The influence of melatonin on stress-induced ultramicroscopic changes of the neurons of the supraoptic nuclei of the rat hypothalamus

The aim: to study the effect of melatonin on the ultrastructural state of the supraoptic nuclei of the hypothalamus of rats under immobilization stress.Materials and methods. The experiments were performed on non-linear male white rats weighing 200-220 g. The animals were divided into 3 study series, in each of which the biomaterial was collected at 2 p.m. and at 2 a.m. using electron microscopic method. Long immobilization stress was simulated by keeping rats in special plastic penal cages for 6 hours daily for 7 consecutive days. Melatonin (Sigma, USA, 99.5% purification degree) at a dose of 0.5 mg/kg, in 1.0 ml of solvent (0.9% ethanol solution on physiologic saline) was injected daily, intraperitoneally.Results. When the animals were kept under the standard light regime, the ultrastructural organization of the hypothalamic nuclei at 2 p.m. indicated their low functional activity in comparison with the studies carried out at 2 a.m. Prolonged exposure of rats to immobilization stress was reflected in a significant rearrangement of the ultrastructural organization of supraoptic nuclei of the hypothalamus. The established changes can be considered as a manifestation of neurosecretory activity suppression, a decrease in neurosecretase production by hypothalamic neurons. Melatonin injections against the background of immobilization stress resulted in relative normalization of ultrastructural state of neurons of supraoptic nuclei of the hypothalamus of animals. In particular, studies at 2 a.m. revealed light neurosecretory cells containing a large nucleus, it was pyknotically altered. Karyolema invaginations, euchromatin dominance in the nucleus were observed. Heterogeneous changes were observed on the part of mitochondria. Enlarged tubules of granular endoplasmic reticulum were seen. At the same time, a small number of ribosomes and few hormonal granules were noticeable in neuroplasm. The mentioned picture of neurosecretory cells reflects a relative improvement in their electron microscopic state, which is evidenced by the appearance of neurosecretory granules. However, the ultrastructure of other organelles of the studied neurons indicates a depleted state caused by prolonged immobilization.Conclusions. 1. In animals under standard photoperiod conditions, the structural organization of supraoptic neurons of the hypothalamic nuclei during the nighttime of the experiment reflects the intensity of intracellular synthesizing processes (at 2 a.m.). A decrease in the activity of the structures under study is noted during the daytime. 2. Under immobilization stress, the ultrastructural organization of the above neurons indicates a pronounced disturbance of reactive nature with the signs of decreased functional ability of the structures and the phenomena of edema and destruction during the period of observation. 3. Melatonin injections against the background of immobilization stress led to a relative improvement in the ultrastructural state of the animals’ hypothalamic nuclei neurons, which is evidenced by the appearance of neurosecretory granules. However, the ultrastructure of other organelles of the studied neurons indicated a depleted state caused by prolonged immobilization.

Central Nervous System Associated With Light Perception and Physiological Responses of Birds

Environmental light that animal receives (i.e., photoperiod and light intensity) has recently been shown that it affects avian central nervous system for the physiological responses to the environment by up or downregulation of dopamine and serotonin activities, and this, in turn, affects the reproductive function and stress-related behavior of birds. In this study, the author speculated on the intriguing possibility that one of the proposed avian deep-brain photoreceptors (DBPs), i.e., melanopsin (Opn4), may play roles in the dual sensory-neurosecretory cells in the hypothalamus, midbrain, and brain stem for the behavior and physiological responses of birds by light. Specifically, the author has shown that the direct light perception of premammillary nucleus dopamine-melatonin (PMM DA-Mel) neurons is associated with the reproductive activation in birds. Although further research is required to establish the functional role of Opn4 in the ventral tegmental area (VTA), dorsal raphe nucleus, and caudal raphe nucleus in the light perception and physiological responses of birds, it is an exciting prospect because the previous results in birds support this hypothesis that Opn4 in the midbrain DA and serotonin neurons may play significant roles on the light-induced welfare of birds.

Study of triclabendazole effects on Fasciola hepatica’s life-supporting organs, spines and suckers responsible for stable position of the parasite in the host

The purpose of the research is to study triclabendazole effects on the Fasciola’s life-supporting organs, spines and suckers which are responsible for stable position of the parasite in the host.Materials and methods. The study material was trematodes Fasciola hepatica (Linneus 1758, family Fasciolidae Railliet 1895), which were collected after the action of triclabendazole (fasinex) (chemically 5-chloro-6-(2,3-dichlorophenoxy)-2-methylthiobenzimidazole)on the 7th day after the drug administered at a single dose of 10 mg/kg for the Active Substance in the treatment of ovine fasciolosis. F. hepatica from untreated animals served as control. Mature F. hepatica collected after treatment with triclabendazole, and marita from the control groups were dehydrated in ascending alcohol series for 1–2 days after fixation; then passed through a mixture of chloroform and absolute alcohol (in a ratio of 1:1), and through pure chloroform in two portions for 10–15 minutes. The material was then soaked in a mushy mixture of chloroform and paraffin in a thermostat at 37 °C for 12–18 hours, and in paraffin in a thermostat at 56 °C for 30–45 minutes; and then embedded in paraffin with added wax. The resulting paraffin blocks were broken down into serial sections of 5–7 μm thick, then stained and examined under a light microscope.Results and discussion. Pathomicromorphological analysis of F. hepatica’s spines and suckers, organs that come into adhesive contact with the host organism revealed destructive changes in them after the action of triclabendazole. After the action of triclabendazole on fascioles, the spines look enlarged and swollen, and have a more rounded shape and some changes in color, absorbing eosin in greater concentration. The muscle fibers of the fascioles’ oral and abdominal suckers also look swollen after the action of triclabendazole. Although the musculature of the F. hepatica’s pharynx retained its structure, it has changes. It thickened sharply, which is clearly visible on the transverse and longitudinal sections of the helminths; neurosecretory cells are destroyed, and voids are observed in their place.

A nutrient-responsive hormonal circuit mediates an inter-tissue program regulating metabolic homeostasis in adult Drosophila

Animals maintain metabolic homeostasis by modulating the activity of specialized organs that adjust internal metabolism to external conditions. However, the hormonal signals coordinating these functions are incompletely characterized. Here we show that six neurosecretory cells in the Drosophila central nervous system respond to circulating nutrient levels by releasing Capa hormones, homologs of mammalian neuromedin U, which activate the Capa receptor (CapaR) in peripheral tissues to control energy homeostasis. Loss of Capa/CapaR signaling causes intestinal hypomotility and impaired nutrient absorption, which gradually deplete internal nutrient stores and reduce organismal lifespan. Conversely, increased Capa/CapaR activity increases fluid and waste excretion. Furthermore, Capa/CapaR inhibits the release of glucagon-like adipokinetic hormone from the corpora cardiaca, which restricts energy mobilization from adipose tissue to avoid harmful hyperglycemia. Our results suggest that the Capa/CapaR circuit occupies a central node in a homeostatic program that facilitates the digestion and absorption of nutrients and regulates systemic energy balance.

A local insulin reservoir ensures developmental progression in condition of nutrient shortage in Drosophila

Insulin/IGF signalling (IIS) controls many aspects of development and physiology. In Drosophila, a conserved family of insulin-like peptides (Ilp) is produced by brain neurosecretory cells and exerts systemic functions. Here, we describe the local uptake and storage of Ilps in the Corpora Cardiaca (CC), a group of alpha cell homolog that produces the glucagon-like hormone AKH. Dilp uptake relies on the expression of Impl2, an IGF-BP that accumulates in the CCs. During nutrient shortage, this specific reserve of Ilps is released and activates IIS in a paracrine manner in the prothoracic gland, securing accelerated entry into pupal development through the production of the steroid hormone ecdysone. We therefore uncover a sparing mechanism whereby local Ilp storage and release activates the production of steroids and ensures early developmental progression in adverse food conditions.

Neuroendocrine control of cocoon production in native earthworm Perionyx ceylanensis subjected to seasonal variation

Aim: The aim of the present study was to observe the role of cerebral ganglionic neurosecretory cells (NSCs) during cocoon production in native earthworm species Perionyx ceylanensis subjected to amputation and seasonal variations. Methodology: Histological studies (using Aldehyde Fuchsin and Chrome Alum Haematoxylin Phloxin stain) were carried out on brain NSCs in the two groups of earthworms (Group I and Group II) maintained in earthen culture pots (2L) with cowdung as food. Group I comprised of brain amputed earthworms was subjected to observe the role of brain NSCs in production of cocoon and Group II earthworms subjected to seasonal changes in the cerebral NSCs during cocoon production. Five replications were kept for Group I (1 individual per pot) and Group II (1 pair per pot). Results: Group I debrained earthworms started to lay cocoons from the 31st day following regeneration of cerebral ganglionic type A NSCs. In group II worms the highest neurosecretory activity was registered in the cerebral type A cells, especially during monsoon coinciding with the hike of cocoon generation. Interpretation: Appearance of type A NSCs in regenerated brain and peak of type A neurosecretory cell activity during peak reproductive period of earthworm species (as indicated by peak of cocoon production) indicates the possible role of cerebral type A NSCs in cocoon laying.

Unveiling the sensory and interneuronal pathways of the neuroendocrine connectome in Drosophila

Neuroendocrine systems in animals maintain organismal homeostasis and regulate stress response. Although a great deal of work has been done on the neuropeptides and hormones that are released and act on target organs in the periphery, the synaptic inputs onto these neuroendocrine outputs in the brain are less well understood. Here, we use the transmission electron microscopy reconstruction of a whole central nervous system in the Drosophila larva to elucidate the sensory pathways and the interneurons that provide synaptic input to the neurosecretory cells projecting to the endocrine organs. Predicted by network modeling, we also identify a new carbon dioxide-responsive network that acts on a specific set of neurosecretory cells and that includes those expressing corazonin (Crz) and diuretic hormone 44 (Dh44) neuropeptides. Our analysis reveals a neuronal network architecture for combinatorial action based on sensory and interneuronal pathways that converge onto distinct combinations of neuroendocrine outputs.

THE ORAL SUCKER OF SOME GASTROINTESTINAL TREMATODES: HISTOLOGICAL AND HISTOCHEMICAL RESEARCH

We conducted histological and histochemical studies of the oral sucker of gastrointestinal trematodes of the family Paramphistomatidae, Fischoeder, 1901 living in the rumen of ruminants, namely, Liorchis scotiae, Paramphistomum cervi and Paramphistomum ichikawai. The oral sucker of paramphistomes and the Liorchis scotiae trematode is a complex muscular organ modified into a pharynx-sucker, the muscle complex of which is formed from longitudinal, circular and radial muscle fibers. In the thick pharynx wall, we found secretory cells, single neurosecretory cells and many desmoblastic cells of connective tissue. Histochemical stains showed intense staining with alcian blue, toluidine blue, bromophenol blue and a positive periodic acid Schiff reaction, which indicates the presence of glycosaminoglycans, total proteins and glycoproteins. Due to this structure, the pharynx sucker of gastrointestinal trematodes is involved in capturing food and evacuating its undigested residues from the helminth's body to the outside. In addition, the substances produced by secretory cells of the pharynx carry out a partial chemical treatment of the food consumed by the parasite and protect the parasite from substances that are metabolites of the host tissues and waste products of symbionts and commensals that inhabit the rumen of ruminants. Thus, trophic adaptation of the parasite in its ecological niche, the rumen of polygastric mammals, is ensured.