The mechanism of resistance to paraquat is strongly temperature dependent in resistant Hordeum leporinum Link and H. glaucum Steud.

Paraquat-resistant biotypes of the closely-related weed species Hordeum leporinum Link and H. glaucum Steud. are highly resistant to paraquat when grown during the normal winter growing season. However, when grown and treated with paraquat in summer, these biotypes are markedly less resistant to paraquat. This reduced resistance to paraquat in summer is primarily a result of increased temperature following herbicide treatment. The mechanism governing this decrease in resistance at high temperature was examined in H. leporinum. No differences were observed between susceptible and resistant biotypes in the interaction of paraquat with isolated thylakoids when assayed at 15, 25, or 35 °C. About 98 and 65% of applied paraquat was absorbed through the leaf cuticle of both biotypes at 15 and 30 °C, respectively. Following application to leaves, more herbicide was translocated in a basipetal direction in the susceptible biotype compared to the resistant biotype at 15 °C. However, at 30 °C more paraquat was translocated in a basipetal direction in the resistant biotype. Photosynthetic activity of young leaf tissue from within the leaf sheath which had not been directly exposed to paraquat was measured 24 h after treatment of plants with para. quat. This activity was inhibited in the susceptible biotype when plants were maintained at either 15 °C or 30 °C after treatment. In contrast, photosynthetic activity of such tissue of the resistant biotype was not inhibited when plants were maintained at 15 °C after treatment, but was inhibited at 30 °C. The mechanism of resistance in this biotype of H. leporinum correlates with decreased translocation of paraquat and decreased penetration to the active site. This mechanism is temperature sensitive and breaks down at higher temperatures.We are grateful to Zeneca Agrochemicals, Jealotts Hill, Berkshire, UK who provided [¹⁴C]paraquat. E.P. was supported through a Ph.D. scholarship from the Australian International Development Assistance Bureau and C.P. was the recipient of an Australian Research Council Postdoctoral Fellowship.     

Primate terminal complement inhibitor homologues of human CD59

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers L22862 (African green monkey CD59) and L22863 (baboon CD59)     

Structural and immunochemical identification of Leb glycolipids in the plasma of a group O Le(a-b-) secretor

Total non-acid glycosphingolipids were isolated from the plasma of a healthy red blood cell group O Le(a-b-) salivary ABH secretor individual. Glycolipids were fractionated by HPLC and combined into eight fractions based on chromatographic and immunoreactive properties. These glycolipid fractions were analysed by thin-layer chromatography and tested for Lewis activity with antibodies reactive to the type 1 precursor (Le^c), H type 1 (Le^d), Le^a and Le^b epitopes. Fractions were structurally characterized by mass spectrometry (EI-MS and LSIMS) and proton NMR spectroscopy. Expected blood group glycolipids, such as H type 1, (Fuc1-2Gal1-3GlcNAc1-3Gal1-4Glc1-1Cer) were immunochemically and structurally identified. Inconsistent with the red cell phenotype and for the first time, small quantities of Le^b blood group glycolipids (Fuc1-2Gal1-3(Fuc1-4)GlcNAc1-3Gal1-4Glc1-1Cer) were immunochemically and structurally identified in the plasma of a Lewis-negative individual. These findings confirm recent immunological evidence suggesting the production of small amounts of Lewis antigens by Lewis negative individuals. Abbreviations: HPLC, high performance liquid chromatography; TLC, (high performance) thin layer chromatography; EI-MS, electron impact ionisation mass spectrometry; LSIMS, liquid secondary ion mass spectrometry; NMR, nuclear magnetic resonance spectroscopy. The sugar types are abbreviated to Hex for hexose, HexNAc forN-acetylhexosamine and dHex for deoxyhexose (fucose). The ceramide types are abbreviated to d for dihydroxy and t for trihydroxy base, n for non-hydroxy and h for hydroxy fatty acids; LCB, long chain base.     

Influence of muscle activity on the forces in the femur: An in vivo study

Experiments were performed on two patients with custom-made instrumented massive proximal femoral prostheses implanted after tumour resection. In vivo axial forces transmitted along the prostheses were telemetered during level walking, single- and double-leg stance, and isometric exercises of the hip muscles. These activities varied the lever arms available to the external loads: minimum for double-leg stance and maximum for hip isometric exercises. Kinematic, force plate, EMG and telemetered force data were recorded simultaneously. The force magnification ration (FMR; the ratio of the telemetered axial force to the external force) was calculated. The FMRs ranged from 1.3 (during double-leg stance) to 29.8 (during abductors test), indicating that a major part of the axial force in the long bones is a response to muscle activity, the strength of which depends on the lever arms available to the external loads. From these results, it was shown that the bulk of the bending moment along limbs is transmitted by a combination of tensile forces in muscles and compressive forces in bones, so moments transmitted by the bones are smaller than the limb moments. It was concluded that appropriate simulation of muscle forces is important in experimental or theoretical studies of load transmission along bones.     

Immobilization of tyrosinase for use in nonaqueous media: Enzyme deactivation phenomena

Summary We have investigated features for minimizing the inactivation of tyrosinase (E.C. 1.14.18.1) that is caused by immobilization on glass beads and Celite^®. The degree of inactivation is dependent on the enzyme loading and the carrier's surface area. Addition of a sacrificial protein during the immobilization procedure offers a protective effect with increased residual activity on the basis of comparable enzyme loading.     

Isolation and amino-terminal sequences of subunits from the photosynthetic reaction center of Rhodopseudomonas capsulata

The amino-terminal sequences have been determined by Edman degradation for the reaction center polypeptides from a carotenoidless mutant of Rhodopseudomonas capsulata. Individual polypeptides were isolated by preparative electrophoresis and electroelution. By comparison with the sequences deduced from the DNA (Youvan, D.C., Alberti, M., Begush, H., Bylina, E.J. and Hearst, J.E. (1984) Proc. Natl. Acad. Sci. USA 81, 189–192) we conclude that the M and L subunits are processed so as to remove the amino-terminal methionine, whereas the H subunit is not processed at the amino-terminus after translation. None of the subunits is synthesized with a significant amino-terminal extension peptide.     

Protamines in plant sperm

Sperm protamines have been isolated from representatives of three major plant groups: algae (Chara corallina ), bryophytes ( Marchantia polymorpha), and ferns ( Marsilea vestitia ). We previously reported the complete displacement of histones by protamines in Marchantia (Reynolds W F & Wolfe, S L, Exp cell res 116 (1978) 269 [8] ). Marchantia protamines appear as four components on acid-urea gels, whereas Chara and Marsilea protamines comigrate as a single band with a mobility comparable to salmon protamine. The amino acid compositions of the plant protamines show these to be arginine-rich, highly basic (35-42%) proteins which display overall similarity in amino acid composition (84-91%). The molecular weights of Chara and Marsilea protamines are approx. 4700-5300 D.     

Incorporation of [14C]cinnamate into hydrolase-resistant components of the primary cell wall of spinach

[¹⁴C]Cinnamate was taken up very rapidly by cultured spinach cells and completely incorporated into low-MW conjugates within 20 min. The ¹⁴C-labelled products were similar whether the [¹⁴C]cinnamate was supplied continuously over a period of hours via a peristaltic pump or instantaneously. Radioactivity was slowly recruited from the low-MW pool into aromatic components of the cell-wall fraction. Saponification of the radioactive wall fraction yielded, in addition to radioactive ferulate and p-coumarate, large amounts of ethyl acetate-soluble radioactive material with the properties of oxidatively coupled phenols. The coupled material was associated with the most highly ‘Driselase’-resistant fractions of the cell wall. In contrast, ‘Driselase’ released most of the wall's ferulate and p-coumarate on disaccharide fragments. It is suggested that the oxidatively coupled phenols are formed from simpler phenols by peroxidase and that they cross-link the polysaccharides to which they are attached, making these polysaccharides relatively ‘Driselase’-resistant.     

Phonotaxis in the painted reed frog (Hyperolius marmoratus)

Summary A detailed study was conducted of the three-dimensional accuracy of phonotaxis by femaleHyperolius marmoratus. This analysis involved videotape recordings of phonotactic approaches to an elevated loudspeaker through a three-dimensional grid. Females readily resolved the sound source elevation, but the jump error angles describing the precision of approach were considerably greater in this three-dimensional analysis than in the more conventional two-dimensional ground approach analysis. Extensive use was made of visual cues in elevated phonotactic approach and lateral head scanning prior to jumps, often accompanied by vertical changes in head orientation, was frequent. The ability of such small anurans to localize a sound source in both the horizontal and vertical plane is remarkable.On leave from the Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853, USA     

Effects of testosterone on messenger ribonucleic acid and protein synthesis in rat seminal vesicle

In a previous report [Higgins et al. (1976) Biochem. J. 158, 271–282] we described the effects of alterations in androgen status on the synthesis of two basic secretory proteins of the rat seminal vesicle. In the present paper we examine the effects of testosterone on the activity of mRNA in the seminal vesicle. Total cellular poly(A)-rich RNA was isolated and translated in a cell-free system prepared from wheat germ. Translation products were separated on denaturing polyacrylamide gels and the protein bands corresponding to the two basic secretory proteins were identified immunologically. Incorporation of radioactive methionine into these bands was taken as a measure of the individual mRNA activities. Total mRNA activity was estimated by radioactivity in total acid-precipitable material. The results show that 1 to 2 weeks after castration the activities of mRNA molecules for the basic secretory proteins were decreased 10–20-fold on a tissue basis. Testosterone given in vivo rapidly and substantially restores mRNA activity to normal. Since these changes correlate closely with variations in the rates of synthesis of the secretory proteins in whole cells it suggests that androgenic steroids control protein synthesis chiefly via mRNA availability. In this respect their action resembles those of other steroid hormones acting in other systems. However, these effects of testosterone on the mRNA molecules for the major secretory proteins could not be distinguished from those on total mRNA. Thus the proportion of the total mRNA population accounted for by the two specific mRNA molecules showed less than a 2-fold variation with androgen status. Similarly the two secretory proteins always accounted for 25–33% of general protein synthesis. This is in sharp contrast with the markedly differential effects of other steroid hormones controlling synthesis of major proteins in other well-studied systems. We interpret our results as indicating that testosterone regulates the mRNA population of the seminal vesicle as a whole.