Biomedical subjects

Shigeo Negi

Publications and source records attributed to Shigeo Negi.

8 recordsLinked to original sources

PubMed2004

Biochemical and cellular effects of direct maxacalcitol injection into parathyroid gland in uremic rats.

The most important etiological factors of resistance to medical treatments for secondary hyperparathyroidism are the decreased contents of the vitamin D receptor (VDR) and Ca-sensing receptor (CaSR) in parathyroid cells and a severely swollen parathyroid gland (PTG) as a result of hyperplasia. The effects of direct maxacalcitol (OCT) injection into PTG in terms of these factors were investigated in this study. The PTG of Sprague-Dawley rats that were 5/6 nephrectomized and fed a high-phosphate diet were treated by a direct injection of OCT (DI-OCT) or vehicle (DI-vehicle). The changes in serum intact parathyroid hormone (PTH), Ca(2+), and phosphorus levels, in VDR and CaSR expression levels in parathyroid cells, and in Ca(2+)-PTH curves were examined. Apoptosis was analyzed by the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling method and DNA electrophoresis for PTG. DI-OCT markedly decreased serum intact PTH level, and a significant difference in this level between DI-OCT and DI-vehicle was observed. However, serum Ca(2+) and phosphorus levels did not changed markedly in both groups. The upregulations of both VDR and CaSR, the clear shift to the left downward in the Ca(2+)-PTH curve, and the induction of apoptosis after DI-OCT were observed. These findings were not observed in the DI-vehicle-treated rats. Moreover, these effects of DI-OCT were confirmed by the DI-OCT into one PTG and DI-vehicle alone into another PTG in the same rat. DI-OCT may introduce simultaneous VDR and CaSR upregulations and the regression of hyperplastic PTG, and these effects may provide a strategy for strongly suppressing PTH levels in very severe secondary hyperparathyroidism.

Animals↗

PubMed2004

[Renal osteodystrophy].

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Chronic Kidney Disease-Mineral and Bone Disorder↗

PubMed2004

Calcimimetic compound upregulates decreased calcium-sensing receptor expression level in parathyroid glands of rats with chronic renal insufficiency.

The reduced expression level of the calcium-sensing receptor (CaR) is attributed to the hyposensitivity of parathyroid cells to extracellular calcium concentration [Ca2+]o, which plays a crucial role in the pathogenesis of secondary hyperparathyroidism (SHPT) in patients and rats with chronic renal insufficiency (CRI). Calcimimetic compounds have been demonstrated to improve the decreased sensitivity of CaR to extracellular calcium concentration and to suppress both parathyroid hormone (PTH) oversecretion and parathyroid cell proliferation. However, the effect of calcimimetics on the reduced CaR expression level in parathyroid cells in CRI remains unclarified. The aim of this investigation was to examine the effect of the calcimimetic compound NSP R-568 (R-568) on the CaR expression in the parathyroid cells of rats with experimental CRI. Subtotally nephrectomized rats were fed a high-phosphorus diet for 8 (n = 12; Nx-8 group) or 9 wk (n = 11; Nx-9 group) to induce severe SHPT. Another group of uremic rats were fed a high-phosphorus diet for 8 wk and then orally administered R-568 (100 micromol/kg body wt) once a day for 7 d (n = 11; Nx+R-568 group). Sham-operated rats that were fed a standard diet for 9 wk were used as controls (n = 8). R-568 treatment induced a significant reduction in plasma PTH level with significant decrease in serum calcium and without change in serum phosphorus concentration. Serum 1,25(OH)2D3 level was not affected by R-568 administration. CaR mRNA and protein levels in the Nx-8 and Nx-9 groups significantly decreased compared with those in the controls; however, no significant difference in these parameters was observed between the Nx-8 and Nx-9 groups. In the Nx+R-568 group, CaR mRNA and protein levels significantly increased compared with those in either the Nx-8 or Nx-9 group. R-568 was effective in reducing the number of proliferating cell nuclear antigen-positive cells along with parathyroid gland growth suppression in the Nx+R-568 group compared with that in the Nx-9 group. The results suggest that the calcimimetic compound R-568 upregulates decreased CaR expression, and the upregulation possibly has an enhancement effect on PTH secretion and parathyroid cell hyperplasia through the improved sensitivity of CaR to [Ca2+]o.

Analysis of Variance↗

PubMed2004

[Hemoperfusion].

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Acute Kidney Injury↗

PubMed2003

Management of secondary hyperparathyroidism of dialysis patients.

Hyperphosphatemia, vitamin D deficiency, and resulted hypocalcemia have been regarded as classical pathogeneses of secondary hyperparathyroidism. These factors have been treated by the administration of phosphorus binder and vitamin D derivatives. However, these therapies have not brought about a successful result for the prevention and treatment of secondary hyperparathyroidism. The reason could be mainly attributed to the hypercalcemia that results from the administration of calcium salts as a phosphorus binder and the calcemic action of vitamin D. To prevent hypercalcemia, non-calcium containing phosphorus binder (sevelamer hydrochloride) and vitamin D analogues, which suppress PTH secretion with minimum calcemic action, have been developed. These new vitamin D analogues include 19-nor-1-alpha, 25-dihydroxyvitamin D2 (paricalcitol), 1-alpha-hydroxyvitamin D2 (doxercalciferol), 22oxa-calcitriol (maxacalcitol) and F6-calcitriol (falecalcitriol). Furthermore, calcimimetics that stimulate calcium-sensing receptor of parathyroid cells as calcium and suppress PTH secretion are now under clinical trial. Percutaneous direct injection therapy of vitamin D, vitamin D analogue or calcimimetics into parathyroid gland has also been reported. The combination of these new strategies is expected to effectively and safely suppresses secondary hyperparathyroidism that has been resistant to conventional medical treatments.

Ethanol↗

PubMed2003

Percutaneous maxacalcitol injection therapy regresses hyperplasia of parathyroid and induces apoptosis in uremia.

BACKGROUND: A high level of parathyroid hormone (PTH) is considered to be an indicator of poor prognosis and a poor quality of life of dialysis patients; therefore, an effective and safe therapy for secondary hyperparathyroidism (SHPT) has been developed. METHODS: In 20 patients with SHPT resistant to maxacalcitol (OCT) intravenously administered, all detectably enlarged parathyroid glands were treated by percutaneous maxacalcitol injection therapy (PMIT) under ultrasonographic guidance consecutively 6 times, which was followed by OCT that was intravenously administered. The clinical effects of PMIT were evaluated based on the changes in the serum intact-PTH, adjusted Ca, phosphorus, and bone marker levels, and the parathyroid gland volume determined by ultrasonography. Morphologic examination, apoptosis analysis, and PTH mRNA expression level determination by reverse transcription-polymerase chain reaction (RT-PCR) using parathyroid tissues obtained by a biopsy technique were performed. RESULTS: PMIT and subsequent intravenous OCT administrations significantly decreased the serum intact-PTH level and parathyroid gland volume for at least 12 weeks after PMIT without major complications. Parathyroid tissues obtained after PMIT exhibited some partial defects of parathyroid cells, a marked increase in the number of the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells, the ladder formation determined by DNA electrophoresis, and the decrease in the PTH mRNA expression level. CONCLUSION: PMIT is effective and safe for the treatment of refractory SHPT, and a locally high level of OCT suppresses PTH secretion and regresses parathyroid hyperplasia, which is involved in the induction of apoptosis of parathyroid cells.

Administration, Cutaneous↗

PubMed2003

New strategies for the treatment of secondary hyperparathyroidism.

Classic pathogeneses of secondary hyperparathyroidism (2HPT), hyperphosphatemia, vitamin D deficiency, and hypocalcemia, have been treated by the administration of phosphorus binders and vitamin D derivatives. However, these therapies have not brought about a successful result. The main reason could be attributed to hypercalcemia resulting from the administration of calcium salts as a phosphorus binder and the calcemic action of vitamin D. To prevent hypercalcemia, non-calcium-containing phosphorus binders and vitamin D analogues, which suppress parathyroid hormone (PTH) secretion with minimum calcemic action, have been developed. Furthermore, calcimimetics that stimulate the calcium-sensing receptor of parathyroid cells and suppress PTH secretion are now under clinical trial. Direct injection therapy of vitamin D analogues or calcimimetics into the parathyroid gland also has been reported. These new strategies are expected to effectively and safely suppress 2HPT, which has been resistant to conventional medical treatments.

Animals↗

PubMed2003

Effect of percutaneous calcitriol injection therapy on secondary hyperparathyroidism in uraemic patients.

BACKGROUND: The impetus to develop percutaneous calcitriol injection therapy (PCIT) was the lack of therapeutic tools to treat secondary hyperparathyroidism (2HPT) resistant to medical therapy. METHODS: Nine dialysis patients resistant to intravenous calcitriol or calcitriol analogues underwent daily PCIT 5-10 times consecutively. The PCIT involved the injection of a volume of calcitriol equal to that of the enlarged parathyroid glands (PTGs) under ultrasonographic guidance. All patients had follow-up intravenous calcitriol after PCIT. RESULTS: The serum intact PTH concentration was markedly reduced following PCIT and was maintained for 12 weeks with intravenous calcitriol without significant changes in serum adjusted calcium and phosphorus concentrations. All patients tolerated PCIT without serious adverse events. Serum bone alkaline phosphatase concentrations and the volume of the enlarged PTGs were also significantly reduced. CONCLUSION: PCIT is a safe and effective treatment, which may also suppress parathyroid hyperplasia and improve bone turnover for refractory 2HPT.

Aged↗