Decreased levels or impaired function of protein S, a vitamin K-dependant physiological anticoagulant, leads to decreased degradation of factor Va and factor VIIIa and an increased propensity to venous thrombosis.

Types

There are three types of hereditary protein S deficiency:

Type I - decreased protein S activity: low levels of free protein S, normal levels of bound protein S
Type IIa - decreased protein S activity: low levels of free protein S, low levels of bound protein S
Type IIb - decreased protein S activity: normal levels of free protein S, normal levels of bound protein S

Decreased activity is present in an acquired form in vitamin K deficiency or treatment with warfarin. This generally also impairs the coagulation system itself (factors II, VII, IX and X), and therefore predisposes to bleeding rather than thrombosis. Protein S levels are also lower in pregnancy and liver disease.

Protein S deficiency is the underlying cause of a small proportion of cases of disseminated intravascular coagulation (DIC), deep venous thrombosis (DVT) and pulmonary embolism (PE).

Hereditary PSD is an autosomal dominant condition, resulting in a 50 precent chance of passing the disease to offspring. Less than half of those diagnosed with PSD will experience thrombosis, and those who do usually are affected only from the age of the late teens onwards. A positive blood test can lead to the loss of health insurance benefits and/or employment, and the social downsides need to be balanced against the actual medical benefit of accurate diagnosis. Screening of young children is usually deferred because early testing is often inaccurate, and it is better to wait until they are old enough to decide for themselves whether they want to be tested.

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One-third of Americans have iron deficiency
From Nutrition Health Review, 3/22/04

The World Health Organization has estimated that more than one-third of the world's population has iron deficiency, making it the most prevalent nutritional problem in the world today. However, a researcher at the University of Missouri-Columbia is taking steps to help change those statistics for the betterment of society.

Elizabeth Rogers, Assistant Professor of Nutritional Sciences, is trying to understand how plants acquire iron from the soil and how to identify and characterize the genes involved in iron sensing, regulation, and transport in plants. Understanding iron uptake in plants is extremely important because one-third of the world's soils are deficient in iron.

"For most people, plant material is the major source of iron, so assisting plants to have higher stores of bioavailable iron will help both plant productivity and human nutrition," she said.

Dr. Rogers is using the model plant Arabidopsis thalilana to examine how plants obtain iron from soil. First, the plant determines whether it has enough iron for growth or whether it needs to obtain more from soil. She is taking a closer look at the process used by plants to sense iron levels.

If a plant does need additional iron, a group of biochemical responses are "turned on" in the plant's roots to help bring in iron from the soil. Some of these processes are understood, but Dr. Rogers hopes to discover additional mechanisms that are as yet unknown.

Iron is called a "micronutrient" because the mineral is essential for life in very small amounts. Iron is a critical component of hemoglobin, the protein that carries oxygen in red blood cells. Hemoglobin delivers oxygen to cells throughout the human body, where it is used to produce energy. When humans do not get enough iron, their red blood cells do not carry as much oxygen, which results in tiredness and weakness. Iron deficiency also is associated with decreased immune function, a attention span, and a reduced ability to learn.

Iron needs are greatest during periods of rapid growth, such as in childhood, adolescence, pregnancy, and childbearing years for women. However, too much iron can cause heart problems.

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