Thyrocalcitonin: evidence for release in a spontaneous hypocalcemic disorder

Astragalus membranaceus Additive Improves Serum Biochemical Parameters and Reproductive Performance in Postpartum Dairy Cows

The purpose of the study was to assess the recovery, immune function, and breeding efficiency of postpartum dairy cows fed Astragalus membranaceus (AM) as a feed additive. The experiment used a completely randomized design. Cows were randomly assigned to two groups: (1) Control group fed total mixed ration (TMR; CON group, n = 15); (2) AM group fed TMR and AM (AM group, n = 15). The AM group was fed 675 g/day. The experimental results showed that compared with the CON group. The breeding interval of the AM group of dairy cows had a tendency to shorten (0.05 < p < 0.1). Plasma viscosity (PV), Plasma fibrinogen (FIB), the red cell aggregation index (TRCAI), Calcitonin (CT), Immunoglobulin M (IgM), and Luteinizing hormone (LH) results of AM group showed a time-treatment interaction (p < 0.05). Furthermore, the result of the study revealed that feeding AM as feed additives to dairy cows during the postpartum period had positive effects on wound recovery, immune function, endocrine regulation, and breeding efficiency.

Ultrastructural Evaluation of Thyroid Parafollicular Cells of Pigs with Naturally Occurring Atrophic Rhinitis

The thyroid parafollicular cells of 4-month-old control pigs and pigs with naturally occurring atrophic rhinitis were evaluated ultrastructurally. Significant difference was not observed in populations of parafollicular cells between the 2 groups of pigs. Parafollicular cells occurred in actively synthesizing and storage phases of the secretory cycle in both groups. Actively synthesizing cells had a well-developed endoplasmic reticulum, aggregated ribosomes, and prominent Golgi apparatuses with prosecretory granules. The cytoplasm of parafollicular cells in the storage phase was packed with electron-dense secretory granules. The Golgi apparatus and ergastoplasm were less prominent. There was no evidence to suggest that an interference in the synthesis or release of thyrocalcitonin by parafollicular cells was of criologic importance in the pathogenesis of atrophic rhinitis.

Influence of different calcium contents in diets supplemented with anionic salts on bone metabolism in periparturient dairy cows

At the initiation of lactation, Ca homeostatic mechanisms have to react to a tremendous increase in demand for Ca. Mobilization of Ca from bone and increased absorption from the gastrointestinal tract are required to re-establish homeostasis. It has been shown that dietary anions play an important role in the prevention of milk fever by mobilizing Ca from bone and by increasing Ca absorption in the GI tract. The purpose of the present study was to investigate the influence of different Ca contents in diets supplemented with anionic salts on bone metabolism of dairy cows. Twenty-four holstein cows (housed inside, second to fourth lactation) without a milk fever history were divided into four groups (A, B, C, D). Each group was fed a different diet which was given from day 263 of gestation till the day of parturition. Group A and B received a low calcium diet (4 g/kg DM) whereas group C and D received a high Ca diet (8 g/kg DM). In addition group B and D received anionic salts. The DCAD was calculated with the formula: DCAD (mEq/kg DM)=(0.2 Ca2++0.16 Mg2++Na++K+)-(Cl-+0.6 S2-+0.65 P3-). Blood and urine samples were collected on days 256, 270 and 277 of gestation, on the day of parturition as well as the following 5 days and on days 9, 14 and 19 after parturition. Serum Ca, P, Mg, ICTP, OC, VITD, PTH and urinary pH were analysed. The bone resorption marker ICTP showed a significant increase after parturition in all the groups. On the contrary, the bone formation marker OC decreased after parturition in all the groups. The VITD concentrations in group D and the urinary pH in group B were significantly lower compared to the other groups (p<0.05). The Ca concentrations tended to be higher in group B around parturition than in all the other groups. No significant influence of the four different diets on all the other parameters could be shown. In conclusion, this data showed that the addition of anions and the different Ca contents had no significant influence on bone resorption and bone formation markers. This may be because of the fact that the dietary cation-anion balance was not low enough (DCAD-group A: 181 mEq/kg DM, group B: -48 mEq/kg DM, group C: 210 mEq/kg DM and group D: 28 mEq/kg DM) to induce a metabolic acidosis with all its positive effects on calcium metabolism.

Pathophysiology of calcium and phosphorus disorders

Hypocalcemia and hypophosphatemia are relatively common in periparturient cows. This article reviews the etiologic factors that contribute to the development of these conditions. The physiologic role of magnesium in calcium homeostasis and the physiologic effect of dietary cation-anion difference at the cellular level are discussed in depth. A theory to explain the development of periparturient hypophosphatemia is developed.

Endocrine control of calcium and magnesium metabolism in ruminants

Although the importance of calcium and magnesium homoeostasis has been recognized for many years the precise mechanisms by which this is achieved are still not clearly understood. Over recent years interest in blood calcium regulation has been stimulated by the discovery, isolation and synthesis of calcitonin. Its significance in normal adults, however, remains in some doubt (vide infra). In this paper is outlined our present knowledge of the endocrine factors which help to regulate the control of plasma calcium and magnesium concentration in ruminants through the operation of negative feedback mechanisms. Mention will also be made of those hormones which, although capable of altering the plasma concentrations of either calcium or magnesium, are secreted independently of these concentrations. It will be seen that in many instances the chemical similarity between calcium and magnesium is reflected in hormone effects or in hormone secretion rates. However, this is not always found to be so, e.g. the control of calcitonin secretion appears to be affected in different directions by plasma calcium and magnesium concentrations.

Endocrine control of calcium and magnesium metabolism in ruminants

Although the importance of calcium and magnesium homoeostasis has been recognized for many years the precise mechanisms by which this is achieved are still not clearly understood. Over recent years interest in blood calcium regulation has been stimulated by the discovery, isolation and synthesis of calcitonin. Its significance in normal adults, however, remains in some doubt (vide infra). In this paper is outlined our present knowledge of the endocrine factors which help to regulate the control of plasma calcium and magnesium concentration in ruminants through the operation of negative feedback mechanisms. Mention will also be made of those hormones which, although capable of altering the plasma concentrations of either calcium or magnesium, are secreted independently of these concentrations. It will be seen that in many instances the chemical similarity between calcium and magnesium is reflected in hormone effects or in hormone secretion rates. However, this is not always found to be so, e.g. the control of calcitonin secretion appears to be affected in different directions by plasma calcium and magnesium concentrations.

Calcitonin. A review of experimental and clinical investigations

In 1962 Copp proposed the existence of a hypocalcaemic hormone. Subsequent studies have shown him to be right.

Calcitonin is a potent inhibitor of bone resorption. By its action it lowers systemic blood calcium. It is secreted in response to hypercalcaemia by a distinct endocrine system within the thyroid in mammals and within the ultimobranchial bodies in fish, amphibia and reptiles. The active principle from pig has now been isolated and found to be a polypeptide composed of thirty-two amino acid residues. Together with parathyroid hormone, the hormone provides precise regulation of calcium concentration in the blood and controls bone remodelling and mineral turnover. Calcitonin in man may be secreted in excessive amounts by medullary carcinoma of the thyroid. In addition, aberrations in its secretion may play a role in pseudohyper-parathyroidism and ostepetrosis.