Muscle-specific growth hormone receptor (GHR) overexpression induces hyperplasia but not hypertrophy in transgenic zebrafish

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of thyroid hormone T3 on Myosin-Va expression in the central nervous system

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ultrastructural modifications in the venom glands of workers of Apis mellifera L. (Hymenoptera : Apidae) promoted by topical application of juvenile hormone

The present study analyzed, the influence of the treatment with juvenile hormone on the ultrastructure of Apis mellifera L. workers' venom glands. Newly emerged workers received topical application of 1 mu l of juvenile hormone diluted in hexane, in the concentration of 2 mu g/mu l. Two controls were used; one control received no treatment (group C1) and other received topical application of 1 mu l of hexane (group C2). The aspect of the glandular cells, in not treated newly emerged workers, showed that they are not yet secreting actively. Cellular modifications happened according to the worker age and to the glandular area considered. The most active phase of the gland happened from the emergence to the 14th day. At the 25th day the cells had already lost their secretory characteristic, being the distal area the first to suffer degeneration. The treatment with juvenile hormone and hexane altered the temporal sequence of the glandular cycle, forwarding the secretory cycle and degeneration of the venom gland.

Alterations induced by the juvenile hormone in glandular cells of the Apis mellifera venom gland: Applications on newly emerged workers (Hymenoptera, Apidae)

Histological and histochemical analyses were carried out in order to evaluate the influence of the topical application of a synthetic juvenile hormone on the secretory cycle and degeneration of the venom gland of Apis mellifera. Newly emerged workers received the topical application of synthetic hormone and the results were compared to the normal development of the secretory cycle in virgin and mated queens. The first worker group received the juvenile hormone diluted in hexane (2 mu g/mu L), the second received only mu L of hexane, and the third did not receive any kind of application. After the application the workers were returned to the colony and collected at the ages of 14 and 25 days of adult life. The groups with virgin queens and the other with mated queens, did not receive the treatment. The results show that the individuals treated with juvenile hormone and with pure hexane presented differences in the histological and cytochemical aspects of the secretory cells of the venom gland. The data indicate that both the juvenile hormone and hexane accelerate the activity of the secretory cycle and the degeneration of the venom gland; however, the juvenile hormone proved to be more effective than hexane. (c) 2006 Elsevier Ltd. All rights reserved.

Forest fragment size and microhabitat effects on palm seed predation

The establishment of plant species depends crucially on where the seeds are deposited. However, since most studies have been conducted in continuous forests, not much is known about the effects of forest fragmentation on the maintenance of abiotic and biotic characteristics in microhabitats and their effects on seed survival. in this study, we evaluated the effects of forest fragmentation on the predation upon the seeds of the palm Syagrus romanzoffiana in three microhabitats (interior forest, forest edge and gaps) in eight fragments of semi-deciduous Atlantic forest ranging in size from 9.5 ha to 33,845 ha in southeastern Brazil. Specifically, we examined the influence of the microhabitat structure, fauna and fragment size on the pattern of seed predation. Fragments < 100 ha showed similar abiotic and biotic characteristics to those of the forest edge, with no seed predation in these areas. Forest fragments 230-380 ha in size did not present safe sites for S. romanzoffiana seed survival and showed high seed predation intensity in all microhabitats evaluated. In fragments larger than 1000 ha, the seed predation was lower, with abiotic and biotic differences among gaps, interior forests and forest edges. In these fragments, the survival of S. romanzoffiana seeds was related to squirrel abundance and interior forest maintenance. Based on these results, we concluded that there are no safe sites for S. romanzoffiana seed establishment in medium- and small-sized fragments as result of the biotic and abiotic pressure, respectively We suggest that on these forest fragments, management plans are needed for the establishment of S. romanzoffiana, such as interior forest improvement and development in small-sized sites in order to minimize the edge effects, and on medium-sized fragments, we suggest post-dispersal seed protection in order to avoid seed predation by vertebrates. our findings also stress the importance of assessing the influence of forest fragmentation on angiosperm reproductive biology as part of the effective planning for the management of fragmented areas. (c) 2006 Elsevier Ltd. All rights reserved.

Morphomettic changes on honeybee Apis mellifera L. workers fat body cells after juvenile hormone topic application at emergence

The effect of topical application of juvenile hormone (JH) over the lifetime of worker bees was evaluated in Apis mellifera, by measuring the area of the two cell types, trophocytes and oenocytes, found in the fat body. Topical application of 1 mu l of a 1 mu g/mu l solution of JH in acetone to the abdomens of newly emerged workers produced an increase in cell size, in both types of cell of 5-day-old treated workers in relation to the untreated control. The treatment was more effective on the oenocytes, since there were significant differences compared to the averages of the treatments and the interaction of the treatments with the age of the workers. The developmental pattern seemed to differ from the treated group. However, subsequent effects were probably dependent on different, natural variations in hormonal levels. (c) 2007 Elsevier Ltd. All rights reserved.

Effect of topical application of juvenile hormone (JH) in honeybee worker larvae on the development of the Dufour's and Koschewnikow's glands

In order to investigate the action of the juvenile hormone (JH) on honeybee caste differentiation two exocrine glands, Koschewnikow and Dufour glands, were chosen for study. Two combs (I & II) were taken from a single posture of a queen to use for this research. In comb I the larvae were treated with a topical application of JH in Acetone, and those from the comb II (control group) received only Acetone. Immediately after the emergence of the workers, their glands were dissected and prepared for microscopic measurements. The results showed cell area reduction in the Koschewnikow gland induced by the JH application. The results for the Dufour gland displayed taller epithelial cells with the JH application. The difference in glandular responses to the JH relates to gland function, hormone targets, and individual homeostasis.

Granivorous birds as potentially important post-dispersal seed predators in a Brazilian forest fragment

In tropical forests, rodents exert a prominent role as post-dispersal seed predators, while other vertebrates apparently have a minor effect on seed predation. In some forest fragments in southeast Brazil, however, the density of rodents is unusually low, whereas terrestrial granivorous birds are abundant. In this study, we used seeds of a second-growth tree (Croton priscus, Euphorbiaceae) to investigate experimentally the relative importance of rodents and birds as seed predators in a forest fragment. We also estimated the density of terrestrial granivorous birds and trapped small mammals. Results indicate that, as a consequence of decreased rodent population and increased bird abundance, the latter are at least as important as the former as the main post-dispersal seed predators of C priscus. We interpret such apparent imbalance in the interaction between C priscus and their seed predators as a possible consequence of forest fragmentation.

Massive seed predation of Pseudobombax grandiflorum (Bombacaceae) by parakeets Brotogeris versicolurus (Psittacidae) in a forest fragment in brazil

Here we report massive seed predation of Pseudobombax grandiflorum (Bombacaceae) by Botogeris versicolurus (Psittacidae) in a forest fragment in Brazil. The intensity of seed predation was very high when compared to other studies in continuous forest, perhaps resulting from a scarcity of resources in such areas. This scarcity may limit the range of parrot's diet to a few plant species. It suggests that studies of Psittacidae seed predation may be important for conservation of some plants in fragments.

Associations of Forest Cover, Fragment Area, and Connectivity with Neotropical Understory Bird Species Richness and Abundance

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Factors affecting seed predation of Eriotheca gracipiles (Bombacaceae) by parakeets in a cerrado fragment

Psittacids are important pre-dispersal seed predators. However, little is known about the parameters that may determine seed predation rates by these birds, such as plants' characteristics and microhabitat. Eriotheca gracilipes (Bombacaceae) is a semi-deciduous tree widely distributed in the Brazilian cerrado. The fruits are dehiscent pods and the seeds are wind-dispersed. Some individuals lose their leaves during the fruiting season, getting very conspicuous. Here we tested the hypothesis that the absence of leaves in E. gracilipes during the fruiting season may increase pre-dispersal seed predation by psittacids. We also tested the hypotheses that (1) seed predation intensity increases with increasing plant size and (2) number of fruits, (3) seed predation decreases with the increasing number of conspecific plants in a range of 15 m, and (4) seed predation intensity is lower in plants with higher vegetation cover over their crowns. The small parakeet Brotogeris versicolurus was the only species observed preying upon the seeds of E. gracilipes. The percentage of fruits damaged by the parakeets ranged from 0 to 100% (66.98 +/- 43.11%, n = 72) among the different plants. Our data give weak support to the hypothesis that the absence of leaves may facilitate plants and/or fruits detection by the parakeets. However, seed predation intensity was significantly affected by crop size. The hypothesis that conspecific fruiting plants surrounding the studied individuals may reduce predation rate was not supported. Nevertheless, trees without higher vegetation cover over their crowns were significantly affected by increased seed predation. This suggests that seed predation by parakeets can be a potential selective factor influencing fruit crop sizes in E. gracilipes. (c) 2007 Elsevier Masson SAS. All rights reserved.

Structure and dynamics of a Cariniana estrellensis (Lecythidaceae) population in a fragment of Atlantic Forest in Minas Gerais, Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of physical training on serum and pituitary growth hormone contents in diabetic rats

The present study investigated the effects of moderate physical training on some of the parameters in the GH-IGF axis in experimental diabetic rats. Male Wistar rats were allocated into the following groups: sedentary control, trained control, sedentary diabetic, trained diabetic. Diabetes was induced by alloxan (32 mg/kg, b.w. iv). The physical training protocol consisted of 1 h swimming session/day, 5 days/week for 8 weeks supporting a load corresponding to 90% of maximal lactate steady state. After the experimental period, blood was collected to measure serum glucose, insulin, triglycerides, albumin, insulin-like growth factors-I (IGF-I), and growth hormone (GH). Pituitary gland was removed for GH quantification. Diabetes increased blood glucose and triglycerides and decreased insulin, IGF-I, serum and pituitary GH. Physical training decreased glucose and triglycerides, and also counteracted the reduction of serum IGF-I in diabetic rats. In conclusion, physical training recovered serum IGF-I showing no alteration of serum or pituitary GH levels.

Diet of buffy tufted-eared marmosets (Callithrix aurita) in a forest fragment in southeastern Brazil

The feeding ecology of the Atlantic forest marmosets (Callithrix spp.) in southeastern Brazil is poorly known, and few studies have focused on buffy tufted-eared marmosets, Callithrix aurita. We determined the food items and investigated the seasonal variation in the diet of a group of four Callithrix aurita in a 17-ha semideciduous forest fragment in southern Minas Gerais State, Brazil. We recorded daily feeding activities between October 1994 and September 1995 using scan sampling at 5-min intervals. The marmosets devoted feeding rime to gums (50.5%), fruits (11%), and animal prey (38.5%) in a fetal of 499 records. Plant resources comprised 27 species from 16 families. They used Acacia paniculata (Mimosoideae, Leguminosae), the main gum source (82%), year-round Maclura tinctoria (Moraceae) was the fruit species that they consumed most (22%). The marmosets preyed on caterpillars (33%), katydids (5%), and homopterans (4%). Feeding on fruits varied seasonally and was inversely related to gum feeding. Consumption of animal prey remained constant over the year. The wide and year-round dependence on gum suggests that Acacia may play a critical role in marmoset persistence in forest fragments.