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     

Development of Nitrogen Assimilation Enzymes during Photoautotrophic Growth of Chenopodium rubrum Suspension Cultures

We have shown previously that ethylene, which accumulates in the air spaces of submerged stem sections of rice (Oryza sativa L. cv “Habiganj Aman II”), is involved in regulating the growth response caused by submergence. The role of gibberellins in the submergence response was studied using tetcyclacis (TCY), a new plant growth retardant, which inhibits gibberellin biosynthesis. Stem sections excised from plants that had been watered with a solution of 1 micromolar TCY for 7 to 10 days did not elongate when submerged in the same solution or when exposed to 1 microliter per liter ethylene in air. Gibberellic acid (GA₃) at 0.3 micromolar overcame the effect of TCY and restored the rapid internodal elongation in submerged and ethylene-treated sections to the levels observed in control sections that had not been treated with TCY. The effect of 0.01 to 0.2 micromolar GA₃ on internodal elongation was enhanced two- to eight-fold when 1 microliter per liter ethylene was added to the air passing through the chamber in which the sections were incubated. GA₃ and ethylene caused a similar increase in cell division and cell elongation in rice internodes. Thus, ethylene may cause internodal elongation in rice by increasing the activity of endogenous GAs. In internodes from which the leaf sheath had been peeled off, growth in response to submergence, ethylene and GA₃ was severely inhibited by light.     

Potentiating effect of caffeine on the teratogenicity of acetazolamide in C57BL/6J mice

Pregnant C57BL/6J mice were treated with 0 or 50 mg of caffeine (CAFF) per kg, and 0, 200 mg/kg (L) or 1,000 mg/kg (H) of acetazolamide (ACZM) during day 9 of gestation (9DPC). Individual fetuses were examined for gross morphological abnormalities and skeletal variations. The increase in fetal malformations seen, especially right forelimb electrodactyly, was augmented at both dose levels of acetazolamide by concomitant exposure to caffeine. Both frequency and severity of ectrodactyly were potentiated by caffeine. Skeletal examination revealed a reduction of the number of ossified cervical and caudal vertebral centra among litters exposed to ACZM at either dose. In either case (ACZM-H, ACZM-L) that effect was augmented by co-administration of CAFF. The first cervical vertebra (C1) appeared to provide the most sensitive index of teratogenic exposure. This study provides evidence that a subteratogenic dose of caffeine can potentiate the teratogenic effect of acetazolamide in C57BL/6J mice when dams are treated on day 9 of gestation. In addition, skeletal examination provided evidence that simultaneous treatment with both agents delayed fetal development. Many litters exposed to ACZM or both agents displayed a reduction in skeletal ossification even in the absence of gross morphological abnormalities, suggesting that ossification can be used as an indicator of prenatal exposure to potentially harmful substances in the C57BL/6 mouse strain.     

DNA analysis and sorting of rat testis cells using two-parameter flow cytometry

By use of two-parameter flow cytometry of rat testis cell suspensions stained with mithramycin for DNA (the peak amplitude of the fluorescence signal versus total fluorescence intensity integrated over time), eight cell compartments could be distinguished without pre-enrichment of the samples. Cells in these compartments were identified by sorting and subsequent microscopic examination.     

The potential of greenhouse sinks to underwrite improved land management

The current agricultural systems of broad areas of Australia are unsustainable, with large projected increases in salinization, decreases in water quality, wind erosion, and losses of biodiversity. It is well known that these problems can be partially resolved by farmland reforestation; however, a major issue is financing the scale of activity required. The international response to global warming, the United Nations Framework Convention on Climate Change and its Kyoto Protocol, includes provisions that enable greenhouse sinks (sequestration of carbon in soils and vegetation) to be used by parties to fulfil their obligations. The Kyoto Protocol also allows for trading in emission reductions, and this opens the possibility that investment in carbon sinks may help underwrite broader natural resource management objectives. This paper examines the possibilities for improved land management in Western Australia arising from the development of carbon sinks by considering: (a) the likelihood of a carbon market developing and the likely depth of that market as a result of current national and international policies, (b) the data available to provide estimates on different types of sinks, and (c) the likely benefits of wide-scale sink investment.It was estimated that the total amount of carbon that could be sequestered by reforesting 16.8 Mha of cleared farmland is 2200 Mt CO₂-e, and between 290 and 1170 Mt CO₂-e by destocking 94.8 Mha of rangelands. There were insufficient data to produce estimates of sequestration following changes in tillage practice in cropping systems or the revegetation of already salinized land. We conclude that carbon sinks are only likely to become profitable as a broad-scale stand-alone enterprise when carbon prices reach AUD$15/t CO₂-e, with this threshold value varying with carbon yield and project costs. Below this price, their value can be significant as an adjunct to reforestation schemes that are aimed at providing other products (wood, pulp, bioenergy) and land and water conservation benefits. Irrespective of this, carbon sinks provide an opportunity to both sequester carbon in a least-cost fashion and improve soil and watershed management.     

Drug use among youths

The levels of drug use among youths under 14 have remained extremely low for the past few years, as well as in most European countries. Yet, patterns of early drug use are often related to high-risk behaviours that require specific public policy strategies. Over the last years, the Government has set the target of reducing levels of drug use among specific groups such as young people: an awareness-raising media campaign has been launched and a specific outpatients clinics setting has been implemented for cannabis users in particular. This paper examines the relationship between health service providers and criminal justice authorities underlying the effectiveness of the current system. It underlines the need for an early screening and early interventions so as to avoid the shift from simple use to misuse or dependence.     

The development of rating of perceived exertion-based tests of physical working capacity

The purpose of the present study was to use ratings of perceived exertion (RPE) from the Borg (6-20) and OMNI-Leg (0-10) scales to determine the Physical Working Capacity at the Borg and OMNI thresholds (PWC(BORG) and PWC(OMNI)). PWC(BORG) and PWC(OMNI) were compared with other fatigue thresholds determined from the measurement of heart rate (the Physical Working Capacity at the Heart Rate Threshold: PWC(HRT)), and oxygen consumption (the Physical Working Capacity at the Oxygen Consumption Threshold, PWC(VO2)), as well as the ventilatory threshold (VT). Fifteen men and women volunteers (mean age +/- SD = 22 +/- 1 years) performed an incremental test to exhaustion on an electronically braked ergometer for the determination of VO2 peak and VT. The subjects also performed 4 randomly ordered workbouts to exhaustion at different power outputs (ranging from 60 to 206W) for the determination of PWC(BORG), PWC(OMNI), PWC(HRT), and PWC(VO2). The results indicated that there were no significant mean differences among the fatigue thresholds: PWC(BORG) (mean +/- SD = 133 +/- 37W; 67 +/- 8% of VO2 peak), PWC(OMNI) (137 +/- 44W; 68 +/- 9% of VO2 peak), PWC(HRT) (135 +/- 36W; 68 +/- 8% of VO2 peak), PWC(VO2) (145 +/- 41W; 72 +/- 7% of VO2 peak) and VT (131 +/- 45W; 66 +/- 8% of VO2 peak). The results of this study indicated that the mathematical model used to estimate PWC(HRT) and PWC(VO2) can be applied to ratings of perceived exertion to determine PWC(BORG) and PWC(OMNI) during cycle ergometry. Salient features of the PWC(BORG) and PWC(OMNI) tests are that they are simple to administer and require the use of only an RPE scale, a stopwatch, and a cycle ergometer. Furthermore, the power outputs at the PWC(BORG) and PWC(OMNI) may be useful to estimate the VT noninvasively and without the need for expired gas analysis.