Fatty acid positional distribution in phospholipids of a psychrophilic bacterium during changes in growth temperature

The major phospholipids of the psychrophilic bacteriumMicrococcus cryophilus, phosphatidylethanolamine and phosphatidylglycerol, have similar fatty acid compositions, comprising almost entirely palmitoleic and oleic acids. We show that there is a preference for the longer chains in thesn-1 position of both phosphatidylethanolamine and phosphatidylglycerol, both during isothermal growth and after temperature shifts, despite the fact that the overall phospholipid C18/C16 acyl chain ratio decreases with a lowering of growth temperature. Although it has been shown using model systems that the isomeric configurationsn-1-long,sn-2-short lowers lipid melting temperature, this paper reports the first clear-cut demonstration of such an isomeric preference in a natural system. We discuss how this acyl chain configuration contributes to membrane fluidity inM. cryophilus, in terms of adaptation to its psychrophilic habitat.     

Intragenic Sequences Affect the Expression of the Gene Encoding Glial Fibrillary Acidic Protein

We show that the expression of the gene encoding glial fibrillary acidic protein (GFAP) gene is affected by at least three cis-acting elements. A positive regulatory element that is located between nucleotides -1,631 and -1,479 can confer cell type-specific expression on a heterologous gene. A second regulatory element is located between nucleotides -97 and -80. The third is a negative regulatory element that is located within the first intron of the gene. Deletion of this element activates GFAP expression in HeLa cells, and affects promoter function in glioma cells.     

Computer-assisted image analysis of the distributions of peptidergic terminals in the central nucleus of the amygdala: A preliminary study

When viewed under dark-field illumination, peptidergic terminals in sections stained by the Sternberger PAP immunocytochemical method are seen as individual points of light. Under high magnification, the degree of brightness of various areas of immunoreactive terminals is seen to be a function of the density of terminals in these areas. By analyzying the relative brightness of the immunostained central nucleus of the amygdala (CNA) with an EyeCom II PDP-$\text{11}\text{34}$ image analysis system, we have obtained a relative evaluation of the density distribution of neurotensin (NT)-, substance P (SP), VIP-, angiotensin II (AII), m-enkephalin (m-ENK) and somatostatin (SS)-immunoreactive terminals in terms of normal morphology and following a brain lesion. The EyeCom II system divides the presented image into 307200 picture elements (pixels) and assigns one of 256 grey values to the average brightness with each pixel. We have aggregated the grey level frequencies into 5 levels where level 1 corresponds to the highest terminal density and level 5 to the lowest density. At level 1, only NT- and VIP-immunoreactive terminals occupy a significant percentage of the cross-sectional area of the CNA (20%). About 15% of the area of the CNA has VIP terminals with level 5 density. The distributions of the top 20% of the terminal density range of NT, SP, AII and VIP support a classical medial/lateral division of the nucleus. The distribution of the same range of SS- and ENK terminals suggests a dorsoventral division of the CNA. A preliminary study indicates that comparison of grey level frequency histograms generated by image analysis from homologous lesioned and unlesioned sections of the CNA can yield useful information regarding post-lesion changes in the distribution of immunoreactive terminals.     

Electron Microscopic Study of Development in a Sea Cucumber,Stichopus tremulus (Holothuroidea), from Unfertilized Egg through Hatched Blastula

In this, the first fine structural study of sea cucumber embryology, eggs and embryos of Stichopus tremulus developing at 7.5°C are described from spawning through hatched blastulae. Spawned eggs are at about first meiotic metaphase and are surrounded by a jelly layer that remains around the embryos until hatching. No vitelline coat can be demonstrated, but whether it is truly absent or removed by electron microscopic processing is not known. Insemination initiates a rapid cortical reaction, completed within 2 min., which involves a wave of cortical granule exocytosis and fertilization envelope formation. The compactly fibrous fertilization envelope is about 50 nm thick and appears to consist entirely of ejected cortical granule material (if one assumes that there is no vitelline coat). As the fertilization envelope elevates, no hyaline layer appears in the perivitelline space. The first and second polar bodies are emitted, respectively, at about 9 and 15 min. after insemination. The first seven or so cleavages are equal, radial, and occur approximately every 4 hr. The blastocoel opens up at the four-cell stage and, during the earlier cleavages, remains connected with the perivitelline space via numerous gaps between the roughly spherical blastomeres. At the 64-cell stage, these gaps begin to close as the blastomeres start to become cuboidal; in addition, an embryonic cuticle is produced on the apical surface of each blastomere. In embryos of several hundred cells, the blastomeres become associated apicolaterally by junctional complexes, each consisting of a zonula adherens and a septate junction. Several hours before hatching, a single cilium is produced at the apical surface of most blastomeres. At hatching (about 50 hr after insemination), the ciliated blastula leaves behind the fertilization envelope and jelly layer. Swimming blastulae soon begin to elongate in the animal-vegetal axis, and a basal lamina develops on blastomere surfaces facing the blastocoel. The discussion includes a fine structural comparison of egg coats among the five classes of the phylum Echinodermata.     

Serotonin-containing neurones in vertebrate retinas

Abstract: It has been established by a combination of HPLC and electrochemical detection that frog, lizard, goldfish, rabbit, and bovine retinas contain both dopamine and serotonin. Immunohistological and immunoradiographical methods show that serotonin is localised in amacrine perikarya and processes situated in the inner plexiform layers of frog, lizard, and goldfish retinas. The amount of serotonin in the mammalian retina appears to be too low for detection in neurones. The serotonin in the bovine retina is located mainly in the inner nuclear and plexiform layers, suggesting that the amine is present in the same types of cells as found for frog, lizard, and goldfish retinas. Retinas incubated in [³H]serotonin showed that radioactivity is associated with processes in the inner plexiform layer and amacrine perikarya. These results suggest that the neuronal elements that contain endogenous serotonin also have the capacity to accumulate exogenous amine and are consistent with the opinion that serotonin has a neuronal function in retinas of a variety of vertebrates.     

Comparative evaluation of macrophage stimulation and depression on tumor growth and macrophage content and function in mice

Summary In a syngeneic murine adenocarcinoma model, the administration of glucan, an RE stimulant, inhibited tumor growth and increased tumor macrophage populations. Conversely, the administration of methyl palmitate, an RE depressant, potentiated tumor growth and decreased the number of tumor macrophages. Glucan and methyl palmitate also produced diverse alterations in serum lysozyme levels that reflected their contrasting influences on RE functional status, thus supporting the role of serum lysozyme as an index of macrophage function. The diverse results produced by macrophage stimulation or depression in regard to tumor growth, tumor macrophage population, and serum lysozyme concentration indicate that a relationship may exist between macrophage functional activity and host resistance to neoplasia.