Development of kisspeptin-GnRH neural circuit in utero and mapping of GnRH receptor neurons in mice brain

'Gonadotropin releasing hormone (GnRH)'-Neurone repräsentieren die gemeinsame ZNS-Endstrecke zur hormonalen Kontrolle der Keimdrüsen. Dabei unterliegt die GnRH-Freisetzung einer Feedback-Regulation durch das gonadale Steroidhormon Östrogen. GnRH-Neurone exprimieren selbst allerdings nicht Östrogen-Rezeptor-alpha (ER), was nahelegt, dass das Feedback-Signal über einen vorgeschalteten Steroid-sensitiven Signalweg auf GnRH-Neurone übertragen wird. Tatsächlich fungieren 'Kisspeptin'-Neurone als Upstream-Regulator der GnRH-Freisetzung und dienen als Angriffspunkt für Steroidhormone in der Regulation der GnRH-Sekretion. GnRH-Neurone exprimieren den Kisspeptin-Rezeptor GPR54. Kisspeptin-Neurone sind im Gehirn vor allem im Nucleus arcuatus (ARC) und im anterolateralen Nucleus paraventricularis (AVPV) lokalisiert. Kisspeptin-Neurone projizieren in die mediane Eminenz und auf GnRH-Neurone der prä-optischen Region. Kisspeptin bindet an GPR54 und stimuliert GnRH-Neurone der prä-optischen Region zur GnRH-Freisetzung in die Zirkulation. In der vorliegenden Arbeit wurde das genaue raumzeitliche Expressionsmuster der dem GnRH-Neuron vor- und nachgeschaltetem Neuronensysteme, des 'Kisspeptin'-Systems und des GnRH-exprimierenden Systems, bestimmt. Dazu wurde zunächst das Einsetzen der Expression von Kisspeptin und seinem Rezeptor GPR54 in männlichen KissIC/eR26-GFP-Embryonen sowie in männlichen GPIC/eR26-GFP-Embryonen untersucht. Kisspeptin und GPR54 erschienen gleichzeitig am Embryonaltag E13.5. Während der ganzen embryonalen Hirnentwicklung wurde Kisspeptin nur im ARC des Hypothalamus gefunden. Hingegen blieb die Expression von GPR54 auf GnRH-Neurone beschränkt. Die detailierte Analyse zeigt jedoch, dass das GPR54-Expressionsmuster unabhängig von der Lage der GnRH-Neuronen war. Zur Bestimmung des Zeitpunkts, an dem Kisspeptin-Neurone sensitiv gegenüber Sexualsteroiden werden, wurde die Expression von Östrogen-Rezeptor ER und von Androgen-Rezeptor (AR) in ARC Kisspeptin-Neuronen untersucht. Es stellte sich heraus, dass ER und AR-positive Neurone die embryonale Hirnregion markieren, in der sich Kisspeptin-Neurone entwickeln. Trans-synaptisches Tracing zeigte schließlich, dass im männlichen embryonalen Mäusegehirn Kisspeptin-Neurone des ARC mit dem GnRH-Neuronensystem kommunizieren. Die Verbindung zwischen ARC-Kisspeptin-Neuronen und GnRH-Neuronen ist unabhängig von der Lage der Neurone im männlichen embryonalen Mäusegehirn. Diese Beobachtung legt den Schluß nahe, dass im Gegensatz zum adulten Gehirn, in dem Kisspeptin-Neurone eine geschlechtsspezifische Verteilung aufweisen, Beginn und Entwicklung des Kisspeptin-GPR54-Systems im männlichen embryonalen Mäusegehirn eher dem weiblichen Mäusegehirn ähneln und dass der Sexualdimorphismus erst später in der Entwicklung entsteht. Es folgte die Untersuchung des Downstream-Targets, dem Gonadotropin releasing hormone receptor (GnRHR)-Neurons. In der Hypophyse triggert GnRH-Rezeptorbindung die Synthese und Freisetzung von Luteinisierungshormon (LH) und von follikelstimulierendem Hormon (FSH). Die Rolle von GnRHR in den gonadotropen Zellen der Hypophyse ist bekannt, aber die Funktion der GnRHR-Neurone im Gehirn ist noch nicht vollständig geklärt. Zur Bearbeitung dieser Frage wurde die Verteilung der GnRHR-Neurone im embryonalen Gehirn von weiblichen GnRHR/eR26-GFP-Mäuseembryonen kartiert. Es stellte sich heraus, dass ihre Anzahl signifikant im Lauf der Entwicklung ansteigt. Die GnRHR-Neuronen reicherten sich in der olfaktorischen Hirnregion und in Sexualzentren wie der medialen Amygdala (MeA), der medialen prä-optischen Region (MPA), dem ventromedialen Hypothalamus (VMH) und der peri-aquaeduktalen grauen Substanz (PAG) an. Die GnRHR-Neuronen der olfaktorischen Regionen und Sexualzentren erwiesen sich als sensitiv gegenüber Sexualsteroiden. Erstmalig konnte die olfaktorische Stimulation von GnRHR-exprierenden Neuronen gezeigt werden. Die Ergebnisse der vorliegende Untersuchung liefern Einblicke in die Entwicklung des Kisspeptin-GPR54-Systems und können zum besseren Verständnis von Störungen der Geschlechtsentwicklung wie dem hypogonadotrophen Hypogonadismus oder der Pubertas praecox beitragen. Die anatomische Kartierung der GnRHR-Neurone im Gehirn beleuchtet die Rolle von GnRH-Signalwegs in der Säugetier-Hypothalamus/Hypophysen/Gonaden-Achse.Gonadotropin releasing hormone (GnRH) neurons are the final common output pathway by which brain controls reproduction. Gonadal steroid hormone, estrogen regulates GnRH release by feedback signaling. Interestingly, GnRH neurons do not express estrogen receptors (ER suggesting that a steroid sensitive pathway might mediate these effects on GnRH neuron. Kisspeptin, a key upstream regulator of GnRH secretion serves as a target for steroid hormone in the control of GnRH secretion. GnRH neurons express kisspeptin receptor, GPR54. Kisspeptin neurons are primarily located in two major locations of the hypothalamus, the arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV). Kisspeptin neurons project to GnRH neurons located in the preoptic area (and to the median eminence). Kisspeptin binds to GPR54 to stimulate GnRH neuron in the preoptic area to release GnRH into the circulation. The goal of this study is to determine the precise spatio-temporal expression pattern of the upstream and the downstream target of GnRH neuron, Kisspeptin system and GnRHR expressing neurons respectively. I examined the onset of kisspeptin and its receptor, GPR54 in the KissIC/eR26-GFP and GPIC/eR26-GFP male mouse embryo respectively. Interestingly expression of Kisspeptin and its receptor GPR54 initiates at the same time (E13.5). Throughout the embryonic brain development kisspeptin neurons remain restricted to the ARC of the hypothalamus whereas GPR54 expression is restricted to the GnRH neuron. Detailed analysis revealed that the GPR54 expression is independent of the location of the GnRH neuron. Next I analyzed when kisspeptin neurons becomes sensitive to gonadal steroid hormones. I investigated the expression of estrogen receptor alpha (ER) and androgen receptor (AR) in the ARC kisspeptin neuron. I observed that ERand AR positive neurons marks the birthplace of kisspeptin neuron in the embryonic brain. Transsynaptic tracing in the embryonic mouse brain revealed that ARC kisspeptin neurons communicate with GnRH neurons in utero. The connectivity between ARC kisspeptin neurons and GnRH neurons is independent of the location of the GnRH neurons in the embryonic male mouse brain. These observations suggests that in contrast to the adult brain where kisspeptin neurons are present in sexually dimorphic manner, onset and the development of Kisspeptin-GPR54 system in embryonic male brain is highly similar to female brain and sexual dimorphism arises later in development. Next, I investigated the downstream target of GnRH neuron, gonadotropin releasing hormone receptor (GnRHR) expressing neurons. GnRH binds to its receptor in pituitary to trigger the synthesis and release of luteinizing hormone (LH) and follicle stimulating hormone (FSH). The role of GnRHR in pituitary gonadotropes is well understood but the function of GnRHR neurons in the brain is not well established. Using GnRHR/eR26-GFP mouse I mapped the distribution of GnRHR neurons in the female brain. I observed that the GnRHR neurons are concentrated in olfactory processing areas and reproductive centers in the brain such as medial amygdala (MeA), medial preoptic area (MPA), ventromedial hypothalamus (VMH) and periaqueductal grey (PAG). I found that the number of GnRHR neurons significantly increases across developmental stage I also observed that GnRHR neurons in olfactory and reproductive centers are sensitive to steroid hormones. For the first time I also identified that GnRHR expressing neurons are activated upon olfactory stimulation. Taken together, the present study provides insight into the (I) development of kisspeptin-GPR54 system which will help to better understand reproductive disorders such as hypogonadotropic hypogonadism and precocious puberty (II) detailed anatomical mapping of GnRHR neurons in the brain will help in understanding the role of GnRH signaling in the mammalian brain and its effect on reproductive axi

Ionic-strength-dependent transition of hen egg-white lysozyme at low pH to a compact state and its aggregation on thermal denaturation

Equilibrium acid-induced unfolding of hen egg-white lysozyme has been investigated by a combination of optical methods, size-exclusion chromatography, and differential scanning calorimetry. The results showed the presence of a partially folded state of hen egg-white lysozyme at pH 1.5, characterized by a substantial secondary structure, a large solvent exposure of non-polar clusters, and significantly disrupted tertiary structure. A large enthalpy was also associated with the conversion of the acid-unfolded state to a fully unfolded state. Size-exclusion chromatography and 8-anilino-1-naphthalenesulphonic acid-binding studies showed an ionic-strength-induced transition of the partially folded state to a compact conformation. Furthermore, an ionic-strength-dependent aggregation on thermal unfolding of the partially folded intermediate was also observed. These observations provide insights into the possible features responsible for the stabilization of intermediates in the folding of hen egg-white lysozyme

Orbit of a point in Dynamical Systems

In this paper, we have proved the necessary and sufficient condition for a weakly mixing and topologically mixing function. Some properties of the monoid, periodic points and eventually periodic points are obtained. Some relations between weakly mixing, transitive and topologically mixing functions are obtained. Some results of considerable importance about the orbit of a point and relation with eventually periodic point are proved. Some results of the set theory that play an important role in our studies are included. Some new terms like singly transitive and lately transitive are introduced

THE POTENTIAL OF REMDESIVIR AGAINST SARS COV 2: A REVIEW

Covid 19, the pandemic originated in the Chinese city of Wuhan, had the entire world conquered. The structure and transmission of the causative organism, Coronavirus is well studied. Remdesivir, the product of Gilead pharmaceuticals, was effective against many viral infections, including Ebola and SARS. It comes under the category of nucleoside prodrug and has given promising results in the early trials against SARS COV 19. In depth, research is taking place at a rapid pace, so that Remdesivir will be available to the therapeutic community as an effective remedy for the pandemic caused by SARS COV2. If this meets success, the darkest era in the modern history of mankind may become a memory in the near future

Alkaline unfolding and salt-induced folding of bovine liver catalase at high pH

We have studied the alkaline unfolding of bovine liver catalase and its dependence on ionic strength by enzymic activity measurements and a combination of optical methods like circular dichroism, fluorescence and absorption spectroscopies. Under conditions of high pH (11.5) and low ionic strength, the native tetrameric enzyme dissociates into monomers with complete loss of enzymic activity and a significant loss of α-helical content. Increase in ionic strength by addition of salts like potassium chloride and sodium sulphate resulted in folding of alkaline-unfolded enzyme by association of monomers to tetramer but with significantly different structural properties compared to native enzyme. The salt-induced tetrameric intermediate is characterized by a significant exposure of the buried hydrophobic clusters and significantly reduced α-helical content compared to the native enzyme. The refolding/reconstitution studies showed that the salt-induced partially folded tetrameric intermediate shows significantly higher efficiency of refolding/reconstitution as compared to alkaline-denatured catalase in the absence of salts. These studies suggest that folding of multimeric enzymes proceeds probably through the hydrophobic collapse of partially folded multimeric intermediate with exposed hydrophobic clusters

Effective Image Clustering with Differential Evolution Technique

The paper presents a novel approach of clustering image datasets with differential evolution (DE) technique. The differential evolution is a parallel direct search population based optimization method. From our simulations it is found that DE is able to optimize the quality measures of clusters of image datasets. To claim the superiority of DE based clustering we have compared the outcomes of DE with the classical K-means and popular Particle Swarm Optimization (PSO) algorithms for the same datasets. The comparisons results reveal the suitability of DE for image clustering in all image datasets

Performance Assessment of Pre-processing Filters for Infrared Search and Track Applications

To enhance detection probability and to reduce false alarms, infrared imagery is pre-processed before subjecting it to detection algorithms in infrared search and track systems. Pre-processing algorithms are used to predict the complex background and then to subtract the predicted background from the original image. The difference image is passed to the detection algorithm to further distinguish between the target and the background and/ or noise more accurately. A number of pre-processing algorithms have been reported in literature, with their relative advantages and disadvantages. This paper brings out the computational complexities and simulation results of various algorithms for assessing their relative performances. Based on these parameters, statistical algorithms in general and max-min algorithms in particular, are recommended to be used for infrared search and track systems.Defence Science Journal, 2011, 61(3), pp.251-256, DOI:http://dx.doi.org/10.14429/dsj.61.6

Few-Shot Domain Adaptation for Low Light RAW Image Enhancement

Enhancing practical low light raw images is a difficult task due to severe noise and color distortions from short exposure time and limited illumination. Despite the success of existing Convolutional Neural Network (CNN) based methods, their performance is not adaptable to different camera domains. In addition, such methods also require large datasets with short-exposure and corresponding long-exposure ground truth raw images for each camera domain, which is tedious to compile. To address this issue, we present a novel few-shot domain adaptation method to utilize the existing source camera labeled data with few labeled samples from the target camera to improve the target domain's enhancement quality in extreme low-light imaging. Our experiments show that only ten or fewer labeled samples from the target camera domain are sufficient to achieve similar or better enhancement performance than training a model with a large labeled target camera dataset. To support research in this direction, we also present a new low-light raw image dataset captured with a Nikon camera, comprising short-exposure and their corresponding long-exposure ground truth images.Comment: BMVC 2021 Best Student Paper Award (Runner-Up). Project Page: https://val.cds.iisc.ac.in/HDR/BMVC21/index.htm