Muscle temperature in free-swimming giant Atlantic bluefin tuna (Thunnus thynnus L.)

Muscle temperature was measured by telemetry in giant Atlantic bluefin tuna whilst the tuna were free-swimming in large pounds. Muscle temperature tended to remain steady at about 24°C; water temperature ranged from 9 to 17°C. Muscle temperature was much less variable than stomach temperature in these fish. Muscle temperature varied less than 3°C whereas stomach temperature varied by as much as 14°C.     

The performance of fungal xylan-degrading enzyme preparations in elemental chlorine-free bleaching for Eucalyptus pulp

Cellulase-free xylan-degrading enzyme preparations from Acrophialophora nainiana, Humicola grisea var. thermoidea and two Trichoderma harzianum strains were used as bleaching agents for Eucalyptus kraft pulp, prior to a chlorine dioxide and alkaline bleaching sequence. In comparison to the control sequence (performed without xylanase pretreatment), the sequence incorporating enzyme treatment was more effective. Removal of residual lignin was indicated by a reduction in kappa number. Overall, enzyme preparations from T. harzianum were marginally more effective in reducing pulp viscosity and chlorine chemical consumption and improving the brightness of the kraft pulp. However, the highest reduction in pulp viscosity was mediated by the xylanase preparation from A. nainiana. Xylanase pretreatment compares very favorably with that of chemical pulping. Journal of Industrial Microbiology & Biotechnology (2002) 28, 204–206 DOI: 10.1038/sj/jim/7000227 Received 27 April 2001/ Accepted in revised form 03 November 2001     

Plant regeneration from undeveloped ovules and embryogenic calli of Citrus: Embryo production,germination, and plant survival

Embryogenic cultures were initiated from undeveloped ovules of several polyembryonic Citrus species on a basal medium supplemented with either malt extract, 2,4-D alone, or 2,4-D in combination with BA or daminozide. Primary embryos of all responsive cultivars were harvested directly from ovule cultures; secondary embryo harvests were made from Handin orange ovule cultures and long-term embryogenic callus. Differences were observed among cultivars and treatments in percentage of responsive ovules and total number of embryos produced. The most effective treatment for embryo production varied among cultivars. Embryo germination and plant establishment frequencies were determined for this plant regeneration system. Differences among cultivars with respect to regenerate survival percentage were minimal. Plant regeneration via secondary or long-term callus-derived embryos was as efficient as from primary embryos. Critical factors influencing plant production and survival were the production of normal viable embryos, balanced germination, and successful acclimatization to the external environment.     

Intergeneric somatic hybrid plants from sexually incompatible woody species: Citrus sinensis and Severinia disticha

Summary The fusion of Citrus sinensis cv. Hamlin (sweet orange) protoplasts isolated from an embryogenic suspension culture with Severinia disticha (Philippine box orange) protoplasts isolated from epicotyl-derived callus with organogenic potential, resulted in the regeneration of allotetraploid somatic hybrid plants. Plant regeneration was a function of complementation, combining the capacity for somatic embryogenesis of C. sinensis with the organogenic ability of S. disticha. Confirmation of somatic hybrid identity was based on leaf morphology, chromosome number, and analyses of phosphoglucose mutase (PGM) and malate dehydrogenase (MDH) zymograms. Hybrid plants were multiplied organogenically and exhibited morphology intermediate to that of the parents. This is the first example of somatic hybrid plants produced between sexually incompatible woody genera.Florida Agricultural Experiment Station Journal Series No. 8198     

Translational suppression by Ca2+ ionophores: Reversibility and roles of Ca2+ mobilization, Ca2+ influx, and nucleotide depletion

The divalent cation selective ionophores A23187 and ionomycin were compared for their effects on the Ca²⁺ contents, nucleotide contents, and protein synthetic rates of several types of cultured cells. Both ionophores reduced amino acid incorporation by approximately 85% at low concentrations (50–300 nmol/L) in cultured mammalian cells without reducing ATP or GTP contents. At these concentrations A23187 and ionomycin each promoted substantial Ca²⁺ efflux, whereas at higher concentrations a large influx of the cation was observed. Ca²⁺ influx occurred at lower ionophore concentrations and to greater extents in C6 glioma and P3X63Ag8 myeloma than in GH₃ pituitary cells. The ATP and GTP contents of the cells and their ability to adhere to growth surfaces declined sharply at ionophore concentrations producing increased Ca²⁺ influx. Prominent reductions of nucleotide contents occurred in EGTA-containing media that were further accentuated by extracellular Ca²⁺. Ionomycin produced more Ca²⁺ influx and nucleotide decline than comparable concentrations of A23187. The inhibition of amino acid incorporation and mobilization of cell-associated Ca²⁺ by ionomycin were readily reversed in GH₃ cells by fatty acid-free bovine serum albumin, whereas the effects of A23187 were only partially reversed. Amino acid incorporation was further suppressed by ionophore concentrations depleting nucleotide contents. Mitochondrial uncouplers potentiated Ca²⁺ accumulation in response to both ionophores. At cytotoxic concentrations Lubrol PX abolished protein synthesis but did not cause Ca²⁺ influx. Nucleotide depletion at high ionophore concentrations is proposed to result from increased plasmalemmal Ca²⁺-ATPase activity and dissipation of mitochondrial proton gradients and to cause intracellular Ca²⁺ accumulation. Increased Ca²⁺ contents in response to Ca²⁺ ionophores are proposed as an indicator of ionophore-induced cytotoxicity.Abbreviations BSA bovine serum albumin - EGTA [ethylenebis(oxyethylenenitrilo)]tetraacetic acid - PKR double-stranded RNA-regulated protein kinase - ER endoplasmic reticulum - eIF eukaryotic initiation factor     

Linkage of restriction fragment length polymorphisms and isozymes in Citrus

Summary Genetic linkage analysis was performed using two segregating populations of citrus. One population arose from an intergeneric backcross of Citrus grandis (L.) Osb. cv Thong Dee and Poncirus trifoliata (L.) Raf. cv Pomeroy, using the former as the recurrent (female) parent. The other population came from an interspecific backcross of C. reticulata Blanco cv Clementine and C. x paradisi Macf. cv Duncan, using the former as the recurrent (male) parent. A total of 11 isozyme and 58 restriction fragment length polymorphisms were found to segregate in a monogenic fashion in one or both populations. Linkage analysis revealed that 62 of the loci examined mapped to 11 linkage groups, while 7 loci segregated independently from all other markers. Gene order was highly conserved between the maps generated from the two divergent segregating populations. Possible applications of the use of such maps in tree fruit breeding are discussed.     

Characterization of zygotic and nucellar seedlings from sour orange-like citrus rootstock candidates using RAPD and EST-SSR markers

A series of crosses designed for introgression of mandarin (Citrus reticulata Blanco) and pummelo (C. maxima Merr.) germplasm, to develop an alternative rootstock to sour orange (C. aurantium L.), were carried out. It is necessary to identify those hybrids that yield nucellar seedlings for rootstock propagation. Rootstocks can be developed through traditional plant breeding methods; however, the ability to screen and select for economically important traits (such as production of true nucellar seedlings) in an efficient fashion is limited by the difficulties of screening techniques based on whole plant performance. To address these problems, we have used randomly amplified polymorphic DNA (RAPD) and fluorescently labeled expressed sequence tag simple sequence repeat (EST-SSR) molecular markers. A total of 204 individual seedlings obtained from 34 hybrid parental plants were successfully characterized using five RAPD primers. Ten hybrid parents and their progenies, found to be genetically similar among themselves, were selected for more scrutiny using eight EST-SSR primer pairs. The degrees of genetic similarity (nucellars) among progeny seedlings were determined and compared with that of their parents. The mean genetic similarity varied from 67–99% among the selected rootstock candidates screened. The genetic similarity relationship identified using RAPD and EST-SSR molecular markers was highly concordant (p = 0.001). Two elite rootstock candidates (B6R5T56; B6R11T129) that seem to be ideal for future mandarin and pummelo derived rootstock breeding programs have been identified. Our results indicate that either RAPD or EST-SSR analyses could be equally successful in identifying true nucellars among the progenies obtained from introgression crosses of mandarin and pummelo, thus improving the accuracy of early selection in a citrus rootstock breeding program.