micron2, as well as in the number/micron2 and area of gap junctions/micron2, while the density of background particles/micron2 is dramatically increased. Correlational analysis revealed that changes in gap and tight junctions were significantly related to each other and to the increase in background particle density. The diameter of background particles within the normal and post-breakdown dystrophic junctions was measured in order to see whether the dispersal of gap and tight junctional particles (8-10 nm) into the surrounding membrane contributes to the increased particle density. These measures showed that background particles in all size ranges were more numerous in the dystrophic RPE, but that the largest increase was in the smallest diameter particles (6-7 nm). Thus, while gap and tight junctional sized particles contribute to the increase, particles from other sources may also be involved. Particle density of apical and basal membranes in the normal and in the 10 week and older dystrophic RPE was analyzed to study the effects of tight junctional breakdown on the distribution of intramembrane particles. These measures showed that particle density was greater basally than apically in the normal RPE and that particle density in both membranes decreased slightly in the dystrophic RPE, but that their ratio remained unchanged. It has been shown previously that even a single intact tight junctional strand is sufficient to maintain differences in particle density between apical and basal surfaces [14, 15] and in the majority of abnormal dystrophic junctional complexes at least one tight junctional strand remains intact.(ABSTRACT TRUNCATED AT 400 WORDS)