![]() This is a metabolic disorder that can disrupt neuronal function before causing ischemic-type degeneration or necrosis that is visible with the light microscope. It is important to appreciate that in severe cases the clinical signs represent a much more diffuse neuronal dysfunction than the distribution of histologic lesions seen at necropsy. Within the CNS, specific groups of neurons are more susceptible to this interference with aerobic metabolism than others (i.e., neocortex, lateral geniculate nucleus, and caudal colliculus). The brain is at great risk when thiamine is inadequate because of the brain’s dependence on aerobic metabolism for which TPP is a critical participant. Thiamine (as TPP) also participates as a cofactor in the production of adenosine triphosphate (ATP) in the Krebs cycle. Erythrocyte transketolase is important in the pentose phosphate shunt pathway for glucose metabolism in the bovine brain. Thiamine must be present in adequate levels to allow production of the coenzyme TPP (also called thiamine diphosphate), which is the active form of thiamine that works as a coenzyme for several enzymatic reactions such as those involving red blood cell transketolase, and both pyruvate and α-ketoglutarate dehydrogenases. Thiamine is present in tissue as free thiamine or derivatives of thiamine, with thiamine pyrophosphate (TPP) being the most biologically active form and a coenzyme/cofactor in several key pathways of energy metabolism. The cause of PEM has been the subject of much research regarding thiamine metabolism, thiaminase activity in the rumen, the effect of various feedstuffs on rumen microbial flora related to thiamine production or destruction, and chemicals that alter thiamine levels in ruminants. Adult dairy cattle are rarely affected unless associated with acute ruminal acidosis. The most common age for sporadic PEM in dairy calves is 2 to 8 months of age calves younger than 3 weeks of age are seldom at risk for PEM. In dairy calves, the disease usually is sporadic, but in grouped yearling heifers, the morbidity may reach 10% to 25%, similar to herd outbreaks in beef feeder calves or yearlings. Polioencephalomalacia (PEM) or cerebrocortical necrosis is a thiamine-responsive disease that occurs in ruminant calves and less commonly in adult cattle. Divers, Alexander de Lahunta, in Rebhun's Diseases of Dairy Cattle (Third Edition), 2018 Etiology ![]() Read more about vaping health risks.Thomas J. The Texas Department of State Health Services recommends that youth, young adults, pregnant women and all non-tobacco users avoid vaping because of the potential increased risk for viral infection and other diseases. In Texas, an individual must be at least 21 years old to legally buy or own tobacco products, including e-cigarettes or vape devices. The more you know about vaping, the better you can help teens avoid its dangers. Millions of teens vape, but research shows most don’t know vaping exposes them to addictive and dangerous chemicals. Vaping devices are small and easily concealed.They have friends or family members who vape. ![]() Some reasons teens vape is because they believe it is safer than smoking cigarettes. An estimated 5,700 young people start vaping every day! Despite the dangers, vaping continues to grow in popularity. More than 2,700 people have been hospitalized with lung damage. Some teens developed severe lung illness after vaping for a short time, while others have suffered burns, seizures and the effects of nicotine addiction. Vaping reached epidemic status among teens in 2018, only about a decade after the devices hit the market.
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