Ivan Zaletel

The role of gut hormones in appetite regulation (review)

Eating process is an aggregate of complex and different forms of behavior. Its regulation is based on energy homeostasis and appetite control which includes two components: the homeostatic and the hedonistic control. Important signals in appetite regulation are gut-derived hormones. They are produced by enteroendocrine cells in response to nutrient and energy intake, and achieve their effects by influencing brain structures involved in food intake regulation. The key brain structure involved in this process is the hypothalamus. Gut hormones reach the hypothalamus from the circulation or by the vagal nerve via the nucleus of the solitary tract. Among gut peptides, ghrelin is the only orexigenic hormone, leading to an increase in food intake and body weight. All others, such as cholecystokinin, glucagon like peptide-1, oxyntomodulin, peptide tyrosine tyrosine or pancreatic polypeptide, are anorexigenic, leading to decrease in food intake. Also, gut-derived endocannabinoids exert orexigenic effect on appetite. Keeping in mind the growing problem of obesity, the crucial issue when considering gut derived peptides is to understand their mechanisms of acting because of potential role in clinical therapy, and discovering long-lasting gut peptides or their analogues, with no or minimal side effects.

Chronic stress, hippocampus and parvalbumin-positive interneurons: what do we know so far?

Abstract The hippocampus is a brain structure involved in the regulation of hypothalamic-pituitary-adrenal (HPA) axis and stress response. It plays an important role in the formation of declarative, spatial and contextual memory, as well as in the processing of emotional information. As a part of the limbic system, it is a very susceptible structure towards the effects of various stressors. The molecular mechanisms of structural and functional alternations that occur in the hippocampus under chronic stress imply an increased level of circulating glucocorticoids (GCs), which is an HPA axis response to stress. Certain data show that changes induced by chronic stress may be independent from the GCs levels, opening the possibility of existence of other poorly explored mechanisms and pathways through which stressors act. The hippocampal GABAergic parvalbumin-positive (PV+) interneurons represent an especially vulnerable population of neurons in chronic stress, which may be of key importance in the development of mood disorders. However, cellular and molecular hippocampal changes that arise as a consequence of chronic stress still represent a large and unexplored area. This review discusses the current knowledge about the PV+ interneurons of the hippocampus and the influence of chronic stress on this intriguing population of neurons.

Fractal dimension of apical dendritic arborization differs in the superficial and the deep pyramidal neurons of the rat cerebral neocortex

Pyramidal neurons of the mammalian cerebral cortex have specific structure and pattern of organization that involves the presence of apical dendrite. Morphology of the apical dendrite is well-known, but quantification of its complexity still remains open. Fractal analysis has proved to be a valuable method for analyzing the complexity of dendrite morphology. The aim of this study was to establish the fractal dimension of apical dendrite arborization of pyramidal neurons in distinct neocortical laminae by using the modified box-counting method. A total of thirty, Golgi impregnated neurons from the rat brain were analyzed: 15 superficial (cell bodies located within lamina II-III), and 15 deep pyramidal neurons (cell bodies situated within lamina V-VI). Analysis of topological parameters of apical dendrite arborization showed no statistical differences except in total dendritic length (p=0.02), indicating considerable homogeneity between the two groups of neurons. On the other hand, average fractal dimension of apical dendrite was 1.33±0.06 for the superficial and 1.24±0.04 for the deep cortical neurons, showing statistically significant difference between these two groups (p<0.001). In conclusion, according to the fractal dimension values, apical dendrites of the superficial pyramidal neurons tend to show higher structural complexity compared to the deep ones.

Quantification of structural changes in acute inflammation by fractal dimension, angular second moment and correlation.

The aim of the study was to examine alteration and possible application of fractal dimension, angular second moment, and correlation for quantification of structural changes in acutely inflamed tissue.

Hippocampal BDNF in physiological conditions and social isolation

Abstract Exposure of an organism to chronic psychosocial stress may affect brain-derived neurotrophic factor (BDNF) expression that has been implicated in the etiology of psychiatric disorders, such as depression. Given that depression in humans has been linked with social stress, the chronic social stress paradigms for modeling psychiatric disorders in animals have thus been developed. Chronic social isolation in animal models generally causes changes in hypothalamic-pituitary-adrenal axis functioning, associated with anxiety- and depressive-like behaviors. Also, this chronic stress causes downregulation of BDNF protein and mRNA in the hippocampus, a stress-sensitive brain region closely related to the pathophysiology of depression. In this review, we discuss the current knowledge regarding the structure, function, intracellular signaling, inter-individual differences and epigenetic regulation of BDNF in both physiological conditions and depression and changes in corticosterone levels, as a marker of stress response. Since BDNF levels are age dependent in humans and rodents, this review will also highlight the effects of adolescent and adult chronic social isolation models of both genders on the BDNF expression.

Modified Richardson's method versus the box-counting method in neuroscience

BACKGROUND The morphology of dendrites, including apical dendrites of pyramidal neurons, is already well-known. However, the quantification of their complexity still remains open. Fractal analysis has proven to be a valuable method of analyzing the degree of complexity of dendrite morphology. NEW METHOD Richardsons method is a technique of measuring the fractal dimension of open and closed lines of objects. This method was modified in order to measure the fractal dimension of neuronal arborization. The focus of this experiment was on the apical dendrites of superficial and deep pyramidal neurons in the rat cerebral cortex. RESULTS Apical dendrites of superficial cortical pyramidal neurons have a higher mean value of the fractal dimension as compared to deep pyramidal neurons. COMPARISON WITH EXISTING METHOD Using the modified Richardsons method we showed that the mean value of the fractal dimension of apical dendrites in superficial pyramidal neurons is highly statistically significant as compared to the value of the fractal dimension in deep pyramidal neurons. On the other hand, the mean values of the fractal dimension between the same groups of apical dendrites measured by the most popular box-counting method showed merely a statistically significant difference. CONCLUSION The modified Richardsons method of fractal analysis is an efficient mathematical method for calculating the fractal dimension of dendrites and could be used in order to calculate the complexity of dendrite arborization.

The opposite effects of nandrolone decanoate and exercise on anxiety levels in rats may involve alterations in hippocampal parvalbumin–positive interneurons

The aim of this study was to evaluate the behavioral effects of chronic (six weeks) nandrolone decanoate (ND, 20 mg/kg, s.c., weekly in single dose) administration (in order to mimic heavy human abuse), and exercise (swimming protocol of 60 minutes a day, five days in a row/two days break), applied alone and simultaneously with ND, in male rats (n = 40). Also, we evaluated the effects of those protocols on hippocampal parvalbumin (PV) content and the possible connection between the alterations in certain parts of hippocampal GABAergic system and behavioral patterns. Both ND and exercise protocols induced increase in testosterone, dihydrotestosterone and estradiol blood levels. Our results confirmed anxiogenic effects of ND observed in open field (OF) test (decrease in the locomotor activity, as well as in frequency and cumulative duration in the centre zone) and in elevated plus maze (EPM) test (decrease in frequency and cumulative duration in open arms, and total exploratory activity), that were accompanied with a mild decrease in the number of PV interneurons in hippocampus. Chronic exercise protocol induced significant increase in hippocampal PV neurons (dentate gyrus and CA1 region), followed by anxiolytic-like behavioral changes, observed in both OF and EPM (increase in all estimated parameters), and in evoked beam-walking test (increase in time to cross the beam), compared to ND treated animals. The applied dose of ND was sufficient to attenuate beneficial effects of exercise in rats by means of decreased exercise-induced anxiolytic effect, as well as to reverse exercise-induced augmentation in number of PV immunoreactive neurons in hippocampus. Our results implicate the possibility that alterations in hippocampal PV interneurons (i.e. GABAergic system) may be involved in modulation of anxiety level induced by ND abuse and/or extended exercise protocols.

Expression of p300 and p300/CBP associated factor (PCAF) in actinic keratosis and squamous cell carcinoma of the skin

p300 and p300/CBP-associated factor (PCAF) are histone modifiers and transcriptional co-factors involved in a number of cell processes. We investigated their expression patterns in 79 actinic keratoses (AK), 45 cases of Bowens disease (BD), and 168 invasive squamous cell carcinomas of the skin (SCC). Using tissue microarray and immunohistochemistry, we evaluated p300 and PCAF expression in relation to the type of the lesion and SCC prognostic parameters (grade, diameter, thickness and level of invasion). High nuclear expression of p300 (>60% of positive cells) (p=0.001) and absent cytoplasmic expression (p=0.026) were more frequent in SCC compared to AK and BD, respectively. Cytoplasmic expression of p300 was associated with the SCC invasion of subcutaneous fat and deeper tissues (p=0.049). Diffuse distribution of cells with p300 nuclear expression was more commonly seen in BD and SCC compared to AK (p<0.001), in moderately- and poorly-differentiated SCC compared to well-differentiated SCC (p<0.001), in tumors thicker than 6mm (p<0.001), and in deeply invading tumors (p=0.001). More frequent loss of PCAF nuclear expression was observed in SCC than in AK and BD (p<0.001). Diffuse distribution of cells with PCAF cytoplasmic expression was more common in BD and SCC compared to AK (p<0.001), and in poorly-differentiated SCC compared to well- and moderately-differentiated SCC (p<0.001). Our results suggest that increase in nuclear expression of p300, as well as the presence of cytoplasmic but loss of nuclear expression of PCAF, could play an important role in the development and progression of cutaneous SCC.

Open Fracture Management in Low-Resource Settings: A Medical Training Experience in Cambodian Hospitals

IntroductionA prospective interventional study has been carried out on the teaching effect and sustainability of low-cost trauma training program in open tibia fracture management for health workers.Materials and methodsIn 2007, an external fixator and a patella-bearing orthosis were developed at a rural workshop in Cambodia. From 2010 to 2016, a core group of nine Cambodian health workers was trained in open fracture management by Norwegian senior surgeons, using the locally made fixator and brace. The training outcome was also assessed by a questionnaire comprising of assertions regarding theoretical understanding, technical skills and self-confidence in understanding the biomechanical properties of locally made external fixator and its application; the use of handmade orthosis and principle in covering of soft-tissue defects.ResultsThe students managed 23 cases with the new technique with a primary healing rate of 70% (95% CI 48.1–85.5). A significant increase in self-reported technical skills, understanding, and self-confidence was reported.ConclusionThis study demonstrates that the capacity building of reconstructive surgery in low-resource settings by local doctors and paramedics is clearly a reasonable option that may substantially reduce amputation of the limbs.

The role of neuropeptide-Y in nandrolone decanoate-induced attenuation of antidepressant effect of exercise

Since the increased prevalence of anabolic androgenic steroids abuse in last few decades is usually accompanied by various exercise protocols, the scope of our study was to evaluate the effects of chronic nandrolone decanoate administration in supraphysiological dose and a prolonged swimming protocol (alone and simultaneously with nandrolone decanoate) on depressive state in male rats. Simultaneously, we investigated the possible alterations in neuropeptide Y (NPY) content in blood and the hippocampus, in order to determine the role of NPY in the modulation of depressive-like behavior.Exercise induced antidepressant effects in tail suspension test (decrease of the total duration of immobility), as well as significant increase in the number of hippocampal NPY-interneurons in CA1 region. Chronic nandrolone decanoate treatment attenuated the beneficial antidepressant effects of exercise as measured by the tail suspension test parameters. Simultaneously, nandrolone decanoate treatment resulted in diminution of NPY content both in blood (decreased serum levels) and in hippocampus (the significant decrease in NPY expression in all three investigated hippocampal regions—CA1, CA2/3 and DG). Our findings indicate that alterations in serum and hippocampal NPY contents may underlie the changes in depressive state in rats. The exercise was beneficial as it exerted antidepressant effect, while chronic nandrolone decanoate treatment resulted in depressive-like behavior. Furthermore, the behavioral indicators of depression showed strong correlations with the serum levels and the hippocampal content of NPY.