The interaction of 1-anilino-8-naphthalenesulfonate with thyroid lipids and membranes: A nuclear magnetic resonance study

The proton magnetic resonance (PMR) spectra of thyroid cell membranes and their total lipid extracts, in the presence of 1-anilino-8-naphthalenesulfonate (ANS), have been studied. The addition of ANS causes a shifting of the head group PMR signal, a splitting of the signal into two components and an increase in total spectral intensity. The data suggest that ANS interacts with phospholipid in the membrane as it does in total lipid vesicles. Evidence is also presented for the removal of lipids from the membrane, by ANS, and the subsequent formation of micelles. The membrane results are compatred with our earlier work on the interaction of ANS with egg phosphatidycholine (P.C.) vesicles and the results are used in explaining the inhibition of iodide transport in isolated thyroid slices.     

Expression of cDNAs encoding wild-type and mutant neuromodulins in Escherichia coli: comparison with the native protein from bovine brain

Murine cDNA that encodes neuromodulin, a neurospecific calmodulin binding protein, was inserted into the plasmid pKK223-3 for expression in Escherichia coli. After being transformed into E. coli strain SG20252 (lon-), the expression vector directed the synthesis of a protein that was recognized by polyclonal antibodies raised against bovine neuromodulin. The recombinant protein expressed in E. coli was found to be tightly associated with insoluble cell material and was extractable only with guanidine hydrochloride or sodium dodecyl sulfate. Following solubilization with guanidine hydrochloride, the protein was purified to apparent homogeneity by a single CaM-Sepharose affinity column step with a yield of 0.2 mg of protein/L of E. coli culture. The availability of the purified recombinant neuromodulin made it possible to answer several specific questions concerning the structure and function of the protein. Despite the fact that murine neuromodulin is 12 amino acid residues shorter than the bovine protein and the recombinant protein expressed in E. coli may lack any posttranslational modifications, the two proteins displayed similar biochemical properties in almost all respects examined. They both had higher affinity for CaM-Sepharose in the absence of Ca2+ than in its presence; they were both phosphorylated in vitro by protein kinase C in a Ca2+- and phospholipid-dependent manner; neither form of the proteins was autophosphorylated, and the phosphorylated form of the proteins did not bind calmodulin. The recombinant neuromodulin and neuromodulin purified from bovine brain had similar, but not identical, affinities of calmodulin, indicating that the palmitylation of the protein that occurs in animal cells is not crucial for calmodulin interactions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of the surface microlayer on nutrients,chlorophyll and algal diversity of a small eutrophic bog pond

Nutrients, chlorophyll, phaeophytin and algal abundances were investigated in the surface microlayer and at subsurface depths in a small eutrophic bog pond. Nutrient levels were consistently higher in the microlayer while algal abundance was sometimes higher but sometimes lower in the microlayer than at near subsurface depths. Algal diversity values were strongly influenced by the depth of flagellate blooms, and in contrast to previous studies, diversity in the microlayer was higher than at near subsurface depths. These results are discussed in terms of weather parameters, affinity of algal species for the surface and differences between microlayer ecology in shallow and deep water systems.     

Social stimulation and the resumption of copulation in Rhesus (Macaca mulatto) and stumptail (Macaca arctoides) Macaques

Copulatory data derived from observations of social groups of rhesus and stumptail macaques were analyzed to test the hypothesis that pairs of animals would resume copulation significantly sooner if a second male copulated with the female shortly after the first male’s ejaculation. Data from both groups supported the hypothesis. These results, extending previous studies in Macaca nemestrina,suggest that the shortening of copulatory intervals by social stimuli occurs in several species, both in social groups and in experimentally created triads. These findings also are consistent with the hypothesis that socially mediated resumption of mating is related to intrasexual competition among males.     

The effects of high pressure upon ligated and deoxyhemoglobins and myoglobin. An optical spectroscopic study

The effects of high pressure (0.1-3.4 gigapascal (GPa)) on the ferrous heme active sites of human adult hemoglobin, sperm whale myoglobin, and Glycera dibranchiata hemoglobin (Fraction II) were probed using resonance Raman and absorption spectroscopies. High-to-low spin transitions of the heme iron occur for hemoglobin, myoglobin, and Glycera hemoglobin at 0.35, 0.75, and 0.50 GPa, respectively, for the deoxy species. These interspecies differences result from variations in the composition of the hemepockets and/or their rigidity to pressure-induced volume changes. Heme active sites initially bound to CO or O2 exhibit distinctive behavior at high pressures. For all proteins studied, O2 apparently dissociates from the heme at only moderately high pressure, while CO remains bound to the heme moiety even at extreme pressures. The Raman spectra demonstrate the differences in the ligated and deoxy species at 3.4 GPa in the high frequency region. Discrete changes (i.e. iron spin-state transitions and dissociation of O2) occur that are commensurate with the collapse of the distal pocket, while continuous shifts in the absorption and Raman spectra are observed at pressures above those required for pocket collapse.     

A new major histocompatibility complex class I b gene expressed in the mouse blastocyst and placenta

 Because of the role major histocompatibility complex (MHC) class I b molecules may play during mouse embryonic development, we thought it would be interesting to search for additional MHC class I b molecules that might be expressed in preimplantation embryos, and in particular in the trophoblastic lineage. We therefore screened a mouse preimplantation blastocyst cDNA library for MHC class I sequences. This search led to the identification and characterization of a new MHC class I b gene, blastocyst MHC. Sequences identical to the exons and 3′ untranslated region of this gene have been found in many laboratory mouse strains, as well as in the related mouse species Mus spreciligus. The presence of this gene in mouse strains of different MHC class I haplotypes argues that blastocyst MHC is a unique, newly-described gene rather than a new allele of a previously described mouse MHC class I gene. Blastocyst MHC has the structure of an MHC class I b gene, with the six exons characteristic of T-region genes. It is linked to H2-D. The amino acid sequence encoded by this gene maintains all the features of a functional antigen-presentation domain. The blastocyst MHC gene, like the human class I b gene HLA-G, is expressed at the blastocyst stage and in the placenta, and may be the mouse analog for HLA-G. Received: 31 May 1996 / Revised: 19 August 1996     

A comparison of phytoplankton assemblages in the Chesapeake and Delaware estuaries (USA), with emphasis on diatoms

The Delaware Bay is characterized as having greater nutrient and turbidity levels than the Chesapeake Bay. In reference to these differences, a one year study was conducted to identify any similarities and differences in the phytoplankton populations in these estuaries. The results indicated patterns of similarity in the diatom composition, with the total phytoplankton assemblage forming two site groups along a salinity gradient in each bay. These site groups were associated with stations located in the tidal fresh-oligohaline and meso-polyhaline regions of both estuaries. The seasonal concentrations of diatoms and total phytoplankton in both of these regions were higher in the Chesapeake Bay.Subtle differences between the two estuaries include a more diversified and abundant assemblage of neritic phytoplankters (including dinoflagellates) are present in the lower Chesapeake Bay. In contrast, a diatom dominated community is more characteristic of Delaware Bay. It is suggested the entry of neritic species into lower regions of the estuaries was enhanced by the reduced amount of rainfall and flow rates that occurred during the study period. The greater success of neritic species in the Chesapeake Bay is attributed to the lower turbidity of that estuary compared to Delaware Bay.     

Solvent-accessible surfaces of nucleic acids

Static solvent-accessible surface areas were calculated for DNA and RNA double helices of varied conformation, composition and sequence, for the single helix of poly(rC), and for a transfer RNA. The results show that for DNA and RNA double helices, two thirds of the water-accessible surface area become buried on double helix formation; phosphate oxygens retain near maximal exposure while the bases are 80% buried. Transfer RNA exposes slightly less surface per residue than does double-helical RNA, despite the presence of several additional “modified” groups, all of which are exposed significantly.When a probe corresponding to a single water molecule is used, both the total and atom type exposures are very similar for A-DNA and B-DNA, although marked differences appear in the major and minor groove exposures between the two conformations. For a given base-pair, the accessible surface area buried upon double-helical stacking is nearly constant (within 5%) for different sequences of neighboring base-pairs.For probes larger than single water molecules, there exist considerable differences in the total and atom type exposures of A-DNA and B-DNA. Conformational transitions between the A-DNA and B-DNA helical forms can thus be related to differences in the accessible areas for “structured” water, or a secondary hydration shell, rather than to interactions with individual water molecules of the primary hydration shell. The base-composition dependence of DNA helical conformation can be explained in terms of the opposing effects of thymine methyl groups of A · T base-pairs and the amino groups of G · C base-pairs upon the solvent within the grooves.The area calculations show that primarily the major groove of B-DNA and the minor groove of A-DNA have sufficient accessible surface area to be recognized by a probe size corresponding to the side-chains of amino acids.