Cytogenetic characterization of <Emphasis Type="Italic">Hydrangea involucrata</Emphasis> Sieb. and <Emphasis Type="Italic">H. aspera</Emphasis> D. Don complex (Hydrangeaceae)<Emphasis Type="Italic">:</Emphasis> genetic,evolutional, and taxonomic implications

The subsection Asperae of genus Hydrangea L. (Hydrangeaceae) has been investigated for three reasons: several ambiguous classifications concerning Hydrangea aspera have been published, unexpected differences in genome size among seven accessions have been reported Cerbah et al. (Theor Appl Genet 103:45–51, 2001), and two atypical chromosome numbers (2n = 30 for Hydrangea involucrata and 2n = 34 for H. aspera) have been found when all other species of the genus present 2n = 36. Therefore, these two species and four subspecies of Hydrangea in all 29 accessions were analyzed for their genome size, chromosome number, and karyotype features. This investigation includes flow cytometric measurements of nuclear DNA content and bases composition (GC%), fluorochrome banding for detection of GC- and AT-rich DNA regions, and fluorescent in situ hybridisation (FISH) for chromosome mapping of 5 S and 18 S-5.8 S-26 S rDNA genes. In the H. aspera complex, the genome size ranged from 2.98 (subsp. sargentiana) to 4.67 pg/2C (subsp. aspera), an exceptional intraspecific variation of 1.57-fold. The mean base composition was 40.5% GC. Our report establishes the first karyotype for the species H. involucrata, and for the subspecies of H. aspera which indeed present different formulae, offering an element of discrimination. FISH and fluorochrome banding revealed the important differentiation between these two species (H. involucrata and H. aspera) and among four subspecies of the H. aspera complex. Our results are in agreement with the Chinese classification that places the groups Kawakami and Villosa as two different species: Hydrangea villosa Rehder and Hydrangea kawakami Hayata. This knowledge can contribute to effective germplasm management and horticultural use.     

Change in bone mineral density as a function of age in women and men and association with the use of antiresorptive agents

Background

Measurement of bone mineral density is the most common method of diagnosing and assessing osteoporosis. We sought to estimate the average rate of change in bone mineral density as a function of age among Canadians aged 25–85, stratified by sex and use of antiresorptive agents.

Methods

We examined a longitudinal cohort of 9423 participants. We measured the bone mineral density in the lumbar spine, total hip and femoral neck at baseline in 1995–1997, and at 3-year (participants aged 40–60 years only) and 5-year follow-up visits. We used the measurements to compute individual rates of change.

Results

Bone loss in all 3 skeletal sites began among women at age 40–44. Bone loss was particularly rapid in the total hip and was greatest among women aged 50–54 who were transitioning from premenopause to postmenopause, with a change from baseline of –6.8% (95% confidence interval [CI] –7.5% to –4.9%) over 5 years. The rate of decline, particularly in the total hip, increased again among women older than 70 years. Bone loss in all 3 skeletal sites began at an earlier age (25–39) among men than among women. The rate of decline of bone density in the total hip was nearly constant among men 35 and older and then increased among men older than 65. Use of antiresorptive agents was associated with attenuated bone loss in both sexes among participants aged 50–79.

Interpretation

The period of accelerated loss of bone mineral density in the hip bones occurring among women and men older than 65 may be an important contributor to the increased incidence of hip fracture among patients in that age group. The extent of bone loss that we observed in both sexes indicates that, in the absence of additional risk factors or therapy, repeat testing of bone mineral density to diagnose osteoporosis could be delayed to every 5 years.Low bone mineral density is one of the most important risk factors for fracture.^1,2,3–7 Treatment with antiresorptive agents has been widely used for several decades, and the results of randomized controlled trials have shown that at least part of their efficacy is associated with their capacity to increase or stabilize bone density.⁴ Although clinical guidelines recommend measurement of bone density, among other important risk factors, when assessing a patient''s risk for fracture,^3,8,9 there is no international consensus on the optimal age at which to begin measurement, or on the frequency of measurement.¹⁰ The Canadian guidelines recommend it for patients aged 65 and older, even in the absence of risk factors or treatment, and suggest a frequency of every 2–3 years.⁸ Furthermore, it has been suggested that the rate of decline rather than a single measurement of bone density may better identify patients with an elevated risk for fracture.¹¹ Consequently, determining changes in bone density over time may provide clues on the pathophysiology of fractures and provide more accurate estimates of the optimal timing for repeat measurement.Previous studies of change in bone mineral density as a function of age have had a number of limitations. Many were cross-sectional; had small samples, limited age ranges or differing inclusion and exclusion criteria; and most excluded men.^12–20 The third National Health and Nutrition Examination Survey,²¹ a large cross-sectional study based in the United States included women and men aged 20 years and older but excluded only those who were pregnant or who had a fracture in both hips. It reported that, based on a single measurement of bone density in the hip, age-dependent bone loss in the hips begins early (20–40 years) and continues in both sexes throughout life. Cross-sectional data from the ongoing Canadian Multicentre Osteoporosis Study suggested that, although this finding may hold true for the femoral neck, which consists of both cortical and trabecular bone, it is not true for the largely trabecular lumbar spine.²² Furthermore, the use of cross-sectional data to estimate changes over time has fundamental limitations: the effect of age cannot be separated from the effect of birth cohort and survivorship, and estimates are based on between-group differences rather than changes in an individual participant.The use of longitudinal data would allow examination of the rate of change of bone mineral density over time with and without antiresorptive therapy. We sought to assess the average rate of change in bone density as a function of age among Canadians aged 25–85, stratified by sex and use of antiresorptive agents.     

Age-dependent increase in hydrogen peroxide production by cardiac monoamine oxidase A in rats

Oxidative stress is one of the factors involved in age-related impairment of cardiac function. In the present study, we investigated the role of the catecholamine-degrading enzyme monoamine oxidase (MAO) in H(2)O(2) production in the hearts of young, adult, and old rats. MAO-dependent H(2)O(2) production, measured by a chemiluminescence-based assay, increased with age, reaching the maximum in 24-mo-old rats (7.5-fold increase vs. 1-mo-old rats). The following observations indicate that the age-dependent increase in H(2)O(2) generation was fully related to the MAO-A isoform: 1) at all the ages tested, chemiluminescence production was inhibited by the MAO-A inhibitor clorgyline but not by the MAO-B inhibitor RO-19 6327; 2) enzyme assay, Western blot, and semiquantitative RT-PCR analysis showed an age-dependent increase in cardiac MAO-A activity, immunodetection, and mRNA expression, respectively; and 3) the MAO-B isoform was undetectable by enzyme assay and Western blot analysis. These results suggest that MAO-A could be a major source of H(2)O(2) in the aging heart.     

Adriamycin induced resistance of sensitive K 562 cells to natural killer lymphocyte attack

Summary The effect of Adriamycin (ADM) on eryhtroleukaemia K 562 cell susceptibility to human natural killer (NK) cell activity has been studied. When cultivated for 3 days in the presence of 10 to 40 nM ADM, K 562 cells decreased their susceptibility to NK-mediated lysis in a dose-dependent fashion. At a concentration of 40 nM, previously found to induce optimal differentiation-associated properties in K 562 cells, the induced resistance to NK-mediated lysis increased progressively from day 1 to day 3 of culture. ADM treatment did not induce K 562 cells to release factors which interfered with NK activity since supernatants from ADM-treated K 562 cell cultures caused no significant modification in the NK lytic process. Binding to NK of ADM-treated K 562 cells was unaffected since treated and untreated cells had identical capacities in a conjugate-forming cell assay or adsorption of NK cells on target cell monolayers. In cold target competition assays ADM-treated K 562 cells acted as more effective competitors than untreated K 562 cells. These observations imply that the reduced killing of the ADM-treated K 562 cells was independent of target-NK cell recognition, and suggest that ADM treatment could allow malignant cells to escape NK surveillance.     

Sensitivity of Na+-coupled d-glucose uptake,Mg2+-ATPase and sucrase to perturbations of the fluidity of brush-border membrane vesicles induced by n-aliphatic alcohols

The aim of our work is to show the importance of the role of hydrophobic bonds in maintaining Mg²⁺-ATPase or sucrase activity and Na⁺-coupled d-glucose uptake normal for the brush border of rat enterocytes. The activity of the two enzymes and the d-glucose uptake were therefore measured under the action of $\text{n-}\text{aliphatic alcohols}$ and related to the fluidity determined by ESR. Three concentrations were used for the first eight alcohols, those of octanol being about 1500-times lower than those of methanol. For each alcohol the d-glucose uptake and the fluidity were linear functions of the logarithm of the concentration, the linear regressions being practically parallel and equidistant. The concentrations ($\text{C}$) of the eight alcohols inhibiting the d-glucose uptake by 80% were similar to those increasing the membrane fluidity by 3%. The linear relationship which existed in both cases between log 1 / $\text{C}$ and log $\text{P, P}$ being octanol / water partition coefficients of the alcohols, was evidence of great sensitivity to the hydrophobic effect of the alcohols. Only the first alcohols, however, produced any notable inhibition of Mg²⁺-ATPase and sucrase. Hydrophobic bonds are thus shown to have little influence in maintaining the activity of Mg²⁺-ATPase and sucrase, but they modulate the Na⁺-coupled d-glucose uptake.     

Sensitivity of Na-coupled d-glucose uptake, Mg-ATPase and sucrase to perturbations of the fluidity of brush-border membrane vesicles induced by n-aliphatic alcohols

The aim of our work is to show the importance of the role of hydrophobic bonds in maintaining Mg²⁺-ATPase or sucrase activity and Na⁺-coupled d-glucose uptake normal for the brush border of rat enterocytes. The activity of the two enzymes and the d-glucose uptake were therefore measured under the action of n-aliphatic alcohols and related to the fluidity determined by ESR. Three concentrations were used for the first eight alcohols, those of octanol being about 1500-times lower than those of methanol. For each alcohol the d-glucose uptake and the fluidity were linear functions of the logarithm of the concentration, the linear regressions being practically parallel and equidistant. The concentrations (C) of the eight alcohols inhibiting the d-glucose uptake by 80% were similar to those increasing the membrane fluidity by 3%. The linear relationship which existed in both cases between log 1 / C and log P, P being octanol / water partition coefficients of the alcohols, was evidence of great sensitivity to the hydrophobic effect of the alcohols. Only the first alcohols, however, produced any notable inhibition of Mg²⁺-ATPase and sucrase. Hydrophobic bonds are thus shown to have little influence in maintaining the activity of Mg²⁺-ATPase and sucrase, but they modulate the Na⁺-coupled d-glucose uptake.     

The combined effects of blue light and dilution rate on lipid class and fatty acid composition of <Emphasis Type="Italic">Tisochrysis lutea</Emphasis>

The lipid class and the fatty acid compositions of microalgae highly influence bivalve larval and post-larval development. Light is an essential environmental factor for microalgal culture, and quantity and quality of light may induce changes in the biochemical composition of the algae. The objective of this study was to investigate the effect of light spectrum (blue vs. white light) on lipid class and fatty acid compositions of Tisochrysis lutea cultured in a chemostat. Two different dilution rates (D) were assayed for each light spectrum: 0.2 and 0.7 day^?1. Triacylglycerol (TAG), sterol, and hydrocarbon (HC) content increased sharply at low D. The proportion of alkenones was significantly reduced under blue light. Polyunsaturated fatty acids (PUFA), and particularly n-3 PUFA, content in phospholipids (PL) increased under blue light compared to white light at low D. Thus, blue light raised 22:6(n-3) levels in total lipids of T. lutea at low D. The cultivation of T. lutea in a chemostat at low D under blue light may improve nutritional value as feed for bivalve larvae by modifying the PUFA profile, especially increasing 22:6(n-3).     

Evolution of winter molting strategies in European and North American migratory passerines

Molt is critical for birds as it replaces damaged feathers and worn plumage, enhancing flight performance, thermoregulation, and communication. In passerines, molt generally occurs on the breeding grounds during the postbreeding period once a year. However, some species of migrant passerines that breed in the Nearctic and Western Palearctic regions have evolved different molting strategies that involve molting on the overwintering grounds. Some species forego molt on the breeding grounds and instead complete their prebasic molt on the overwintering grounds. Other species molt some or all feathers a second time (prealternate molt) during the overwintering period. Using phylogenetic analyses, we explored the potential drivers of the evolution of winter molts in Nearctic and Western Palearctic breeding passerines. Our results indicate an association between longer photoperiods and the presence of prebasic and prealternate molts on the overwintering grounds for both Nearctic and Western Palearctic species. We also found a relationship between prealternate molt and generalist and water habitats for Western Palearctic species. Finally, the complete prealternate molt in Western Palearctic passerines was linked to longer days on the overwintering grounds and longer migration distance. Longer days may favor the evolution of winter prebasic molt by increasing the time window when birds can absorb essential nutrients for molt. Alternatively, for birds undertaking a prealternate molt at the end of the overwintering period, longer days may increase exposure to feather‐degrading ultra‐violet radiation, necessitating the replacement of feathers. Our study underlines the importance of the overwintering grounds in the critical process of molt for many passerines that breed in the Nearctic and Western Palearctic regions.     

Efficient Agrobacterium-mediated transformation and recovery of transgenic plants from pear (Pyrus communis L.)

An efficient and reproducible method was established for genetic transformation of one pear variety (Conferénce) usingAgrobacterium tumefaciens-mediated gene transfer. Wounded leaves of in vitro micropropagated plants were cocultivated with the disarmed strain EHA101 harbouring the binary vector pFAJ3000 carrying the chimaericnptII andgus genes. The protocol included a 3–6 month dark period on a regeneration medium solidified with gelrite, which contained 100 mg/l kanamycin. Up to 42% of inoculated leaves produced transformed buds or bud clusters. Expression, presence and integration of transgenes was confirmed by a histochemical test, polymerase chain reaction and Southern blot hybridisation, respectively. The transgenec plants could be successfully acclimatized in the glasshouse. This transformation procedure was also successfully applied to two other pear varieties, namely Doyenné du Cornice and Passe-Crassane, albeit at much lower transformation rates.     

Modulation of the Suppressor of fused protein regulates the Hedgehog signaling pathway in Drosophila embryo and imaginal discs

The Suppressor of fused (Su(fu)) protein is known to be a negative regulator of Hedgehog (Hh) signal transduction in Drosophila imaginal discs and embryonic development. It is antagonized by the kinase Fused (Fu) since Su(fu) null mutations fully suppress the lack of Fu kinase activity. In this study, we overexpressed the Su(fu) gene in imaginal discs and observed opposing effects depending on the position of the cells, namely a repression of Hh target genes in cells receiving Hh and their ectopic expression in cells not receiving Hh. These effects were all enhanced in a fu mutant context and were suppressed by cubitus interruptus (Ci) overexpression. We also show that the Su(fu) protein is poly-phosphorylated during embryonic development and these phosphorylation events are altered in fu mutants. This study thus reveals an unexpected role for Su(fu) as an activator of Hh target gene expression in absence of Hh signal. Both negative and positive roles of Su(fu) are antagonized by Fused. Based on these results, we propose a model in which Su(fu) protein levels and isoforms are crucial for the modulation of the different Ci states that control Hh target gene expression.