Effects of guanine nucleotides on cns neuropeptide receptors

The effect of nucleotides on central nervous system neuropeptide receptor binding was investigated. The guanine nucleotides, guanosine-5′-triphosphate and guanylyl-5′-imidodiphosphate, significantly inhibited the binding of radiolabeled vasoactive intestinal polypeptide but not that of [Tyr⁴]bombesin to rat brain membranes. Vasoactive intestinal polypeptide binding was inhibited by guanine nucleotides in a dose-dependent manner. Using a 20 μM dose, 60% of the specific vasoactive intestinal polypeptide binding was inhibited by guanylyl-5′-imidodiphosphate, which was more potent than guanosine-5′-triphosphate, whereas other nucleotides were not effective. This reduction in binding was a consequence of lower affinity of the receptor for vasoactive intestinal polypeptide, which in turn resulted from an increased rate of dissociation.     

Lymphocytes express Ia antigens of foreign haplotype following treatment with neuraminidase

Evidence is presented which indicates that neuraminidase (NA) treatment of spleen cells both destroys old Ia antigens and reveals new Ia specificities which are not normally expressed by splenocytes. It was found that NA treatment unmasked alien I-A^k-like specificities on A.TH (I ^s ) spleen cells, and I^s-like antigens on A.TL (I ^k ) spleen cells. These conclusions were based on direct testing of NA-treated targets with a range of alloantisera and on cell-absorption experiments. Furthermore, the cellular distribution of NA-exposed antigens resembled that of convential Ia antigens, the new antigens being expressed on more than 90 percent of splenic B cells and a subpopulation of splenic T cells. However, although some of the antigens exposed by NA on A.TH cells appeared to resemble the Ia. 3 and 15 specificities, additional antigens were involved which did not correlate with any previously described Ia antigens.Sugar inhibition experiments demonstrated the NA-exposed antigens to be carbohydrate in nature, D-galactose being an effective inhibitor in these studies. The proportion of- and-linked D-galactose residues associated with the new antigens depended upon the target cell used and the anti-Ia serum tested. Furthermore, glycolipid extracts from lymphoid cells were shown to contain the NA-exposed antigens.Collectively, these results support the existence of carbohydrate-defined Ia antigens. The simplest interpretation of the findings is that NA clips off terminal sialic acid residues from carbohydrate-defined Ia antigens on the cell surface and exposes subterminal sugars which resemble antigens expressed by otherI-region haplotypes.     

Partial trisomy 10p and familial translocation t(7;10)(p22;p12)

Summary A girl with partial trisomy for the short arm of chromosome 10(p12pter) due to mal chromosome segregation in the father 46,XY,t(7;10)(p22;p12) is described. The major abnormalities in this case are: mottled skin, mid-facial hypoplasia, low percentiles for weight, length, and head circumference, and club feet.To whom offprint requests should be sent     

Packing analysis of carbohydrates and polysaccharides. V. Crystal structures of two polymorphs of pachyman triacetate

The crystal structures of two polymorphic forms of pachyman triacetate, the fully acetylated derivative of a naturally occuring β-(1 → 3)-D -glucan, were determined by a combination of stereochemical and x-ray diffraction analysis. The two polymorphs could be obtained depending on the temperature and the degree of stretching of film specimens of the substance: polymorph I resulted from stretching 25–50% at 125°C and polymorph II resulted from further stretching to 300% at 215°C. Both polymorphs had previously been shown to have sixfold helical chain conformations, but of unequal pitch. Subsequent detailed structure refinement performed with bond lengths, bond angles, conformational angles, and helix-packing parameters as refinement variables, and the simultaneous minimization of packing and conformational energy and the crystallographic R-factor as refinement criteria, resulted in a complete determination of the two crystal structures. Pachyman triacetate I was found to be a right-handed helix packing with antiparallel polarity and space group P2₁2₁2₁ symmetry (unit-cell parameters a = 11.0, b = 19.0, c (fiber repeat) = 22.38 Å). The acetate groups were nearly planar and the O(2) and O(4) acetates were oriented in such a fashion that the carbonyl double-bond nearly eclipsed the corresponding C—H bond of the ring. The O(6) was in the tg position and its acetate was oriented in such a fashion that the bond sequence C(6)—O(6)—C(6C)—C(6M) was nearly trans-planar, with the carbonyl double-bond bisecting the tetrahedral angle formed by C(6) and its two hydrogens. The final R = 0.221. Pachyman triacetate II was similarly found to be a right-handed helix, but packing as a 50:50 mixture of parallel and antiparallel polarities (unit-cell parameters a = 11.49, b = 20.13, c (fiber repeat) = 18.6 Å). The acetate positions in pachyman triacetate II were substantially the same as in pachyman triacetate I. The final R for the 50:50 mixture was 0.234. Probable reasons for the change in packing polarities are discussed, as are the difficulties encountered in the structure refinement of acetate derivatives.     

A model for the density ofAeromonas hydrophila in Albemarle Sound,North Carolina

The abundance ofAeromonas hydrophila was measured monthly at 29 sites in Albemarle Sound, North Carolina and its tributaries from April 1977 through July 1979. Simultaneous measurements included heterotrophic plate count bacteria, fecal coliform bacteria, and 18 physical and chemical parameters. Using only 6 water quality parameters, multiple correlation and regression analysis of the data produced a best-fit regression which explained 38% of the variation observed inA. hydrophila density. The 6 water quality parameters included dissolved oxygen, temperature, orthophosphate, chlorophyll A trichromatic, total Kjeldahl nitrogen, and ammonia. Heterotrophic plate count bacteria and fecal coliform densities were highly correlated withA. hydrophila density, but made the model very unstable. The model was successfully tested against similar data collected for 2 other North Carolina reservoirs, Lake Norman and Badin Lake. Data from 10 sites in Badin Lake over 18 months and from 7 sites on Lake Norman over 5 months were not significantly different from the Albemarle Sound model. Conditions of water quality that may give rise to “blooms” ofA. hydrophila will simultaneously contribute to the probability of increased epizootics in fish in the southeastern United States.     

Phytochrome assembly. The structure and biological activity of 2(R),3(E)-phytochromobilin derived from phycobiliproteins.

The unicellular rhodophyte, Porphyridium cruentum, and the filamentous cyanobacterium, Calothrix sp. PCC 7601, contain phycobiliproteins that have covalently bound phycobilin chromophores. Overnight incubation of solvent-extracted cells at 40 degrees C with methanol liberates free phycobilins that are derived from the protein-bound bilins by methanolytic cleavage of the thioether linkages between bilin and apoprotein. Two of the free bilins were identified as 3(E)-phycocyanobilin and 3(E)-phycoerythrombilin by comparative spectrophotometry and high pressure liquid chromatography. Methanolysis also yields a third bilin free acid whose absorption and 1H NMR spectra support the assignment of the 3(E)-phytochromobilin structure. This novel bilin is the major pigment isolated from cells that are pre-extracted with acetone-containing solvents. Since phytochrome- or phytochromobilin-containing proteins are not present in either organism, the 3(E)-phytochromobilin must arise by oxidation of phycobilin chromophores. This pigment is not obtained by similar treatment of a cyanobacterium and a rhodophyte that lack phycoerythrin. Therefore, 3(E)-phytochromobilin appears to be derived from phycoerythrobilin-containing proteins. Comparative CD spectroscopy of 3(E)-phytochrombilin and 3(E)-phycocyanobilin suggests that the two bilins share the R stereochemistry at the 2-position in the reduced pyrrole ring. Incubation of 2(R),3(E)-phytochromobilin with recombinant oat apophytochrome yields a covalent bilin adduct that is photoactive and spectrally indistinguishable from native oat phytochrome isolated from etiolated seedlings. These results establish that the phycobiliprotein-derived 2(R),3(E)-phytochromobilin is a biologically active phytochrome chromophore precursor.     

Effects of nitrogen limitation on species replacement dynamics during early secondary succession on a semiarid sagebrush site

Summary A soil nitrogen (N) availability gradient was induced on a disturbed sagebrush site in northwestern Colorado by fertilizing with nitrogen (high available N), applying sucrose (low available N), and applying neither nitrogen nor sucrose (control). Species composition was studied for 3 years. At the end of the study, N concentration of aboveground tissue of 3 major species was determined. The rate of species replacement was most rapid on plots receiving the sucrose treatment and was slowest on plots receiving the N treatment. Early-seral dominats had greater tissue N concentrations when availability of the resource was high but lower tissue N concentrations when available soil N became limited. Midseral dominants displayed the opposite pattern. These results suggest that the supply of available soil N, and therefore the dynamics of N incorporation in perennial plant tissue, is a primary mechanism in controlling the rate of secondary succession within this semiarid ecosystem.     

Sequence of an oleocin cDNA from Brassica napus

Antibodies raised against purified rapeseed 19 kDa oleosin protein were used to screen an embryo-derived gt11 expression library from Brassica napus. A near full-length cDNA clone, BnV, was isolated. The 781 bp cDNA contained an open reading frame of 549 bp followed by an untranslated region of 222 pb and a poly(A) region of 10 bp. Comparisons between this cDNA and a different oleosin cDNA previously isolated from the same library showed high degrees of sequence similarity in the central domain region and in the 3 untranslated region. Sequence similarities between the derived protein sequence of this cDNA and all other known oleosin protein sequences are discussed.     

Chemotaxis ofAeromonas hydrophila to the surface mucus of fish

Isolates ofAeromonas hydrophila from various sources show different chemotactic responses to mucus from the surface of freshwater fish. Some isolates were nonchemotactic to fish surface mucus. Isolates ofA. hydrophila from fish lesions had a significantly higher chemotactic index than isolates ofA. hydrophila from water. Maximum chemotactic responses occurred more often to diluted fish mucus than to undiluted samples. Fish which were experimentally stressed did not produce mucus that was more or less chemotactic than that of unstressed fish. Fish with red-sore lesions produced surface mucus which was not chemotactic toA. hydrophila. Differences between fish, for any isolate, were also not significant. The chemotactic substance(s) in fish mucus has a molecular weight of approximately 100,000 and did not appear to be labile when heated to 56°C.     

Effect of α-Methylphenylalanine and Phenylalanine on Brain Polyribosomes and Protein Synthesis

Abstract: A chronic hyperphenylalanemia was effectively produced in developing mice by daily administrations of phenylalanine (2 mg/g body wt) and a phenylalanine hydroxylase inhibitor α-methyl-D, L-phenylalanine (0.43 mg/g body wt). The presence of α-methylphenylalanine in newborn mice inhibited 65–70% of hepatic phenylalanine hydroxylase activity within 12 h. Since this maximum inhibition persisted for 24 h or longer, decreased enzyme activity was maintained by daily administrations. Whereas concentrations of phenylalanine increased approximately 40-fold in both plasma and brain following injection of α-methylphenylalanine and phenylalanine, plasma levels of tyrosine were not altered significantly. Concomitant with changes in phenylalanine concentrations we observed the brain polyribosomes' disaggregation, which reached a maximum 3 h after injection and persisted as long as 18 h. Polyribosomes did not become refractory to as many as 10 daily injections of α-methylphenylalanine and phenylalanine. In addition to polyribosome disaggregation, chronic hyperphenylalanemia reduced the rates of polypeptide chain elongation on polyribosomes isolated from brain homogenates.