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| 2. |
- Baker, Thomas C., et al.
(författare)
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Adaptation of antennal neurons in moths is associated with cessation of pheromone-mediated upwind flight
- 1988
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 85:24, s. 9826-9830
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Tidskriftsartikel (refereegranskat)abstract
- A wind-borne plume of sex pheromone from a female moth or a synthetic source has a fine, filamentous structure that creates steep and rapid fluctuations in concentration from a male moth flying up the plume's axis. The firing rates from single antennal neurons on Agrotis segetum antennae decreased to nearly zero within seconds after the antennae were placed in a pheromone plume 70 cm downwind of a high-concentration source known from previous studies to cause in-flight arrestment of upwind progress. In a separate experiment, the fluctuating output from chilled neurons on Grapholita molesta antennae became attenuated in response to repetitive, experimentally delivered pheromone pulses. The attenuation was correlated with a previously reported higher percentage of in-flight arrestment exhibited by moths flying at cooler compared to warmer temperatures. These results indicate that two peripheral processes related to excessive concentration, complete adaptation of antennal neurons, or merely the attenuation of fluctuations in burst frequency, are important determinants of when upwind progress by a moth flying in a pheromone plume stops and changes to station keeping. Also, adaptation and attenuation may affect the sensation of blend quality by preferentially affecting cells sensitive to the most abundant components in airborne pheromone blends.
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| 3. |
- de Luca, S., et al.
(författare)
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Proteoglycans from chick limb bud chondrocyte cultures. Keratan sulfate and oligosaccharides which contain mannose and sialic acid
- 1980
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 255:13, s. 6077-6083
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Tidskriftsartikel (refereegranskat)abstract
- The precursors, [ 35S]sulfate and [2- 3H]mannose, were used to study the biosynthesis of keratan sulfate and other oligosaccharides on proteoglycans isolated from Day 8 cultures of chick limb bud chondrocytes. After alkaline borohydride treatment, three fractions with sialic acid were separated by molecular sieve chromatography. The first contained keratan sulfate which was purified by digestion with chondroitinase to remove chondroitin sulfate, followed by molecular sieve and ion exchange chromatography. The purified keratan sulfate contained about 8% of the 35S activity originally in monomer. The chains had an average length of about 40 monosaccharides and contained only trace amounts of mannose (less than 1 residue/three to four chains). The second fraction contained the majority of the [ 3H]mannose originally in monomer, but no 35S activity. This fraction appears to contain oligosaccharide-peptides of the asparagine-N-glycosylamine type because there were no reduced sugars present and the alkaline borohydride treatment extensively degraded the core protein. The composition of the oligosaccharides, with high proportions of mannose, N-acetylglucosamine, galactose, and sialic acid, was consistent with this suggestion. The third fraction consisted of a series of oligosaccharides with sizes between three to six saccharides. They contained N-acetylgalactosaminitol, indicating that they were attached to the core protein by O-glycoside bonds between N-acetylgalactosamine and hydroxyl groups on serine and threonine. Thus, proteoglycans contain two classes of oligosaccharides, a mannose-rich class characteristic of glycoproteins and an O-glycoside class characteristic of mucins, in addition to the chondroitin sulfate and keratan sulfate chains.
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| 6. |
- Lofstedt, Christer, et al.
(författare)
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Pheromone dialects in European turnip moths Agrotis segetum
- 1986
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Ingår i: Oikos. - : JSTOR. - 0030-1299. ; 46:2, s. 250-257
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Tidskriftsartikel (refereegranskat)abstract
- Female pheromone gland extracts from cultures of Agrotis segetum originating from Sweden, France, Hungary and England were analysed for pheromone components and precursors (fatty acids). The pheromone blends were similar in moths from the Swedish, English and Hungarian populations, whereas the French diverged with a much higher amount of (Z)-7-decenyl acetate relative to the homologous pheromone components (Z)-7-dodecenyl acetate and (Z)-9-tetradecenyl acetate. -from Authors
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| 7. |
- Lohmander, Stefan, et al.
(författare)
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Formation of proteoglycan aggregates in rat chondrosarcoma chondrocyte cultures treated with tunicamycin
- 1983
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 258:20, s. 12280-12286
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Tidskriftsartikel (refereegranskat)abstract
- Proteoglycan monomer and link protein isolated from the Swarm rat chondrosarcoma both contain glycosylamine-linked oligosaccharides. In monomer, these N-linked oligosaccharides are concentrated in a region of the protein core which interacts specifically with both hyaluronate and link protein to form proteoglycan aggregates present in the cartilage matrix. Chondrocyte cultures were treated with tunicamycin to inhibit synthesis of the N-linked oligosaccharides, and the ability of the deficient proteoglycan and link protein to form aggregates was studied. Cultures were pretreated with tunicamycin for 3 h and then labeled with either [3H]mannose, [3H]glucosamine, [3H]serine, or with [35S]sulfate for 6 h in the presence of tunicamycin. Formation of link protein-stabilized proteoglycan aggregates in the culture medium was inhibited by up to 40% when the cells were treated with 3 μg of tunicamycin/ml, a concentration which inhibited 3H incorporation with mannose as a precursor by about 90%, but by only 15% with glucosamine as a precursor. When exogenous proteoglycan aggregate was added to the culture medium, however, it was found that both endogenous monomer and link protein synthesized in the presence of tunicamycin were fully able to form link-stabilized aggregates. This suggests that glycosylamine-linked oligosaccharides on monomer and on link protein are not necessary for their specific interactions with hyaluronate and with each other. Further, although tunicamycin did not inhibit net synthesis of hyaluronate, transfer of hyaluronate from the cell layer to the culture medium was retarded. This phenomenon accounted for most if not all of the decrease in the amount of proteoglycan which formed aggregates in the medium of cultures treated with tunicamycin.
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| 8. |
- Lohmander, Stefan, et al.
(författare)
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Post-translational events in proteoglycan synthesis : Kinetics of synthesis of chondroitin sulfate and oligosaccharides on the core protein
- 1986
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Ingår i: Archives of Biochemistry and Biophysics. - : Elsevier BV. - 0003-9861. ; 250:1, s. 211-227
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Tidskriftsartikel (refereegranskat)abstract
- Chondrocytes isolated from the Swarm rat chondrosarcoma were incubated in culture with [1-3H]glucose for 30 min to 8 h. Labeled proteoglycans were isolated, treated with borohydride under alkaline conditions, and the three complex sugar structures purified: N- and O-linked oligosaccharides and chondroitin sulfate chains. The amount of incorporated radioactivity into each component sugar was analyzed by HPLC after enzyme digestion and hydrolysis. The kinetic data for labeling of each sugar over the time course of the experiment were fit to first-order rate equations and the half times (t 1 2) to linear labeling were calculated. The t 1 2 values were essentially the same, 5-8 min, for galactose in all three complex sugar structures and for chain glucuronic acid in chondroitin sulfate, while that for xylitol in chondroitin sulfate, 15.8 min, was significantly longer. Thus, oligosaccharide synthesis is concomitant with chondroitin sulfate chain synthesis; the addition of the chondroitin sulfate linkage galactose occurs at or nearly at the same time as chain elongation while the addition of linkage xylose residues to the core protein may precede chain synthesis by up to 8 min. Since the intracellular t 1 2 of the core protein precursor for these cells is 45 to 90 min, the data strongly suggest that the addition of xylose is not completed to any significant extent while the polypeptide is still nascent or shortly after its release into the rough endoplasmic reticulum. It is proposed that the addition of xylose to the core protein precursor is a late endoplasmic reticulum or early Golgi event. The analytical data were consistent with the presence of ester phosphate on about 80% of the xylose residues of the newly synthesized proteoglycan.
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| 9. |
- Lohmander, Stefan, et al.
(författare)
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Xylosyl transfer to the core protein precursor of the rat chondrosarcoma proteoglycan
- 1989
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 264:31, s. 18775-18780
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Tidskriftsartikel (refereegranskat)abstract
- Rat chondrosarcoma chondrocytes were labeled with [3H]serine or [3H]mannose as a precursor. Intracellular proteoglycan core protein precursor was purified from cell lysates by immunoprecipitation with polyclonal antibodies against the hyaluronic acid-binding region, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The core precursor was eluted from the gels and treated with alkaline borohydride in order to convert serine residues substituted with xylose or N-acetylgalactosamine to alanine (or with alkaline sulfite to convert them to cysteic acid). After acid hydrolysis, the proportions of labeled serine and alanine (or cysteic acid) were determined by high performance liquid chromatography, and the results were compared with those obtained for the completed proteoglycan molecules isolated from the same cultures. In the completed proteoglycans, about 55% of the serine residues were substituted with xylose or N-acetylgalactosamine, while the corresponding figure for the intracellular precursor molecules was less than 5%. These results indicate, in agreement with our previous kinetic data, that the major part of the xylosyl transfer to the chondrosarcoma proteoglycan core protein precursor must occur late in the processing sequence, i.e. after about 85% of its intracellular lifetime and no more than 7 min before the addition of the rest of the chondroitin sulfate chain. The ratio of [3H]mannose to [3H]fucose in the core precursor was about 19, while that for the complete proteoglycan was about 2. This indicates the presence of high mannose, N-linked oligosaccharides on the core protein precursor which are converted to the complex forms on the completed proteoglycan. These data provide further support that the core precursor resides mainly in the pre-Golgi compartment and that xylosylation occurs mainly in a Golgi compartment.
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| 10. |
- Nakazawa, K., et al.
(författare)
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Defective processing of keratan sulfate in Macular corneal dystrophy
- 1984
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 259:22, s. 13751-13757
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Tidskriftsartikel (refereegranskat)abstract
- macular corneal dystrophy is a human genetic disorder characterized by corneal opacities that arise, in part, from a failure to synthesize mature keratan sulfate proteoglycans. The macromolecules in macular corneas and in keratoconus corneas, an abnormality not involving proteoglycans, were biosynthetically labeled with [3H]mannose and [14C]glucosamine in organ culture, and the keratan sulfate proteoglycans were immunoprecipitated with antibodies against the protein core of monkey keratan sulfate proteoglycan. The chondroitin sulfate proteoglycans, which did not react with the antibody, were oversulfated in corneas from patients with macular corneal dystrophy. Characterization of the immunoprecipitates showed that macular corneas did not make keratan sulfate proteoglycan but did synthesize an immunoreactive glycoprotein in nearly equal amounts as keratan sulfate proteoglycan was synthesized by the keratoconus cornea. The oligosaccharides on the immunoprecipitated macular glycoprotein appeared to be normal. However, the macromolecules contained an unsulfated glycoconjugate that was nearly as large as the normal keratan sulfate chains isolated from the keratoconus keratan sulfate-proteoglycan and contained the same relative proportions of labeled glucosamine, mannose, and fucose. This glycoconjugate was resistant to digestion with keratanase. These observations indicate that macular corneal dystropy is caused by an error in the synthesis of keratan sulfate, possibly involving the specific sulfotransferases involved in sulfation of the lactosaminoglycan backbone of the chains.
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