VePHY M4 Part 2 Flashcards by Danica Polbos

True or False. PTHrP expression is increased when smooth muscle is relaxed and
PTHrP induces contraction

False. PTHrP expression is increased when smooth muscle is stretched and it induces relaxation of smooth muscles and reduce contraction.

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functions as a paracrine regulator of vascular tone causing vasodilation and modulating vasoconstriction

PTHrP

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These species PTHrP gene is more closely related to the human PTHrP gene

Canine

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Calcitonin (CT) other name

thyrocalcitonin (TCT)

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second calcium-regulating hormone secreted in response to hypercalcemia responsible for the reduction of the plasma concentration of calcium

Calcitonin

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These cells are distinct from the follicular cells of the thyroid gland that are responsible for the secretion of
thyroxine (T4) and triiodothyronine (T3)

C-cells

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Name the distinctive feature of the C-cell of the thyroid gland

Presence of numerous small membrane-limited secretory granules in the cytoplasm

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True or False. In man and other adult mammals, C-cells often remain more
numerous near the hilus and the point of fusion with the ultimobranchial body.

True.

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Precursor molecule of Calcitonin

preprocalcitonin

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In which cell compartment is preproPTH is converted to procalcitonin?

Golgi apparatus

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Give other humoral factors secreted by C-cells derived from neural crest under pathologic conditions

serotonin
bradykinin
ACTH
prostaglandins

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the neuropeptide that participates in nociception, ingestive behavior, and modulation of the nervous and endocrine systems

Pre-procalcitonin gene-related peptide

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True or False. Structure of calcitonin differs considerably between species. But, , the amino terminal portion of the calcitonin molecule is similar in all species.

True.

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most potent in lowering blood calcium than any of the other calcitonins when administered to mammals & man

Salmon calcitonin

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principal physiologic stimulus for the secretion of calcitonin by C-cells

Concentration of Ca2+ in plasma and ECF

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Calcitonin is secreted continuously under conditions of?

normocalcemia

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Under normal conditions C-cells store substantial amounts of calcitonin in their cytoplasm in the form of?

membrane-limited secretory granules

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Once hypercalcemia occurs, stored Calcitonin is discharged to?

Interfollicular capillaries

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important in triggering the early release of calcitonin to prevent the development of hypercalcemia following the ingestion of a high calcium meal

Gastrointestinal hormones

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The effects of calcitonin on plasma
calcium and phosphorus are most evident in which animals

young or older animals with increased rates of skeletal turnover

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In which cells calcitonin exerts its function?

bone, kidney, intestinal cells

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Both PTH and Calcitonin decrease the renal tubular reabsorption of this ion

Phosphorus

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develops from a direct action of calcitonin on increasing the rate of movement of
phosphate out of plasma into soft tissue and bone

Hypophosphatemia

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True or False. Calcitonin is not dependent on Vitamin D.

True.

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A tumor in bulls and humans associated with low rates of skeletal turnover and densely mineralized bone

Calcitonin-secreting C-cell neoplasms

act in concert to provide a negative feedback mechanism to maintain the concentration of calcium in extracellular fluids within narrow limits

Calcitonin and PTH

Major factor concerned with the minute-to-minute regulation of blood levels of calcium and protects against the development of hypocalcemia

PTH

True or False. There is only low incidence of calcitonin-secreting neoplasms and metabolic disorders resulting from abnormal levels of calcitonin

True.

The vitamin D family

1. vitamin D3 (cholecalciferol) 2. vitamin D2 (ergocalciferol or irradiated ergosterol) 3. 1,25-dihydroxycholecalciferol (calcitriol; 1,25-dihydroxyvitamin D)

Cholecalciferol is ingested in small amounts in the diet, it is synthesized in?

Epidermis

A high-affinity vitamin D-binding protein in the serum transports cholecalciferol from its site of synthesis in the skin to the?

liver

Cholecalciferol is synthesized from _________ in the skin by a photochemical reaction caused by ultraviolet irradiation

7-dehydrocholesterol

Cholecalciferol obtained from dietary resources or produced endogenously binds to an ______ in the blood for transport to the liver

alpha2-globulin

First step in the metabolic activation of vitamin D

Conversion of cholecalciferol to 25- dihydroxycholecalciferol

Where does first step of metabolic activation of Vit. D occurs?

liver

Enzyme which converts cholecalciferol to 25-dihydroxycholecalciferol

calciferol-25-hydroxylase

Primarily serves as a precursor for the formation of the more active metabolites of vitamin D

25-OH-CC

High circulating levels of ______ serve as a reservoir of vitamin D for the synthesis of the active forms of vitamin D by the kidney

25-OH-CC

(25-OH-CC) conversion to 1,25-(OH)2- CC takes place in which tissues

renal epithelial cells (PCT)

Enzyme that converts (25-OH-CC) to 1,25-(OH)2- CC

25-hydroxycholecalciferol-1α-hydroxylase

True or False. Conversion of 25-OH-CC to 1,25-(OH)2-CC is the rate-limiting steps in vitamin D metabolism

True.

The main control for the final step of metabolic activation of vitamin D

Concentration of calcium in the plasma

increases the conversion of 25-OH-CC to 1,25-(OH)2-CC

PTH

Inhibits conversion of 25-OH-CC to 1,25-(OH)2-CC under certain conditions

Calcitonin

A low concentration of phosphorus in the blood _______ the rate of formation of 1,25-(OH)2-CC

Increases.

High phosphorus concentration _______ the formation of active hormone 1,25-(OH)2-CC

suppresses

Major biologically active metabolite of cholecalciferol that interacts with target cells in the intestine and bone

Dihydroxyvitamin D3 (1,25-(OH)2-CC)

Vitamin D and its metabolites function to increase the absorption of these 2 ions in the intestine

Calcium, phosphorus

act in such a way as to cause the retention of sufficient mineral ions to ensure that the mineralization of bone matrix is adequate

Vitamin D

These hormone and its ‘permissive effect’ of vitamin D maintains the proper ratio of calcium to phosphorus in the extracellular fluids

PTH

major target for (1,25-(OH)2-CC)

absorptive cells of the mucosa of the small intestine

In proximal part of SI, (1,25-(OH)2-CC) increases the active transcellular transport of?

calcium

In distal part of SI, (1,25-(OH)2-CC) increases the active transcellular transport of?

Phosphorus

What is the role of the hormone-receptor complex in the mechanism of action of 1,25-(OH)₂-CC in the nucleus?

Stimulate gene expression and synthesize Calcium-binding protein

In response to 1,25 dihydroxycholecalciferol, the absorptive cells of the intestine synthesize?

calcium-binding protein (CaBP)

True or False. The absorptive capacity of the intestine for calcium is a direct function of the amount of calcium-binding protein that is present.

True.

required for the orderly growth of bone and mineralization of cartilage in the growth plate in young animals

Vitamin D

Young animals fed diets deficient in vitamin D and housed indoors without exposure to ultraviolet irradiation develop?

Rickets

also result in rickets because of the failure to maintain an adequate ion product of serum calcium and phosphorus at the zones of mineralization in bone

Phosphorus deficiency

necessary for osteoclastic resorption and calcium mobilization from bone

Vitamin D

Necessary to permit osteolytic cells to respond to PTH (“permissive effect”) under physiologic conditions

Small amounts of vitamin D or its active metabolite

enzyme that is essential for metabolic activation of precursor molecules

renal 1α-hydroxylase

True or False. Active metabolites of vitamin D also have a direct effect on the parathyroid gland

True.

directly interact with parathyroid cells to diminish the secretion of PTH

Vitamin D metabolites

useful to evaluate the potential for a dietary deficiency of vitamin D or the excess intake of vitamin D

Measurement of serum levels of 25-hydroxyvitamin D

Increases the rate of intestinal calcium and phosphorus absorption and produces hypercalcemia and hyperphosphatemia in cattle

Solanum malacoxylon

a plant that contains substantial amounts of 1,25-(OH)2-CC and has caused a debilitating disease in cattle and horses

Cestrum diurnum (‘day-blooming jessamine’)

metabolic disorder in which excessive amounts of PTH secreted by pathologic parathyroid glands cause disturbances of mineral and/or skeletal homeostasis

Hyperparathyroidism

characterized by increased bone resorption, decreased radiographic density, and incomplete fractures

osteodystrophy (osteitis fibrosa)

This disease is encountered more frequently in older dogs but is less common than secondary hyperparathyroidism of either renal or nutritional origin

primary hyperparathyroidism

Primary or Secondary Hyperparathyroidism? Mineralization of renal tubule and formation of multiple calculi.

primary hyperparathyroidism

form of hyperparathyroidism is a metabolic disease characterized by an excessive, but not autonomous, rate of PTH secretion caused by chronic renal failure

secondary renal hyperparathyroidism

Type of hyperparathyroidism encountered most frequently in dog but also occurs in cats and other animal species

Renal Hyperparathyroidism

End results as response to compensatory mechanisms to increase hormonal synthesis and secretion in response to hypocalcemia

Cellular hyperplasia

Condition due to the accelerated rate of resorption that bones become softened and are readily pliable and the jaws fail to close properly

rubber-jaw disease

Dietary mineral imbalances of etiologic importance in the pathogenesis of nutritional hyperparathyroidism

(a) a low content of calcium (b) excessive phosphorus with normal or low levels of calcium (c) inadequate amounts of vitamin D3

does not stimulate the parathyroid gland directly but does so indirectly, by virtue of the ability to lower blood calcium

Hyperphosphatemia

In horses, the most frequent nutritional imbalance involves the ingestion of excessive amounts of _______

phosphorus

Horses develop nutritional hyperparathyroidism after pasturing on grasses with a high _______ content

oxalate

appear to form insoluble complexes with calcium in the intestine resulting in an elevated fecal calcium; phosphorus ratio

oxalates

results from the secretion of subnormal amounts of parathyroid hormone by pathologic parathyroid glands

Hypoparathyroidism

usually associated with diffuse lymphatic parathyroiditis resulting in extensive degeneration of chief cells and partial replacement by fibrous connective tissue

idiopathic hypoparathyroidism

Malignancies commonly associated with hypercalcemia

(i) adenocarcinoma of the anal glands in dogs (ii) T-cell lymphomas (iii) miscellaneous carcinomas in cats and horses

2 examples of hypocalcemic syndromes of major economic and veterinary significance

Parturient hypocalcemia is dairy cows and puerperal tetany of bitches

metabolic disease of high-producing dairy cows characterized by the development of severe hypocalcemia and hypophosphatemia

Parturient hypocalcemia

may increase reciprocally as calcium levels decline during parturient hypocalcemia

Serum magnesium

Increased or suppressed? Concentration of glucose in the blood in response to hypocalcemia

Increased due to interference with the secretion of insulin from the beta cells of the pancreas

true or false. adequate level of ionized calcium in the extracellular fluid is required for insulin secretion in response to glucose

True.