Enzyme histochemical investigations of the mammalian carotid body

The carotid body (CB) in mammals is a small cluster of chemosensory and supporting cells located at the carotid bifurcation. It has been proposed that the chemoreceptor glomus cells release a variety of neurotransmitters that trigger upon hypoxia an action potential through the afferent fibers, thus conveying the chemosensory information to the central nervous system. By means of histochemical techniques the presence and distribution of certain metabolic enzymes was demonstrated in the CB of rats, guinea pigs and rabbits. In particular, we have revealed that the glomus cells expressed hydrolytic enzymes such as alkaline phosphatase (AP), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and ATPase as well as oxidoreductases including oxidases like monoamine oxidase (MAO) and dehydrogenases like succinate dehydrogenase (SDH), lactate dehydrogenase (LDH), isocitrate dehydrogenase (IDH), glucose-6-phosphate dehydrogenase (G6PD), glutamate dehydrogenase (GDH) and NADPH dehydrogenase (NADPH-diaphorase). In addition, the sustentacular cells also contained, although in a much lesser degree, AP, BChE, LDH, G6PD, GDH and NADPH-d. Some AP and SDH activity was seen in the CB microvasculature as well. Our results provide evidence that the two types of parenchymal CB cells display a different enzyme content and that the glomus cells possess enzymatic properties necessary for the secretory process. It can also be inferred that the chemoreceptor function and the nerve impulse conduction need an intensive molecular and cation exchange, and energy supply

Morphology of the rat carotid body

The carotid body (CB) is the main peripheral arterial chemoreceptor that registers the levels of pO2, pCO2 and pH in the blood and responds to their changes by regulating breathing. It is strategically located in the bifurcation region of each common carotid artery. The organ consists of "glomera" composed of two cell types, glomus and sustentacular cells, interspersed by blood vessels and nerve bundles, and separated by connective tissue. The neuron-like glomus or type I cells contain numerous cytoplasmic organelles and dense-cored vesicles that store and release neurotransmitters. They form both conventional chemical and electrical synapses between each other and are contacted by peripheral nerve endings of petrosal ganglion afferent neurons. The glial-like sustentacular or type II cells sustain physiologic neurogenesis in the adult CB and are thus supposed to be progenitor cells. This new source of adult stem cells may be potentially useful for tissue repair after injury or for cell therapy against neurodegenerative diseases. The CB is a highly vascularized organ and its intraorgan hemodynamics possibly plays a role in the process of chemoreception. There is also evidence that chronic hypoxia induces marked morphological and neurochemical changes within the CB but the detailed molecular mechanisms by which these affect the hypoxic chemosensitivity still remain to be elucidated. Dysregulation of the CB function is implicated in various physiological and pathophysiological conditions, including ventilatory altitude acclimatization and sleep-disordered breathing. Knowledge of the morphological and functional aspects of the CB will contribute to our better understanding of respiratory homeostasis in health and disease.Biomedical Reviews 2011; 22: 41-55

Diagnostic and Prognostic Microbial Biomarkers in Inflammatory Bowel Diseases

The microbiome plays multifaceted roles in the pathogenesis of inflammatory bowel diseases (IBD). Accordingly, the clinical challenge of patient heterogeneity in disease phenotype and response to treatment should in part be addressed by biomarkers that detect the host response to microbiota, and the levels of microbial taxa and products eliciting the host response in susceptible individuals. Molecular analysis has revealed much evidence for microbial taxonomic membership and microbial products in association with IBD, but their utility as clinical biomarkers is still in its infancy. A rich area of progress has been the development and validation of host serologic microbial biomarkers, which have achieved a distinctive position in the diagnosis and prognosis in IBD, and as a template for defining other categories of microbial biomarkers in disease state and phenotype