Immunocytochemical localization of parathyroid hormone in hamster parathyroid gland

The immunocytochemical localization of parathyroid hormone was examined in the hamster parathyroid gland by using the protein A-gold technique. Protein A-gold particles were concentrated over secretory granules, large secretory granules thought to be storage granules and Golgi vacuoles. No protein A-gold particles were detected over large vacuolar bodies and cisternae of the granular endoplasmic reticulum.     

The fine structure of the parathyroid gland

The fine structure of the parathyroid of the macaque is described, and is correlated with classical parathyroid cytology as seen in the light microscope. The two parenchymal cell types, the chief cells and the oxyphil cells, have been recognized in electron micrographs. The chief cells contain within their cytoplasm mitochondria, endoplasmic reticulum, and Golgi bodies similar to those found in other endocrine tissues as well as frequent PAS-positive granules. The juxtanuclear body of the light microscopists is identified with stacks of parallel lamellar elements of the endoplasmic reticulum of the ergastoplasmic or granular type. Oxyphil cells are characterized by juxtanuclear bodies and by numerous mitochondria found throughout their cytoplasm. Puzzling lamellar whorls are described in the cytoplasm of some oxyphil cells. The endothelium of parathyroid capillaries is extremely thin in some areas and contains numerous fenestrations as well as an extensive system of vesicles. The possible significance of these structures is discussed. The connective tissue elements found in the perivascular spaces of macaque parathyroid are described.     

The biosynthesis of ubiquitin by parathyroid gland

Data are presented on the isolation, biosynthesis, and identification of a small peptide (H) from parathyroid gland. Under our experimental conditions this peptide (H) represents, in addition to secretory protein-I and proparathyroid hormone, the other major protein which is rapidly synthesized during shorterm incubations of tissue slices. N-terminal sequence analysis was performed on samples of peptide H and the resulting data used to conduct a search of the sequence data bank. The search established the identity of peptide H as ubiquitin. These findings establish parathyroid gland as another system which rapidly produces ubiquitin $\text{in}$$\text{vitro}$, in addition to the systems employing hypothalamus and pituitary where ubiquitin biosynthesis was initially observed by Seidah $\text{et}$$\text{al}$ and Scherrer $\text{et}$$\text{al}$.     

Endothelin receptors in human parathyroid gland.

We studied whether specific receptors for endothelins (ETs) exist in human parathyroid tissues and whether ETs may have any effect on secretion of PTH from parathyroid cells. Binding studies using [125I]ET-1 to the parathyroid membranes obtained from patients with hyperparathyroidism (2 adenomas, 2 hyperplasias) revealed that ET-1 competitively inhibited the binding of [125I]ET-1 to the membranes (the apparent Kd: 62 +/- 18 pM), whereas ET-3 showed biphasic and less steep inhibition curve than ET-1 in all tissue membranes examined. Northern blot analysis of poly(A)+ RNA from the parathyroid adenoma clearly demonstrated gene expression of both ETA and ETB receptors as well as preproET-1. ET-1 inhibited basal PTH secretion from dispersed adenoma cells more potently than ET-3. The present study clearly demonstrates the presence of both ETA and ETB receptor subtypes in human parathyroid tissues through which ETs may modulate PTH secretion in an autocrine and/or paracrine manner.     

Stromal fat content of the parathyroid gland

The proportion of stromal fat cells to parenchymal cells in 100 normal parathyroid glands was determined by the image analyzing computer technique. The parathyroid glands were resected at the time of thyroidectomy in 86 patients with thyroid tumors. None of the patients had any evidence of parathyroid dysfunction preoperatively. In the histologic sections of the parathyroid glands, the average percentage of stromal fat cell content was 38%. The percentage of stromal fat cells was correlated with the age and the body constitution of the patients, but the percentages of fat cells varied widely among glands in the given age and body constitution ranges. It was therefore not possible to discriminate a normal parathyroid gland from an abnormal gland solely on the basis of microscopic determination of stromal fat cell content.     

Calcium-binding proteins in the parathyroid gland. Detailed studies of parathyroid secretory protein

In order to identify calcium (Ca2+)-binding proteins in the parathyroid gland, we used electrophoretic blots of proteins separated by a two-dimensional nondenaturing/denaturing gel system and incubated them with 45Ca2+. Parathyroid secretory protein (PSP) and proteins with approximate molecular weights of 98,000, 88,000, 58,000, and 30,000 were noted to bind Ca2+ in cytosolic fractions from bovine parathyroid, adrenal, and pituitary glands. However, differences in the binding affinity and capacity of the various proteins were observed. PSP displayed a low affinity and high binding capacity for Ca2+. In the presence of 5 mM MgCl2 and 60 mM KCl, native PSP (immobilized on nitrocellulose filters) bound 7.5 mol of Ca2+/mol of protein monomer with an apparent Kd of 1.1 mM. Immunoblotting identified the association of PSP with parathyroid cell membranes in a Ca2+-dependent manner. This property, together with its heat stability, distinguished PSP from other cytosolic Ca2+-binding proteins which were identified. There was also evidence for a Ca2+-dependent protein-protein interaction (aggregation) of PSP present in a Nonidet P-40 extract of cell membranes. The high Ca2+ binding capacity of PSP and its Ca2+-dependent membrane association may be features that make PSP a potentially important protein in secretory cells.     

The effect of ricin on the parathyroid gland

On the basis of the performed experiments it seems that under the influence of ricin there is a parathyroid hyperactivity in the organism.     

Video‐assisted parathyroid gland mapping with autofocusing

Preservation of the parathyroid gland (PTG) in neck endocrine surgery is important for regulating the amount of calcium in the blood and within the bones. Localization of the PTG has been attempted using various methods such as ultrasound, sestamibi, computerized tomography, magnetic resonance imaging and indocyanine green fluorescence imaging. These methods cannot be used during surgery, have high sensitivity or have PTG specificity. However, autofluorescence technique has shown high sensitivity and does not require exogenous contrast. In this study, a new optical system was designed and developed into a clinical system. The system enabled easier and faster focusing on the surgical area and high‐resolution video imaging while maintaining a clear image. The system was located above the head of the surgeon. The surgeon was able to see the real‐time autofluorescent image on the monitor next to the operating table at any time to locate the PTG. The PTG buried in the adipose tissue and connective tissue was located easily and accurately. The clinical trial conducted in this study consisted of 56 parathyroid cases in 26 patients. For the statistical results, the sensitivity and accuracy in this redesigned autofluorescent imaging system were 98.1% and 96.4%, respectively.      

Conversion of proparathyroid hormone to parathyroid hormone by a particulate enzyme of the parathyroid gland.

The conversion of proparathyroid hormone (proparathormone) to parathyroid hormone (parathormone) by subcellular fractions of the bovine parathyroid has been investigated. The identification of the conversion product as parathormone was established by its elution postion during ion exchange chromatography and gel filtration, and by partial amino acid sequence analysis of its NH2-terminal region. Total homogenates and derived subcellular fractions (600 X g pellet, 5,000 X g pellet, 20,000 X g pellet, 190,000 X g pellet, and 190,000 X g supernatant) all catalyzed the conversion of exogenous [3H]- or [14C]prohormone. Over 60% of the converting activity was in the particulate fractions; the 190,000 X g particulate fraction contained the highest specific converting activity. The converting activity appeared to be an integral component of the membranes since it could only be partially removed by extraction with Triton X-100. The production of parathormone by the particulate converting enzyme increased with time and the concentration of enzyme protein. The optimum pH range was between 7 and 9, and the enzyme was inactive below pH 6. Conversion by the particulate enzyme was inhibited by benzamidine or chloroquine, but not by pancreatic trypsin inhibitor, indicating its dissimilarity to trypsin. When a mixture of [14C]proparathormone and [3H]parathormone was used as substrate, the particulate enzyme did not metabolize the hormone despite over 70% conversion of the prohormone to hormone and other peptides. There was a close correlation between the subcellular distribution of converting activity and that of newly formed parathormone found in the membrane fraction. These data suggest that the particulate converting activity is that concerned with the formation of parathormone in vivo.