Nutrition Chapter 15

Osteomalacia

"Soft bones." Vitamin D deficiency in adults. It is characterized by poor calcification of newly synthesized bone, resulting in fractures in the hip, spine, and other bones. Most likely to occur in adults with kidney or liver disease (which impairs synthesis of calcitrol) or intestinal diseases that impair fat absorption (such as Crohn's disease). Other adults at risk of deficiency include those with dark skin and those with limited UV exposure.

Preterm

Infants born before 37 weeks of gestation (also referred to as premature).

Remodeling

Lifelong process of building and breaking down of bone.

Synapse

The junction between the nerve and its target cells.

Wean

To accustom an infant to a diet containing foods rather than just milk.

Redox Agents

Because an antioxidant protects other compounds by becoming oxidized itself, in a chemical sense, antioxidants are more correctly called this ______. In other words, they can undergo both oxidation (losing an electron) and later reduction (regaining an electron).

Calmodulin

Calcium-binding protein occurring in many tissues and participating in the regulation of many biochemical and physiological processes. Calcium ions help regulate metabolism in the cell by participating in this system. Each of these bind 4 calcium ions. When calcium enters a cell (often because of hormone action) and binds to this protein, the resulting calcium and _______ complex activates many intracellular enzymes, including one that initiates the breakdown of glycogen.

Hemolytic Anemia

Disorder that causes red blood cells to break down faster than they can be replaced.

Stem Cells

Unspecialized cells that can be transformed to specialized cells.

Conjunctiva

Mucous membrane covering the front surface of the eye and the lining of the eyelids.

Dark Adaptation

Process by which the rhodopsin concentration int eh eye increases in dark conditions, allowing improved vision int eh dark.

Osteocytes

The most numerous cells in bones. Biochemically active; they can take up calcium from the blood and release it back into the blood, as well as help bone become more dense, if needed.

Retinoids

A collective term for the biologically active forms of vitamin A. Called preformed vitamin A because they do not need to be converted in the body to become biologically active, unlike carotenoids. Exist in three forms: retinol, retinal, and retinoic acid.

Provitamin

Carotenoids that can be converted into vitamin A.

Teratogenic

Causing birth defects. Most serious and tragic effects of hypervitaminosis A.

Connective Tissue

Cells and their protein products that hold different structures of the body together. Tendons and cartilage are composed largely of connective tissue. Connective tissue also forms part of bone and the nonmuscular structures of arteries and veins.

Osteoclasts

Cells on the surface of bone that dissolve bone by releasing acid and enzymes. Their activity is stimulated by parathyroid hormone, often in conjunction with Vitamin D. During times of growth, their activity is lower than osteoblast activity.

Macular Degeneration

Chronic eye disease that occurs when tissue in the macula (the part of the retina responsible for central vision) deteriorates. It causes a blind spot or blurred vision in the center of the visual field.

Hydroxyapatite

Compound composed primarily of calcium and phosphate; it is deposited in bone bone protein matrix to give bone strength and rigidity; Ca10(PO4)6OH2

Free Radicals

Compounds with an unpaired electron, which causes it to seek an electron from another compound. Free radicals are strong oxidizing agents.

Follicular Hyperkeratosis

Condition in which keratin, a protein, accumulates around hair follicles.

Xerophthalmia

Condition marked by dryness of the cornea and eye membranes that results from vitamin A deficiency and can lead to blindness.

Tetany

Continuous, forceful muscle contraction without relaxation. Nerve impulses develop spontaneously if insufficient calcium is available. Hypocalcemia. Characterized by muscle spasms because the muscles receive continual nerve stimulation. Inadequate parathyroid hormone release or action is the typical cause of hypocalcemia.

Epithelium

Covering of the internal and external surfaces of the body, such as the lungs, GI tract, blood vessel linings, and skin.

Superoxide Dimutase (SOD)

Enzyme that deactivates a superoxide free radical (O2-). SOD can contain the trace minerals copper and zinc or manganese.

Metalloenzymes

Enzymes that contain metals such as iron, copper or zinc (usually as an ion), as part of their structures. When these catalyze a reaction, the metal ion becomes oxidized.

Cortical Bone

Outer, dense shell of bone. Makes up about 75% of the skeletal mass.

Hyperparathyroidism

Overproduction of parathyroid hormone by the parathyroid glands, usually caused by a nonmalignant tumor or abnormal growth of the glands. In most cases, there are no symptoms except hypercalcemia, but, in more severe cases, weakness, confusion, nausea, and bone and joint pain occur. Bone fractures and kidney stones are also problems.

Peroxyl Radical

Peroxide compound containing a free radical; designated R-O-O*, where R is a carbon-hydrogen chain broken off of a fatty acid and the * is an unpaired electron. Also called reactive oxygen species.

Previtamin D3

Precursor of 1 form of vitamin D, produced as a result of sunlight opening a ring on 7-dehydrocholesterol in the skin. Prolonged sun exposure is not likely to result in vitamin D synthesis beyond needs or in toxic amounts because excess amounts of ______ in the skin are rapidly degraded. Overall, those who do not receive enough UV light exposure to synthesize adequate amounts of Vitamin D3 should make certain that they have adequate vitamin D in their diets.

Bleaching Process

Process by which light depletes the rhodopsin concentration int eh eye by separating opsin from all-trans-retinal. This fall in rhodopsin concentration allows the eye to become adapted to bright light.

Bone Resorption

Process in which osteoclasts break down bone and release minerals, resulting in a transfer of calcium from bone to blood.

Hemolysis

Breakdown of red blood cell membranes. Recommendation of RDA of Vitamin E is based on amount needed to prevent this from happening.

Psoriasis

Immune system disorder that causes a chronic inflammatory skin condition (painful patches of red, scaly skin).

Catalase

Important for the removal of hydrogen peroxide. This heme iron-dependent enzyme is found in the peroxisomes of cells.

Collagen

Major fibrous protein that holds together the various structures of the body. Very strong and elastic. Important constituents of connective tissues.

Cones

Responsible for the visual processes occurring under bright light, translating objects into color images. Retina.

Neutrophils

A type of white blood cells whose high concentrations may be for protection against the free radicals produced during immune functions.

RXR, RAR

Abbreviations for retinoid-X receptor and retinoid acid receptor. Bind to specific DNA sites that regulate the formation of messenger RNA and the subsequent formation of proteins through gene expression.

Kyphosis

Abnormal convex curvature of the spine, resulting in a bulge at the upper back.

Hemorrhaging

Although vitamin E is relatively nontoxic, excessive amounts from supplements can interfere with the role of vitamin K in blood clotting. This causes insufficient clotting and a risk of _______.

Glutathione Peroxidase

An enzyme located in the cytoplasm and mitochondria of cells. Important in catalyzing the breakdown of hydrogen peroxides and lipid peroxides, which are reactive oxygen species that can form free radicals if they combine with other compounds. The activity of this depends on the mineral selenium.

Osteoblasts

Bone-building cells that produce collagen and add minerals to form healthy bone. Some of the fully mineralized osteoblasts mature to form osteocytes.

Trabecular Bone

Hard, spongy network of rods, plates, and needle-like spines that add strength without much weight. Other 25% of skeletal mass. Abundant at the ends of long bones, inside the spinal vertebrae, and inside the flat bones of the pelvis. Where the most calcium and other minerals move into and out of bone.

Prohormone

Most scientists classify Vitamin D as a vitamin. However, in the presence of sunlight, skin cells can synthesize a sufficient supply of vitamin D from a derivative of cholesterol. Because a dietary source is not required if synthesis is adequate to meet needs, vitamin D is more correctly classified as a "conditional" vitamin or ___________, which is a precursor of an active hormone. In the absence of UV-light exposure, an adequate dietary intake of vitamin D is essential to prevent the deficiency diseases rickets and osteomalacia and to provide for cellular needs.

Rods

Responsible for the visual processes that occur in dim light, translating objects into black-and-white images and detecting motion. Retina.

Rickets

The skeleton will not mineralize normally without adequate calcium and phosphorus in the blood for deposition in bone. This causes the bones to weaken and bow under pressure. When these effects occur in the growing bones of a child, this vitamin D deficiency disease called ________ includes an enlarged head, joints, and rib cage, deformed pelvis, and bowed legs. In developed countries this is most commonly associated with fat malabsorption, as seen in children with cystic fibrosis. However an increase in cases has been seen in infants with dark skin pigmentation, low milk intakes, and or minimal sun exposure.

Oxidative Stress

Vitamin E reduces this damage to proteins, lipids, and DNA caused by free radicals in the body.

Carotenoids

Yellow-orange pigmented materials in fruits and vegetables, some of which are provitamins. Of the 600 or more known carotenoids, only alpha-carotene, beta-carotene, and beta-crytoxanthin can be converted to biologically active forms of vitamin A. Other carotenoids, such as lycopene, do not have vitamin A activity in humans.