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.     

Light effects on leaf development and photosynthetic capacity of Hydrocotyle bonariensis Lam.

Rates of net CO₂ uptake were examined in developing leaves of Hydrocotyle bonariensis. Leaves that developed under high photosynthetically active radiation (48 mol m^-2 day^-1 PAR) were smaller, thicker, and reached maximum size sooner than did leaves that developed under low PAR (4.8 mol m^-2 day^-1). Maximum net CO₂ uptake rates were reached after 5 to 6 days expansion for both the low and the high PAR leaves. Leaves grown at high PAR had higher maximum photosynthetic rates and a higher PAR required for light saturation but showed a more rapid decline in rate with age than did low PAR leaves. To assess the basis for the difference observed in photosynthetic rates, CO₂ diffusion conductances and the mesophyll surface available for CO₂ absorption were examined for mature leaves. Stomatal conductance was the largest conductance in all treatments and did not vary appreciably with growth PAR. Mesophyll conductance progressively increased with growth PAR (up to 48 mol m^-2 day^-1) as did the mesophyll surface area per unit leaf area, but the cellular conductance exhibited most of its increase at low PAR (up to 4.8 mol m^-2 day^-1).     

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     

Analysis of Immunoprecipitated Surface Glycoproteins in Measles Virions and in Membranes of Infected Cells

Measles viral envelope proteins were immune precipitated from membranes of infected cells and from purified virus and analyzed by polyacrylamide gel electrophoresis. Under reducing conditions, specific precipitates contained two major polypeptide bands, designated virus glycopeptides 1 and 2 (VGP-1 and VGP-2). Both polypeptides appeared to be glycosylated, as indicated by their incorporation of [¹⁴C]glucosamine in infected cells. VGP-2 appeared as a single band in specific precipitates of infected cells and as a double band in precipitates of purified virus. Trypsin treatment of infected cells showed that reduced VGP-2 may be composed of two unrelated polypeptides. One may be F₁, which is unglycosylated, and the other may correspond to the proteolytic cleavage product of VGP-1, which is glycosylated. The relation of VGP-1 and VGP-2 to smaller surface antigens (X and Y) obtained by tryptic treatment of infected cells remains to be elucidated. In cells taken at various times postinfection and analyzed for viral membrane proteins, VGP-1 was detected at all times, indicating that the input virus VGP-1 was inserted into the cell and could not be differentiated from newly synthesized VGP-1. VGP-2 was not detectable before 24 h postinfection. In precipitates of cells 4 h postinfection and of infected cells incubated at pH 5.8, an additional polypeptide band migrated immediately ahead of VGP-1. We conclude that VGP-2 (molecular weight, 42,000) possibly consists of two components, one of which is the tryptic cleavage product of VGP-1 and the other of which is the unglycosylated polypeptide, F₁.     

Expression of ia antigens by murine keratinizing epithelial langerhans cells

Immunofluorescent and immunoelectron-microscopic staining methods were utilized to investigate the localization of Ia antigens in murine keratinizing epithelia. Approximately 3-5% of epidermal cells were shown to be Ia positive. Only dendritic Langerhans cells in the interfollicular epidermis and outer root sheaths were found to express Ia antigens. These Ia determinants were shown to be controlled by both theI- A andI- EC subregions of theH-2 complex. The results were confirmed by identifying positively stained cells containing Langerhans cell granules at the ultrastructural level. No staining was noted on the surface of keratinocytes, melanocytes, or immigrant lymphocytes. The results presented are in close agreement with those previously reported for Ia-bearing Langerhans cells in human and guinea pig epidermis.     

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.     

Degradation of HeLa S3 cell chromatin by auromomycin and its chromophore

The antitumor protein agent auromomycin was found to degrade chromatin structure primarily by inducing strand scissions in linker regions. The reaction was stimulated by dithiothreitol. The chromophore form of the drug caused similar effects on chromatin, but it appeared to function at a more rapid rate. There was no evidence that auromomycin could cause breakage in core regions of chromatin.