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Phase II Reactions: Methylation Reactions01:17

Phase II Reactions: Methylation Reactions

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Methylation is a phase II biotransformation process involving the attachment of a methyl group to a substrate. Enzymes known as methyltransferases orchestrate this reaction.
The mechanism of methylation unfolds in two stages. The first stage sees a methyltransferase enzyme facilitating the transfer of a methyl group from S-adenosylmethionine (SAM) to the substrate, forming S-adenosylhomocysteine (SAH). The second stage involves further metabolism of SAH into homocysteine, which can be recycled...
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Hypoxia is a medical condition characterized by an inadequate oxygen supply to body tissues. It typically manifests as a bluish discoloration of the skin and mucosae, especially in fair-skinned individuals, when hemoglobin (Hb) saturation drops below 75%.
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Hemoglobin is a globular protein made up of four subunits. Two of these subunits are alpha chains, and the other two are beta chains. Each subunit contains a molecule of heme, which has an iron atom and can bind to oxygen. When an oxygen molecule binds to one heme group, it changes the shape of hemoglobin, making it easier for the other heme groups to bind oxygen as well.
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Hyperventilation refers to a higher-than-normal rate and depth of breathing, often associated with anxiety attacks. This excessive breathing surpasses the body's need to expel CO2, leading to a condition known as hypocapnia - an unusually low level of carbon dioxide in the blood. Hypocapnia can constrict cerebral blood vessels, reducing blood flow to the brain, which may result in dizziness or fainting. Early signs include tingling and muscle spasms in the hands and face, caused by falling...
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Hemoglobin (Hb) is a crucial molecule in the human body, consisting of four polypeptide chains, each bound to an iron-containing heme group. This unique structure enables hemoglobin to bind to oxygen, with each molecule capable of combining with four molecules of oxygen, leading to rapid and reversible oxygen loading. When fully loaded with oxygen, it is called oxyhemoglobin, while hemoglobin that has released oxygen is called reduced hemoglobin or deoxyhemoglobin. As hemoglobin binds oxygen,...
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Measurement of Heme Synthesis Levels in Mammalian Cells
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Headache and Methemoglobinemia.

Fawad Ahmed Khan1,2,3, Caley McIntyre2,4, Abdul Mukhtadir Khan5

  • 1The McCasland Family Comprehensive Headache Center, Ochsner Neuroscience Institute, Ochsner Clinic Foundation, New Orleans, LA, USA.

Headache
|November 15, 2019
PubMed
Summary

Methemoglobinemia can cause secondary headaches due to hypoxia. Recognizing this condition is crucial for timely diagnosis and treatment, preventing delays in managing progressive hypoxia.

Keywords:
International Classification of Headache Disorderscyanosishypoxiamethemoglobin percentagemethemoglobinemiasecondary headaches

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Area of Science:

  • Neurology
  • Toxicology
  • Emergency Medicine

Background:

  • Methemoglobinemia is a condition where hemoglobin is oxidized, reducing oxygen delivery to tissues.
  • Hypoxia, a common consequence of methemoglobinemia, can trigger headaches through various mechanisms including cerebral vasodilation and oxidative stress.

Observation:

  • A case report details a patient with acute holocranial headache, paresthesia, cyanosis, and dyspnea, initially misdiagnosed as migraine.
  • Symptoms resolved with methylene blue treatment, highlighting methemoglobinemia as a treatable cause of severe headache.

Findings:

  • Headaches in methemoglobinemia may arise from nociceptor stretching during cerebral vasodilation and hypoxia-induced oxidative stress.
  • The study reviews the pathophysiology, clinical presentation, and management of methemoglobinemia-associated headaches.

Implications:

  • Clinicians should consider methemoglobinemia in the differential diagnosis of acute, severe headaches, especially with accompanying cyanosis or hypoxia.
  • The authors advocate for classifying "Headache attributed to Methemoglobinemia" as a distinct subtype in the International Classification of Headache Disorders.