Humoral vasopressor agents in primary hypertension

In essential hypertension and in the spontaneously hypertensive rat, there are indications for a yet unidentified vasopressor agent which may play an important role in pathogenesis. It has been demonstrated in the spontaneously hypertensive rat by parabiosis, cross-circulation, cross-transplantation of kidneys and by injection of hypertensive plasma fractions. In plasma from essential hypertensives, an agent sensitizing the vasculature to pressor hormones and a substance with direct vasopressor actions have been found. The relationship of the hypertensive factor to the natriuretic hormone is not clear.     

Immunohistochemical identification of calcitonin gene-related peptide and substance P in nerves of the bovine parathyroid gland

Summary Although peptide neurotransmitters have been shown to modulate hormone secretion in many glands, there are very few studies of neurotransmitters in the parathyroid gland. Bovine parathyroid glands were collected at a local abattoir, fixed with paraformaldehyde, sectioned using a cryostat, and stained by indirect immunohistochemistry for calcitonin gene-related peptide and substance P. We were able to positively identify both neuropeptides. Nerve fibres containing calcitonin gene-related peptide and substance P were identified in contact with the tunica media of arteries and arterioles and dispersed throughout the stroma of the gland. While many of the fibres encircled parenchymal lobules, no intimate contact with the peripheral chief cells was observed. All immunoreactive fibres were found to contain both neuropeptides. Since calcitonin gene-related peptide and substance P are vasodilators, they may increase blood flow within the gland. In addition, the neuropeptides may diffuse from perilobular nerve fibres into the parenchyma, thereby modulating secretion of parathyroid hormone.     

The triiodothyronine antagonistic effect of gamma-L-glutamyl-taurine (litoralon).

A recently recognized bioactive substance of the parathyroid glands, gamma-L-glutamyl-taurine antagonises the metamorphosis enhancing effect of triiodothyronine. Shortening of the body-length of tadpoles is significantly delayed by the substance. The experimental results imply that it fulfills the role of a balance hormone.     

Characterization of a vasopressor substance generated in human plasma by incubation

Incubation of human plasma at 37 degrees C for several hours leads to the formation of a non-dialysable vasopressor substance termed the active pressor principle. Some of the chemical and physical natures of active pressor principle were investigated in anesthetized and ganglion blocked rats. It was found to have properties characteristic of protein. The substance was crudely purified to about 25-fold in alcoholic trichloroacetic acid solution after placing the plasma in a boiling water bath for 5 minutes ("active fraction"). After treatment of the vasoactive plasma or "active fraction" with Pronase, the pressor activity was almost abolished. The molecular weight of this fraction as determined by gel filtration was about 68,000. With addition of diisopropyl fluorophosphate before incubation of the plasma, no vasopressor substance was generated. After treatment of the rat with captopril, an angiotensin converting enzyme inhibitor, the pressor effect of incubated plasma was not inhibited. These findings suggest that a vasoactive protein, which is clearly different from renin, is generated during simple incubation of plasma, and that a serine protease is involved in the formation of this substance.     

Ultrastructure of mass of floccular substance in the parathyroid gland of golden hamster.

Mass of floccular substance was observed in the parathyroid glands of fetal, newborn and infantile golden hamsters. Mass composed of floccular substances was spherical with no limiting membrane around it. It was located near the nucleus and the Golgi area, but was also observed in the peripheral cytoplasm. No cell organelles were detected within area of mass.     

Effect of plasma from essential hypertensives on vascular tone of aortic strips, isolated perfused mesentery and isolated perfused kidney

Different vascular models of normotensive Wistar rats, including aortic strips, isolated perfused mesentery and isolated perfused kidney, were used to study hemodynamic effects of plasma fractions obtained by gel filtration from the blood of essential hypertensive and normotensive subjects. Plasma fractions from essential hypertensives studied had been shown to increase blood pressure after intravenous injection in rats. In the aortic strips, 50 microliters of a hypertensive fraction (HF) elicited a calcium-dependent contraction of 0.14 +/- 0.035 mN (n = 20, p less than 0.05), which was inhibited by nifedipine, whereas tension of the strips was not significantly changed by normotensive fractions (NF) (n = 17). In the isolated perfused mesentery preparation, no significant change of perfusion pressure by HF or NF could be demonstrated (n = 10). In the isolated perfused kidney, a transient increase of perfusion pressure was induced by HF (19.5 +/- 16.6 mm Hg, n = 40, P less than 0.001) but not by NF. This increase was abolished in calcium-free, 2 mmol/l EGTA containing perfusion medium. The response was diminished, but not abolished by nifedipine. These data demonstrate vasopressor properties of plasma from essential hypertensives, which might be the consequence of a circulating vasoconstrictor substance in the blood of essential hypertensives.     

Phase‐sensitive fluorescence detector for parathyroid glands during thyroidectomy: A preliminary report

Despite advances in medical technology, the parathyroid glands are still damaged during thyroid surgery. Our previous studies exploring methods for locating the parathyroid glands using autofluorescence have limitations, such as turning off the surgical light or requiring additional matching between the autofluorescence image and real‐surgical field‐of‐view. We developed a probe‐type parathyroid autofluorescence detector using a phase‐sensitive process and optical filtering to overcome these limitations. A preliminary clinical trial was performed on eight parathyroid glands in four patients. The normalized mean signal of the normal parathyroid glands was 332% stronger than that of the thyroid, and 384%, 459% and 286% stronger than the signal of the muscle, trachea and fat, respectively. Additionally, the device also detected fluorescence from indocyanine green.     

Identification of immunoreactive sites in bovine parathyroid cells to antibodies raised against the NH2-terminal sequence of parathyroid hormone.

The NH2-terminal sequence of bovine parathyroid hormone (1-84) was localized with different immunocytochemical methods on the light and electron microscopic level in bovine parathyroid glands and in isolated bovine parathyroid parenchymal cells. The peroxidase labeled staphylococcal protein A and the peroxidase anti-peroxidase method were found to be advantageous for light and electron microscopic localization, respectively. Reaction product was found light microscopically in the cytoplasma of the parenchymal cells and electron microscopically largely over the secretion granules of the parenchymal cells. The immunoreactive sites were subsequently identified to represent only intact parathyroid hormone (1-84) by gel electrophoresis derived enzyme linked immunosorbent assay.     

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.     

Ultrastructure of the water-clear cell in the parathyroid gland of SAMP6 mice

Although the parathyroid water-clear cell is very rare, it has clinical significance because of its association with parathyroid hyperplasia or adenoma. SAMP6, a substrain of senescence-accelerated mouse, was developed as an animal model for senile osteoporosis. We investigated the morphology of the parathyroid glands in SAMP6 and age-matched normal mouse SAMR1. The parathyroid water-clear cells, which contained numerous vacuoles and the crystalloid inclusions, were found in SAMP6 mice at 5, 8 and 12 months of age. It was noted that the number of water-clear cells increased with aging, which are fairly consistent with the change of the serum parathyroid hormone (PTH) level. We did not find any water-clear cells in the parathyroid glands of SAMR1 mice. The existence of water-clear cells may represent hyperfunction of the parathyroid glands in SAMP6.     

DNA ploidy pattern of parathyroid parenchymal cells in renal secondary hyperparathyroidism with relapse.

The nuclei of parathyroid parenchymal cells, analyzed using image cytometry (ICM), in relapsing and non-relapsing secondary hyperparathyroidism due to uremia, showed a DNA-distribution pattern of diploid type. Nevertheless, some differences were observed within the groups, as regards the concept of 'scattered cells' in ICM DNA histograms. The relative incidence of 'scattered cells' was particularly high in the histograms from parathyroid glands with nodular hyperplasia and in those from parathyroid parenchyma grafted into the skeletal musculature. In these two kinds of parathyroid specimens, the 'scattered cells' were both of chief-cell and oxyphil-cell types. In contrast, 'scattered cells' were not so conspicuous when parenchymal cells of glands with diffuse hyperplasia were analyzed. As there is some clinical and histopathological evidence that the cells in both nodular-hyperplastic and autografted parathyroid parenchyma have increased growth potential, it is hypothesized that the relative incidence of the 'scattered cells' in the ICM DNA histograms indicates an increased proliferative activity.     

Do parathyroid glands from individuals of different age and gender contain lymph vessels?

Whereas lymph vessels in some endocrine glands have been thoroughly investigated, data on these vessels in human parathyroid glands are often contradictory and deficient in available literature. Therefore, the aim of this study was to histomorphologically investigate whether lymph vessels could be found in human parathyroid glands postnatally and, if so, whether their presence was age- and gender-dependent. A total of 44 parathyroid glands from subjects of both genders, aged 4-90 years, were studied. The glands were divided into three groups. Those from the 1st and the 2nd age group demonstrated similar morphological structure of parenchyma with predominant chief cells with pale-staining cytoplasm, while the frequency of lymph vessels was lower in the 2nd group. Unlike in these groups, chief cells with dark- staining cytoplasm predominated in the glandular parenchyma of the 3rd age group where lymph vessels were not found in any of the examined glands. The frequency of lymph vessels in parathyroid glands was almost the same for both genders. Histomorphologic occurrence of lymph vessels coincided with the presence of endocrine cells with pale-staining cytoplasm, which allowed the assumption that lymph vessels were also one of the signs of functional activity of human parathyroid glands.     

Effects of isoproterenol treatment on the parathyroid glands in golden hamsters of different ages, with special reference to the frequency of lipid droplets

The frequency of lipid droplets in the parathyroid glands of young, adult and senile golden hamsters after treatment with isoproterenol was investigated. In the parathyroid glands of the young and senile animals the number of lipid droplets increased gradually by 1 h, and thereafter it remained almost unchanged at 3 h after administration. In the glands of adult animals it increased, at first rapidly and then gradually, by 3 h after administration. It is considered that in the parathyroid glands of the golden hamsters stimulated by isoproterenol there is a relationship between the number of lipid droplets and aging.     

Ultrasound-guided fine needle aspiration cytology of parathyroid lesions. A review of 72 cases

OBJECTIVE: To elucidate the specific cytomorphologic patterns and diagnostic pitfalls in fine needle aspiration cytology (FNAC) of parathyroid lesions. STUDY DESIGN: Seventy-two cases of surgically excised and pathologically verified hyperparathyroidism (20 cases of parathyroid hyperplasia, 51 of parathyroid adenoma and one of parathyroid carcinoma) received preoperative, ultrasound-guided FNAC examination for enlarged parathyroid glands. The smears were reviewed and analyzed. RESULTS: Parathyroid lesions were diagnosed cytologically in 60 cases (83.3%). The presence of colloidlike substance, macrophages or follicular structures in smears led to six cases (8.3%) being misinterpreted as thyroid lesions. The cellularity of the smears was insufficient for interpretation in six cases (8.3%); however, two of these cases were diagnosed by determination of parathyroid hormone (PTH) levels in the fluid. Parathyroid hyperplasia had more tightly cohesive cell clusters with monomorphism, while parathyroid adenoma had more dispersed or loosely cohesive cells with pleomorphism and anisokaryosis. High PTH concentration in an aspirate was noted in all four cases of cystic lesions.     

The degradation of proparathormone and parathormone by parathyroid and liver cathepsin B.

Purified cathepsin B from porcine parathyroid glands was allowed to act upon radioactive bovine parathormone and proparathormone at various ratios of enzyme to substrate and for different times. The reaction products were isolated by ion exchange chromatography and analyzed by gel electrophoresis, amino acid composition, sequence analysis, and bioassay. The enzyme cleaved parathormone between residues 36 and 37 yielding a major carboxyl and amino fragment and appeared to cleave proparathormone at the same locus. The amino fragments were degraded further by removal of small peptides (possibly, di- or tripeptides) from their COOH termini. In contrast there was little if any degradation of the carboxyl fragment (residues 37 to 84). Despite the ease with which the enzyme cleaved the arginyl bond in the synthetic substrate benzyloxycarbonyl-Val-Lys-Lys-Arg-(4-methoxy)-2-naphthylamide, it did not remove the near homologous NH2-terminal hexapeptide extension of proparathormone (Lys-Ser-Val-Lys-Lys-Arg-R)--a reaction that would lead to the formation of parathormone from proparathormone. Purified liver cathepsin B cleaved the hormonal substrates in a fashion identical with that of the parathyroid enzyme.     

Experimental study of the origin of the parathyroid glands.

The origin of the parathyroid glands was investigated in chick embryos (Gallus domesticus). Pieces of the third branchial arch were grafted, and its ectodermal layer formed a new structure (parathyroid III), which became separated from the placodial ectoderm. This structure continued to develop until, together with neural crest cells which gave rise to the mesenchyme, it formed a distinct parathyroid III gland by stage 28 of Hamburger and Hamilton.     

A membrane-bound metallo-endopeptidase from rat kidney. Characteristics of its hydrolysis of peptide hormones and neuropeptides.

A membrane-bound metallo-endopeptidase that hydrolyzes human parathyroid hormone (1-84) and reduced hen egg lysozyme between hydrophilic amino acid residues was isolated from rat kidney [Yamaguchi et al. (1991) Eur. J. Biochem. 200, 563-571]. In this study, the hydrolyses of various peptide hormones and neuropeptides by the metallo-endopeptidase were examined using an automated gas-phase protein sequencer. The purified enzyme hydrolyzed the oxidized insulin B chain and substance P most rapidly, followed by big endothelin 1, neurotensin, angiotensin 1, endothelin 1, rat alpha-atrial natriuretic peptide and bradykinin, in this order. The enzyme mainly cleaved these peptides at bonds involving a hydrophilic amino acid residue. However, it cleaved bonds between less hydrophilic amino acid pairs in several short peptides, e.g. at the His5-Leu6 bond in oxidized insulin B chain, the Ile28-Val29 bond in big endothelin-1 and the Ile5-His6 and Phe8-His9 bonds in angiotensin 1. The enzyme cleavage sites of oxidized insulin B chain and angiotensin 1 were different from the reported sites cleaved by meprin and by endopeptidase 2, respectively. Kinetic determination of bradykinin hydrolysis by the purified enzyme yielded values of Km = 18.1 microM and kcat = 0.473 s-1, giving a ratio of kcat/Km = 2.62 x 10(4) s-1.M-1. The Km value was about 20-fold lower than that reported for meprin and endopeptidase 2. These results indicate that the membrane-bound metallo-endopeptidase from rat kidney is distinguished from meprin and endopeptidase 2 in its substrate specificity and is not parathyroid hormone specific, but has potential capacities to inactivate various biologically active peptide hormones and neuropeptides in vivo.     

S-100 protein and neuron-specific enolase in parathyroid glands and C-cells of the thyroid

Normal parathyroid glands and parafollicular cells (C-cells) of man, rat and rabbit, and also human parathyroid adenomas and medullary carcinomas were investigated for the presence of S-100 protein and neuron-specific enolase (NSE). For determination of the proteins immunoperoxidase methods were applied, i.e., the PAP method and the avidin-biotin system. The antisera, of polyclonal origin, were specifically directed against cow S-100 protein and rat or bovine NSE. The respective antisera are known to crossreact with S-100 protein from man, rat, and rabbit, as well as with NSE from man and rat. Surprisingly, the test for S-100 protein was found to be strongly positive in the parathyroid glands of rat and rabbit and was focally positive in normal and adenomatous human parathyroid glands, but completely negative in C-cells and medullary carcinoma cells. NSE was present in C-cells of rat and man, and in medullary carcinoma cells, but was absent in normal and adenomatous parathyroid cells. The results support data that indicate that both parathyroid cells and C-cells are derived from elements of the neural crest, but undergo different maturation processes during embryological development.     

Abnormal calcium distribution in human parathyroid adenomas as possible cause of primary hyperparathyroidism

Current knowledge suggests that normal parathyroid glands and parathyroid adenomas have different sensitivities to environmental calcium. In search for morphological equivalents, 5 normal human and 10 porcine parathyroid glands, as well as 10 human parathyroid adenomas were investigated with regard to intracellular and extracellular calcium distribution. The glands were incubated for 2, 4, 6 and 20 h in tissue cultures using HAM's F10 medium with various calcium concentrations. For visualization of the calcium distribution in the tissue the method of pyroantimonate precipitation was applied. Specificity of the reaction was controlled by X-ray microanalysis. Shifts of the calcium pyroantimonate precipitates were quantitated by morphometry using an area-counting system. The results demonstrate that in normal parathyroid glands calcium precipitates are distributed randomly. Incubation of normal glands in medium with low calcium concentration (0.6 mM) provoked reduced amounts of intracellular and extracellular calcium complexes. When the incubations were performed in medium with high calcium content (2.6 mM), calcium accumulated inside parathyroid and stroma cells. In contrast to normal parathyroid glands, parathyroid adenomas fixed immediately after surgery showed an atypical calcium distribution with low amounts of intracellular and high amounts of extracellular calcium grains. The data suggest that in normal parathyroid glands the intracellular calcium concentration follows the extracellular environmental calcium concentration. Thus, calcium modulates parathyroid hormone (PTH) secretion via intracellular regulatory mechanisms. In parathyroid adenomas the calcium transport via the tumor cell membrane appears to be disturbed resulting in lowered intracellular calcium levels. This is remarkable since the environmental calcium concentration is elevated due to the hypercalcemia of primary hyperparathyroidism.(ABSTRACT TRUNCATED AT 250 WORDS)