Biomedical subjects

L J Deftos

Publications and source records attributed to L J Deftos.

At least 91 records · Page 5Linked to original sources

PubMed1993

Effect of daily oral vitamin D and calcium therapy, hypophosphatemia, and endogenous 1-25 dihydroxycholecalciferol on parathyroid hormone and phosphate wasting in renal transplant recipients.

Ten stable, normocalcemic renal transplant patients with good allograft function, hyperparathyroidism, and variable hypophosphatemia were treated for 2 to 9 months with oral calcium carbonate and replacement doses of vitamin D analogues. Parathyroid hormone levels (PTH) and renal phosphate wasting were not autonomous or fixed but decreased with therapy. Although serum 1-25(OH)2D3 levels could be shown to rise appropriately during oral vitamin D therapy and fall afterwards, a separate study in a larger group of patients showed no effect of elevated parathyroid hormone or hypophosphatemia to increase endogenous 1-25(OH)2D3 levels. Some 42% of patients with elevated carboxy-terminal PTH, had elevated N-terminal PTH, which was closely associated with more severe phosphate wasting. Aggressive oral calcium and vitamin D supplementation in certain normocalcemic renal transplant patients may decrease endogenous PTH levels, improve hypophosphatemia, and provide a physiologic increase in levels of 1-25(OH)2D3.

Administration, Oral↗

PubMed1993

Management of primary hyperparathyroidism.

Primary hyperparathyroidism is a common disease that can be accurately diagnosed and effectively treated in most patients. The diagnosis is established by a persistent elevation of serum calcium and parathyroid hormone and by clinical evaluation. Surgery is the appropriate treatment, and preoperative localization procedures are seldom indicated. Selected patients with mild disease may be followed by procedures devised to identify deterioration of skeletal, neurological, and renal function. The accurate diagnosis and effective treatment of primary hyperparathyroidism are rewarding clinical experiences for the endocrinologist and surgeon.

Female↗

PubMed1993

Parathyroid hormone-like protein is a secretory product of atrial myocytes.

Parathyroid hormone-like protein (PLP) was originally identified from tumors associated with hypercalcemia. Recently, it has been found to be expressed in a stretch-responsive manner in several types of smooth muscle. We studied adult rat heart muscle for the presence of the PLP. Using immunohistology and the PCR, we demonstrated the presence of PLP and its mRNA in all heart chambers. Immunoelectron microscopy demonstrated PLP in secretory vesicles of atrial mycocytes. Using immunoassay, we demonstrated that atria contained a higher concentration of PLP than ventricles. Furthermore, primary cultures of both chambers released PLP into conditioned medium, with atria secreting more than ventricles. Considered with studies of the role of PLP in other tissues, our observations suggest that the production and secretion of PLP by cardiac myocytes represents a calcium-related regulatory function for this stretch-responsive polypeptide in the cardiovascular system. PLP in the heart may be the calcium counterpart for the atrial natriuretic-sodium regulatory axis of the cardiovascular system.

Animals↗

PubMed1993

Synthesis and release of calcitonin-like immunoreactivity by anterior pituitary cells: evidence for a role in paracrine regulation of prolactin secretion.

Calcitonin (CT) is a potent and specific inhibitor of basal and TRH-induced PRL release and PRL mRNA levels in rat anterior pituitary (AP) cells, an action mediated through specific inhibition of the Ca(2+)-inositol phosphate messenger system. Because CT and CT-like peptides have been reported to be present in the AP, the present studies investigated 1) whether 35S-labeled CT-like substances can be precipitated from rat AP cell lysates, 2) whether immunoreactive CT is secreted from rat AP cells, as assessed from a cell blot assay and from RIA of spent medium from cultured AP cells, and 3) whether the release of PRL from cultured rat AP cells can be influenced by immunoneutralization of endogenous CT. Dispersed rat AP cells were labeled with [35S]cysteine, CT-like substances were immunoprecipitated from the lysate with antihuman CT (anti-hCT) and antisalmon CT (anti-sCT) immunoglobulin G conjugated to protein-A-Sepharose beads, and the immunoprecipitates were fractionated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified by fluorography. The results revealed that both anti-sCT and anti-hCT sera precipitated three major bands of 35S-labeled material from AP cell lysates, with approximate molecular masses of 23, 6.5, and 3.5 kilodaltons. Synthetic sCT completely displaced anti-sCT-precipitable bands and partially displaced anti-hCT precipitates. The cell blot assay revealed the presence of CT-immunopositive AP cells, and secretion of this substance was indicated by zones of secretion surrounding these cells. Immunoreactive CT was also detected in spent medium from cultured rat AP cells, and the average rate of release over 4 days of culture was approximately 1 ng sCT eq/3 million AP cells.24 h. Both anti-sCT and anti-hCT sera significantly stimulated PRL release from rat AP cells, and the stimulatory effect of anti-sCT serum was dose dependent up to a concentration of 1:50. The present findings demonstrate that CT-like peptide(s) is synthesized and released from cultured AP cells and suggest that this peptide may participate in the regulation of PRL secretion via paracrine or autocrine actions.

Animals↗

PubMed1992

The parathyroid hormone-related protein (PTHrP) gene preferentially utilizes a GC-rich promoter and the PTHrP 1-139 coding pathway in normal human amnion.

Parathyroid hormone-related protein (PTHrP) is an oncofetal protein that is widely expressed in mammalian tissues. The PTHrP gene is a complex with three transcriptional start-sites, two TATA boxes and a GC-rich region, and three predicted polypeptide products, PTHrP 1-141, PTHrP 1-139, and PTHrP 1-173. The originally discovered form of PTHrP, PTHrP 1-141, and the classical TATA box promoters are generally assumed to be the major pathways of PTHrP gene expression. We have used the polymerase chain reaction (PCR) to study PTHrP gene expression in the human amnion. Our studies demonstrate that the GC-rich promoter is preferentially used and that PTHrP 1-139 is the major PTHrP mRNA expressed in human amnion. PTHrP 1-139 lacks the carboxy-terminal arginine and histidine residues of PTHrP 1-141; these two basic amino acids could have significant effects on the biological activity of PTHrP. These preferential pathways for PTHrP gene expression are shared by malignant and normal human tissues.

Amnion↗

PubMed1992

Presence of calcitonin-like immunoreactivity (iCT) in human prostate gland: evidence for iCT secretion by cultured prostate cells.

Immunoreactive calcitonin (iCT) has been detected in human prostate tissue extracts as well as seminal plasma. The present studies were undertaken to examine whether iSCT (immunoreactive salmon CT-like human peptide) co-exists with iHCT (thyroid CT-like substance) in human prostate tissue extracts, and whether these substances are secreted by primary prostate cells in culture. Since the local secretion of these substances seems to increase in some neoplasms, a second objective of the study was to examine whether basal secretion of iCTs from primary prostate cells is increased in carcinoma. The present results have shown that both iHCT and iSCT were present in prostate tissue extracts. The mean iHCT levels in extracts of benign hyperplastic prostates (BPH) were 0.59 ng/g prostate, and these were significantly lower than iHCT concentrations in prostatic carcinoma (PC) (2.53 ng/g). No significant differences in their iSCT contents were observed. However, the results from culture of over 90 individual prostate tissue specimens from BPH or PC indicate that primary prostate cells secreted detectable quantities of iSCT and the basal release of this material from PC prostate cultures was almost four-fold higher than that from BPH prostate cultures. These results suggest that a CT-like immunoreactive material is secreted by primary prostate cells in culture, and the basal secretion of this material is significantly higher in PC cells as compared to BPH cells. Endogenous secretion of prostatic CT, and the elevation of its expression in PC suggest that it may serve as a regulatory factor in the pathophysiology of the prostate gland.

Aged↗

PubMed1992

Multiple hamartoma syndrome (Cowden's disease) associated with renal cell carcinoma and primary neuroendocrine carcinoma of the skin (Merkel cell carcinoma).

A case of multiple hamartoma syndrome (Cowden's disease) associated with renal cell adenocarcinoma and primary neuroendocrine carcinoma of the skin is described. Neither of these neoplasms has been documented previously in association with this genodermatosis. A search for epidermal growth factor receptor (c-erb-B protooncogene) gene abnormalities in the kidney, liver, and thyroid, as well as in tissue of the primary neuroendocrine carcinoma, was negative. Serum obtained from the patient before his death contained elevated levels of both chromogranin A (2641 ng/mL; normal level, less than 20 ng/mL) and calcitonin (517 pg/mL; normal level, less than 200 pg/mL), suggesting that the patient's principal tumor was neuroendocrine in origin.

Aged↗

PubMed1992

Mineral metabolic effects of thyroidectomy and long-term outcomes in a family with MEN 2A.

We have followed a family with multiple endocrine neoplasia type 2A for 18 years. Four members have undergone total thyroidectomy for medullary thyroid carcinoma or C-cell hyperplasia, and one has required bilateral adrenalectomy for pheochromocytoma. None has developed hypercalcemic hyperparathyroidism, although parathyroid hormone levels were relatively high prethyroidectomy and fell postoperatively in the patients with high calcitonin levels. In three of the four cases, intestinal calcium absorption decreased following thyroidectomy.

Adrenal Gland Neoplasms↗

PubMed1992

Two-site immunoradiometric assay of intact salmon calcitonin.

We developed a two-site immunoradiometric assay (IRMA) of salmon calcitonin (SCT) that detects intact SCT(1-32) and not peptide fragments of the hormone. This was accomplished by using monoclonal antibodies prepared against the peptide fragments SCT(1-11) and SCT(11-32). Two antibodies with specificity for each of the peptides were purified from their respective ascites and evaluated in a two-site format wherein one of the antibodies was adsorbed to polystyrene beads and the other was radioiodinated. In this assay format, the antibody pair detected intact SCT(1-32) but did not react with either SCT(1-11) or SCT(11-32). The sensitivity of the assay could be increased by exchanging the antibodies with respect to bead adsorption and radioiodination. Furthermore, by increasing the incubation time and volume of incubation of sample with the polystyrene-bead-adsorbed antibody, the effective detection limit of the assay could be improved. This assay system can be used to detect intact SCT when the presence of fragments of the hormone might otherwise complicate interpretation of assay data.

Adsorption↗

PubMed1992

Two-site assays of bone gla protein (osteocalcin) demonstrate immunochemical heterogeneity of the intact molecule.

We developed a panel of monoclonal antibodies to human bone gla protein (BGP; osteocalcin) peptides that span the linear sequence of the molecule, specifically BGP 1-12 (N-terminal), BGP 15-30 (midregion), and BGP 38-49 (C-terminal). These antibodies were evaluated in various combinations of two-site formats in studies of serum BGP concentrations. For clinical studies, we selected from a panel of antibodies the two most sensitive antibody pairs for the intact molecule (N-C); we also used a polyclonal RIA based on BGP-C. For the two-site format, we used two N-terminal antibodies, 029 and 052, adsorbed to polystyrene beads, and radioiodinated a C-terminal antibody, 663. The standard for each of the assays was purified human BGP. The following BGP serum concentrations (microgram/L, mean +/- SE) were measured with the various assays: by the 029-663 assay, results for normal subjects were 7 +/- 3, for patients with renal failure 25 +/- 8, and for patients with Paget disease 12 +/-4; by the 052-663 assay, the respective results were 22 +/- 4, 44 +/- 12, and 31 +/- 7; by the polyclonal assay, the results were 3 +/- 0.2, 13 +/- 2, and 5 +/- 1. The two intact (N-C) assays were significantly (P < 0.01) correlated (r = 0.94), but their serum values differed by more than twofold in terms of the same BGP standard. The polyclonal assay significantly correlated with each of the intact assays (r = 0.83, 0.77), but it, too, gave different serum values for BGP. These studies demonstrate the immunochemical heterogeneity of circulating BGP, heterogeneity that is manifest even in immunoassays specific for the same region of the molecule.

Antibodies, Monoclonal↗

PubMed1991

Parathyroid hormone-related protein, chromogranin A, and calcitonin gene products in the neuroendocrine skin carcinoma cell lines MKL1 and MKL2.

We studied the production of parathyroid-hormone-related protein, chromogranin A, calcitonin and calcitonin-gene-related peptide in the neuroendocrine skin cell line, MKL1, and a subsequently derived cell line designated MKL2. Both cell lines had cytological, histological and electron-microscopic features typical of neuroendocrine differentiation. Immunohistology and radioimmunoassay studies demonstrated the presence of parathyroid-hormone-related protein, chromogranin A, calcitonin-gene-related peptide, and calcitonin in the MKL2 cell line and the last three substances in both cell lines. The secretion of each of the first three substances was regulated by phorbol in the MKL2 cells. Additional immunohistochemical studies demonstrated the variable expression of bombesin, substance P, and vasoactive intestinal polypeptide in MKL2 cells, and the expression of synaptophysin in both MKL1 and MKL2 cells. These studies demonstrate the neuroendocrine characteristics of the MKL cell lines and provide a novel model for studies of the production and interactions of several neuroendocrine proteins and peptides by human skin cells.

Bombesin↗

PubMed1991

Liposome-entrapped calcitonin and parathyroid hormone are orally effective in rats.

We have demonstrated that liposomally entrapped calcitonin (CT) and parathyroid hormone (PTH) can be orally effective in regulating blood calcium. Liposomal CT produced hypocalcemia and liposomal PTH produced hypercalcemia upon oral administration to rats. Specific liposomal formulations were necessary to affect the appropriate decrease and increase in blood calcium concentration. Future extension of these studies may lead to clinically valuable forms of liposomal-peptide preparations.

Animals↗

PubMed1991

Bone alkaline phosphatase in Paget's disease.

The measurement of bone proteins and peptides and their derived products has been very useful in the diagnosis and management of patients with skeletal disease. This group of assays includes alkaline phosphatase (AP) and bone Gla protein (BGP). We here describe the comparison of a new immunoassay that is specific for bone alkaline phosphatase (BAP) to measurements of total alkaline phosphatase (TAP) and BGP in Paget's disease. In our studies, we demonstrated that BAP was increased in the serum of patients with Paget's disease. Comparisons with the other measurements revealed that BAP correlated better with total AP (r = 0.92) than with BGP (r = 0.51); the lowest correlation occurred between BGP and total AP (r = 0.26). In patients with liver disease, the BAP was indistinguishable from normal whereas the TAP was elevated. These studies indicate that BAP assesses different aspects of bone cell function than BGP in Paget's disease. This discordancy also exists between BGP and total serum AP activity. BAP measurements by immunoassay offer a novel method of assessing skeletal status. Thus, the information that measurement of different bone-specific proteins provides should be separately useful in assessing the skeleton for a variety of metabolic bone diseases.

Alkaline Phosphatase↗

PubMed1991

Plasma chromogranin A as a marker of sympathochromaffin activity in humans.

The extent to which the sympathochromaffin system compared with other endocrine/neuroendocrine tissues contributes to the plasma chromogranin A pool has not been defined. To test the hypothesis that the sympathochromaffin system is the major source of circulating chromogranin A only when that system is activated markedly, we measured chromogranin A concentrations in 200 human plasma samples known to have a broad range of norepinephrine and epinephrine concentrations, reflecting therefore a broad range of sympathochromaffin activity at the time of sampling. Plasma chromogranin A and norepinephrine concentrations were highly correlated when the sympathochromaffin system was activated markedly (cardiac arrest samples, n = 13, r = 0.8392, P less than 0.0005) and when there was release of large amounts of norepinephrine from tumors (pheochromocytoma samples, n = 17, r = 0.8132, P less than 0.001). However, when the sympathochromaffin system was activated less markedly, resulting in plasma catecholamine concentrations that spanned the physiological and lower pathophysiological range (nonpheochromocytoma noncardiac arrest samples, n = 170), correlations between plasma chromogranin A and norepinephrine (r = 0.2877, P less than 0.0001) and epinephrine (r = 0.3814, P less than 0.0001) levels were relatively weak, although still statistically significant. Thus, at basal through moderate stress levels, norepinephrine and epinephrine concentrations accounted for only approximately 10-15% of the variance in plasma chromogranin A levels. We conclude that, although plasma chromogranin A concentrations are a valid marker of sympathochromaffin activity in humans, they are not a sensitive marker under physiological conditions.

Adrenal Gland Neoplasms↗

PubMed1991

Chromogranin A: its role in endocrine function and as an endocrine and neuroendocrine tumor marker.

CgA is a 49 kilodalton protein that is present in the secretory granules of most endocrine and many neuroendocrine cells. Detection of CgA in cells by immunocytochemistry and measurement of CgA in serum by immunoassay can serve as tissue and serum markers for CgA-producing tumors. CgA is of diagnostic value in classical endocrine tumors, in hormone-negative tumors, and in endocrine tumors in which other diagnostic procedures have their limitations. Although the biological function of CgA is yet unknown, it may serve as a precursor molecule, like POMC, for a family of biologically active peptides. CgA is an important new tool for the endocrinologist in the diagnosis and management of patients with endocrine and neuroendocrine tumors.

Amino Acid Sequence↗

PubMed1991

Calcium-stimulated parathyroid hormone-like protein secretion: potentiation through a protein kinase-C pathway.

The effect of altering intracellular calcium levels on PTH-like protein (PLP) secretion was assessed in the NCI-H727 cell line. Ionomycin stimulated PLP secretion in a dose- and time-dependent manner, with a maximum rate of secretion occurring within minutes. Phorbol esters (phorbol 12-myristate 13-acetate and phorbol 12,13-didecanoate) stimulated PLP secretion at 10(-7)-10(-5) M, whereas forskolin treatment had no effect. When cells were treated initially with phorbol esters, ionomycin-stimulated PLP secretion was potentiated. The kinetics of this effect were rapid (t1/2, less than 1 min), and pretreatment with cycloheximide or actinomycin-D before phorbol ester and ionomycin treatment did not alter PLP secretion. Pretreatment for 24 h with phorbol 12-myristate 13-acetate to desensitize the cells or use of inactive phorbol ester isomer 4 alpha-phorbol 12,13-didecanoate did not potentiate the ionomycin-stimulated PLP secretion. Treatment with exogenously added phospholipase-C caused a dose-dependent increase in PLP secretion. These data indicate that PLP secretion can be stimulated through a phospholipase-C-mediated mechanism.

Calcium↗

PubMed1991

All major lung cancer cell types produce parathyroid hormone-like protein: heterogeneity assessed by high performance liquid chromatography.

We examined the production of parathyroid hormone-like protein (PLP) by all major lung cancer cell types, including epidermoid, small cell, and adenocarcinoma. We demonstrated that cell lines derived from each cell type released PLP into culture medium. To determine the predominant species of PLP produced by the cell lines, guanidine hydrochloride extracts were prepared and analyzed for PLP by high performance size exclusion chromatography under denaturing conditions. Cell lines from each of the major lung tumors produced multiple and different forms of PLP. The estimated molecular sizes of the PLP species ranged from 3.5-11.7 kilodaltons. Our results demonstrate that PLP is produced by all major lung cancer cell types and extend these observations to adenocarcinoma and large cell carcinomas of the lung. Furthermore, we observed PLP heterogeneity among these different cell types, which may represent tissue-specific PLP processing among different human lung tumors.

Chromatography, High Pressure Liquid↗

PubMed1991

Bone protein and peptide assays in the diagnosis and management of skeletal disease.

The measurement in blood of bone proteins is an important adjunct to imaging procedures for clinical assessment of the skeleton. The discovery of new bone proteins and their structural characterization has led to immunochemical procedures of improved sensitivity and specificity for their quantification. An appreciation of the advantages and disadvantages of these evolving methodologies will assist in their clinical application.

Acid Phosphatase↗