ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
Chains of two or more AMINO ACIDS. Adjacent amino acids are linked together by a chemical bond called a peptide bond (a single bond between a nitrogen and carbon molecule). Peptides are different from PROTEINS only in that they are smaller; a peptide is considered to be less than 10 kilodaltons in molecular weight. In terms of structure, one end of the peptide has an amino group at one end (referred to as the N-terminus) and a carboxyl group at the other. Since all peptides have these structural features in common, the individual chemical identity of different peptides is rendered by the existence of differing side-chains. Like proteins, peptides are synthesized in the RIBOSOMES of cells, where MESSENGER RNA codes for their structure. Peptides are broken down by a type of ENZYME called PEPTIDASE. Peptides in the nervous system, called NEUROPEPTIDES, act as NEUROTRANSMITTERS and neuromodulators (see NEUROMODULATION) and have an important role in neural signalling.
Perspective
Sami I. Said in Proinflammatory and Antiinflammatory Peptides, 2020
Numerous biologically active peptides have been identified in mammalian and nonmammalian systems. Most of these peptides are synthesized and released by neuronal cells and hence are known as neuropeptides. As neurotransmitters in the central and peripheral nervous systems, neuropeptides are in a position to exert wide-ranging and important regulatory influences on almost all body functions. Peptides may also act as endocrine or neuroendocrine messengers, or by paracrine, neuro-crine, or autocrine mechanisms (1). Functions that are influenced by peptides include digestion, absorption, and gastrointestinal motility; metabolism; electrolyte balance; blood pressure, cardiac performance and blood flow to vital organs; vascular and nonvascular smooth muscle responses; cellular and humoral immune mechanisms; hormonal and neurohormonal secretion; and cell proliferation and differentiation. Peptides may also have antibacterial (2) and other activities.
Structure and Function of the Lower Urinary Tract
Anthony R. Mundy, John M. Fitzpatrick, David E. Neal, Nicholas J. R. George in The Scientific Basis of Urology, 2010
Several of these putative neurotransmitters are peptides, which have been grouped together as neuropeptides. This group includes substance P (36,37) vasoactive intestinal polypeptide (38,39) and neuropeptide Y, to name but a few. Substance P is thought to be involved in afferent neurotransmission (36). Vasoactive intestinal polypeptide relaxes detrusor smooth muscle (39) and has been shown in some studies to be coreleased with acetylcholine. Similarly, neuropeptide Y has been colocalized in adrenergic neurons. This concept of colocalization, corelease and cotransmission is interesting as it provides a means of modifying the effects of neural activity either temporally or spatially. Thus, the same nerves could produce two transmitters with different effects, both being simultaneously released but with one predominating in one area and the other in the other area. For example, an excitatory and an inhibitory transmitter, if coreleased, might cause bladder contraction if the former predominated in the bladder and relaxation of the bladder neck if the latter predominated at that site. This is indeed what is thought to happen with acetylcholine and nitric oxide, colocated in and coreleased from the parasympathetic nerves that supply this area (17,40). This type of neuromodulatory activity could have other effects, which would less dramatically act to “fine tune” the actions of the lower urinary tract.
Neurotensin/IL-8 pathway orchestrates local inflammatory response and tumor invasion by inducing M2 polarization of Tumor-Associated macrophages and epithelial-mesenchymal transition of hepatocellular carcinoma cells
Published in OncoImmunology, 2018
Pei Xiao, Xinxin Long, Lijie Zhang, Yingnan Ye, Jincheng Guo, Pengpeng Liu, Rui Zhang, Junya Ning, Wenwen Yu, Feng Wei, Jinpu Yu
Recently, neuropeptides were identified as a new category of proinflammatory molecules in the liver. Neuropeptides are the largest group of cell-cell signaling molecules comprising more than 100 types of small-molecule peptides that regulate a number of diverse physiological processes.4 Some neuropeptides were reported to promote the development and progression of HCC via participation in the generation of the inflammatory microenvironment.5-7 Our previous study observed the ectopic expression of neurotensin (NTS), a special neuropeptide in HCC, correlated with significant tumor invasion and poor clinical outcome in HCC patients.8,9 Furthermore, NTS overexpression was accompanied by enhanced inflammatory responses and epithelial-mesenchymal transition (EMT) features in situ. However, the major molecular mechanisms involved were not disclosed.
Worms sleep: a perspective
Published in Journal of Neurogenetics, 2020
Each of the four worm sleep papers published in this edition of the Journal of Neurogenetics carries an important message. The van Buskirk lab paper (Goetting, et al, J. Neurogenet., in press) contributes to our understanding of the mechanism of SIS. They also describe a new trigger for SIS: skin injury, which is relevant to the human complaint of severe fatigue after an operation. The Bringmann lab paper (Busack et al, J. Neurogenet., in press) describes a method for long-term optogenetic manipulation of worms. Developing such methods is important because prior worm tools have been optimized for much shorter durations of manipulation and observations. The Nelson lab describes the role of orcokinins, neuropeptides conserved among molting animals, in regulating sleep (Honer et al, J. Neurogenet., in press). This study again emphasizes the important, but complex roles of neuropeptides in behavioral state modulation. Finally, the Hart lab paper reminds us that not all that stops moving is sleep and that we must remain self-skeptical as a field. They suggest that cessation of swimming is better explained by neuromuscular fatigue than by sleep (Schuch et al, J. Neurogenet., in press).
The role of neuropeptide Y, orexin-A, and ghrelin in differentiating unipolar and bipolar depression: a preliminary study
Published in Nordic Journal of Psychiatry, 2022
Mehmet Ünler, İrem Ekmekçi Ertek, Nigar Afandiyeva, Mustafa Kavutçu, Nevzat Yüksel
Currently, the distinction between unipolar and bipolar patients in the depressive episode poses difficulties for clinicians, and there are no markers that can be used to differentiate these two clinical states. Recent studies of mood disorders investigating peripheral biomarkers have focused on three areas; cell growth, survival, and synaptic plasticity, including brain-derived neurotrophic factor; inflammation, particularly pro- and anti-inflammatory cytokines; and energy metabolism, particularly oxidative stress, and mitochondrial function [10]. In addition, studies on hypothalamic neuropeptides, which are involved in the regulation of vegetative functions such as appetite and sleep may also contribute to this area. Nevertheless, studies evaluating these neuropeptides in mood disorders have yielded contradictory and complex results due to methodological problems.
Related Knowledge Centers
- Depolarization
- Golgi Apparatus
- Substance P
- Vasoactive Intestinal Peptide
- Vesicle
- Amino Acid
- Neuron
- G Protein-Coupled Receptor
- Protein Precursor
- Endoplasmic Reticulum