Heliconia acuminata reproductive success is independent of local floral density

Reproductive plants in tropical forests are patchily distributed, with some in large aggregations of reproductive consepecifics while others are relatively isolated. This variation in floral density is hypothesized to have a major effect on plant reproductive success, since individuals in higher density neighborhoods can attract more or higher quality pollinators. We experimentally tested this hypothesis with populations of the understory herb Heliconia acuminata in central Amazonia. We created replicated plots in which reproductive plant density spanned the range of naturally occurring floral neighborhood size, then measured three surrogates of plant fitness in focal plants in each array. There was no significant difference between any of the three floral neighborhood treatments in total seed production, fruit set, or the number of seeds produced per fruit. Pollinator visitation rates to plants in all treatments were extremely low, with many plants not visited at all during the observation period. This could be because H. acuminata's hummingbird pollinators are unable to find the widely scattered reproductive plants, however this hypothesis appears unlikely. Instead, natural flowering plant densities may simply be below the threshold value at which neighborhood effects become important, even in "high-density" aggregations. Nutrient limitation, selective fruit abortion, and reproduction via male rather than female function may also be playing a role. We argue the absence of neighborhood effects may be a general phenomenon in central Amazonian forests, though additional experiments with other plant-pollinator systems are needed to determine the extent to which this hypothesis is supported.

QUALITY OF PROCESSING TOMATO FRUITS IN COMPETITION WITH Solanum americanum

ABSTRACT Five experiments were conducted to evaluate the hypothesis that Solanum americanum density and time of coexistence affect the quality of processing tomato fruit. The tomato crop was established using either the direct drilling or the transplanting technique. The factors evaluated consisted of weed density (from 0 up to 6 plants m-2) and time of weed interference (early bloom stage, full flowering stage, fruit filling, and harvest time). The effects of competition on tomato fruit quality were analysed using a multiple model. Tomato variables evaluated included industrial fruit types (which depended on ripeness and disease infection) and soluble solids level(obrix). Tomato fruit quality is dependent on the factors tested. Under low densities (< 6 plants m-2) of S. americanum there was a small impact on the quality of the tomato fruits. The percentage of grade A (mature fruit with red color and without pathogen infection) tomato fruits is the variable most affect by the independent variables. The impact of these independent variables on the percentage of grade C (green and/or with more than 15% disease infection) tomato yield was of smaller magnitude and in an inverse trend as the observed for grade A. The level of soluble solids was influenced by the weed interference on only two experiments, but the impact was of small magnitude. The impact of the results on current and future crop management practices is discussed.

Impaired beta-adrenergic response and decreased L-type calcium current of hypertrophied left ventricular myocytes in postinfarction heart failure

Infarct-induced heart failure is usually associated with cardiac hypertrophy and decreased ß-adrenergic responsiveness. However, conflicting results have been reported concerning the density of L-type calcium current (I Ca(L)), and the mechanisms underlying the decreased ß-adrenergic inotropic response. We determined I Ca(L) density, cytoplasmic calcium ([Ca2+]i) transients, and the effects of ß-adrenergic stimulation (isoproterenol) in a model of postinfarction heart failure in rats. Left ventricular myocytes were obtained by enzymatic digestion 8-10 weeks after infarction. Electrophysiological recordings were obtained using the patch-clamp technique. [Ca2+]i transients were investigated via fura-2 fluorescence. ß-Adrenergic receptor density was determined by [³H]-dihydroalprenolol binding to left ventricle homogenates. Postinfarction myocytes showed a significant 25% reduction in mean I Ca(L) density (5.7 ± 0.28 vs 7.6 ± 0.32 pA/pF) and a 19% reduction in mean peak [Ca2+]i transients (0.13 ± 0.007 vs 0.16 ± 0.009) compared to sham myocytes. The isoproterenol-stimulated increase in I Ca(L) was significantly smaller in postinfarction myocytes (Emax: 63.6 ± 4.3 vs 123.3 ± 0.9% in sham myocytes), but EC50 was not altered. The isoproterenol-stimulated peak amplitude of [Ca2+]i transients was also blunted in postinfarction myocytes. Adenylate cyclase activation through forskolin produced similar I Ca(L) increases in both groups. ß-Adrenergic receptor density was significantly reduced in homogenates from infarcted hearts (Bmax: 93.89 ± 20.22 vs 271.5 ± 31.43 fmol/mg protein in sham myocytes), while Kd values were similar. We conclude that postinfarction myocytes from large infarcts display reduced I Ca(L) density and peak [Ca2+]i transients. The response to ß-adrenergic stimulation was also reduced and was probably related to ß-adrenergic receptor down-regulation and not to changes in adenylate cyclase activity.

Early life, current socioeconomic position and serum lipids in young adulthood of participants in a cohort study initiated in 1978/1979

The association between socioeconomic position (SEP) and serum lipids has been little studied and the results have been controversial. A total of 2063 young adults born in 1978/79 were evaluated at 23-25 years of age in the fourth follow-up of a cohort study carried out in Ribeirão Preto, SP, Brazil, corresponding to 31.8% of the original sample. Total serum cholesterol (TC), triglycerides, high-density cholesterol (HDL cholesterol) and low-density cholesterol (LDL cholesterol) were analyzed according to SEP at birth and during young adulthood. SEP was classified into tertiles of family income and a cumulative score of socioeconomic disadvantage was created. TC was 11.85 mg/100 mL lower among men of lower SEP in childhood (P < 0.01) but no difference was found in women, whereas it was 8.46 lower among men (P < 0.01) and 8.21 lower among women of lower SEP in adulthood (P < 0.05). Individuals of lower SEP had lower LDL and HDL cholesterol, with small differences between sexes and between the two times in life. There was no association between SEP and triglyceride levels. After adjustment of income at one time point in relation to the other, some associations lost significance. The greater the socioeconomic disadvantage accumulated along life, the lower the levels of TC, LDL and HDL cholesterol (P < 0.05). The socioeconomic gradient of TC and LDL cholesterol was inverse, representing a lower cardiovascular risk for individuals of lower SEP, while the socioeconomic gradient of HDL cholesterol indicated a lower cardiovascular risk for individuals of higher SEP.

Women with primary ovarian insufficiency have lower bone mineral density

The aim of the present study was to assess the prevalence of osteoporosis in a sample of 32 patients with spontaneous primary ovarian insufficiency (POI) in comparison to reference groups of 25 pre- and 55 postmenopausal women. Hip (lumbar) and spinal bone mineral density (BMD) measurements were performed by dual-energy X-ray absorptiometry in the three groups. The median age of POI patients at the time of diagnosis was 35 years (interquartile range: 27-37 years). The mean ± SD age of postmenopausal reference women (52.16 ± 3.65 years) was higher than that of POI (46.28 ± 10.38 years) and premenopausal women (43.96 ± 7.08; P = 0.001) at the time of BMD measurement. Twenty-seven (84.4%) POI women were receiving hormone replacement therapy (HRT) at the time of the study. In the postmenopausal reference group, 30.4% were current users of HRT. Lumbar BMD was significantly lower in the POI group (1.050 ± 0.17 g/cm²) compared to the age-matched premenopausal reference group (1.136 ± 0.12 g/cm²; P = 0.040). Moreover, 22 (68.7%) POI women had low bone density (osteopenia/osteoporosis by World Health Organization criteria) versus 47.3% of the postmenopausal reference group (P = 0.042). In conclusion, the present data indicate that BMD is significantly lower in patients with POI than in age-matched premenopausal women. Also, the prevalence of osteopenia/osteoporosis is higher in POI women than in women after natural menopause. Early medical interventions are necessary to ensure that women with POI will maintain their bonemass.