Musings on the wanderer: what's new in our understanding of vago-vagal reflexes? I. Morphology and topography of vagal afferents innervating the GI tract

An understanding of the events initiating vago-vagal reflexes requires knowledge of mechanisms of transduction by vagal afferents. Such information presumes an understanding of receptor morphology and location. Anatomic studies have recently characterized two types of vagal afferents, both putative mechanoreceptors distributed in gastrointestinal (GI) smooth muscle. These two receptors are highly specialized in that they 1) are morphologically distinct, 2) have different smooth muscle targets, 3) form complexes with dissimilar accessory cells, and 4) vary in their regional distributions throughout the GI tract. By comparison, information on the architecture and regional distributions of other classes of vagal afferents, notably chemoreceptors, has only begun to accumulate. Progress on the study of the two mechanoreceptors, however, illustrates general principles and delineates experimental issues that may apply to other submodalities of vagal afferents. By extension from morphological and physiological observations on the two species of smooth muscle endings, it is reasonable to hypothesize that additional classes of vagal receptors are also differentiated morphologically and that they vary in structure, accessory cells, regional distributions, and other features. A full appreciation of vago-vagal reflexes will require thorough structural and regional analyses of each of the types of vagal receptors within the GI tract.     

Musings on the wanderer: what's new in our understanding of vago-vagal reflexes?: II. Integration of afferent signaling from the viscera by the nodose ganglia

To understand vago-vagal reflexes, one must have an appreciation of the events surrounding the encoding, integration, and central transfer of peripheral sensations by vagal afferent neurons. A large body of work has shown that vagal afferent neurons have nonuniform properties and that distinct subpopulations of neurons exist within the nodose ganglia. These sensory neurons display a considerable degree of plasticity; electrophysiological, pharmacological, and neurochemical properties have all been shown to alter after peripheral tissue injury. The validity of claims of selective recordings from populations of neurons activated by peripheral stimuli may be diminished, however, by the recent demonstration that stimulation of a subpopulation of nodose neurons can enhance the activity of unstimulated neuronal neighbors. To better understand the neurophysiological processes occurring after vagal afferent stimulation, it is essential that the electrophysiological, pharmacological, and neurochemical properties of nodose neurons are correlated with their sensory function or, at the very least, with their specific innervation target.     

Musings on the wanderer: what's new in our understanding of vago-vagal reflexes? V. Remodeling of vagus and enteric neural circuitry after vagal injury

The vago-vagal reflexes mediate a wide range of digestive functions such as motility, secretion, and feeding behavior. Previous articles in this series have discussed the organization and functions of this important neural pathway. The focus of this review will be on some of the events responsible for the adaptive changes of the vagus and the enteric neutral circuitry that occur after vagal injury. The extraordinary plasticity of the neural systems to regain functions when challenged with neural injury will be discussed. In general, neuropeptides and transmitter-related enzymes in the vagal sensory neurons are downregulated after vagal injury to protect against further injury. Conversely, molecules previously absent or present at low levels begin to appear or are upregulated and are available to participate in the survival-regeneration process. Neurotrophins and other related proteins made at the site of the lesion and then retrogradely transported to the soma may play an important role in the regulation of neuropeptide phenotype expression and axonal growth. Vagal injury also triggers adaptive changes within the enteric nervous system to minimize the loss of gastrointestinal functions resulting from the interruption of the vago-vagal pathways. These may include rearrangement of the enteric neural circuitry, changes in the electrophysiological properties of sensory receptors in the intramural neural networks, an increase in receptor numbers, and changes in the affinity states of receptors on enteric neurons.     

Musings on the wanderer: what's new in our understanding of vago-vagal reflex? IV. Current concepts of vagal efferent projections to the gut

Vagal efferents, consisting of distinct lower motor and preganglionic parasympathetic fibers, constitute the motor limb of vagally mediated reflexes. Arising from the nucleus ambiguus, vagal lower motor neurons (LMN) mediate reflexes involving striated muscles of the orad gut. LMNs provide cholinergic innervation to motor end plates that are inhibited by myenteric nitrergic neurons. Preganglionic neurons from the dorsal motor nucleus implement parasympathetic motor and secretory functions. Cholinergic preganglionic neurons form parallel inhibitory and excitatory vagal pathways to smooth muscle viscera and stimulate postganglionic neurons via nicotinic and muscarinic receptors. In turn, the postganglionic inhibitory neurons release ATP, VIP, and NO, whereas the excitatory neurons release ACh and substance P. Vagal motor effects are dependent on the viscera's intrinsic motor activity and the interaction between the inhibitory and excitatory vagal influences. These interactions help to explain the physiology of esophageal peristalsis, gastric motility, lower esophageal sphincter, and pyloric sphincter. Vagal secretory pathways are predominantly excitatory and involve ACh and VIP as the postganglionic excitatory neurotransmitters. Vagal effects on secretory functions are exerted either directly or via release of local mediators or circulating hormones.     

Assessment of the efficacy of parasiticides for the control of tick infection in dogs under field conditions: what's new?

For their biological and ecological characteristics, ticks are vectors of the widest variety of pathogens causing tick-borne diseases (TBDs). Little information is available about the ways in which time spent by ticks to feed on hosts, transmission times and TBD prevention are related and it is exclusively limited to laboratory reports on adult stages. In particular, the time required by immature stages to transmit pathogens has not been determined for most TBDs. Considering their importance for animal and human health, effective control of immature ticks is advisable to reduce the damage ticks cause. Recently, the efficacy of a combination of imidacloprid 10%/permethrin 50% was compared with that of fipronil 10%/S-methoprene 9% against ticks when administered to naturally infected dogs. A semi-quantitative method was used to assess the methodological parameters to calculate drug efficacy on immature stages. On adult ticks, the efficacy of both products was high and overall very similar, whereas for the immature stages the combination of imidacloprid 10% and permethrin 50% had a higher efficacy than fipronil 10% and methoprene 9% throughout the observation period (statistically significant difference on day + 28 only). The semi-quantitative method proposed for the evaluation of immature stages can be considered a useful tool for calculating the efficacy of a drug in the field. Due the important role of immatures in the spread of TBDs, the immature tick load should be calculated to assess the efficacy of acaricidal products both under laboratory and field conditions.     

Value of endoscopic retrograde cholangiopancreatography-guided brushings in preoperative assessment of pancreaticobiliary strictures: what's new?

Brush cytology plays a prominent role in confirming the presence of extrahepatic biliary tract malignancy. However, its value is limited by its relatively low and widely variable sensitivity values. Various factors seem to influence the accuracy of cytologic diagnosis and are attributed to sampling, technical and interpretation errors. Ancillary methods, such as immunocytochemistry, flow cytometry, image analysis, fluorescence in situ hybridization (FISH) and the newly discovered method of global analysis of gene expression are helpful in resolving cases with inconclusive cytology and are vigorously investigated for their value in assessing the expression of novel tumor markers for the diagnosis and prognosis of pancreatic and bile duct carcinomas. However, their routine use in clinical practice remains in doubt. To increase the sensitivity of brush cytology and strengthen its role in the preoperative assessment of patients with pancreaticobiliary malignancies, the following are of the utmost importance: improvement of current sampling and cytopreparation techniques, introduction of a uniform system for reporting epithelial abnormalities based on strict and clearly distinct morphologic criteria for each pathologic entity and incorporation of experience and knowledge derived from standard cytologic methods and novel diagnostic technologies in clinical practice without compromising the high specificity associated with brush cytology.     

The foraging behavior of honeybees on hairy vetch. III. — Differences in the vetch

Summary The time required for each of 50 honeybees to forage from a hairy vetch blossom, and the time required for each bee that tripped blossoms to trip a different blossom was measured three times each in two fields. There were highly significant differences in the speed with which bees tripped and foraged from blossoms in the two fields. It appeared that the blossoms in one field were easier to trip than the blossoms in the other. The bees spent less time foraging from the blossoms in the field in which tripping was most rapid, probably because there was less nectar in the blossoms in that field than in the other field. The bees that did not trip blossoms foraged from blossoms more rapidly than the bees that did trip the blossoms. After all known sources of variation had been removed there was a highly significant correlation between the times required for bees to trip and to forage from blossoms; this is interpreted as indicating differences in the efficiency of individual bees. In one of the fields many of the bees foraged through punctures in the blossoms made by carpenter bees. An attempt was made to measure the relationship of the amount of sugar collected by bees per unit time to the attractiveness of competing plants.Published as Technical Contribution No. 4636 from theTexas Agricultural Experiment Station.     

Hidden prenatal malnutrition in the rat: role of β₁-adrenoceptors on synaptic plasticity in the frontal cortex

Moderate reduction in the protein content of the mother's diet (hidden malnutrition) does not alter body and brain weights of rat pups at birth, but leads to dysfunction of neocortical noradrenaline systems together with impaired long-term potentiation and visuo-spatial memory performance. As β?-adrenoceptors and downstream protein kinase signaling are critically involved in synaptic long-term potentiation and memory formation, we evaluated the β?-adrenoceptor density and the expression of cyclic-AMP dependent protein kinase, calcium/calmodulin-dependent protein kinase and protein kinase Fyn, in the frontal cortex of prenatally malnourished adult rats. In addition, we also studied if β?-adrenoceptor activation with the selective β? agonist dobutamine could improve deficits of prefrontal cortex long-term potentiation presenting these animals. Prenatally malnourished rats exhibited half of β?-adrenoceptor binding, together with a 51% and 65% reduction of cyclic AMP-dependent protein kinase α and calcium/calmodulin-dependent protein kinase α expression, respectively, as compared with eutrophic animals. Administration of the selective β? agonist dobutamine prior to tetanization completely rescued the ability of the prefrontal cortex to develop and maintain long-term potentiation in the malnourished rats. Results suggest that under-expression of neocortical β?-adrenoceptors and protein kinase signaling in hidden malnourished rats functionally affects the synaptic networks subserving prefrontal cortex long-term potentiation. β?-adrenoceptor activation was sufficient to fully recover neocortical plasticity in the PKA- and calcium/calmodulin-dependent protein kinase II-deficient undernourished rats, possibly by producing extra amounts of cAMP and/or by recruiting alternative signaling cascades.     

Polynuclear chromium(III) carboxlylates: Part 2. Chromium(III) acetate — what's in it?

Chromium(III) acetate has been widely used in industry for decades. The commercial material is an ill-defined substance, which represents a large number of compounds having different compositions, physical properties and appearances. Several samples of Cr(III) acetate, from various commercial sources were examined by ion-exchange chromatography. All the samples were found to contain several species such as [Cr₃O(O₂CCH₃)₆(H₂O)₃]⁺ and other positively charged purple complexes. They also contain various amounts of the neutral violet complex [Cr₈(OH)₈(O₂CCH₃)₁₆] (1) which crystallizes upon slow evaporation of its aqueous solution. 1 is a cyclic octanuclear complex with hydroxo and acetate ligands bridging the adjacent Cr(III) ions. The structure of a well-defined Cr(III) acetate, namely, [Cr(H₂O)₆](O₂CCH₃)₃ (2) has been determined crystallographically and its decomposition products were examined by ion-exchange chromatography. Compound 2 decomposes under ambient conditions, releasing acetic acid and water producing neutral and charged polynuclear Cr(III) complexes.     

Towards the understanding of tetrahydroquinolines action in Aedes aegypti: larvicide or adulticide?

Aedes aegypti is an important vector of arboviruses such as dengue, yellow fever, chikungunya and Zika. Among the various types of insecticides used to combat this vector, the insect growth regulators have been developed and recommended for control of their larvae. In this work compounds with proven regulatory action, tetrahydroquinolines will be studied. These regulators act on the hormones responsible for the insect development. Ecdysone, one of the main hormones involved in this process has a specific receptor (EcR), where tetrahydroquinolines derivatives can bind, disrupting the normal action of this hormone, because they have structure similar to hormone 20-hydroxyecdysone (20E). In addition, studies show that this class of compounds interacts strongly in the potassium channel activated by calcium (BK channel). Thus, the goal is to study the action of compounds (tetrahydroquinolines) as insecticides and evaluate their larvicidal action (action on the ecdysone receptor) or adulticide (action on the BK channel) through homology modelling techniques, molecular docking and molecular dynamics simulations and aiming to propose a compound that presents both actions (larvicide / adulticide).