Previous studies have demonstrated that the hypothalamus regulates neuroendocrine and autonomic function and behavior. Within the hypothalamus, the paraventricular nucleus (PVN) is an integratory node that contains neurons associated with the control of neuroendocrine and autonomic responses. The PVN also has one of the highest density of blood vessels within the brain. Alterations of normal PVN angiogenesis by dexamethasone could potentially result in long-term modifications of brain and endocrine functions.
Timed-pregnant Sprague Dawley female rats received DEX on gestational days 18-21 and the resulting progeny were sacrificed at Postnatal Day (PND) 0, 4, 14, and 21. A tomato lectin, Lycopersicon Esculentum labeled with DyLight594 was used to stain blood vessels in the PVN and scanning confocal microscopy was used to analyze the experimental brains for PVN blood vessel density
Analysis of data using a 3-way analysis of variance (ANOVA) with age, sex and treatment as main factors, showed a significant age effect in vascular density. Analysis of female data by 2-way ANOVA demonstrated a significant effect of age, but no treatment or interaction effects. Post-hoc analysis shows significant differences at PND 2, 4, 14, and 21 compared to PND0. A Student‘s t-test of a planned comparison on PND2 showed a significant reduction by DEX treatment (p < 0.05). Analysis of data from females, using 2-way ANOVA demonstrated a significant effect of age, but no treatment or interaction effects. Post-hoc analysis shows significant differences at PND 2, 4, 14, and 21 compared to PND0. A planned comparison at PND 2 using Student’s t-test indicated a significant reduction by dex treatment.
The results of these studies demonstrate that there is significant postnatal angiogenic programming and that the vascular density of the PVN is altered by prenatal dexamethasone administration at PND2. The time-course shows developmental fluctuations in vessel density that may prove to be physiologically significant for normal brain function and developmental programming of brain and behavior.
Background: Phosphatase and TENsin (PTEN) homolog is a negative regulator that takes part in IIS (insulin/insulin-like signaling) and Egfr (epidermal growth factor receptor) activation in Drosophila melanogaster. IIS and Egfr signaling events are also involved in the developmental process of queen and worker differentiation in honey bees (Apis mellifera). Here, we characterized the bee PTEN gene homologue for the first time and begin to explore its potential function during bee development and adult life.
Results: Honey bee PTEN is alternatively spliced, resulting in three splice variants. Next, we show that the expression of PTEN can be down-regulated by RNA interference (RNAi) in the larval stage, when female caste fate is determined. Relative to controls, we observed that RNAi efficacy is dependent on the amount of PTEN dsRNA that is delivered to larvae. For larvae fed queen or worker diets containing a high amount of PTEN dsRNA, PTEN knockdown was significant at a whole-body level but lethal. A lower dosage did not result in a significant gene down-regulation. Finally, we compared same-aged adult workers with different behavior: nursing vs. foraging. We show that between nurses and foragers, PTEN isoforms were differentially expressed within brain, ovary and fat body tissues. All isoforms were expressed at higher levels in the brain and ovaries of the foragers. In fat body, isoform B was expressed at higher level in the nurse bees.
Conclusion: Our results suggest that PTEN plays a central role during growth and development in queen- and worker-destined honey bees. In adult workers, moreover, tissue-specific patterns of PTEN isoform expression are correlated with differences in complex division of labor between same-aged individuals. Therefore, we propose that knowledge on the roles of IIS and Egfr activity in developmental and behavioral control may increase through studies of how PTEN functions can impact bee social phenotypes.
In vitro rearing is an important and useful tool for honey bee (Apis mellifera L.) studies. However, it often results in intercastes between queens and workers, which are normally are not seen in hive-reared bees, except when larvae older than three days are grafted for queen rearing. Morphological classification (queen versus worker or intercastes) of bees produced by this method can be subjective and generally depends on size differences. Here, we propose an alternative method for caste classification of female honey bees reared in vitro, based on weight at emergence, ovariole number, spermatheca size and size and shape, and features of the head, mandible and basitarsus. Morphological measurements were made with both traditional morphometric and geometric morphometrics techniques. The classifications were performed by principal component analysis, using naturally developed queens and workers as controls. First, the analysis included all the characters. Subsequently, a new analysis was made without the information about ovariole number and spermatheca size. Geometric morphometrics was less dependent on ovariole number and spermatheca information for caste and intercaste identification. This is useful, since acquiring information concerning these reproductive structures requires time-consuming dissection and they are not accessible when abdomens have been removed for molecular assays or in dried specimens. Additionally, geometric morphometrics divided intercastes into more discrete phenotype subsets. We conclude that morphometric geometrics are superior to traditional morphometrics techniques for identification and classification of honey bee castes and intermediates.