scholarly journals Regulation of vitamin D metabolism by calcium and phosphate ions in isolated renal tubules

1981 ◽  
Vol 196 (1) ◽  
pp. 187-193 ◽  
Author(s):  
E Spanos ◽  
H Freake ◽  
S J MacAuley ◽  
I MacIntyre
Keyword(s):  
Vitamin D ◽  
Experimental Period ◽  
Renal Tubules ◽  
Long Term Effects ◽  
Hydroxylase Activity ◽  
Experimental Conditions ◽  
Vitamin D Metabolism ◽  
Stimulation Of

The acute and long-term effects of Ca2+ and Pi on vitamin D metabolism were studied in vitro with isolated renal tubules from vitamin D-deficient and vitamin D-supplemented chicks. Ca2+ depletion, achieved by isolating renal tubules in Ca2+-free buffers, led to suppression of 1 alpha-hydroxylase activity. Re-introduction of Ca2+ during incubation caused an acute stimulation of this enzyme. This stimulatory effect of Ca2+ was prevented by prior treatment of Ca2+-depleted renal tubules for 6 h with 1,25-dihydroxycholecalciferol. Ca2+ and Pi produced marked acute affects on 1 alpha-hydroxylase activity, which persisted for the whole 8 h experimental period, in Ca2+-depleted renal tubules from vitamin D-deficient chicks. The effects of either ion were influenced by the concentration of the other. However, the effects of these ions could not be reproduced in either Ca2+-depleted renal tubules from vitamin D-supplemented chicks or in renal tubules from vitamin D-deficient chicks, isolated in Ca2+-containing buffers. Isolation of renal tubules from vitamin D-supplemented chicks in Ca2+-containing buffers and subsequent incubation for 8 h in the presence of increased [Ca2+] led to a modest but statistically significant suppression of 1 alpha-hydroxylase and stimulation of 24-hydroxylase activity. It is concluded that the acute effects of Ca2+ and Pi on 1 alpha-hydroxylase activity of Ca2+-depleted renal tubules from vitamin D-deficient chicks are not regulatory but the results of the experimental conditions. In contrast the long-term effects of Ca2+ on both hydroxylases of renal tubules from vitamin D-supplemented chicks may be of physiological significance.

Effect of parathyroid hormone-like peptides on 25-hydroxyvitamin D-1 alpha-hydroxylase activity in rodents

1990 ◽  
Vol 258 (2) ◽  
pp. E297-E303 ◽  
Author(s):  
A. T. Walker ◽  
A. F. Stewart ◽  
E. A. Korn ◽  
T. Shiratori ◽  
M. A. Mitnick ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Maximal Activity ◽  
Hydroxylase Activity ◽  
Humoral Hypercalcemia Of Malignancy ◽  
Vitamin D Metabolism ◽  
Control Activity ◽  
Humoral Hypercalcemia ◽  
Stimulation Of

The role of vitamin D metabolism in the humoral hypercalcemia of malignancy syndrome (HHM) is unclear. We studied in vivo and in vitro effects of synthetic parathyroid hormone-like peptides (PTH-LPs) on rodent renal 25-OHD-1 alpha-hydroxylase activity. Infusion of mice with PTH-LP-(1-36) at 10 pmol/h for 12 and 24 h showed significant (429 +/- 139% and 937 +/- 413%, respectively) stimulation of control enzyme activity. Infusion for 36 h demonstrated diminution of activity to levels nearer to the unstimulated state (228 +/- 36% of control). In that maximal activity was observed after 24 h of infusion, we examined 1 alpha-hydroxylase activity after variable dosages of PTH-LP-(1-36) at this time point. Animals infused with PTH-LP-(1-36) at dosages of 2.5, 10, and 30 pmol/h for 24 h demonstrated 1 alpha-hydroxylase activities of 0.71 +/- 0.12, 4.74 +/- 2.09, and 9.91 +/- 1.01 ng.mg protein-1.20 min-1 (means +/- SD), respectively, all significantly greater than control activity (0.51 +/- 0.20 ng.mg protein-1.20 min-1). PTH-LP-(1-36) and PTH-LP-(1-74) were comparable in potency to bovine (b)PTH-(1-34) in stimulating 1 alpha-hydroxylase. Direct in vitro incubation of PTH-LP-(1-36) with renal slices resulted in stimulation of 1 alpha-hydroxylase activity up to 200% of control levels, comparable to that seen with equimolar concentrations of bPTH-(1-34).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals The Long-term Effects of Gastric Bypass on Vitamin D Metabolism

2006 ◽  
Vol 243 (5) ◽  
pp. 701-705 ◽  
Author(s):  
Jason M. Johnson ◽  
James W. Maher ◽  
Eric J. DeMaria ◽  
Robert W. Downs ◽  
Luke G. Wolfe ◽  
...  
Keyword(s):  
Vitamin D ◽  
Gastric Bypass ◽  
Long Term Effects ◽  
Vitamin D Metabolism

Effect of magnesium depletion on metabolism of 25-hydroxyvitamin D in rats

1987 ◽  
Vol 253 (1) ◽  
pp. E106-E113
Author(s):  
T. O. Carpenter ◽  
D. L. Carnes ◽  
C. S. Anast
Keyword(s):  
Vitamin D ◽  
Animal Studies ◽  
Magnesium Deficiency ◽  
Hydroxylase Activity ◽  
Vitamin D Metabolism ◽  
Hydroxyvitamin D ◽  
Magnesium Depletion ◽  
25 Hydroxyvitamin D

Resistance to vitamin D in magnesium depletion has been observed in humans and in animal studies. Variable levels of 1,25-dihydroxyvitamin D [1,25(OH)2D] have been reported in patients with magnesium depletion, and studies of vitamin D metabolism in states of magnesium depletion have not yielded consistent results. We examined effects of magnesium deprivation on circulating 1,25(OH)2D levels before and after a loading dose of 25-hydroxyvitamin D3 [25(OH)D3], on in vivo conversion of small doses of radiolabeled 25(OH)D3 to 1,25(OH)2D3 in intact rats, and on in vitro 25-hydroxyvitamin D-1 alpha-hydroxylase (1 alpha-hydroxylase) activity in rat renal mitochondria. The effects of magnesium-free media on mitochondrial 1 alpha-hydroxylase activity was examined. Magnesium depletion did not affect in vivo conversion of 25(OH)D to 1,25(OH)2D. In vitro 1 alpha-hydroxylase activity was comparable in magnesium-replete and -deplete animals and was evident in the absence of added magnesium in incubation media. Our in vivo and in vitro studies are consistent with one another and demonstrate that in the rat conversion of 25(OH)D to 1,25(OH)2D is unimpaired in magnesium deficiency. Resistance to vitamin D in magnesium depletion is likely due to the impaired skeletal responsivity to 1,25(OH)2D, as demonstrated in earlier studies.

Effect of phenobarbital treatment on metabolism of vitamin D by rat liver

1983 ◽  
Vol 245 (1) ◽  
pp. E55-E59
Author(s):  
D. T. Baran
Keyword(s):  
Vitamin D ◽  
Rat Liver ◽  
Blood Levels ◽  
Perfusion System ◽  
Vitamin D Metabolism ◽  
Hepatic Perfusion ◽  
Hydroxyvitamin D ◽  
25 Hydroxyvitamin D

Phenobarbital has been postulated to impair hepatic conversion of vitamin D to 25-hydroxyvitamin D [25(OH)D] either by accelerating the conversion of vitamin D to biologically inactive products or by directly inhibiting 25(OH)D production. The effect of a dose of phenobarbital documented to decrease circulating 25(OH)D levels on hepatic vitamin D metabolism has been investigated in rachitic rats with a recycling in vitro hepatic perfusion system. Phenobarbital (75 mg/kg/day) administered intraperitoneally to D-replete rats increased circulating 25(OH)D blood levels after 4 wk of therapy but was attended by decreased levels after 6 and 8 wk. Rachitic rats were then injected daily with phenobarbital for either 4 or 8 wk and the livers removed and perfused at a rate of 15 ml/min for 3 h. The concentrations of [3H]25(OH)D in the hepatic perfusate at 3 h was decreased after both 4 and 8 wk of phenobarbital. Although total [3H]-25(OH)D production (hepatic plus perfusate) was unaffected by phenobarbital, the efficiency of hepatic production was decreased after 8 wk of treatment and the release of [3H]-25(OH)D from the liver into the perfusate was inhibited after both 4 and 8 wk. The data indicate that chronic phenobarbital therapy decreases both the release of [3H]25(OH)D from the liver into the perfusate and the efficiency of hepatic [3H]-25(OH)D production. Phenobarbital-induced inhibition of 25(OH)D release from the liver may be another mechanism for the low 25(OH)D levels noted in humans after long-term phenobarbital therapy.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

Electrical stimulation of referred sensation area alleviates phantom limb pain

2021 ◽  
pp. 1-10
Author(s):  
Michihiro Osumi ◽  
Daisuke Shimizu ◽  
Yuki Nishi ◽  
Shu Morioka
Keyword(s):  
Electrical Stimulation ◽  
Single Case ◽  
Phantom Limb Pain ◽  
Phantom Limb ◽  
Long Term Effects ◽  
Limb Pain ◽  
Short Term ◽  
Analgesic Effects ◽  
Stimulation Of

Background: Patients with brachial plexus avulsion (BPA) usually experience phantom sensations and phantom limb pain (PLP) in the deafferented limb. It has been suggested that evoking the sensation of touch in the deafferented limb by stimulating referred sensation areas (RSAs) on the cheek or shoulder might alleviate PLP. However, feasible rehabilitation techniques using this approach have not been reported. Objective: The present study sought to examine the analgesic effects of simple electrical stimulation of RSAs in BPA patients with PLP. Methods: Study 1: Electrical stimulation of RSAs for 60 minutes was conducted for six BPA patients suffering from PLP to examine short-term analgesic effects. Study 2: A single case design experiment was conducted with two BPA patients to investigate whether electrical stimulation of RSAs was more effective for alleviating PLP than control electrical stimulation (electrical stimulation of sites on side opposite to the RSAs), and to elucidate the long-term effects of electrical stimulation of RSAs. Results: Study 1: Electrical stimulation of RSAs evoked phantom touch sensations in the deafferented limb, and significantly alleviated PLP (p <  0.05). Study 2: PLP was alleviated more after electrical stimulation on RSAs compared with control electrical stimulation (p <  0.05). However, the analgesic effects of electrical stimulation on RSAs were observed only in the short term, not in the long term (p >  0.05). Conclusions: Electrical stimulation of RSAs not only evoked phantom touch sensation but also alleviated PLP in the short term. The results indicate that electrical stimulation of RSAs may provide a useful practical rehabilitation technique for PLP. Future studies will be required to clarify the mechanisms underlying immediate PLP alleviation via electrical stimulation of RSAs.

scholarly journals Long-term effects of the proline-rich antimicrobial peptide Oncocin112 on the Escherichia coli translation machinery

2020 ◽  
Vol 295 (38) ◽  
pp. 13314-13325
Author(s):  
Yanyu Zhu ◽  
James C. Weisshaar ◽  
Mainak Mustafi
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Peptides ◽  
Binding Site ◽  
Elongation Factor ◽  
Microscopy Study ◽  
Single Step ◽  
Long Term Effects ◽  
Bacterial Membranes

Proline-rich antimicrobial peptides (PrAMPs) are cationic antimicrobial peptides unusual for their ability to penetrate bacterial membranes and kill cells without causing membrane permeabilization. Structural studies show that many such PrAMPs bind deep in the peptide exit channel of the ribosome, near the peptidyl transfer center. Biochemical studies of the particular synthetic PrAMP oncocin112 (Onc112) suggest that on reaching the cytoplasm, the peptide occupies its binding site prior to the transition from initiation to the elongation phase of translation, thus blocking further initiation events. We present a superresolution fluorescence microscopy study of the long-term effects of Onc112 on ribosome, elongation factor-Tu (EF-Tu), and DNA spatial distributions and diffusive properties in intact Escherichia coli cells. The new data corroborate earlier mechanistic inferences from studies in vitro. Comparisons with the diffusive behavior induced by the ribosome-binding antibiotics chloramphenicol and kasugamycin show how the specific location of each agent's ribosomal binding site affects the long-term distribution of ribosomal species between 30S and 50S subunits versus 70S polysomes. Analysis of the single-step displacements from ribosome and EF-Tu diffusive trajectories before and after Onc112 treatment suggests that the act of codon testing of noncognate ternary complexes (TCs) at the ribosomal A-site enhances the dissociation rate of such TCs from their L7/L12 tethers. Testing and rejection of noncognate TCs on a sub-ms timescale is essential to enable incorporation of the rare cognate amino acids into the growing peptide chain at a rate of ∼20 aa/s.

scholarly journals Problems in differential diagnosis of secondary hyperparathyroidism

2021 ◽  
Vol 38 (1) ◽  
pp. 161-167
Author(s):  
S. G. Shulkina ◽  
D. O. Sirin ◽  
E. N. Smirnova ◽  
V. G. Zhelobov ◽  
N. Yu. Kolomeets ◽  
...  
Keyword(s):  
Vitamin D ◽  
Differential Diagnosis ◽  
Kidney Disease ◽  
Secondary Hyperparathyroidism ◽  
Vitamin D Deficiency ◽  
Clinical Case ◽  
Kidney Diseases ◽  
Active Form ◽  
Renal Tubules ◽  
Vitamin D Metabolism

Hyperparathyroidism is an endocrine disease characterized by excessive production of parathyroid hormone in the main cells of the parathyroid glands. Depending on the cause of this disease, there are primary, secondary (SHPT) and tertiary hyperparathyroidism. The most common causes of SHPT are vitamin D deficiency and chronic kidney disease (CKD). Vitamin D is converted to its active form by hydroxylation in the renal tubules. Developmental abnormalities and chronic kidney diseases lead to atrophy of the tubular epithelial cells that causes a violation of vitamin D metabolism and the development of SHPT, which in turn are accompanied by a violation of calcium-phosphorus metabolism and a syndrome of musculoskeletal disorders. This article presents an analysis of a clinical case of a patient diagnosed secondary hyperparathyroidism against the background of vitamin D deficiency combined with polycystic kidney disease. This clinical case reflects the complexity of the differential diagnosis of the disease and the tactics of patient's management.

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