Search PubMed⌕ Search

Biomedical subjects

C Chaimovitz

Publications and source records attributed to C Chaimovitz.

At least 19 recordsLinked to original sources
PubMed1998

Interleukin-15, a leukocyte activator and growth factor, is produced by cortical tubular epithelial cells.

Many renal diseases, including transplant rejection, are mediated by mononuclear cells. Interleukin-15 (IL-15) has been recently described as a cytokine with IL-2-like activity. IL-15 is an effective leukocyte growth factor, activator, and chemoattractant. In rejected human kidney allografts, elevated IL-15, but not IL-2, mRNA is expressed, suggesting a role for IL-15 in the rejection process. The aim of this study was to investigate whether human cortical tubular epithelial cells (HTC) are able to produce IL-15 and whether IL-15 expression is regulated by inflammatory mediators. HTC were isolated and characterized, and IL-15 expression was analyzed by reverse transcription-PCR, enzyme-linked immunosorbent assay, and bioactivity. It was found that HTC constitutively express IL-15. Upon stimulation of HTC with interferon-gamma (IFN gamma), the levels of both mRNA and protein increased up to twofold. In contrast, lipopolysaccharide, IL-1, IL-2, and tumor necrosis factor-alpha had no detectable effect. IFN gamma action on HTC was dose-dependent from concentrations of 5 U/ml, reaching a plateau at 50 U/ml. HTC supernatants induced proliferation of the T cell line CTLD, which could be partially blocked (50%) by specific IL-15 antibodies. This study shows that IL-15 is secreted by HTC and that the Th1-cytokine IFN gamma upregulates IL-15 expression. This suggests that HTC play a role in cell-mediated renal diseases by releasing IL-15.

Base Sequence↗
PubMed1997

Deoxyribonucleic acid ploidy and the clinical pattern of grade 2 superficial bladder cancer.

PURPOSE: We attempted to find an objective and quantitative parameter that would enable us to differentiate between aggressive and nonaggressive grade 2 superficial transitional cell carcinoma of the bladder. This type of tumor belongs to a heterogeneous group, 30% of which behave aggressively by invading lamina propria and muscle tissue in the course of the evolution. The remaining 70% of tumors have less aggressive qualities, are nonprogressive and have a low recurrence rate. To date to our knowledge there is no way to differentiate between these 2 subpopulations of tumors. MATERIALS AND METHODS: We performed a retrospective flow cytometric analysis of deoxyribonucleic acid (DNA) ploidy and cell cycle phases on primary and solitary formalin fixed and paraffin embedded tumor tissue. RESULTS: Of the 41 specimens studied 16 were aneuploid and 25 were diploid. Aneuploidy was associated with progressive disease and high mortality rates, particularly in patients who did not receive postoperative adjuvant intravesical instillation. DNA diploidy was equated with lack of mortality and a low progression rate. The use of intravesical bacillus Calmette-Guerin as an adjuvant postoperative treatment was associated with low recurrence rates. In this group elevated G2M percent and S phase fractions correlated with higher recurrence rates. CONCLUSIONS: DNA ploidy was a prognostic factor in stage Ta grade 2 bladder transitional cell carcinoma and should be considered as a complementary test to histopathological analysis. Adjuvant instillation with bacillus Calmette-Guerin is advised after transurethral resection of primary solitary aneuploid stage Ta grade 2 bladder transitional cell carcinomas and of primary solitary diploid tumors with elevated G2M percent and S phase fraction.

Carcinoma, Transitional Cell↗
PubMed1996

TNF-receptors on human peritoneal mesothelial cells: regulation of receptor levels and shedding by IL-1 alpha and TNF alpha.

Human peritoneal mesothelial cells (HPMC) respond to tumor necrosis factor alpha (TNF alpha) by releasing various cytokines that may activate the endothelium and induce recruitment of leukocytes during peristonitis. We characterized the receptors for TNF on HPMC to elucidate their functions in peritonitis. Scatchard analysis determined the presence of 70 x 10(3) TNF receptors/cell with a kDa of 0.44 nM. TNF receptor 1 (TNF-R1, p55) and TNF-R2 (p75) mRNA were demonstrated by reverse-transcriptase-PCR (RT-PCR). TNF-R1 protein was solely detected by flow cytometry (FCM). Interleukin-1 alpha (IL-1 alpha) induced down-regulation of TNF-R1. This was concomitant with accumulation of soluble TNF-R1 (sTNF-R1) detected by specific ELISA. LPS had a lower TNF-R1-shedding activity while TNF alpha did not induce shedding. The IL-1-induced-sTNF-R1-shedding was suppressed by the protein-kinase-A (PKA) inhibitor, H-8, or by H-7, the inhibitor of both PKC and PKA, but not by the specific PKC inhibitor GF. These experiments suggest a role for PKA in the IL-1-shedding signal. No change in TNF-R1 mRNA levels was observed after IL-1 alpha or TNF alpha stimulation while TNF-R2 (p75) mRNA basal levels transiently increased three to fivefold, reaching a peak after four hours followed by an accumulation of sTNF-R2 in the supernatant. Our data suggest that the main receptor expressed on HPMC is TNF-R1. Down-regulation and shedding of TNF-R1 induced by IL-1, and the transient expression of TNF-R2 induced by IL-1 and TNF, may regulate the responses to TNF by HPMC. These results may be important in understanding the inflammatory process of peritonitis were TNF plays a major role.

Epithelial Cells↗
PubMed1996

Successful treatment of secondary hyperparathyroidism in hemodialysis patients with oral pulse 1-alpha-hydroxy-cholecalciferol therapy.

We have used high-dose oral pulse therapy with 1 alpha-hydroxycholecalciferol (1 alpha-OH-D3) to treat 40 hemodialysis patients suffering form secondary hyperparathyroidism. Forty patients with intact parathyroid hormone (PTH) levels of > 150 pg/ml were treated with 4 micrograms oral 1 alpha-OH-D3 twice weekly for 1 year. The mean PTH level was 515 +/- 50 pg/ml prior to treatment, which fell to 191 +/- 42 pg/ml after 6 months of treatment (p < 0.00001), and to 164 +/- 39 pg/ml after 12 months of treatment. Patients with very high PTH levels (> 800 pg/ml) suppressed less well than patients with lower levels (150-300 pg/ml). The therapeutic end point of PTH < 100 pg/ml was achieved in 23 patients (58%). The main side effect of the treatment was hypercalcemia, but this was symptomatic in only 3 patients, all above the age of 70 years. In summary, oral high-dose pulse therapy with 1 alpha-OH-D3 was highly effective in suppressing PTH levels in hyperparathyroid hemodialysis patients, and side effects were relatively few.

Administration, Oral↗
PubMed1995

Commercial dialysate inhibits TNF alpha mRNA expression and NF-kappa B DNA-binding activity in LPS-stimulated macrophages.

Continuous ambulatory peritoneal dialysis is known to interfere with the normal inflammatory responses of macrophages in the peritoneal cavity. Commercial peritoneal dialysis solution (CDS) has been shown to inhibit tumor necrosis factor alpha (TNF alpha) release from LPS stimulated peritoneal macrophages. To further dissect the mechanism of this inhibition, we used human blood-derived macrophages or the murine macrophage cell line, P388D1, that were stimulated with LPS after pretreatment with CDS, and tested TNF alpha mRNA levels by Northern hybridization or reverse transcriptase polymerase chain reaction. Time course studies demonstrated that CDS lowered TNF alpha mRNA levels within 15 minutes of pretreatment of cells. In addition, the CDS inhibited DNA binding activity of NF-kappa B that is probably involved in regulation of LPS-mediated transcriptional activation of the TNF alpha gene. Inhibition was dependent on both the low pH and the lactate in the CDS, but was independent of the osmolarity or glucose concentration. The rate of catabolism of TNF alpha mRNA was not affected by CDS as demonstrated by actinomycin D chase experiments. Thus, impairment of LPS-stimulated macrophage function by CDS is associated with low TNF alpha mRNA which may be the result of the low activity of NF-kappa B. Since NF-kappa B is involved in transcription regulation of a large number of "early activation" genes, CDS may interfere with the production of additional immunomodulatory proteins that are encoded by genes possessing NF-kappa B site(s) in their promoter region.

Base Sequence↗
PubMed1995

Intracellular acidification mediates the inhibitory effect of peritoneal dialysate on peritoneal macrophages.

Commercial peritoneal dialysis solution (CDS) is known to have a detrimental effect on the capacity of peritoneal macrophages (PM phi) to kill bacteria and produce acute phase cytokines. This cytotoxic effect is largely caused by the low pH of CDS. Because the cytoplasmic pH (pHi) is an important determinant of cellular function, the effect of CDS on the pHi of PM phi from continuous ambulatory peritoneal dialysis patients was studied. The pHi of PM phi was measured fluorometrically in N-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-buffered salt solution (HBSS) or CDS at pH values of 5.3, 6.5, and 7.0, values that represent the pH existing in dialysate during the first 30 min of dwell time. For any given pH of the experimental medium, the pHi was always more acidic in CDS than in HBSS. When PM phi were incubated with a lactate-containing HBSS, a cellular acidification was observed that was similar to that attained by exposure to CDS at the same pH. This supports the hypothesis that the decrease in pHi was due to the influx of lactic acid from the CDS into the PM phi. In order to demonstrate a causal association between the CDS-induced cellular acidification and a defect in phagocytosis and cytokine production, these functions were studied after pHi clamping by means of K+/nigericin. It was found that clamping pHi to values below 6.5 led to a markedly reduced tumor necrosis factor-alpha production and phagocytosis. However, at values of pHi > 6.5, these functions were normal. (ABSTRACT TRUNCATED AT 250 WORDS)

Cell Survival↗
PubMed1994

Human peritoneal mesothelial cells synthesize IL-1 alpha and beta.

We studied the ability of human peritoneal mesothelial cells (HPMC) to produce the major pro-inflammatory cytokines interleukin-1 alpha (IL-1 alpha) and -beta when stimulated by lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF alpha) or IL-1 alpha, or combinations of these three factors. Biological activity of IL-1 was measured by bioassay, and levels of IL-1 alpha and beta were determined using specific radioimmunoassays. We found that HPMC are capable of secreting IL-1 alpha and -beta in response to stimulation by these substances, but stimulation with a combination of LPS + TNF alpha, LPS + IL-1 alpha, or TNF alpha + IL-1 alpha, had a marked synergistic effect on cytokine production. A combination of all three substances together had a significantly enhanced synergistic effect. Using reverse transcription PCR, we found a peak in IL-1 alpha and beta mRNA levels three hours after stimulation. We found that LPS, TNF alpha and IL-1 alpha alone, or in combination, caused an increase in IL-1 alpha and -beta mRNA levels. Cycloheximide and actinomycin D blocked the production of IL-1 alpha and -beta protein, showing that de novo production of IL-1 or synthesis of mRNA stabilizing proteins are needed after stimulation. We thus conclude that HPMC play an important role in the amplification of the initial peritoneal inflammatory response which originates in the peritoneal macrophages, and these findings are of importance in understanding the peritoneal response to infection in continuous ambulatory peritoneal dialysis (CAPD) patients.

Base Sequence↗
PubMed1993

The relationship between plasma and dialysate lipoproteins and apoproteins in patients treated by continuous ambulatory peritoneal dialysis.

End-stage renal disease is frequently associated with lipoprotein abnormalities, manifested primarily by elevated very low-density lipoprotein levels combined with a decrease in high-density lipoprotein levels. These lipoprotein disturbances are further exacerbated in continuous ambulatory peritoneal dialysis. We examined the lipoprotein and apolipoprotein profiles in the blood and dialysate effluents of eight normolipidemic and five hypertriglyceridemic patients with end-stage renal failure treated with continuous ambulatory peritoneal dialysis. The normolipidemic patients were found to have significantly greater losses, as expressed by the fractional catabolic rates through the dialysate, for protein, total cholesterol, and very low-density lipoprotein cholesterol. These results suggest that the hypertriglyceridemia associated with continuous ambulatory peritoneal dialysis may be mitigated in some patients by the excessive loss of very low-density lipoprotein, or some other plasma constituent, into the dialysate effluent.

Apolipoproteins A↗
PubMed1993

1,25-Dihydroxyvitamin D3 inhibits Na(+)-dependent phosphate transport in osteoblastic cells.

In the present work we investigated the influence of vitamin D3 metabolites on Na(+)-dependent phosphate (Pi) transport in the clonal osteoblastic cell line UMR-106. The vitamin D3 metabolite 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] dose-dependently inhibited Pi transport with a half-maximal concentration of approximately 5 x 10(-11) M. The effect of 1,25(OH)2D3 was first observed after 8 h of preincubation period. Inhibition of phosphate uptake was relatively specific for the 1,25(OH)2D3 analogue of vitamin D3. The potency order was 1,25(OH)2D3 >> 24,25-dihydroxyvitamin D3 > 25-[3H]hydroxyvitamin D3. Kinetically, 1,25(OH)2D3 decreased the maximal velocity of the phosphate uptake system, whereas the affinity for phosphate was unaffected. Activation of protein kinase C (PKC) in UMR-106 cells stimulated Na(+)-dependent Pi transport. Nonetheless, the inhibitory effect of 1,25(OH)2D3 on Pi transport was not related to downregulation of PKC. Chemical determination of intracellular Pi showed a 50% reduction after 24-h preincubation with 10(-8) M 1,25(OH)2D3. We conclude that 1,25(OH)2D3 inhibits Na(+)-dependent phosphate transport in osteoblastic cells. This in turn leads to intracellular Pi depletion. The physiological implication of this phenomenon on the effects of vitamin D on osteoblasts in situ is discussed.

Biological Transport↗
PubMed1993

Inhibitory effect of the calcium antagonist, verapamil, on measles and vaccinia replication in cell culture.

Kidney cell lines MA104 and BGM were infected with vaccinia and measles viruses respectively in the presence of 45Ca. Increased 45Ca level was detected in the virally infected cells as compared with control cells. An enhancement of 28 +/- 6% and 37 +/- 13% was shown in vaccinia and measles respectively following 5 h of infection. The effect of the calcium antagonist verapamil was studied in both vaccinia- and measles-infected cells. In one-step growth experiments, the mean inhibitory effect of 90 microM verapamil on viral yield after 13 h was 97 +/- 1% in the case of vaccinia. In the measles virus after 47 h a mean of 76 +/- 5% inhibition was detected. The suitability of verapamil as a potential antiviral agent is suggested and requires further investigation.

Animals↗
PubMed1993

The effect of peritoneal dialysis fluid on the release of IL-1 beta and TNF alpha by macrophages/monocytes.

OBJECTIVE: To study the effect of dialysis fluid on the release of interleukin-1 beta (IL-1 beta) and tumor necrosis factor (TNF alpha) by peritoneal macrophages (PM) and peripheral blood mononuclear cells (MNC), and the time course and factors involved in this effect. DESIGN: PM and MNC were incubated for various periods with Dianeal itself, or Dianeal of varying pH and composition. IL-1 beta was measured by radioimmunoassay and TNF alpha by cytotoxicity assay. PATIENTS: PM were obtained by centrifugation of dialysis effluent from 3 continuous ambulatory peritoneal dialysis (CAPD) patients. MNC were obtained from healthy volunteers. RESULTS: Dialysis fluid inhibited the release of both cytokines. Indomethacin had no effect on the inhibition of TNF alpha release caused by dialysis fluid. Thus prostaglandins are not involved in this inhibition. Solutions of pH 5.2 and high lactate concentration caused an identical inhibition to that caused by dialysate, whereas the presence or absence of glucose had no effect. Thus it seems that pH and lactate are the important inhibitory factors. Time course studies showed that the inhibition of TNF alpha release was substantial after only 15 minutes of incubation with dialysate, whereas the inhibition of IL-1 beta became significant only after 60 minutes of incubation. CONCLUSIONS: Even though dialysate pH rises within 15-30 minutes after instillation into the abdomen, the initial low pH present for only a short time could have a significant effect on TNF alpha release by peritoneal macrophages, and thus on their ability to mount a normal inflammatory response. Lactate also has a significant inhibitory role. It is suggested that commercial dialysis solutions should have a pH of 7.0 and that a physiological buffer other than lactate be used.

Cells, Cultured↗
PubMed1992

[Calcific periarthritis in patients with endstage renal disease on chronic dialysis].

2 patients with end-stage renal disease undergoing dialysis developed calcific periarthritis. A 25-year-old man on hemodialysis developed arthritis of 2 right metacarpophalangeal joints and a 65-year-old man on chronic ambulatory peritoneal dialysis suffered from pain and tenderness in the left buttock. Treatment with nonsteroidal antiinflammatory drugs in the first case and periarticular injection of methylprednisolone (Depomedrol) in the second were successful.

Adult↗
PubMed1992

Assessment of combined 24,25(OH)2D3 and 1 alpha (OH)D3 therapy for bone disease in dialysis patients.

An increasing body of experimental data suggests a role for 24,25(OH)2D3 in bone metabolism. The present study was carried out to assess a possible therapeutic role of this vitamin D metabolite in renal osteodystrophy. Twenty-two chronic dialysis patients, most of whom were previously maintained on 1 alpha (OH)D3 therapy, received additional treatment with 10 micrograms/day 24,25(OH)2D3 and were compared to 19 patients receiving 1 alpha (OH)D3 alone. Analysis of transiliac bone biopsies obtained at study entry and following 10-16 months of treatment revealed that the combined therapy produced a decrease in bone turnover. Specifically, the addition of 24,25(OH)2D3 inhibited an increase in trabecular bone volume (BV/TV) and suppressed osteoclastic parameters. Thus BV/TV increased from 26.2 +/- 8.6 to 32.1 +/- 7.5% (p < 0.01) in the 1 alpha (OH)D3 group, but it remained unchanged in the combined therapy group. In contrast, the eroded surface (ES/BS), the osteoclast surface (Oc.S/BS), and the osteoclast numbers were significantly suppressed in patients receiving both 24,25(OH)2D3 and 1 alpha (OH)D3, as compared with those receiving 1 alpha (OH)D3 alone (p < 0.01, p < 0.01, and p < 0.001, respectively). These improvements were independent of changes in 1 alpha (OH)D3 dosage. The extent of bone aluminium deposits was unrelated to the administration of 24,25(OH)2D3 or to its effect. 24,25(OH)2D3 therapy was not associated with any adverse effects.

24,25-Dihydroxyvitamin D 3↗
PubMed1992

Acute phosphate depletion and in vitro rat proximal tubule injury: protection by glycine and acidosis.

The effects of phosphate (PO4) removal from Krebs Henseleit buffer on freshly isolated rat proximal tubules (rPT) were assessed by measuring Ca2+ uptake (nmol/mg protein), cellular adenosine triphosphate (ATP) (nmol/mg), tissue K+ content (nmol/mg) and lactate dehydrogenase (LDH) as an index of cell integrity. Ca2+ uptake increased by 50% in rPT incubated in zero PO4 medium as compared to control (2.6 +/- 0.1 vs. 3.9 +/- 0.19, P less than 0.001) and LDH release increased 2.5-fold from 14.2 +/- 0.6 to 31.6 +/- 1.6%, P less than 0.001. Neither verapamil (200 microM) nor mepacrine (50 microM) reduced Ca2+ uptake or decreased LDH release suggesting that the increased Ca2+ uptake was not occurring through potential operated channels and that phospholipase-induced cell injury was not the cause of increased LDH release. Either glycine (2 mM) or extracellular fluid acidosis (pH 7.06), however, significantly diminished rPT injury and Ca2+ uptake. Specifically, as compared to the increased LDH released in untreated. PO4-depleted rPT, LDH release was diminished significantly by glycine treatment (31.0 +/- 0.9 vs. 15.5 +/- 1.6%, P less than 0.001) or acidosis (30.3 +/- 0.04 vs. 19.2 +/- 0.9%, P less than 0.01). Ca2+ uptake did not increase in glycine treated tubules (2.6 +/- 0.1 vs. 2.8 +/- 0.2 nmol/mg, NS) or in the presence of acidosis (2.6 +/- 0.1 vs. 2.97 +/- 0.17 nmol/mg, NS). ATP concentrations were markedly reduced by PO4 depletion (2.8 +/- 0.2 vs. 4.8 +/- 0.3 nmol/mg, P less than 0.001) and remained at low levels during either acidosis or glycine-induced protection.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1991

Metabolism of 25-OH-vitamin D3 by peritoneal macrophages from CAPD patients.

The active metabolite of vitamin D, 1,25-dihydroxycholecalciferol (1,25(OH)2D3), is produced mainly by the kidney, but there is evidence for extrarenal production in certain circumstances. We studied whether peritoneal macrophages (PM) from CAPD patients were capable of metabolizing 25-OH-D3 to 1,25(OH)2D3. We found that PM were able to metabolize 25-OH-D3 in vitro; the main product following 16 hours of incubation was 19-nor, 10-oxo, 25-OH-D3 with smaller amounts of 1,25(OH)2D3. However, after shorter incubations of three and five hours a larger portion of 1,25(OH)2D3 was produced. The metabolism of 25-OH-D3 was greatly enhanced in PM harvested during episodes of peritonitis. This property was specific for PM of CAPD patients, and was not found in PM from normal subjects. However, incubation of control PM with peritoneal effluent from CAPD patients resulted in induction of the ability of these cells to metabolize 25-OH-D3. This induction was enhanced by preincubation with peritoneal effluent from CAPD patients suffering from peritonitis. Prostaglandin E2 was found to be involved in this synthesis: addition of PGE2 to normal PM induced metabolism of 25-OH-D3, and incubation of PM from CAPD patients with indomethacin decreased the metabolism of 25-OH-D3. The vitamin D metabolites produced by PM from CAPD patients could have a role in immunological resistance to peritoneal infections.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1991

Oral administration of 24,25(OH)2D3 suppresses the serum parathyroid hormone levels of dialysis patients.

We measured the serum parathyroid hormone (PTH) levels in 20 patients treated with continuous ambulatory peritoneal dialysis before and after oral treatment with 24,25-dihydroxyvitamin D3- 24,25(OH)2D3. This metabolite was given in addition to existing treatment with 1 alpha-OH-D3 and calcium carbonate. Administration of 24,25(OH)2D3 led to a significant decrease in PTH levels (intact molecule) from 382 +/- (SE) 65 to 245 +/- 54 pg/ml in 9 patients whose initial levels were extremely high (p = 0.01). No side effects were observed. On the average, calcium values were unchanged and within the normal range throughout the study period; however, a few episodes of mild asymptomatic hypercalcemia occurred which responded quickly to reduction of the calcium carbonate dosage. The present study suggests that oral administration of 24,25(OH)2D3 combined with 1 alpha-OH-D3 is safe and capable of suppressing the raised serum PTH levels of end-stage renal disease patients without the danger of significant hypercalcemia.

24,25-Dihydroxyvitamin D 3↗