Gland Of Sheep Research Articles

Genetic and environmental variation in the LH response of ovariectomized sheep to LH-RH

The influence of breed and season on the sensitivity of the pituitary gland of sheep to LH-RH was assessed. Ovariectomized ewes of 3 breeds (Finnish Landrace, Scottish Blackface and Tasmanian Merino) with differing normal breeding seasons and with differing ovulation rates were injected (i.v.) with 3 doses of LH-RH (1.56, 6.25 or 25.0 micrograms) at 3 different times of the year covering the anoestrous and the breeding seasons of intact ewes; 9 ewes of each breed (3 per sub-class) were examined on the first and third occasions, 6 (2 per sub-class) on the second. The response was measured in terms of the concentration of LH in peripheral plasma 20, 40, 60 and 80 min after injection. Time of year, but not the breed of sheep, affected the magnitude of the response; the data indicated that the duration of LH secretion was greater during the breeding season than during anoestrus. It was concluded that changes in the spontaneous activity of the hypothalamus/hypophysis could contribute to seasonal changes in LH secretion independently of the modifying effects of gonadal steroids. Such variation in unmodulated activity apparently does not contribute to the differences in ovulation rate among the 3 breeds.

The effect of prolonged Kale feeding on the thyroid glands of sheep

Four groups of sheep were fed the following rations: Group I Kale ad lib., Group II Kale ad lib.+0·22 kg. blood meal/flaked maize mixture, Group III Kale ad lib.+0·22 kg. blood meal/flaked maize mixture and 10 mg. Kl weekly by mouth, Group IV 0·9 kg. hay+0·22 kg. blood meal/flaked maize mixture. They were fed these rations for 17 weeks when the sheep were killed. The thyroids were removed, weighed and pieces were taken for histological examination. The kale had a goitrogenic effect which was overcome by the iodine supplementation. The group receiving kale showed only a three-fold increase in thyroid weight whereas the group receiving the blood meal/flaked maize mixture in addition to the kale showed a six-fold increase in weight. The mixture had no goitrogenic effect when fed without kale to the control group. The mixture appears to increase the goitrogenicity of the kale. The histology shows considerable hypertrophy of follicular epithelial cells and a diminution in colloid and this accounts for the weight incrase of the glands.

Interrelationships Between the Thyroid Gland and Adrenal Cortex During Fear, Cold and Restraint in the sheep

To examine the relationship between the functioning of the adrenal and thyroid glands in sheep, plasma cortisol concentration, concentration of protein-bound 125I from thyroid vein plasma, heart rate and blood pressure were measured in ewes bearing exteriorized thyroid glands. During these measurements stresses were imposed on the animals: fear induced by pistol shots or by a barking dog, cold by cooling and wetting, and physical restraint by a loose harness. Increases in plasma cortisol concentration of 2-6 mug/100 ml were observed with each type of stressor, the response rapidly decreasing with habituation of the animal. Increases in the concentration of protein-bound 125I from thyroid vein plasma were also observed repeatedly during cooling and wetting, occasionally after the introduction of a barking dog, and during continued restraint. Cooling and wetting was the only stress causing consistent parallel activation of the adrenal cortex and thyroid gland; the other stressors resulted in independent fluctuations of secretions, as indicated by plasma cortisol concentration and concentration of protein-bound 125I from thyroid vein plasma. No reciprocal relationship between thyroid gland and adrenal cortex activity was detected. It was concluded taht these ewes, which had been accustomed to normal experimental procedures for a period of 2 years, demonstrated functional independence of thyroid and adrenal cortical secretions when subjected to stress.

Serum calcium and magnesium levels during pregnancy and at calving in heifers and young cows, and the relationship between these components and the incidence of puerperal paresis in older half-sisters: Henricson, B., G. Jönsson and B. Pehrson: Zbl. Vet. Med. A, [formula omitted]: 625, 1975. Department of Animal Genetics, Nutrition and Hygiene, Royal Veterinary College, Stockholm, Sweden and the Research

There is strong evidence that the gonads modulate the hypothalamic–pituitary–adrenal axis. To investigate these sex differences at the adrenal glands of sheep we compared the cortisol response to ACTH (experiment 1) and measured the relative expression of oestrogen receptor alpha (ERS1), androgen receptor (AR), melanocortin 2 receptor (MC2R) and steroid acute regulatory protein (STAR) mRNA in adrenal glands (experiment 2) of gonadectomised rams and ewes either with or without sex steroid replacement. In experiment 1 six castrated adult rams and four ovariectomised adult ewes were used in two ACTH trials. On each trial blood samples were taken every 15 min for 4 h through an indwelling jugular catheter and each animal received 0.5 mg of an ACTH analogue i.v., immediately after the sample at 1 h from the beginning of the trial. Four days after the first trial the males received 100 mg of Testosterone Cyclopentilpropionate (TC) i.m. and the females received 2.5 mg of Oestradiol Benzoate (EB) i.m. At 72 h after TC or EB administration the second trial was performed. In experiment 2 the adrenal glands were obtained from gonadectomised adult rams (n=8) and adult ewes (n=8). Four rams received 100 mg of TC i.m. and four females received 0.5 mg of EB i.m. Blood samples were taken at 0, 12, 24, 48 and 72 h relative to steroid replacement and the animals were thereafter slaughtered. Cortisol, testosterone and 17β-oestradiol were determined by radioimmunoanalysis. The transcripts of ERS1, AR, MC2R and STAR were determined by real-time reverse transcription PCR in adrenal tissue. Cortisol secretion was higher in female sheep than in male sheep, and higher in EB-treated than non-treated ewes. No difference in cortisol secretion was observed between TC-treated and non-treated rams. Gonadectomised rams treated with TC presented greater AR mRNA and MC2R mRNA expression than males without the steroid replacement. Gonadectomised ewes treated with EB tended to present lower AR mRNA than the ones without steroid replacement. Gonadectomised rams with TC also had greater AR mRNA, ERS1 mRNA and MC2R mRNA expression than ewes treated with EB. The relative amount of STAR transcript was not different among the different groups. The results confirm sex differences in ACTH-induced cortisol secretion in sheep, as well as in the expression of the receptor proteins for both 17β-oestradiol and testosterone in the sheep adrenal gland. However, the underlying mechanisms for sex steroid modulation remain unresolved.

Isolation and structure of two prostaglandin endoperoxides that cause platelet aggregation.

Incubation for a short time of arachidonic acid with the microsomal fraction of a homogenate of the vesicular gland of sheep in the presence of 1 mM p-mercuribenzoate followed by extraction and silicic acid chromatography yielded two prostaglandin endoperoxides. The structures of these compounds, i.e., 15-hydroperoxy-9alpha,11alpha-peroxidoprosta-5,13-dienoic acid (prostaglandin G(2)) and 15-hydroxy-9alpha,11alpha-peroxidoprosta-5,13-dienoic acid (prostaglandin H(2)), were assigned mainly by a number of chemical transformations into previously known prostaglandins. The new prostaglandins were 50-200 times (prostaglandin G(2)) and 100-450 times (prostaglandin H(2)) more active than prostaglandin E(2) on the superfused aorta strip. The half-life of the prostaglandin endoperoxides in aqueous medium (about 5 min) was significantly longer than that of "rabbit aorta-contracting substance" released from guinea pig lung, indicating that none of the prostaglandin endoperoxides is identical with this factor. Addition of 10-300 ng/ml of the endoperoxides to suspensions of washed human platelets resulted in rapid aggregation. Furthermore, platelet aggregation induced by thrombin was accompanied by release of material reducible by stannous chloride into prostaglandin F(2alpha), thus indicating the involvement of endogenous prostaglandin endoperoxides in platelet aggregation.

On the Organization and Mechanism of Prostaglandin Synthetase

Abstract The organization and mechanism of prostaglandin synthetase in the vesicular gland of sheep was studied by determining the isotope effects in the transformation of [5,6,8,9,11,12,14,15]-octadeutero-arachidonic acid into prostaglandin E2 (PGE2), 11-dehydro-prostaglandin F2α (PGF2α), PGF2α, and 12-hydroxy-5,8,10-heptadecatrienoic acid. The first two products were formed from deuterated arachidonic acid by cleavage of carbon-deuterium bonds at C-9 and C-11, respectively, whereas the last two products were formed without carbon-deuterium cleavage. The ratio (product ratio) between the first and second category of products increased with time (18 to 300 s) in the presence of glutathione and hydroquinone from 1.8 to 3.5. The ratio between deuterated and unlabeled molecules divided by the same ratio of the substrate (relative D:H ratio) was almost constant during the incubation for PGE2 (0.3 to 0.4) and 11-dehydro-PGF2α (0.6 to 0.7), but increased for PGF2α (from 1.9 to 4.0) and 12-hydroxy-5,8,10-heptadecatrienoic acid in parallel with the product ratio. With l-epinephrine as cofactor, the product ratio remained almost constant during the incubation and also in this case the relative D:H ratio of PFG2α was essentially the same as the product ratio. Elimination of the hydrogen (deuterium) at C-9 in the intermediate endoperoxide is the rate-limiting step in the formation of PGE2 from the endoperoxide. The high relative D:H ratio of PGF2α excludes the existence of a separate synthetase for PGF2α and indicates that a common synthetase provides the endoperoxide precursor for both PGE2 and PGF2α.

The Sialic Acids: XVI. ISOLATION OF A MUCIN SIALYLTRANSFERASE FROM SHEEP SUBMAXILLARY GLAND

Abstract A sialyltransferase that catalyzes the synthesis of mucin from cytidine 5'-monophospho-N-acetylneuraminic acid and sialidase-treated sheep submaxillary mucin has been isolated from sheep submaxillary glands. The partially purified transferase incorporated approximately 70% of the sialic acid cleaved from the mucin by sialidase. Kinetic studies showed that the approximate Km values were 1.9 mm for the sialidase-treated mucin (calculated in terms of the concentration of N-acetylgalactosamine acceptor sites), and 0.57 mm for the CMP-N-acetylneuraminic acid. No metal ion requirement could be demonstrated for the reaction. The purified enzyme could utilize CMP-N-glycolylneuraminic acid in place of CMP-N-acetylneuraminic acid. Active acceptors included polymers containing terminal N-acetylgalactosamine residues such as sialidase-treated mucins from the submaxillary glands of sheep, pig, and cow, as well as fetuin, a glycopeptide from milk, and erythrocyte hemagglutination inhibitor. Crude extracts contained an endogenous acceptor for sialic acid, which was separated from the sialyltransferase and partially characterized as an incomplete mucin. A tissue survey showed the presence of the sialyltransferase in extracts of submaxillary glands of sheep, pig, and cow, and each of the extracts was active with the mucins obtained from any of the species. The requirements for acceptor activity are discussed. The ovine submaxillary mucin synthesized by the purified enzyme was purified and characterized, and periodate oxidation studies showed that the sialic acid was linked to the N-acetylgalactosamine residue at C-6.

Assay of cortisol, corticosterone, 11-deoxycortisol and cortisone in ovine peripheral and adrenal venous plasma.

SUMMARY An assay was devised, using Sephadex LH-20 chromatography and competitive protein binding, to measure cortisol, corticosterone, 11-deoxycortisol and cortisone in a single extract of 4 ml peripheral plasma or 50–300 μl adrenal venous plasma in sheep. The method is especially suited for measuring the low concentrations of these steroids in ovine plasma. Mean values (μg/100 ml) in dexamethasone-suppressed plasma were cortisol, 0·042; corticosterone, 0·004; 11-deoxycortisol, 0·004; and cortisone, 0·021. Mean values (μg/100 ml) in basal plasma were cortisol, 1·11; corticosterone, 0·044; 11-deoxycortisol, 0·020; and cortisone, 0·24. Peripheral concentrations of all four steroids increased in response to corticotrophin, but none increased after angiotensin. Metyrapone administration produced a marked rise in deoxycortisol. The method provided direct evidence that cortisone and deoxycortisol were secreted by the adrenal gland in sheep.

Prenatal growth of the adrenal gland in sheep.

Prenatal growth of the adrenal gland in sheep.

Ultrastructural changes in the abomasal mucosa of lambs experimentally infected with Trichostrongylus axei.

The normal ultrastructure of the abomasal fundic glands in sheep is described and compared with those of sheep infected experimentally with T. axei. Alterations were observed in mucous, mucous neck and zymogen cells and the results are compared with a similar study in normal and infected calves.

Metabolism of [1-14C]palmitate and [1-14C]oleate by the isolated perfused mammary gland of the sheep or goat

SummaryLactating mammary glands of sheep and goats were perfused for several hours in the presence of [1-14C]palmitate or [1-14C]oleate. Adequate quantities of acetate, glucose, amino acids and chylomicrons were added to the perfusate.The fall in specific activity of [1-14C]palmitic acid or [1-14C]oleic acid across the gland and the labelling of milk triglyceride fatty acids indicates an extensive transfer of radioactivity from plasma free fatty acids (FFA). The plasma triglycerides showed large arterio-venous differences in concentration. The small [14C] incorporation in plasma triglycerides decreased across the gland. In a control experiment triglycerides were also slightly labelled.There were no significant arterio-venous differences in cholesterol esters and their fatty acid composition showed only slight changes during passage through the gland. Their specific activity showed a small rise across the gland.In milk components, the [14C] was mainly localized in the triglycerides. An appreciable proportion of the palmitoleate is derived from palmitate by dehydrogenation within the gland, while there is no evidence for the hydrogenation of oleic acid to stearic acid. Elongation of palmitic acid to C18-acids does not occur to any important extent. FFA are catabolized to a variable extent by the gland.The role of FFA in labelling of milk and blood plasma fatty acid fraction is discussed.

Pituitary adrenal interactions in shorn sheep exposed to cold, wet conditions

Newly shorn sheep were exposed to a cold (3°C) wet environment for 8 days; six out of 10 untreated animals died but there were no deaths in a group of 10 that was treated with cortisone. In two other experiments, nine out of 15 control sheep died, but only four out of 15 sheep treated with adrenocorticotrophin (ACTH). In a final experiment approximately one-third of exposed controls died compared with one-tenth of sheep treated with dexamethasone trimethylacetate. A significantly greater proportion (P < 0.05) of sheep given ACTH or 1.5 mg or more of dexamethasone trimethylacetate per kg had rectal temperatures higher than 37.8°C during the first 96 hr of exposure than the comparable controls. The adrenal glands of sheep that died in the cortisone and ACTH experiments were heavier than those taken from survivors that were killed after the experiment; macroscopically, the cortices of some of the adrenals from sheep that succumbed were haemorrhagic and resembled the glands seen in the Waterhouse-Friderichsen syndrome in man; all were heavily infiltrated with lipid when compared with the cortices of survivors. ß-Glucuronidase activity in the serum of cortisone-treated sheep (and in untreated survivors) was elevated during the first 2–3 days of exposure and returned to pre-exposure levels; untreated sheep that succumbed showed continuously increasing enzymatic activity. Acid phosphatase activity was initially depressed in steroid-treated sheep and returned to pre-exposure levels, whereas activity increased continuously in controls that died. Total leucocytes were lower during the first 72 hr of exposure in sheep treated with 1.5–2 mg dexamethasone trimethylacetate per kg, compared with untreated controls. We suggest that the enlarged, fat-laden haemorrhagic adrenals found in sheep that died from cold exposure resulted from excessive ACTH stimulation prior to death. The results suggested a state of adrenocortical insufficiency during the first 96 hr of cold exposure.

Incorporation of DL-[2-14C]ornithine and DL-[5-14C]arginine in milk constituents by the isolated lactating sheep udder.

1. Lactating mammary glands of sheep were perfused for several hours in the presence of dl-[2-(14)C]ornithine or dl-[5-(14)C]arginine and received adequate quantities of acetate, glucose and amino acids. 2. In the [(14)C]ornithine experiment 1.4% of the casein and 1% of the expired carbon dioxide came from added ornithine; 96% of the total radioactivity in casein was recovered in proline; 13% of the proline of casein originated from plasma ornithine. 3. In this experiment the results of chemical degradation of proline of casein as well as relative specific activities in the isolated products are consistent with the view that ornithine is metabolized, by way of glutamic gamma-semialdehyde, to proline or glutamic acid. 4. In the [(14)C]arginine experiments 3% of the casein and 1% of the expired carbon dioxide came from arginine; 84% of the arginine and 9% of the proline of casein originated from plasma arginine. 5. In these experiments the relative specific activities of arginine, ornithine and proline in plasma are in agreement with the view that arginine is metabolized by way of ornithine to proline. The conversion of arginine into ornithine is probably catalysed by arginase, so that arginase in mammary tissue may be involved in the process of milk synthesis.

Oxygenation of Unsaturated Fatty Acids by the Vesicular Gland of Sheep

Abstract The products formed on oxygenation of certain unsaturated fatty acids in preparations of sheep vesicular gland have been studied. Oxygenation of linoleic acid yielded 9-hydroxy-10,12-octadecadienoic acid (82%) and 13-hydroxy-9, 11-octadecadienoic acid (18%). Oxygenation of 8,11,14-eicosatrienoic acid yielded 11-hydroxy-8,12,14-eicosatrienoic acid, 15-hydroxy-8,11,13-eicosatrienoic acid, 12-hydroxy-8,10-heptadecadienoic acid, prostaglandin E1 (PGE1), and prostaglandin F1α. The biosynthesis of 12-hydroxy-8,10-heptadecadienoic acid was studied with the use of [2-14C]-, [9-3H,3-14C]-, [10-3H,3-14C]-, [11-3H,2-14C]-, [13d-3H,3-14C]-, [13l-3H,3-14C]-, and [15-3H,3-14C]8,11,14-eicosatrienoic acids. These experiments showed that C-9, C-10, and C-11 are eliminated from the precursor and that the stereochemistry of the removal of hydrogen from C-13 is identical with that occurring during the biosynthesis of PGE1. The 3-carbon compound formed together with 12-hydroxy-8,10-heptadecadienoic acid from 8,11,14-eicosatrienoic acid was identified as malonaldehyde. The identification could be accomplished by condensing malonaldehyde with l-arginine, yielding δ-N-2(pyrimidinyl)-l-ornithine. The mode of formation of 12-hydroxy-8,10-heptadecadie-noic acid and malonaldehyde from 8,11,14-eicosatrienoic acid is discussed. The compounds are proposed to originate in a cyclic peroxide, which has earlier been postulated to be an intermediate in the biosynthesis of prostaglandins.

Nerve-myoepithelium and nerve-glandular epithelium contacts in the lacrimal gland of the sheep.

Electron microscope studies of several types of secretory glands (6, 17, 18) have shown that myoepithelial cells envelop the acini and resemble smooth muscle cells in their fine structure (15). No close nerve-myoepithelium contacts with a separation of less than 0.1 /i have been described, and it has been suggested, for example in the rat submaxillary gland, that activation of the myoepithelium may occur by diffusion of transmitter substance over relatively long distances (18). In examining the fine structure of the lacrimal gland of sheep, we have observed that nerves are in close association with both the myoepithelium and the acinar epithelium. The material was taken from an animal under fluothane anesthesia, fixed with 1% Os0 in a phosphate buffer, pH 7.6 (10), and embedded in Araldite (8). Unsupported sections, about 1,000 A thick, cut with glass knives in a Cambridge-Huxley-pattern microtome, and double-stained with uranyl nitrate (Merrillees, unpublished observations) and with lead citrate (11), were examined in a Hitachi 1iB electron

Influence of Pineal Body on Melanoma of Hamsters

JORDAN1,2 described the presence of melanic granules in pineal gland of sheep and del Rio-Hortega3–5 found pigment granules in the pinealocytes of human pineal as well as in other mammals. Santamarina and Meyer Arndt6 have more recently shown that the pigment in bovine pineal was true melanin. Ultra-violet spectral curves of bovine pineal melanin showed the same characteristics as those obtained from tyrosine melanin7,8. Pineal melanin differs slightly, however, from the melanin obtained from the choroid of the ox eye. Administration of pineal extract to tadpoles9,10, to toads10 and to fishes11 produces alteration in pigmentation. Thus it is possible that pineal body not only contains melanic pigment but is also capable of inducing some form of change in pigmentation. The hamster pineal body contains pigment granules in abundance (Fig. 1). On the basis of the investigations by Santamarina and Meyer Arndt, these can be assumed to be melanic granules. No data are available at present for the effects of pineal ablation or administration of pineal extract on pigmentation of hamsters. Isolated observations in other species have suggested a possible association between pineal body and pigmentation, however, and therefore a study was undertaken to observe the effect of pineal ablation on the growth and spread of a highly pigmented and spontaneously occurring neoplasm in hamsters.

The effect of adenosine triphosphate on salivation in the dog

SCHWARTZ, LASETER and KRAINTZ (1963) reported an enzymatic basis for active cation transport in the parotid gland of the dog. The enzyme, a magnesium dependent, sodium and potassium activated, microsomal adenosine triphosphatase (ATP-ase), is similar to the ATP-ase of the heart muscle but differed from that prepared from brain, liver, or kidney tissue. The mitochondrial fraction of parotid gland of sheep is also rich in ATP-ase activity (MANNI, GNLLO and AMBROSINO, 1956). The concentration of ATP in the parotid gland of the dog is markedly reduced after pilocarpine administration (GUBERNIEV, KOVYREV and RODZILLER, 1951). The addition of ATP at a level 50 mg/2*5 ml to the perfused submandibular gland of the dog results in the augmentation of pilocarpine-induced salivation (INOUE, 1958). In view of the evidence that ATP and ATP-ase may play a role in the secretory processes involved in salivation, it was of interest to determine whether ATP alone could induce salivation in the anaesthetized dog. The interpretation of results obtained from the study of effects of agents on salivation during pilocarpine-induced secretion has been criticized. Pilocarpine-induced saliva is not identical with that produced by electrical stimulation and the drug also has other systemic effects such as the release of catecholamines (BURGEN, 1964). This report deals with the effect of ATP on the induction of salivation in dogs anaesthetized with sodium pentobarbital (30 mg/kg). The studies were done on five mongrel male dogs weighing 15-20 kg. Wharton’s ducts and Stenson’s ducts were cannulated intra-orally with polyethylene tubing (PE 50). The left carotid artery was catheterized through the thyroid artery with a polyethylene cannula for the purpose of administering the ATP and also monitoring the blood pressure. The arterial blood pressure was measured with a Linear Core (E. & M. Instruments, Houston, Texas) transducer and the salivary flow rates determined with drop counters. The events were monitored with a multi-channel polygraph (Physiograph, E. & M. Instruments, Houston, Texas), ATP as a disodium salt was dissolved in 0.9% sodium chloride to give a concentration of 1 mg/ml. Studies were also made after administration of atropine sulphate 1.0 mg/kg. The ATP was administered into the carotid over a period of approximately 5 sec. It was found that the ATP was able to initiate both parotid and submandibular salivation at a level of 1 mg/kg. Saliva appeared only on the left side with the dosage used. This effect is illustrated by Fig. 1. In addition, a drop in

The biosynthesis of prostaglandin-E1 studied with specifically 3H-labeled precursors.

It was recently shown that 5,8,11,14-eicosatetraenoic acid is a precursor of prostaglandin-E2 (PGE2) in homogenates of the vesicular gland of sheep [1,2]. The conversion of 8,11,14-eicosatrienoic acid [3,4] and 5,8,11,14,17-eicosapentaenoic acid [3] into PGE1 and PGE3, respectively, was also demonstrated later using the same system. In homogenates of guinea pig lung, however, 5,8,11,14-eicosatetraenoic acid was transformed into both PGE2 and PGF2 and also into metabolites of these two compounds [5].

The biosynthesis of prostaglandins

Prostaglandins were biosynthesized to test the hypothesis that essential fatty acids could act as precursors of prostaglandins (PGS). PGE2 the PGs with the greatest biological activity were addressed first. Because of the position of the double bonds and the fact that a bended conformation of arachidonic acid suggests the possibility of trans-annular reactions arachidonic acid was investigated for the biosynthesis of PGE2 and it was found that tritiated arachidonic acid is easily converted to PGE2 by a homogenate of vesicular glands of sheep via thin-layer chromatography. This conversion indicates that the function of essential fatty acids is to act as PG precursors.

PARATHYROID ORIGIN OF CALCITONIN--EVIDENCE FROM PERFUSION OF SHEEP GLANDS.

It has been previously observed that perfusion of the thyroid-parathyroid gland complex in the dog with high calcium blood results in liberation of a hypocalcemic factor, calcitonin. In sheep, the superior parathyroid gland is separated by 2–3 cm from the thyroid and has a distinct blood supply, so that it can be perfused independently. Perfusion of this gland with high calcium blood (10.8–12.8 mg/100 ml) in 6 sheep, 3 of which had been thyroidectomized immediately prior to perfusion, resulted in a prompt fall in systemic plasma calcium, the change in 30 min being -0.530 ±0.074 mg/100 ml. Subsequently, in 5 adult sheep and 5 lambs, the thyroid was first perfused with high calcium blood for 1 hr, and then the superior parathyroid. Perfusion of the thyroid had no significant effect on systemic plasma calcium, but perfusion of the superior parathyroid resulted in a significant fall at 10 min and a change of -0.706 ±0.088 mg/100 ml by 30 min. The drop 30 min following parathyroidectomy was small and not stati...