Effects of growth hormone in the central nervous system

ABSTRACT Growth hormone (GH) is best known for its effect stimulating tissue and somatic growth through the regulation of cell division, regeneration and proliferation. However, GH-responsive neurons are spread over the entire central nervous system, suggesting that they have important roles in the brain. The objective of the present review is to summarize and discuss the potential physiological importance of GH action in the central nervous system. We provide evidence that GH signaling in the brain regulates the physiology of numerous functions such as cognition, behavior, neuroendocrine changes and metabolism. Data obtained from experimental animal models have shown that disruptions in GH signaling in specific neuronal populations can affect the reproductive axis and impair food intake during glucoprivic conditions, neuroendocrine adaptions during food restriction, and counter-regulatory responses to hypoglycemia, and they can modify gestational metabolic adaptions. Therefore, the brain is an important target tissue of GH, and changes in GH action in the central nervous system can explain some dysfunctions presented by individuals with excessive or deficient GH secretion. Furthermore, GH acts in specific neuronal populations during situations of metabolic stress to promote appropriate physiological adjustments that restore homeostasis. Arch Endocrinol Metab. 2019;63(6):549-56

Interactions between prolactin and kisspeptin to control reproduction

ABSTRACT Prolactin is best known for its effects of stimulating mammary gland development and lactogenesis. However, prolactin is a pleiotropic hormone that is able to affect several physiological functions, including fertility. Prolactin receptors (PRLRs) are widely expressed in several tissues, including several brain regions and reproductive tract organs. Upon activation, PRLRs may exert prolactin’s functions through several signaling pathways, although the recruitment of the signal transducer and activator of transcription 5 causes most of the known effects of prolactin. Pathological hyperprolactinemia is mainly due to the presence of a prolactinoma or pharmacological effects induced by drugs that interact with the dopamine system. Notably, hyperprolactinemia is a frequent cause of reproductive dysfunction and may lead to infertility in males and females. Recently, several studies have indicated that prolactin may modulate the reproductive axis by acting on specific populations of hypothalamic neurons that express the Kiss1 gene. The Kiss1 gene encodes neuropeptides known as kisspeptins, which are powerful activators of gonadotropin-releasing hormone neurons. In the present review, we will summarize the current knowledge about prolactin’s actions on reproduction. Among other aspects, we will discuss whether the interaction between prolactin and the Kiss1-expressing neurons can affect reproduction and how kisspeptins may become a novel therapeutic approach to treat prolactin-induced infertility.

The PI3K signaling pathway mediates the biological effects of leptin / A via de sinalização intracelular da PI3K medeia os efeitos biológicos da leptina

The activation of the leptin receptor recruits several intracellular signaling pathways, including the phosphatidylinositol 3-kinase (PI3K) pathway. While some of the leptin-induced signaling pathways, such as the JAK2/STAT3 pathway, induce cellular responses primarily through changes in gene expression, the PI3K pathway affects cellular properties more rapidly, through post-translational changes such as protein phosphorylation. Accordingly, several studies have shown that the PI3K pathway is required for the acute effects of leptin, such as a leptin-induced decrease in food intake. Leptin signaling through PI3K also affects the electrophysiological properties of neurons, including changes in their membrane potential and firing rates. In this review, we summarize the recent advances in our understanding of the role played by the PI3K signaling pathway in controlling food intake and energy balance. In particular, we focus on the importance of the PI3K signaling pathway as a mediator of the effects of leptin on hypothalamic neurons.

A ativação do receptor de leptina recruta diversas vias de sinalização intracelular, entre elas a via da fosfatidilinositol 3-quinase (PI3K). Enquanto algumas dessas vias, como a sinalização pelo JAK2/STAT3, induzem respostas celulares por meio de mudanças na transcrição gênica, a via da PI3K altera propriedades celulares de forma rápida, via fosforilação de proteínas. Em concordância, estudos mostraram que a via da PI3K é necessária para que a leptina induza seus efeitos agudos, como redução da ingestão alimentar, após administração de leptina. A ativação da PI3K pela leptina também afeta as propriedades fisiológicas de neurônios, incluindo mudanças no potencial de membrana e no potencial de ação. Nesta revisão, resumimos os recentes avanços na compreen-são do papel desempenhado pela via de sinalização da PI3K no controle da ingestão alimentar e do balanço energético. Discutimos, principalmente, como a via da PI3K é importante para mediar os efeitos da leptina sobre os neurônios hipotalâmicos.

Innervation of the pronator quadratus muscle

El músculo pronador cuadrado en el Hombre es el responsable de la pronación del antebrazo, ayudado por el músculo pronador redondo. Estudiamos la inervación del músculo pronador cuadrado en 18 antebrazos de cadáveres fijados en formol al 10 por ciento. Examinamos las relaciones entre el nervio interóseo anterior y el músculo pronador cuadrado. La línea articular radiocarpiana fue utilizada como punto de referencia. En el antebrazo derecho el ramo de penetración más proximal en el músculo pronador cuadrado fue 5.4 cm proximal a la línea articular radiocarpiana y 5.6 cm en el lado izquierdo. El ramo de penetración más distal en el músculo pronador cuadrado, fue de 2,5 cm en el lado derecho siendo esta distancia de 2,4 cm en el lado izquierdo con respecto a la línea articular radiocarpiana. Fueron medidos la longitud del nervio interóseo anterior y el ancho del músculo pronador cuadrado. Un buen conocimiento de la distribución anatómica en la región, puede ser de gran ayuda en el tratamiento del síndrome interóseo anterior.

Innervation of the pronator teres muscle

El músculo pronador redondo actúa como motor secundario en la pronación del antebrazo, siendo el músculo pronador cuadrado motor primario de esta acción. Estudiamos la inervación del músculo pronador redondo en 8 antebrazos de cuerpos fijados en formol. Fueron disecados y examinados el nervio mediano y su inervación para el músculo pronador redondo. La línea articular del codo fue usada como punto de referencia. En todos los casos, la mayoría de los ramos del nervio mediano para el músculo pronador redondo se originaban en el tercio distal del brazo, mientras que, la mayor parte de los ramos penetraba en la mitad del antebrazo, proximal al tercio distal (75 por ciento en el miembro superior derecho y 75.8 por ciento en el miembro superior izquierdo). El tratamiento del síndrome pronador podría ser más fácil conociendo mejor la distribución anatómica de los nervios.

Determination of the levels of origin and point of penetration of the nerves that supply the flexor digitorum superficialis muscle

Conociendo la distribución de los ramos nerviosos destinados al músculo flexor superficial de los dedos, sus orígenes y puntos de penetración, facilita el tratamiento de lesiones y, principlamente, otorga auxilio al cirujano durante las intervenciones quirúrgicas, donde estos ramos pueden resultar dañados. Disecamos los miembros superiores de 10 cadáveres formolizados de individuos adultos. Usamos como referencia para las medidas anatómicas, las interlíneas articulares del codo y radiocarpiana. Observamos que el miembro superior izquierdo, el 29,7 por ciento de los ramos del nervio mediano se originaban en el tercio medio de la mitad distal del antebrazo y en el 30.3 por ciento penetraban en el tercio proximal de la mitad proximal del antebrazo. En el miembro superior derecho, el 25,7 por ciento de los ramos del nervio mediano se originaban de la pared distal del brazo y penetraban en el tercio proximal de la mitad distal de antebrazo, en el 30,5 por ciento. Fueron observadas algunas variaciones anatómicas