Biomedical subjects

R Rizzoli

Publications and source records attributed to R Rizzoli.

At least 217 records · Page 12Linked to original sources

PubMed1990

[The role of a parathyroid hormone analogue in the pathogenesis of malignant hypercalcemia].

Patients with malignant hypercalcemia can display not only an increase in bone resorption, but also changes in the renal tubular reabsorption of calcium and phosphate similar to those found in primary hyperparathyroidism. A protein of tumoral origin likely responsible for this syndrome has been described. Even if produced by another gene than parathyroid hormone, it shares a homology in the aminoterminus and seems to exert a similar spectrum of action. Besides its role in malignant hypercalcemia, this analogue may be involved in physiological regulatory processes.

Humans↗

PubMed1989

[PTH-like tumor peptide and malignant hypercalcemia].

Certain patients with malignant hypercalcemia display enhanced bone resorption and changes in renal tubular handling of calcium and phosphate similar to those encountered in primary hyperparathyroidism. A tumoral protein probably responsible for this syndrome has recently been described. Produced by a gene other than that of parathyroid hormone, it shows an aminoterminal homology with the physiological hormone. In some respect both proteins exert similar effects. This parathyroid hormone-analogue may also be involved in physiological regulatory functions.

Amifostine↗

PubMed1989

Natural killer function in flow cytometry. II. Evaluation of NK lytic activity by means of target cell morphological changes detected by right angle light scatter.

Morphological changes that occur in K562 cells after natural killing produce profound changes in cellular light scattering properties. The possibility of gating out all the effector cells by thresholding on perpendicular light scatter and the subsequent identification of two distinct clusters of cells, which correspond to dead and viable targets, have permitted the measurement of natural killer activity in vitro. The changes in scattering properties after cell death are mainly determined by the variation of internal refractive index of the dying cell. A comparison of the scattering and propidium iodide staining procedures showed good correlation. The morphological detection and measurement of cellular death is therefore used to estimate NK lytic activity. This methodology permits the measurement of NK activity without staining the target and the measurement of perpendicular light scatter provides an alternative approach to the study of lytic processes in vitro.

Cytotoxicity, Immunologic↗

PubMed1989

Chromatin organization in rat testis nuclei. Flow cytometric detection of the morphological compaction.

The unusual histone composition of testicular cells generates changes in chromatin organization in order to allow the chromosomal pairing necessary for genetic recombination. Accessibility of testis nuclear DNA was determined by flow cytometry. The observed differences in staining between testis and liver nuclear chromatin, as well as the differences of perpendicular light scatter signal, correlate with alterations in protein composition with the chromatin reorganization.

Animals↗

PubMed1989

Role of bone and kidney in parathyroid hormone-related peptide-induced hypercalcemia in rats.

A protein responsible for the biochemical syndrome similar to primary hyperparathyroidism associated with certain tumors has been recently characterized and its effects at the level of bone and kidney reported. However, the relative role of tubular reabsorption of calcium (Ca) and bone resorption in the pathogenesis of hypercalcemia induced by this factor is still debated. We investigated the effects of a synthetic amino-terminal fragment of parathyroid hormone-related protein [PTHrP-(1-34)] administered chronically by intraperitoneal osmotic minipumps in thyroparathyroidectomized (TPTX) rats. Clearance studies performed on day 6 of treatment after a 24 h fast revealed an increase in renal tubular reabsorption of Ca and a decrease in renal tubular reabsorption of phosphate (Pi), accompanied by an increase in cAMP excretion. PTHrP-(1-34) (90 pmol/h) stimulated bone resorption as evaluated by an increment in fasting urinary Ca excretion. Although the bone resorption inhibitor aminopropylidene diphosphonate fully corrected urinary Ca excretion and reduced plasma Ca from 3.04 +/- 0.07 to 2.44 +/- 0.21 mM (p less than 0.05), this latter value remained considerably higher than in TPTX control rats (1.54 +/- 0.12 mM, p less than 0.01). In contrast, when the agent WR-2721, which is known to decrease the renal tubular reabsorption of Ca by a PTH-independent mechanism, was given, a further drop in plasma Ca and an increase in urinary Ca excretion were observed. These findings are similar to those found in animals implanted with the hypercalcemic Leydig cell tumor.(ABSTRACT TRUNCATED AT 250 WORDS)

Amifostine↗

PubMed1989

High extracellular calcium increases the production of a parathyroid hormone-like activity by cultured Leydig tumor cells associated with humoral hypercalcemia.

Cultured Leydig tumor cells produce a parathyroid hormone (PTH)-like activity, but little is known about the regulation of the release of this factor. In the present work, we investigated the influence of the extracellular calcium concentration on the production of adenylate cyclase-stimulating activity, as evaluated in the osteoblast-like PTH-responsive cell line UMR 106. Medium conditioned in the presence of 0.4 mM or 3 mM Ca elicited a 5.8 +/- 0.4-fold and 10.3 +/- 0.9-fold increase over basal of cAMP production, respectively (p less than 0.001, n = 11 experiments). This effect, which was selective for PTH-like activity, was detectable after 2 h of incubation and maximal at 6-14 h. It was abolished by the protein synthesis inhibitor cycloheximide, but not by actinomycin D or cordycepin, suggesting a post-transcriptional site of action. Thus, the production of a tumoral circulating factor implicated in the pathogenesis of humoral malignant hypercalcemia may be influenced in a positive way by an increase in extracellular calcium concentration.

Adenylyl Cyclases↗

PubMed1989

Pathophysiological aspects and therapeutic approaches of tumoral osteolysis and hypercalcemia.

Malignant tumors can affect the integrity of the skeletal tissue and the homeostasis of the two main components of bone mineral, calcium (Ca) and inorganic phosphate (Pi). Various tumoral cell products can increase bone resorption by influencing the number of osteoclasts and/or their activity. These tumoral products could act either directly on bone cells of the osteoblastic or osteoclastic lineages, or indirectly by influencing cells secreting osteotropic factors, such as interleukin-1, tumor necrosis factors, transforming growth factors, and colony-stimulating factor. Among the classical calciotropic hormones, 1,25-dihydroxyvitamin D3 could be implicated in lymphoma. In hypercalcemia of malignancy, an increase in bone resorption is observed in most patients. However, in many cases an increased tubular reabsorption of Ca has been documented as well. This phenomenon when present after adequate rehydration is probably due to the secretion by the tumoral cells of a parathyroid hormone-related peptide (PTHrP). This factor has been recently identified as a protein containing 141 amino acids. This protein or some very close analogs have been shown to be secreted by lung, kidney and also breast carcinoma. Besides increasing bone resorption and stimulating tubular reabsorption of Ca, PTHrP also selectively decreases the tubular reabsorption of Pi, an action that may explain the hypophosphatemia observed in some types of neoplasm. Therapeutically, administration of antiresorbing agents such as clodronate or other bisphosphonates can normalize the increased osteolysis and, if present, the associated elevation in the plasma level of Ca in most cancer patients. However in some cases, wherein the prevailing hypercalcemic mechanism is due to an enhancement in the tubular reabsorption of Ca, other therapeutic means should be associated with the antiosteolytic bisphosphonate therapy.

Bone and Bones↗

PubMed1989

Cytochemical localization of DNA loop attachment sites to the nuclear lamina and to the inner nuclear matrix.

The rat liver nuclear matrix, obtained by endogenous nuclease digestion and extraction with low and high ionic strength media, contains residual DNA fragments that are considered to represent the attachment sites of the chromatin domains to the nucleoskeleton. These sites, protected against nuclease digestion by their binding with the nucleoskeleton proteins, should be either mainly linked to the peripheral lamina or to the inner nuclear matrix. The DNA fragment distribution at the level of the different components of the nuclear matrix has been evaluated in samples embedded in Epon and in hydrophilic resins by means of the DNase-gold technique. The labeling obtained suggests that the chromatin loops are prevailingly associated with the interior of the matrix; in fact about twice of the label is present in the inner matrix with respect to the peripheral lamina area. These results confirm the hypothesis that in interphase the chromatin maintains an organization similar to that of chromosomes, with loops radiating from a central scaffold, instead of being mainly attached to the lamina as otherwise suggested.

Animals↗

PubMed1989

Phospholipase C digestion induces the removal of nuclear RNA: a cytochemical quantitative study.

It has been reported that the incubation of isolated rat liver nuclear matrices with phospholipase C causes the digestion of the matrix-bound phospholipids and the release of most matrix-linked RNAs (Cocco et al., 1980). In this paper, the presence of phospholipids in nuclear substructures and the effects of their removal by phospholipase C digestion have been investigated by means of enzyme-colloidal gold cytochemistry. The nuclear phospholipids appear to be localized in the interchromatin areas and in the nucleolus and are virtually absent in the heterochromatin, when labelled with phospholipase C-colloidal gold. The double labelling test with ribonuclease A and phospholipase C conjugated with gold particles of different diameters shows that the nuclear phospholipids are co-localized with RNA-containing structures. The enzymatic digestion of phospholipids on thin sections of either isolated nuclei or pancreas embedded in LR White resin results in the decrease of the RNase-A colloidal gold labelling of nuclear RNA-containing structures, but not of the rough endoplasmic reticulum. The data confirm the presence of phospholipids in the nucleus in the absence of possible translocation due to isolation procedures and strengthen the hypothesis that they are involved in interactions between nucleic acids and proteins of the nuclear matrix.

Animals↗

PubMed1989

Nuclear polyphosphoinositides during cell growth and differentiation.

When highly purified nuclei of Swiss mouse 3T3 cells are incubated with gamma-32P-ATP, radioactivity is incorporated into phosphatidic acid and the two polyphosphoinositol lipids, phosphatidylinositol(4)P and (4,5)P2. If the cells are pre-treated with IGF-I, the incorporation into the polyphosphoinositides is decreased. This effect is maximal by 2 min, is transient in that it disappeared by 1 hr, and is increased markedly by the co-addition of bombesin, even though bombesin alone has no effect. Friend cells exhibit a related phenomenon in that the labelling of PIP2 in isolated nuclei is increased by conditions which cause erythroid differentiation (DMSO addition). We suggest that some aspect of nuclear polyphosphoinositide metabolism is modified when the nucleus is induced to divide or to differentiate, and that this change in inositide metabolism is a very early event in the sequence leading to cell division or differentiation.

Animals↗

PubMed1989

Effects of lectins and tunicamycin on cAMP response to parathyroid hormone.

Carbohydrate moieties of cell surface glycoproteins with an external orientation play a role in hormone recognition and/or transmembrane signal transmission. We have examined the effect of various lectins, which interact with specific cell surface glycosyl residues, and of tunicamycin, an antibiotic that inhibits glycosylation of proteins, on the adenosine 3',5'-cyclic monophosphate (cAMP) response to parathyroid hormone (PTH) in confluent cultured osteoblast-like rat osteosarcoma cells (UMR-106) and opossum kidney cells (OK cells). Incubation of both cell lines with wheat germ lectin (WGL), but not with concanavalin A, succinylated wheat germ, ricin, or soybean lectins, markedly reduced the PTH-induced cAMP production, whereas the stimulation obtained with forskolin, a compound that acts directly on the adenylate cyclase enzyme, was not affected. In contrast, tunicamycin did not cause any decrease in the cAMP response to PTH. These results indicate that the masking of sialic acid residue by WGL considerably blunted PTH-stimulated cAMP production in cultured osteoblast-like and kidney cells. An 80% inhibition of glycosylation of cell surface proteins did not appear to affect the response to PTH. Thus the functional role of this carbohydrate moiety in the PTH receptor remains to be determined.

Acetylglucosamine↗

PubMed1989

Morphological development of the human placenta in normal and complicated gestation: a quantitative and ultrastructural study.

In order to evaluate the structural potentialities of the placenta, we analyzed placentas in the following conditions: normal full term gestation, hypertensive status, twin pregnancy and abortion at 8-12 weeks of gestation, comparing cell structures, surface organization and tissue reaction. We quantitatively evaluated (1) the arborization of the placental villous tree, and (2) the microvillous density per unit of surface area, paralleling these data with ultrastructural and immunohistochemical features. In early gestation (8-12 weeks of pregnancy) the limited degree of branching of placental villi parallels a reduced number of clefts per unit of surface area (0.7/1,000 microns2), if compared with controls (2.7/1,000 microns2). In the full term twin placenta, the number of furrows is 2.26/1,000 microns2: this value reflects a low arborization potentiality, testifying to a low placental maturity. On the contrary, a high branching of the placental villous tree is present at term in hypertension. In this gestational condition, the number of sulci of 3.1/1,000 microns2 reveals a compensatory attitude of the placenta, aiming to sustain the impaired fetal-maternal metabolic interchange. In all these cases, syncytiotrophoblastic microvilli are reduced in number in comparison with the normal placenta, and this is likely to be an expression of a low trophoblastic maturation degree. The placenta is a barrier with a highly specialized function that conditions fetal outgrowth, and microenvironmental modifications are promptly faced by this structure through morphofunctional modulations.

Female↗

PubMed1988

Changes in ribonucleoprotein particle and chromatin organization induced by liposomes in isolated nuclei.

Nuclei isolated from rat liver, incubated in the presence of liposomes of different phospholipids, undergo typical modifications: chromatin dispersion and reduction of the interchromatin granules in nuclei incubated with negatively charged liposomes and increase of the chromatin density and of the number and size of the interchromatin granules in nuclei incubated with neutral liposomes. The possibility that the observed modifications are caused by an impairment of the transport and translocation of ribonucleoproteins belonging to the inner nuclear matrix, is suggested by the results obtained by radiotracer techniques on the release of RNA from liposome-incubated nuclei.

Animals↗

PubMed1988

Factor derived from human lung carcinoma associated with hypercalcemia mimics the effects of parathyroid hormone on phosphate transport in cultured renal epithelia.

A decrease in renal tubular reabsorption of inorganic phosphate (Pi) can be observed in hypercalcemia of malignancy. In the present study we investigated the effect of serum-free conditioned medium (CM) from cells, derived from a lung carcinoma (BEN) of a hypercalcemic patient, and of PTH on cyclic AMP (cAMP) production and sodium-dependent Pi transport (NaPiT) in epithelia of two renal cell lines. In opossum kidney cells (OK), PTH is known to enhance cAMP production and inhibit NaPiT; in contrast, in LLC-PK1 cells, PTH has no effect on NaPiT since this kidney cell line is devoid of PTH receptors. In OK cells, BEN CM induced a three- to fourfold increase of cAMP production, which was blunted by the PTH inhibitors bPTH(3-34) and bPTH(7-34). NaPiT, as assessed by measuring the initial rate of Pi uptake, was inhibited in a dose-dependent manner by BEN CM, with an effect maximal between 1h30 and 6 hr of incubation (40 +/- 4% and 47 +/- 4%, respectively), corresponding to the effect produced by 1-3 nM bPTH(1-34). The Na-dependent transport of a glucose analog was affected neither by BEN CM nor by PTH. In LLC-PK1 cells, neither BEN CM nor PTH altered cAMP production nor NaPiT after 1h30 of incubation. At 6 hr, BEN CM caused a slight decrease in NaPiT. In conclusion, these results constitute the first evidence of a direct and selective inhibition by tumor-derived factor(s) of NaPiT in cultured renal epithelia. Most of the renal NaPiT inhibitory activity produced by the lung tumor required the presence of a PTH receptor-adenylate cyclase system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Effect of pertussis toxin on parathyroid hormone-stimulated cyclic AMP production in cultured kidney cells.

The effect of pertussis toxin, which inactivates the guanine nucleotide binding regulatory proteins Gi and Go on cAMP production in response to parathyroid hormone PGE2 or forskolin, was examined in confluent opossum kidney (OK) cells. This effect was compared with that caused by dexamethasone. The response to PTH was increased in cells preincubated with either agent. The effect of pertussis toxin was selective for PTH, since cAMP production in response to neither PGE2 nor forskolin was increased. In contrast, the response to forskolin was enhanced in dexamethasone-treated cells. These results indicate that both stimulatory and inhibitory guanine nucleotides binding regulatory proteins modulate PTH-induced cAMP production in OK cells. Moreover, pertussis toxin and dexamethasone appear to affect different levels of the PTH-receptor-adenylate cyclase complex.

Animals↗

PubMed1988

Gradient fractionation of cycling and resting cells monitored by BrdUrd incorporation.

A number of techniques are currently employed for the fractionation of heterogeneous cell populations or for the separation of cells in different phases of their cycle. With the development of osmotically inert colloidal silica particles media, density gradient centrifugation became an established method for the separation and purification of cells and subcellular particles. We have applied this technique to the separation of cycling from resting Friend erythroleukemia cells, to obtain purified populations for further biological assays. The flow cytometric analysis of DNA content of the different fractions obtained by the gradient and stained with Propidium Iodide (PI), showed the S compartment highly concentrated in the 1.073/77 g/ml interface, while the upper levels of the gradient were highly enriched of cells in G1 phase. Moreover, the dual parameter analysis of DNA content by means of Bromodeoxyuridine (BrdUrd) incorporation and PI staining, showed that part of the cells in the 1.067/73 fraction represented the early S phase even if their DNA level, measured on the basis of PI fluorescence was within the diploid cell cluster. This method seems to be suitable to obtain pure cell fractions even when dealing with numerically large populations.

Animals↗

PubMed1988

Tumoral synthetic parathyroid hormone related peptide inhibits amiloride-sensitive sodium transport in cultured renal epithelia.

The amino-terminal fragment of a tumor parathyroid hormone-related peptide (PTHrP(1-34] produced by a human squamous cell carcinoma of the lung was recently synthesized. In the present work its effect on the amiloride-sensitive sodium transport, taken as an estimate of the Na+/H+ exchanger activity of cultured opossum kidney (OK) epithelia was compared to that of synthetic bovine parathyroid hormone (bPTH(1-34]. Both PTHrP(1-34) and bPTH(1-34) inhibited the initial rate of amiloride-sensitive 22Na transport. Half maximal inhibitory activity was obtained at about 10(-11)M for both PTHrP(1-34) and bPTH(1-34). In conclusion, tumoral PTHrP(1-34) appears to be as effective as bPTH(1-34) for inhibiting the amiloride-sensitive Na transport, and presumably for decreasing the activity of the Na+/H+ exchanger present in the apical membrane of kidney epithelial cells.

Amiloride↗

PubMed1988

Bone and renal components in hypercalcemia of malignancy and responses to a single infusion of clodronate.

Increased bone resorption (BR) and increased renal tubular reabsorption of calcium (TRCa) may both be involved in the pathogenesis of hypercalcemia of malignancy (HM). We have evaluated the relative importance of these two mechanisms in 33 patients with HM after extracellular volume expansion and after single infusion of clodronate (C12MDP: 500 mg iv over 8 h). The fasting urine Ca/creatinine ratio was taken as an index of BR (BRI). An index of TRCa was calculated (TRCaI) from a nomogram based on the relationship between urine Ca excretion per unit of glomerular filtration rate and plasma Ca (PCa). Mean (+/- SEM) PCa fell from 3.29 +/- 0.07 to 2.69 +/- 0.05 mmol/l three days after C12MDP (n = 33, p less than 0.001), a response similar to that obtained with repeated daily iv injections of 500 to 1000 mg C12MDP. The pathogenesis of hypercalcemia varied according to the type of neoplasm. BRI was the highest in multiple myeloma and breast tumors. TRCaI was markedly increased in squamous-cells lung, bladder, kidney and liver carcinomas, reaching levels observed in primary hyperparathyroidism. TRCaI was normal in most cases of multiple myeloma. Breast tumors appeared to be heterogeneous with respect to TRCaI. The fall in PCa in response to a single infusion of C12MDP was usually most marked in cancer patients with elevated BRI and normal TRCaI. It was very modest in patients with high TRCaI and slightly elevated BRI. In conclusion, this study confirms that stimulation of bone resorption is not the only mechanism of the maintenance of hypercalcemia of malignancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Resorption↗