scholarly journals Contractile pericytes determine the direction of blood flow at capillary junctions

2020 ◽  
Vol 117 (43) ◽  
pp. 27022-27033
Author(s):  
Albert L. Gonzales ◽  
Nicholas R. Klug ◽  
Arash Moshkforoush ◽  
Jane C. Lee ◽  
Frank K. Lee ◽  
...  

The essential function of the circulatory system is to continuously and efficiently supply the O2 and nutrients necessary to meet the metabolic demands of every cell in the body, a function in which vast capillary networks play a key role. Capillary networks serve an additional important function in the central nervous system: acting as a sensory network, they detect neuronal activity in the form of elevated extracellular K+ and initiate a retrograde, propagating, hyperpolarizing signal that dilates upstream arterioles to rapidly increase local blood flow. Yet, little is known about how blood entering this network is distributed on a branch-to-branch basis to reach specific neurons in need. Here, we demonstrate that capillary-enwrapping projections of junctional, contractile pericytes within a postarteriole transitional region differentially constrict to structurally and dynamically determine the morphology of capillary junctions and thereby regulate branch-specific blood flow. We further found that these contractile pericytes are capable of receiving propagating K+-induced hyperpolarizing signals propagating through the capillary network and dynamically channeling red blood cells toward the initiating signal. By controlling blood flow at junctions, contractile pericytes within a functionally distinct postarteriole transitional region maintain the efficiency and effectiveness of the capillary network, enabling optimal perfusion of the brain.

1988 ◽  
Vol 134 (1) ◽  
pp. 235-246 ◽  
Author(s):  
JAN-PETER HILDEBRANDT

In the leech, the physiological significance of high-pressure phases (HIP) and lowpressure phases (LOP) of the lateral vessels was studied by intravascular pressure recordings and observation of blood flow in different parts of the circulatory system, and by measurements of the blood flow velocities in the dorsal vessel. Different shapes of the pressure pulses were found in the anterior lateral vessel segments during HIP and LOP phases, according to the different modes of diastolic filling in both phases. Pressure recordings in the lateral abdominal vessels showed the different action of the lateral abdominal sphincters in the HIP and LOP phases of the ipsilateral lateral vessel. The LOP contractions were responsible for the blood supply to the capillary networks of the organs and the body wall, with the possible exception of the intestine. The HIP contractions caused a forward bloodflow within the lateral vessel. In the dorsal vessel, the blood pressure was about 0.9-1.9kPa in different animals. The blood flow was discontinuous with velocities of 0.5-10 mms−1. Average blood flow in the dorsal vessel was 22.9μl min−1. An improved model of the circulation in the leech is presented.


2021 ◽  
Vol 22 (13) ◽  
pp. 6858
Author(s):  
Fanny Gaudel ◽  
Gaëlle Guiraudie-Capraz ◽  
François Féron

Animals strongly rely on chemical senses to uncover the outside world and adjust their behaviour. Chemical signals are perceived by facial sensitive chemosensors that can be clustered into three families, namely the gustatory (TASR), olfactory (OR, TAAR) and pheromonal (VNR, FPR) receptors. Over recent decades, chemoreceptors were identified in non-facial parts of the body, including the brain. In order to map chemoreceptors within the encephalon, we performed a study based on four brain atlases. The transcript expression of selected members of the three chemoreceptor families and their canonical partners was analysed in major areas of healthy and demented human brains. Genes encoding all studied chemoreceptors are transcribed in the central nervous system, particularly in the limbic system. RNA of their canonical transduction partners (G proteins, ion channels) are also observed in all studied brain areas, reinforcing the suggestion that cerebral chemoreceptors are functional. In addition, we noticed that: (i) bitterness-associated receptors display an enriched expression, (ii) the brain is equipped to sense trace amines and pheromonal cues and (iii) chemoreceptor RNA expression varies with age, but not dementia or brain trauma. Extensive studies are now required to further understand how the brain makes sense of endogenous chemicals.


2022 ◽  
Author(s):  
health not provided

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2018 ◽  
Vol 216 (1) ◽  
pp. 60-70 ◽  
Author(s):  
Geoffrey T. Norris ◽  
Jonathan Kipnis

Recent advances have directed our knowledge of the immune system from a narrative of “self” versus “nonself” to one in which immune function is critical for homeostasis of organs throughout the body. This is also the case with respect to the central nervous system (CNS). CNS immunity exists in a segregated state, with a marked partition occurring between the brain parenchyma and meningeal spaces. While the brain parenchyma is patrolled by perivascular macrophages and microglia, the meningeal spaces are supplied with a diverse immune repertoire. In this review, we posit that such partition allows for neuro–immune crosstalk to be properly tuned. Convention may imply that meningeal immunity is an ominous threat to brain function; however, recent studies have shown that its presence may instead be a steady hand directing the CNS to optimal performance.


2018 ◽  
Vol 73 (Suppl. 5) ◽  
pp. 43-52 ◽  
Author(s):  
John D. Fernstrom

The non-essential amino acid glutamate participates in numerous metabolic pathways in the body. It also performs important physiologic functions, which include a sensory role as one of the basic tastes (as monosodium glutamate [MSG]), and a role in neuronal function as the dominant excitatory neurotransmitter in the central nervous system. Its pleasant taste (as MSG) has led to its inclusion as a flavoring agent in foods for centuries. Glutamate’s neurotransmitter role was discovered only in the last 60 years. Its inclusion in foods has necessitated its safety evaluation, which has raised concerns about its transfer into the blood ultimately increasing brain glutamate levels, thereby causing functional disruptions because it is a neurotransmitter. This concern, originally raised almost 50 years ago, has led to an extensive series of scientific studies to examine this issue, conducted primarily in rodents, non-human primates, and humans. The key findings have been that (a) the ingestion of MSG in the diet does not produce appreciable increases in glutamate concentrations in blood, except when given experimentally in amounts vastly in excess of normal intake levels; and (b) the blood-brain barrier effectively restricts the passage of glutamate from the blood into the brain, such that brain glutamate levels only rise when blood glutamate concentrations are raised experimentally via non-physiologic means. These and related discoveries explain why the ingestion of MSG in the diet does not lead to an increase in brain glutamate concentrations, and thus does not produce functional disruptions in brain. This article briefly summarizes key experimental findings that evaluate whether MSG in the diet poses a threat to brain function.


Physiology ◽  
1994 ◽  
Vol 9 (2) ◽  
pp. 80-84 ◽  
Author(s):  
D Piani ◽  
DB Constam ◽  
K Frei ◽  
A Fontana

Cells of the macrophage lineage are ubiquitously distributed in the body, including the central nervous system. They represent an essential host defense system to protect from infections. However, recent evidence indicates that brain macrophages may also be responsible for tissue destruction, including loss of neurons and demyelination.


1997 ◽  
Vol 155 (2) ◽  
pp. 351-358 ◽  
Author(s):  
CM Gillespie ◽  
AL Merkel ◽  
AA Martin

Two studies were conducted to investigate the haemodynamic effects of IGF-I and its analogue LR3IGF-I in normal anaesthetised rats. Infusion of IGF-I intravenously, at a dose of 125 micrograms/kg/h, for 20 min in the first study resulted in renal blood flow being significantly elevated by 35% above baseline. Mean arterial blood pressure (MABP) at this IGF-I dose fell by 18% of baseline, with LR3IGF-I also causing a significant decline in MABP (by 15%) at the dose of 125 micrograms/kg/h. In the second study the intravenous administration of IGF-I or LR3IGF-I, at a dose of 125 micrograms/kg/h, over a period of 60 min, resulted in MABP being significantly lowered by 25% of baseline values. Regional blood flow rates were determined using radioactive microspheres, 15 microns in diameter, injected systemically at the end of the peptide infusion period. The gastrocnemius, a representative skeletal muscle, was the only vascular region to show a significant increase in blood flow after IGF-I (by 58%) or LR3IGF-1 (by 308%) infusion. Vascular resistance in the brain was significantly reduced after infusion of IGF-I (by 60%) or LR3IGF-I (by 48%) as compared with vehicle. Skeletal muscle vascular resistance was also reduced by IGF-I (by 41%) and more particularly by LR3IGF-I (by 77%) in comparison to vehicle. These alterations to vascular tone produced by IGF infusion may be related to the central nervous system and systemic cardiovascular side-effects that have been reported during IGF-I administration in humans.


1951 ◽  
Vol 97 (409) ◽  
pp. 792-800 ◽  
Author(s):  
L. Crome

The problems of the interdependence and unity of the brain and body have been put on a scientific basis by Pavlov and his successors. Bykov (1947) has, for example, been able to demonstrate that the cortex plays a leading part in the regulation of somatic processes, such as secretion of urine, blood pressure, peristalsis and metabolism. It is therefore reasonable to argue that lesions of the central nervous system will be reflected in the pathogenesis and course of morbid processes in the body. It does not follow, however, that this influence will necessarily be in the direction of greater lability, more rapid pathogenesis or more extensive destruction. The outstanding feature of the central nervous system is its plasticity and power of compensation. It is therefore possible and probable that those parts of the nervous system which remain intact will take over and compensate for the function of the lost ones. Emotion may, for example, lead to polyuria, but it does not follow that urinary secretion will be impaired in a leucotomized patient. The brain may well play an important part in the infective processes of a normal person, but the defence against infection in a microcephalic idiot may remain perfectly adequate, and may even be more effective than in a normal person, provided that the mechanism of the immunity and phagocytosis had been more fully mobilized in the course of his previous life.


2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
A. E. Evans ◽  
C. M. Kelly ◽  
S. V. Precious ◽  
A. E. Rosser

The central nervous system is composed of the brain and the spinal cord. The brain is a complex organ that processes and coordinates activities of the body in bilaterian, higher-order animals. The development of the brain mirrors its complex function as it requires intricate genetic signalling at specific times, and deviations from this can lead to brain malformations such as anencephaly. Research into how the CNS is specified and patterned has been studied extensively in chick, fish, frog, and mice, but findings from the latter will be emphasised here as higher-order mammals show most similarity to the human brain. Specifically, we will focus on the embryonic development of an important forebrain structure, the striatum (also known as the dorsal striatum or neostriatum). Over the past decade, research on striatal development in mice has led to an influx of new information about the genes involved, but the precise orchestration between the genes, signalling molecules, and transcription factors remains unanswered. We aim to summarise what is known to date about the tightly controlled network of interacting genes that control striatal development. This paper will discuss early telencephalon patterning and dorsal ventral patterning with specific reference to the genes involved in striatal development.


2021 ◽  
Vol 17 (2) ◽  
pp. 6-15
Author(s):  
L.A. Dziak ◽  
O.S. Tsurkalenko ◽  
K.V. Chekha ◽  
V.M. Suk

Coronavirus infection is a systemic pathology resulting in impairment of the nervous system. The involvement of the central nervous system in COVID-19 is diverse by clinical manifestations and main mechanisms. The mechanisms of interrelations between SARS-CoV-2 and the nervous system include a direct virus-induced lesion of the central nervous system, inflammatory-mediated impairment, thrombus burden, and impairment caused by hypoxia and homeostasis. Due to the multi-factor mechanisms (viral, immune, hypoxic, hypercoagulation), the SARS-CoV-2 infection can cause a wide range of neurological disorders involving both the central and peripheral nervous system and end organs. Dizziness, headache, altered level of consciousness, acute cerebrovascular diseases, hypogeusia, hyposmia, peripheral neuropathies, sleep disorders, delirium, neuralgia, myalgia are the most common signs. The structural and functional changes in various organs and systems and many neurological symptoms are determined to persist after COVID-19. Regardless of the numerous clinical reports about the neurological and psychiatric symptoms of COVID-19 as before it is difficult to determine if they are associated with the direct or indirect impact of viral infection or they are secondary to hypoxia, sepsis, cytokine reaction, and multiple organ failure. Penetrated the brain, COVID-19 can impact the other organs and systems and the body in general. Given the mechanisms of impairment, the survivors after COVID-19 with the infection penetrated the brain are more susceptible to more serious diseases such as Parkinson’s disease, cognitive decline, multiple sclerosis, and other autoimmune diseases. Given the multi-factor pathogenesis of COVID-19 resulting in long-term persistence of the clinical symptoms due to impaired neuroplasticity and neurogenesis followed by cholinergic deficiency, the usage of Neuroxon® 1000 mg a day with twice-day dosing for 30 days. Also, a long-term follow-up and control over the COVID-19 patients are recommended for the prophylaxis, timely determination, and correction of long-term complications.


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