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Journal of Nippon Medical School =... Dec 2004The metabolic rate of the fetus per tissue weight is relatively high when compared to that of an adult. Moreover, heat is transferred to the fetus via the placenta and... (Review)
Review
The metabolic rate of the fetus per tissue weight is relatively high when compared to that of an adult. Moreover, heat is transferred to the fetus via the placenta and the uterus, resulting in a 0.3 degrees C to 0.5 degrees C higher temperature than that of the mother. Therefore, fetal temperature is maternally dependent until birth. At birth, the neonate rapidly cools in response to the relatively cold extrauterine environment. Thus, the neonatal temperature rapidly drops soon after birth. In order to survive, the neonate must accelerate heat production via nonshivering thermogenesis (NST), which is coupled to lypolysis in brown adipose tissue. Heat is produced by uncoupling ATP synthesis via the oxidation of fatty acids in the mitochondria, utilizing uncoupled protein. Thermogenesis must begin shortly after birth and continue for several hours. Since thermogenesis requires adequate oxygenation, a distressed neonate with hypoxemia cannot produce an adequate amount of heat to increase its temperature. In contrast to the neonate, the fetus cannot produce extra heat production. This is because the fetus is exposed to inhibitors to NST, which are produced in the placenta and then enter the fetal circulation. The important inhibitors include adenosine and prostaglandin E2, both of which have strong anti-lypolytic actions. The inhibitors play an important role in the metabolic adaptation of a physiological hypoxic fetus because NST requires adequate oxygenation. Furthermore, the presence of NST inhibitors allows the fetus to accumulate an adequate amount of brown adipose tissue before birth. The umbilical circulation transfers 85% of the heat produced by the fetus to the maternal circulation. The remaining 15% is dissipated through the fetal skin to the amnion, and is then transferred through the uterine wall to the maternal abdomen. As long as fetal heat production and loss are appropriately balanced, the temperature differential between the fetus and the mother remains constant (heat clump). However, when the umbilical circulation is occluded for any reason, the fetal temperature will rise in relation to the extent of the occlusion. The fetal temperature may elevate to the hyperthermic range in cases of acute cord occlusion; if this occurs, fetal growth, including brain development, may be impacted. Experimentally induced cord occlusion, which is recognized as a significant cause of brain damage, results in a rapid elevation of body temperature; however, the brain temperature tends to remain constant. This is considered to be a cerebral thermoregulatory adaptation to hypoxemia, which has the physiologic advantage of protecting the fetus from hyperthermia, a condition that predisposes the fetus to hypoxic injury (cerebral hypometabolism). A number of thermoregularatory mechanisms are in place to maintain normal fetal and neonatal growth. Data has primarily been collected from animal studies; aside from the strict thermal control provided in the newborn nursery, little information exists concerning these mechanisms in the human fetus and neonate. Probably further information on thermoregulation is necessary specially to improve perinatal management for hypoxic fetuses.
Topics: Body Temperature Regulation; Fetus; Humans; Infant, Newborn
PubMed: 15673956
DOI: 10.1272/jnms.71.360 -
American Journal of Respiratory Cell... Mar 2023Microorganisms colonize the human body. The lungs and respiratory tract, previously believed to be sterile, harbor diverse microbial communities and the genomes of...
Microorganisms colonize the human body. The lungs and respiratory tract, previously believed to be sterile, harbor diverse microbial communities and the genomes of bacteria (bacteriome), viruses (virome), and fungi (mycobiome). Recent advances in amplicon and shotgun metagenomic sequencing technologies and data-analyzing methods have greatly aided the identification and characterization of microbial populations from airways. The respiratory microbiome has been shown to play roles in human health and disease and is an area of rapidly emerging interest in pulmonary medicine. In this review, we provide updated information in the field by focusing on four lung conditions, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, and idiopathic pulmonary fibrosis. We evaluate gut, oral, and upper airway microbiomes and how they contribute to lower airway flora. The discussion is followed by a systematic review of the lower airway microbiome in health and disease. We conclude with promising research avenues and implications for evolving therapeutics.
Topics: Humans; Lung; Asthma; Pulmonary Disease, Chronic Obstructive; Microbiota; Cystic Fibrosis
PubMed: 36476129
DOI: 10.1165/rcmb.2022-0208TR -
Diagnostics (Basel, Switzerland) Jun 2023The aorta is the largest elastic artery in the human body and is classically divided into two anatomical segments, the thoracic and the abdominal aorta, separated by the... (Review)
Review
The aorta is the largest elastic artery in the human body and is classically divided into two anatomical segments, the thoracic and the abdominal aorta, separated by the diaphragm. The thoracic aorta includes the aortic root, the ascending aorta, the arch, and the descending aorta. The aorta's elastic properties depend on its wall structure, composed of three distinct histologic layers: intima, media, and adventitia. The different aortic segments show different embryological and anatomical features, which account for their different physiological properties and impact the occurrence and natural history of congenital and acquired diseases that develop herein. Diseases of the thoracic aorta may present either as a chronic, often asymptomatic disorder or as acute life-threatening conditions, i.e., acute aortic syndromes, and are usually associated with states that increase wall stress and alter the structure of the aortic wall. This review aims to provide an update on the disease of the thoracic aorta, focusing on the morphological substrates and clinicopathological correlations. Information on anatomy and embryology will also be provided.
PubMed: 37443560
DOI: 10.3390/diagnostics13132166 -
Regenerative Therapy Dec 2023The human body experiences constant stimulation from Earth's gravity, and the absence of gravity leads to various impacts at the cellular and tissue levels. Simulated... (Review)
Review
The human body experiences constant stimulation from Earth's gravity, and the absence of gravity leads to various impacts at the cellular and tissue levels. Simulated microgravity (s-μg) has been employed on Earth to investigate these effects, circumventing the challenges of conducting experiments in space and providing an opportunity to understand the influence of microgravity on living organisms. Research focusing on stem cells and utilizing s-μg has enhanced our understanding of how microgravity affects stem cell morphology, migration, proliferation, and differentiation. Studies have used systems such as rotating wall vessels, random positioning machines, and clinostats. By uncovering the mechanisms underlying the observed changes in these studies, there is potential to identify therapeutic targets that regulate stem cell function and explore a range of applications, including stem cell-based regenerative medicine. This review will focus on the features of each device designed to simulate microgravity on Earth, as well as the stem cell experiments performed with those devices.
PubMed: 37662695
DOI: 10.1016/j.reth.2023.08.001 -
Parasitology International Apr 2020Proliferative sparganosis is one of the most bizarre and mysterious parasitic diseases ever described. The causative parasite is Sparganum proliferum, which is a... (Review)
Review
Proliferative sparganosis is one of the most bizarre and mysterious parasitic diseases ever described. The causative parasite is Sparganum proliferum, which is a pseudophyllidean cestode distinct from Spirometra tapeworms. Here we overview this rare but fascinating disease with the all original case reports on human patients published in the last 115 years. Proliferative sparganosis is clearly divided into two disease types, cutaneous and internal proliferative sparganosis. Cutaneous type starts with a skin eruption caused by the dermal invasion of a sparganum. Skin lesion progresses to larger areas of the body if left untreated. Various internal organs and body wall can be eventually affected. The clinical symptoms of patients in this group are very similar to each other. Molecular data suggest that cutaneous proliferative sparganosis is caused by S. proliferum of which genetic variation is limited, regardless of the time or localities of the emergence of patients. Internal proliferative sparganosis, on the other hand, is much more heterogeneous. Some cases show aggressive infection in internal organs, while others show only restricted lesions. Some of the cases that had been cited as proliferative sparganosis in the past literature were removed from the list, because they were judged as cyclophyllidean tapeworm infections. DNA sequencing is mandatory for the definite diagnosis of proliferative sparganosis. The Venezuelan strain of S. proliferum is maintained in experimental mice in Japan, which is fully prepared for the experimental study with advanced technologies in modern molecular biology.
Topics: Animals; Humans; Skin Diseases, Parasitic; Sparganosis; Sparganum
PubMed: 31841658
DOI: 10.1016/j.parint.2019.102036 -
Frontiers in Surgery 2022In humans, the incidence of congenital defects of the intraembryonic celom and its associated structures has increased over recent decades. Surgical treatment of... (Review)
Review
In humans, the incidence of congenital defects of the intraembryonic celom and its associated structures has increased over recent decades. Surgical treatment of abdominal and diaphragmatic malformations resulting in congenital hernia requires deep knowledge of ventral body closure and the separation of the primary body cavities during embryogenesis. The correct development of both structures requires the coordinated and fine-tuned synergy of different anlagen, including a set of molecules governing those processes. They have mainly been investigated in a range of vertebrate species (e.g., mouse, birds, and fish), but studies of embryogenesis in humans are rather rare because samples are seldom available. Therefore, we have to deal with a large body of conflicting data concerning the formation of the abdominal wall and the etiology of diaphragmatic defects. This review summarizes the current state of knowledge and focuses on the histological and molecular events leading to the establishment of the abdominal and thoracic cavities in several vertebrate species. In chronological order, we start with the onset of gastrulation, continue with the establishment of the three-dimensional body shape, and end with the partition of body cavities. We also discuss well-known human etiologies.
PubMed: 35874129
DOI: 10.3389/fsurg.2022.891896 -
Respiratory Physiology & Neurobiology Jan 2013Arousal from sleep is a major defense mechanism in infants against hypoxia and/or hypercapnia. Arousal failure may be an important contributor to SIDS. Areas of the... (Review)
Review
Arousal from sleep is a major defense mechanism in infants against hypoxia and/or hypercapnia. Arousal failure may be an important contributor to SIDS. Areas of the brainstem that have been found to be abnormal in a majority of SIDS infants are involved in the arousal process. Arousal is sleep state dependent, being depressed during AS in most mammals, but depressed during QS in human infants. Repeated exposure to hypoxia causes a progressive blunting of arousal that may involve medullary raphe GABAergic mechanisms. Whereas CB chemoreceptors contribute heavily to arousal in response to hypoxia, serotonergic central chemoreceptors have been implicated in the arousal response to CO(2). Pulmonary or chest wall mechanoreceptors also contribute to arousal in proportion to the ventilatory response and decreases in their input may contribute to depressed arousal during AS. Little is known about specific arousal pathways beyond the NTS. Whether CB chemoreceptor stimulation directly stimulates arousal centers or whether this is done indirectly through respiratory networks remains unknown. This review will focus on arousal in response to hypoxia and CO(2) in the fetus and newborn and will outline what we know (and do not know) about the involvement of the carotid body in this process.
Topics: Arousal; Carotid Body; Fetus; Humans; Infant, Newborn; Sleep; Sudden Infant Death
PubMed: 22684039
DOI: 10.1016/j.resp.2012.06.005 -
Antibiotics (Basel, Switzerland) Feb 2020Host-derived lipids are increasingly recognized as antimicrobial molecules that function in innate immune activities along with antimicrobial peptides. Sphingoid bases... (Review)
Review
Host-derived lipids are increasingly recognized as antimicrobial molecules that function in innate immune activities along with antimicrobial peptides. Sphingoid bases and fatty acids found on the skin, in saliva and other body fluids, and on all mucosal surfaces, including oral mucosa, exhibit antimicrobial activity against a variety of Gram positive and Gram negative bacteria, viruses, and fungi, and reduce inflammation in animal models. Multiple studies demonstrate that the antimicrobial activity of lipids is both specific and selective. There are indications that the site of action of antimicrobial fatty acids is the bacterial membrane, while the long-chain bases may inhibit cell wall synthesis as well as interacting with bacterial membranes. Research in this area, although still sporadic, has slowly increased in the last few decades; however, we still have much to learn about antimicrobial lipid mechanisms of activity and their potential use in novel drugs or topical treatments. One important potential benefit for the use of innate antimicrobial lipids (AMLs) as antimicrobial agents is the decreased likelihood side effects with treatment. Multiple studies report that endogenous AML treatments do not induce damage to cells or tissues, often decrease inflammation, and are active against biofilms. The present review summarizes the history of antimicrobial lipids from the skin surface, including both fatty acids and sphingoid bases, in multiple human body systems and summarizes their relative activity against various microorganisms. The range of antibacterial activities of lipids present at the skin surface and in saliva is presented. Some observations relevant to mechanisms of actions are discussed, but are largely still unknown. Multiple recent studies examine the therapeutic and prophylactic uses of AMLs. Although these lipids have been repeatedly demonstrated to act as innate effector molecules, they are not yet widely accepted as such. These compiled data further support fatty acid and sphingoid base inclusion as innate effector molecules.
PubMed: 32054068
DOI: 10.3390/antibiotics9020075 -
FEMS Immunology and Medical Microbiology Apr 2006The occurrence of phages in the human body, especially in the gastrointestinal tract, raises the question of their potential role in the physiology and pathology of this... (Review)
Review
The occurrence of phages in the human body, especially in the gastrointestinal tract, raises the question of their potential role in the physiology and pathology of this system. Especially important is the issue of whether phages can pass the intestinal wall and migrate to lymph, peripheral blood, and internal organs and, if so, the effects such a phenomenon could have (such passage by bacteria, known as bacterial translocation, has been shown to cause various disturbances in humans, from immune defects to sepsis). Available data from the literature support the assumption that phage translocation can take place and may have some immunomodulatory effects. In addition, phages of the gut may play a protective role by inhibiting local immune reactions to antigens derived from gut flora.
Topics: Animals; Bacteriophages; Gastrointestinal Tract; Humans; Mice
PubMed: 16553803
DOI: 10.1111/j.1574-695X.2006.00044.x