Nitrate reductase activity and growth in Paul's Scarlet rose suspension cultures in relation to nitrogen source and molybdenum

Growth and nitrate reductase activity were measured in Paul's Scarlet rose cell suspensions, cultured in media purified from molybdenum and containing nitrate or urea as sole nitrogen source with or without added Mo. Urea could replace nitrate to yield 80% of the fresh weight in nitrate medium. Nitrate reductase activities were compared by in vivo and in vitro assays. The latter varied due to inactivation during extraction. Compared with activities in cells in complete NO₃ ^- medium, activity in NO₃ ^--Mo cells was reduced to 30% and, in urea-grown cells, to trace amounts. Increases in nitrate reductase activity were found when NO₃ ^- alone was added to NO₃ ^- or urea+Mo cultures. In NO₃ ^--Mo cultures, Mo alone or with NO₃ ^- caused a similar increase in activity, whereas urea-Mo cultures required both NO₃ ^- and Mo for enzyme induction.Abbreviations FAD flavin adenine dinucleotide - Mo molybdenum - NADH reduced nicotinamide adenine dinucleotide - NO₃ ^-+Mo standard MX₁ culture medium - NO₃ ^--Mo MX₁ medium purified of Mo and used for continuous subculture with nitrate - NR nitrate reductase - PSR Paul's Scarlet rose - PVP polyvinylpyrrolidone - U urea - U+Mo MX₁ medium containing urea instead of nitrate - U-Mo MX₁ medium containing urea instead of nitrate and also purified of Mo     

Characterization of microsatellite markers in peach [Prunus persica (L.) Batsch]

Microsatellites have emerged as an important system of molecular markers. We evaluated the potential of microsatellites for use in genetic studies of peach [Prunus persica (L.) Batsch]. Microsatellite loci in peach were identified by screening a pUC8 genomic library, a λZAPII leaf cDNA library, as well as through database searches. Primer sequences for the microsatellite loci were tested from the related Rosaceae species apple (Malus×domestica) and sour cherry (Prunus cerasus L.). The genomic library was screened for CT, CA and AGG repeats, while the cDNA library was screened for (CT)_n- and (CA)_n-containing clones. Estimates of microsatellite frequencies were determined from the genomic library screening, and indicate that CT repeats occur every 100 kb, CA repeats every 420 kb, and AGG repeats every 700 kb in the peach genome. Microsatellite- containing clones were sequenced, and specific PCR primers were designed to amplify the microsatellite- containing regions from genomic DNA. The level of microsatellite polymorphism was evaluated among 28 scion peach cultivars which displayed one to four alleles per primer pair. Five microsatellites were found to segregate in intraspecific peach-mapping crosses. In addition, these microsatellite markers were tested for their utility in cross-species amplification for use in comparative mapping both within the Rosaceae, and with the un- related species Arabidopsis thaliana L. Received: 18 June 1999 / Accepted: 6 December 1999     

New species, observations, and a list of new records of brown algae (Phaeophyceae) from the Hawaiian Islands

Two new species of brown algae (Phaeophyceae), Padina moffittiana Abbott et Huisman, sp. nov. and Cutleria irregularis Abbott et Huisman, sp. nov., are described from the Hawaiian Islands (between 19°04′N, 155°35′W and 28°25′N, 178°20′W). In addition, the new combination Cutleria canariensis is proposed for Aglaozonia canariensis. New observations are presented on Nereia intricata Yamada, a species described 67 years ago and known only from its type specimen. New records of a further 14 species are given for the Hawaiian Islands. These 17 taxa bring the total number of species of brown algae recorded for the Hawaiian Islands to 55, an increase of 28%. Of the 15 new records, two are recent ‘accidental’ introductions: Dictyota flabellata (Collins) Setchell et Gardner and Sargassum muticum (Yendo) Fensholt from California. Six records are notable because of their great distances from previously known collections: Nereia intricata Yamada from the Ryukyu Is., Japan; Discosporangium mesarthrocarpum (Meneghini) Hauck, from the Adriatic, Mediterranean, warm Atlantic and southern Australia; Distromium flabellatum Womersley, Spatoglossum macrodontum J. Agardh, and Sporochnus moorei Harvey, from Australia; Desmarestia ligulata (Lightfoot) Lamouroux from temperate and colder waters in the Pacific and Atlantic. A comparison with some Japanese species of Padina confirms that Padina japonica Yamada should be subsumed with Padina sanctae‐crucis Børgesen, as proposed earlier.     

Topography and functions of sulfhydryl groups of the human erythrocyte glucose transport mechanism

Summary Membrane-impermeant and -permeant maleimides were applied to characterize the location and function of the sulfhydryl (SH) groups essential for the facilitated diffusion mediated by the human erythrocyte glucose transport protein. Three such classes have been identified. Type I SH is accessible to membrane-impermeant reagents at the outer (exofacial) surface of the intact erythrocyte. Alkylation of this class inhibits glucose transport; D-glucose and cytochalasin B protect against the alkylation. Type II SH is located at the inner (endofacial) surface of the membrane and is accessible to the membrane-impermeant reagent glutathione maleimide only after lysis of the erythrocyte. D-glucose enhances, while cytochalasin B reduces, the alkylation of Type II SH by maleimides. Reaction of Types I and II SH with an impermeant maleimide increases the half-saturation concentration for binding of D-glucose to erythrocyte membranes. By contrast, inactivation of Type III SH markedly decreases the half-saturation concentration for the binding of D-glucose and other transported sugars. Type III SH is inactivated by the relatively lipid-soluble reagents N-ethylmaleimide (NEM) and dipyridyl disulfide, but not by the impermeant glutathione maleimide. Type III SH is thus located in a hydrophobic membrane domain. A kinetic model constructed to explain these observations indicates that Type III SH is required for the translocation event in a hydrophobic membrane domain which leads to the dissociation of glucose bound to transport sites at the membrane surfaces.     

A backpack system for long-term osmotic minipump infusions into unrestrained marmoset monkeys

A backpack system is described whereby osmotic minipumps are used to infuse gonadotrophin-releasing hormone (GnRH) subcutaneously in a pulsatile manner into infertile socially subordinate female marmoset monkeys (Callithrix jacchus jacchus). This procedure enables long-term infusion of GnRH without the necessity of repeated subcutaneous implantation of pumps and GnRH reservoirs. The backpack and cannulae system is inexpensive and can be constructed from commonly available materials. The GnRH treatment successfully overcame the suppression of pituitary luteinizing hormone secretion imposed by the low social status of female marmoset monkeys.     

Intra- and Interpopulation Genome Variation In Meloidogyne arenaria

The genetic heterogeneity of two M. arenaria race 2 populations (designated Pelion and Govan) was examined using RFLP analysis of 12 clonal lines established from single egg masses (six distinct clonal lines from each population). These populations are essentially identical by traditional biochemical and race identification schemes; however, the Govan population is more aggressive than the Pelion population, producing larger galls and exhibiting greater reproductive capabilities on many soybean cultivars and experimental accessions. Variation at the genomic DNA level was examined using probes representative of expressed DNA sequences present in the eukaryotic genome. Ribosomal DNA, interspersed repeated sequences, and cDNA probes were tested for detection of polymorphism within and between single egg mass lines of each population. Cloned cDNAs and ribosomal intergenic spacer sequences detect polymorphism both within and between populations, demonstrating the usefulness of these sequence classes for molecular genetic analysis of population structure and genome evolution.     

Interaction of bepridil with the cardiac troponin C/troponin I complex

Mammalian cells are characterized by an endomembrane system. Nevertheless, some cells lose these membranes during their terminal differentiation, e.g. red blood cells and lens fiber cells of the eye. 15-Lipoxygenase is believed to be critical for this membrane degradation. Here we use cultivated rabbit reticulocytes in the presence or absence of a lipoxygenase inhibitor to provide further evidence for the importance of 15-lipoxygenase for the in vivo degradation of mitochondria. We find that inhibitor treatment retarded mitochondrial degradation, as shown by persistence of marker proteins and by direct visualization of mitochondria by electron microscopy.