A better diet quality is associated with a reduced likelihood of CKD in older adults

BACKGROUND AND AIMS

Studies of diet in relation to chronic kidney disease (CKD) have focused on individual nutrients. The relationship between overall patterns of food intake and renal function has not been well explored. We aimed to investigate the associations between diet quality with the prevalence, incidence and progression of CKD in a cohort of older adults.

METHODS AND RESULTS

1952 participants aged ≥50 years at baseline were examined between 1992-1994 and 2002-2004. Dietary data were collected using a semi-quantitative food frequency questionnaire. A modified version of the Healthy Eating Index for Australians was developed to determine total diet scores (TDS). Baseline biochemistry including serum creatinine was measured. CKD was defined as MDRD estimated glomerular filtration rate (eGFR) <60 mL min⁻¹·1.73 m⁻². Participants in the highest quartile of mean TDS compared to those in the first quartile (reference), had a 41% reduced likelihood of having eGFR <60 mL min⁻¹·1.73 m⁻², [multivariable-adjusted odds ratio, OR, 0.59 (95% confidence intervals, CI, 0.41-0.85), P-trend = 0.005]. Each unit increase in TDS was associated with a 15% decrease in the odds of having prevalent CKD, multivariable-adjusted OR 0.85 (95% CI 0.74-0.97). A non-significant, inverse association between TDS and CKD incidence was observed (P-trend = 0.10).

CONCLUSION

Older adults with better diet quality had a reduced likelihood of having eGFR <60 mL min⁻¹·1.73 m⁻². Adherence to dietary guidelines were not prospectively associated with CKD incidence or progression. Further studies with adequate power are warranted to assess the longitudinal association between diet quality and CKD.

Differing association of macrophage subsets with atherosclerotic plaque stability

AIM

While initial research suggests that M2 macrophages are athero-protective, more recently, proatherogenic functions, such as a greater uptake of lipid than M1 macrophages, have been demonstrated, raising the question of their actual association with plaque stability. The present study, therefore, assessed the association between macrophage subset and plaque stability. Furthermore, it examined whether the fibrocyte, that we have previously identified in the plaque, represents a subset of M2 macrophages.

METHODS

Twenty human carotid atherosclerotic plaque specimens were examined for the presence of macrophages using immunohistochemistry for pan macrophages (CD68), M1 (CD64, CD86) and M2 (CD163, CD206) subsets. The slides were assessed by digital whole slide scanning/image analysis to quantify the expression of these markers in the plaque. Comparisons in marker distribution and quantity relative to plaque stability were made. Adoption of a fibrocyte phenotype was assessed by double immunofluorescence staining of the markers with procollagen I.

RESULTS

M1 and M2 macrophages were present throughout the plaque including the core and cap. While the levels of CD68 (pan macrophage maker) and CD86 negatively correlated with cap thickness, the levels of the M2 marker, CD163, did not and moreover, did not differ between plaques when they were separated into stable and unstable groups. Notably, collagen production was evident in most but not all M2 macrophages.

CONCLUSION

Our findings demonstrate that while macrophage levels in general negatively correlate with plaque cap thickness, levels of M2 macrophages do not. This may be in part due to their ability to produce collagen (ie adopt a fibrocyte phenotype) in the plaque.

Quantitative grading of a human blastocyst: optimal inner cell mass size and shape

OBJECTIVE

To investigate the predictive value of quantitative measurements of blastocyst morphology on subsequent implantation rates after transfer.

DESIGN

Prospective observational study.

SETTING

Private assisted reproductive technology center.

PATIENT(S)

One hundred seventy-four IVF patients receiving transfers of expanded blastocyst-stage embryos on day 5 (n = 112) or day 6 (n = 62) after oocyte retrieval.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Blastocyst diameter, number of trophectoderm cells, inner cell mass (ICM) size, ICM shape, and implantation and pregnancy rates.

RESULT(S)

Blastocyst diameter and trophectoderm cell numbers were unrelated to implantation rates. Day 5 expanded blastocysts with ICMs of >4,500 microm(2) implanted at a higher rate than did those with smaller ICMs (55% vs. 31%). Day 5 expanded blastocysts with slightly oval ICMs implanted at a higher rate (58%) compared with those with either rounder ICMs (7%) or more elongated ICMs (33%). Implantation rates were highest (71%) for embryos with both optimal ICM size and shape. Pregnancy rates were higher for day 5 transfers of optimally shaped ICMs compared with day 5 transfers of optimally sized ICMs.

CONCLUSION(S)

Quantitative measurements of the inner cell mass are highly indicative of blastocyst implantation potential. Blastocysts with relatively large and/or slightly oval ICMs are more likely to implant than other blastocysts.

Early administration of PDTC in adriamycin nephropathy: effect on proteinuria, cortical tubulointerstitial injury, and NF-kappaB activation

The persistence of NF-kappaB independent inflammatory signals in the cortical tubulointerstitium may explain the incomplete suppression of interstitial monocyte accumulation by the antioxidant NF-kappaB inhibitor, pyrrolidine dithiocarbamate (PDTC), in nephrotic rats with established Adriamycin nephropathy (AN). Because PDTC is known to have anti-proteinuric effects, in this study we investigated whether earlier commencement, during the pre-nephrotic phase of AN, would be more effective in reducing interstitial monocyte accumulation. Male Wistar rats with AN received either vehicle or PDTC (50 mg/kg bd i.p.i.) from d7 until d30 (n = 8 per group). On d30, PDTC reduced renal cortical lipid peroxidation (43%), wet kidney weight and tubulointerstitial injury in AN, but did not decrease proteinuria. Accordingly, inhibition of interstitial ED-1 accumulation remained incomplete (52%). Interestingly, the early administration of PDTC in AN, induced polyuria and renal cortical NF-kappaB DNA-binding activity was reduced by only 35%. These results suggest that: (i) the combination of an anti-proteinuric agent with PDTC may be required to completely suppress interstitial monocyte cell accumulation in AN and, (ii) the timing and duration of PDTC therapy are an important determinant of its efficacy to reduce NF-kappaB activation, in vivo.

Dramatic declines in implantation and pregnancy rates in patients who undergo repeated cycles of in vitro fertilization with blastocyst transfer after one or more failed attempts

OBJECTIVE

To compare the outcome of second and third cycles of in vitro fertilization with blastocyst transfer to the outcome of first attempts at IVF with blastocyst transfer.

DESIGN

Retrospective study.

SETTING

Private ART center.

PATIENT(S)

Three hundred and four patients undergoing treatment with in vitro fertilization with blastocyst transfer, 87 of which underwent at least one cycle of re-treatment after failing to achieve pregnancy in their first cycle.

INTERVENTION(S)

Bipronucleate oocytes were grown for up to 144 hours and subsequently transferred when at least one embryo attained the expanded blastocyst stage.

MAIN OUTCOME MEASURE(S)

Pregnancy and implantation rates.

RESULT(S)

Pregnancy rates per retrieval were significantly higher for patients undergoing their first cycle of in vitro fertilization with blastocyst transfer (36%) compared to those undergoing their second (19%) or their third (9%) cycles of treatment. Implantation rates per embryo were also higher for first cycles of in vitro fertilization with blastocyst transfer (30%) compared to second (18%) or third cycles (8%).

CONCLUSION(S)

Pregnancy and implantation rates decline dramatically in repeated cycles of in vitro fertilization with blastocyst transfer following one or more unsuccessful cycles of in vitro fertilization with blastocyst transfer.

Induction of proteinuric chronic glomerular disease in the rat (Rattus norvegicus) by intracardiac injection of doxorubicin hydrochloride

Adriamycin nephropathy (AN) is a widely used nonimmune-mediated rat model of proteinuric chronic glomerular disease and is usually induced by a single intravenous injection of doxorubicin hydrochloride (DX) into the tail vein. However, this route can be associated with local skin necrosis and variability in disease induction and poses an occupational hazard to the investigator. Here we describe a simple technique of administering DX (1.7 mg) to ketamine:xylazine-sedated adult male Wistar rats (mean +/- 1 standard deviation, 238 +/- 8 g; n = 28) by using a single substernal intracardiac injection. The procedure was associated with minimal morbidity and mortality (1 death related to anesthesia). By day 21, severe nephrotic syndrome with effacement of glomerular epithelial cell foot processes and diffuse cortical tubulointerstitial injury was induced in all animals. Therefore, intracardiac injection of DX is a safe and consistent method of inducing AN in the rat and provides an alternative to the tail-vein route.

Molecular mechanisms by which iron induces nitric oxide synthesis in cultured proximal tubule cells

Nitric oxide (NO) levels are increased after exposure of cultured proximal tubule cells (PTC) to non-haem iron, potentially contributing to PTC injury in disease states associated with increased iron exposure, including proteinuric renal disease. The mechanisms underlying this observed increase were investigated. After 3 h exposure to 400 microM nitrilotriacetate (NTA)-Fe, inducible nitric oxide synthase (iNOS) mRNA expression was significantly increased, with a corresponding increase in iNOS protein after 12 h. The nuclear binding activity of NFkappaB with 400 microM NTA-Fe was increased, and pyrrolidine dithiocarbamate (PDTC), an antioxidant inhibitor of NFkappaB, prevented both activation of NFkappaB and NO production in response to NTA-Fe. Inhibition of protein tyrosine kinase reduced iNOS mRNA, iNOS protein levels and NO production in response to NTA-Fe. The effect of tyrosine kinase inhibition on NFkappaB activation was variable, with herbimycin but not genistein having an inhibitory effect. Activation of either protein kinase A or C increased iNOS mRNA and protein levels, and NO production in response to NTA-Fe, whereas only the protein kinase C activator phorbol dibutyrate (PDBu) had a stimulatory effect on NFkappaB activation. The protein kinase A activator forskolin did not alter iron-induced activation of NFkappaB. These data suggest that the observed increase in NO production by PTC in response to iron is due to increased transcription of iNOS. The transcriptional regulation of this response is complex and involves NFkappaB, protein tyrosine kinase and the protein kinases A and C.

Regulation of tubular cell MCP-1 production by intracellular ions: a role for sodium and calcium

Proximal tubule cells (PTC) in chronic renal disease produce chemokines which cause renal interstitial inflammation, and also transport more Na+ than normal. To investigate whether these two events might be related, monocyte chemoattractant protein-1 (MCP-1) production was examined in rat PTC in primary culture. Amiloride reduced, while ouabain increased levels of MCP-1 mRNA and protein. Amiloride reduced MCP-1 in cells stimulated with ouabain, lipopolysaccharide (LPS) or albumin. Intracellular Na+ rose with ouabain, but not LPS or albumin. Effects of amiloride, ouabain, LPS and albumin were abrogated by sodium-free but not chloride-free culture medium, and were not explained by changes in intracellular pH. Intracellular Ca2+ rose with ouabain, LPS or albumin and sodium-free medium. BAPTA-AM reduced intracellular Ca2+ and MCP-1 mRNA levels in unstimulated cells, and cells stimulated with ouabain, LPS or albumin. Thus, amiloride and ouabain may alter tubular cell MCP-1 by changing intracellular Na+, with secondary changes in intracellular Ca2+, whereas stimulation by LPS and albumin may involve Ca2+ directly.

A comparison of day 5 and day 6 blastocyst transfers

OBJECTIVE

To compare implantation and pregnancy rates according to the day of embryo transfer (day 5 or 6 after oocyte retrieval) when transfer was postponed until expanded blastocysts developed.

DESIGN

Retrospective clinical study.

SETTING

Private ART center.

PATIENT(S)

One-hundred and eighty-three women undergoing blastocyst-stage embryo transfer following in vitro fertilization.

INTERVENTION(S)

Bipronucleate oocytes were grown for up to 144 hours and subsequently transferred only when at least one embryo attained the expanded blastocyst stage.

MAIN OUTCOME MEASURE(S)

Implantation and pregnancy rates.

RESULT(S)

Blastocysts transferred on day 5 implanted at nearly twice the rate of blastocysts transferred on day 6 (36.3% vs. 19.0%). Pregnancy rates were also almost twice as high among the day 5 transfer patients (59.3% vs. 32.3%). In addition, more blastocysts developed (3.6 vs. 2.4), and more were transferred (2.7 vs. 2.3) to the day 5 transfer patients, although the proportion of expanded blastocysts among the blastocysts that were transferred was the same for the two groups (91.7% vs. 93.6%).

CONCLUSION(S)

Embryos that develop to the expanded blastocyst stage and are transferred on day 5 after retrieval are approximately twice as likely to implant compared to those for which expansion and transfer are delayed until day 6.

Tubulointerstitial renal disease

Tubulointerstitial damage, in progressive chronic renal disease of all types, arises because of a complex interplay between factors in the tubular lumen, tubular epithelial cells, peritubular capillaries, resident and infiltrating interstitial cells and extracellular matrix. Particularly in proteinuric renal disease, tubular epithelial cells play a central role in orchestrating these events. In response to mediators arising systemically, in the tubular lumen or from other renal cells, tubular epithelial cells undergo a complex series of structural and functional changes and produce a bewildering number of soluble and fixed mediators, which in turn lead to interstitial inflammation and fibrosis. Knowledge of these interactions has increased exponentially over the past decade, and has defined a number of new targets for treatment. Both expansion and consolidation of this knowledge is needed to determine which of these targets holds the most promise for future treatment.

Role of CD8(+) cells in the progression of murine adriamycin nephropathy

BACKGROUND

Many studies have shown that interstitial inflammation in human and experimental renal disease is characterized by T-cell infiltration, but published data on the involvement of inflammatory cell subsets in progressive tubulointerstitial lesions are often conflicting. A previous study suggested a role for cytotoxic T lymphocytes in the damaging effect of CD4(+) T-cell depletion in murine adriamycin (ADR) nephropathy, a model of focal segmental glomerulosclerosis (FSGS), and tubulointerstitial inflammation. The aim of this study was to investigate the role of CD8(+) cells in this model.

METHODS

Male BALB/c mice were treated with five intraperitoneal injections of anti-CD8 monoclonal antibody (mAb), beginning from five days after ADR treatment, when overt proteinuria was established. Seven mice in each of groups A (ADR + mAb), B (ADR only), and C (saline treated, age matched) were sacrificed at week 6. Changes in renal function and histopathological features were assessed. Tubulointerstitial inflammation and glomerular inflammation were examined immunohistochemically.

RESULTS

mAb treatment reduced CD8(+) cell levels to <2% of normal in spleen. Proteinuria in group A was no different from that in group B at week 6, but was markedly higher than in group C. Creatinine clearance was significantly ameliorated by anti-CD8 treatment (71.8 +/- 4.9 microL/min vs. 29.2 +/- 2.8 in group B and 81.9 +/- 3.7 in group C). Morphometric analysis showed less FSGS in group A compared with group B (6.5 +/- 1.9 vs. 13.0 +/- 2.8, P < 0.001), as well as less tubular atrophy (indicated by increased ratio of tubule cell height to tubular diameter, 0.25 +/- 0.24 in group A vs. 0.04 +/- 0.02 in group B, P < 0.05). CD8 depletion also reduced interstitial expansion (6.3 +/- 2.2% vs. 16.4 +/- 3.1 in group B, P < 0.001) and fibrosis (P < 0.01). Macrophage infiltration in tubulointerstitium was less in group A than in group B (P = 0.052). The number of interstitial CD4(+) cells appeared to increase after anti-CD8 treatment, but was not statistically different between groups A and B.

CONCLUSION

Anti-CD8 treatment protects against renal functional and structural injury in this murine model of chronic proteinuric renal disease.

Depletion of CD4(+) T cells aggravates glomerular and interstitial injury in murine adriamycin nephropathy

BACKGROUND

CD4(+) T cells play an important role in various types of immunologic renal disease, including lupus nephritis, IgA nephropathy, and crescentic glomerulonephritis. CD4(+) T cells are also major infiltrating lymphocytes in chronic tubulointerstitial inflammation associated with nonimmunological renal diseases. We suspected that CD4(+) T cells might contribute to disease progression and loss of renal function in chronic proteinuric renal disease (CPRD). To investigate this possibility, the effect of monoclonal antibody against CD4(+) lymphocytes (anti-CD4) was studied in a murine model (adriamycin nephropathy) of CPRD.

METHODS

Adriamycin nephropathy was produced in male BALB/c mice by a single intravenous injection of adriamycin (11 mg/kg). Anti-CD4 was given by intraperitoneal injection following the development of proteinuria at days 5, 6, 7, 21, and 37 after adriamycin. After six weeks, renal function and histology were studied by histomorphometry, immunohistochemistry, and flow cytometry.

RESULTS

Flow cytometric analysis showed a marked decrease in the number of CD4(+) T cells in blood and spleen of the antibody-treated animals (N = 7, P < 0.01). Adriamycin plus CD4(+) depletion mice had significantly greater mesangial expansion, glomerular sclerosis, and interstitial expansion than the mice on adriamycin alone. Interstitial infiltration with macrophages and CD8(+) cells was significantly increased in adriamycin plus CD4(+) depletion mice. Creatinine clearance (17.5 +/- 0.54 vs. 29.2 +/- 0.89 microL/min, P < 0.001) was significantly worse in the adriamycin plus CD4(+) depletion mice than in adriamycin alone mice and correlated with histologic change in glomeruli and interstitium.

CONCLUSIONS

Depletion of CD4(+) T cells promotes glomerular and interstitial injury in mice with established adriamycin nephropathy. These findings suggest that CD4(+) T cells have a protective role against the progression of adriamycin nephropathy.

Modeling Infection of Strawberry Flowers by Botrytis cinerea Using Field Data

ABSTRACT The incidence of strawberry flower infection by Botrytis cinerea was monitored in unsprayed field plots in three successive years together with meteorological data and numbers of conidia in the air. There were large differences in conidia numbers and weather conditions in the 3 years. Three sets of models were derived to relate inoculum and weather conditions to the incidence of flower infection; by inoculum only, by weather variables only, and by both inoculum and weather variables. All the models fitted the observed incidence satisfactorily. High inoculum led to more infection. Models using weather variables only gave more accurate predictions than models using inoculum only. Models using both weather variables and inoculum gave the best predictions, but the improvement over the models based on weather variables only was small. The relationship between incidence of flower infection and inoculum and weather variables was generally consistent between years. Of the weather variables examined, daytime vapor pressure deficit and nighttime temperature had the greatest effect in determining daily incidence of flower infection. Infection was favored by low day vapor pressure deficit and high night temperature. The accuracy and consistency of the weather-based models suggest they could be explored to assist in management of gray mold.

Cytokine gene expression in Adriamycin nephropathy: effects of antioxidant nuclear factor kappaB inhibitors in established disease

BACKGROUND/AIM

Inhibition of nuclear factor kappaB with the antioxidant pyrrolidine dithiocarbamate (PDTC) reduced tubulointerstitial injury in Adriamycin nephropathy (AN), whereas N-acetylcysteine (NAC) was ineffective. Here we hypothesize that PDTC reduces the renal cortical expression of nuclear factor kappaB dependent cytokines in AN.

METHODS

Male Wistar rats received a single intravenous injection of doxorubicin hydrochloride (7.5 mg/kg). NAC (150 mg/kg twice daily i.p.), PDTC (50 mg/kg twice daily i.p.), or vehicle were commenced on day 14 and continued until day 30.

RESULTS

On day 30, mRNAs of selected cytokines were increased in AN (TNF-alpha 3.4-fold, MCP-1 5.1-fold, IL-10 2.7-fold, TGF-beta1 3.5-fold, all p < 0.05) as determined by RT-PCR. PDTC reduced IL-10 and TGF-beta1 mRNAs (p < 0.05), whereas the upregulation of MCP-1 and TNF-alpha mRNAs was not affected. In contrast, NAC increased TNF-alpha and IL-10 mRNAs (p < 0.05). Nuclear protein levels of activator protein-1 were increased in AN (4.4-fold, p < 0.01) and not significantly altered by PDTC (3.0-fold, p = 0.13) or NAC (5. 2-fold, p = 0.18).

CONCLUSIONS

The protective effects of PDTC in AN are not associated with a local reduction in TNF-alpha and MCP-1 gene expression. The latter may be due to continued transactivation by activator protein-1. These data also suggest that IL-10 and TGF-beta1 mRNA expressions are PDTC dependent and have a role in mediating tubulointerstitial injury.

Progressive adriamycin nephropathy in mice: sequence of histologic and immunohistochemical events

BACKGROUND

As an experimental analogue of human focal glomerular sclerosis (FGS), adriamycin (ADR)-induced nephropathy is well-characterized in rats. Previously, this model has not been fully established in mice. The extension of this model to the mouse would be useful in the application of genetic and monoclonal antibody technology to characterize mechanisms of progressive renal disease. Herein, we describe a stable and reproducible murine model of chronic proteinuria induced by ADR.

METHODS

Male BALB/c mice were intravenously injected with a single dose of ADR (10 to 11 mg/kg). Seven mice were sacrificed at weeks 1, 2, 4, and 6. Renal function, quantitative morphometric analysis, and electron microscopic studies were performed. Peripheral CD4+ and CD8+ T cells were evaluated using flow cytometric analysis of splenocytes. The leukocytic inflammatory pattern was analyzed by immunohistochemical examination.

RESULTS

Overt proteinuria was observed from day 5 and remained significantly elevated throughout the study period. A focal increase in reabsorption droplets in tubular cells appeared at weeks 1 and 2, and numerous intraluminal casts were present after two weeks. Glomerular vacuolation and mild FGS appeared at week 4. At week 6, extensive focal and even global glomerular sclerosis, associated with moderate interstitial expansion and severe inflammation, were observed. A prominent macrophage infiltration appeared within both interstitium and glomeruli at week 2, followed by accumulation of both CD4+ and CD8+ T cells in interstitium but not glomeruli. There were almost no B lymphocytes seen at any time.

CONCLUSION

This model should be useful in unraveling the pathogenesis of glomerular and interstitial inflammation and fibrosis in chronic proteinuric renal disease.

Determinants of haemoglobin carbamylation in haemodialysis and peritoneal dialysis patients

BACKGROUND

Carbamylation is an irreversible process of non-enzymatic modification of proteins by the breakdown products of urea. For haemoglobin (Hb), the extent of carbamylation is a marker of urea exposure and has been proposed as an indicator of the control of uraemia by dialysis, analogous to the use of Hb glycosylation in diabetic patients.

METHODS

We performed a cross-sectional study of haemodialysis (HD) and peritoneal dialysis (PD) patients in order to study potential determinants of carbamylated Hb (CarbHb) and to investigate the relationship between CarbHb and established measures of dialysis dose/adequacy by multivariate analysis.

RESULTS

In 80 HD patients, CarbHb was independently predicted by post-dialysis urea (r=0.40, P:<0.01), serum albumin (r=0.24, P:<0.05) and serum bicarbonate (r=-0.40, P:<0. 05). No correlation was found between CarbHb and measures of dialysis dose/adequacy (Kt/V, urea reduction ratio, weekly dialysis duration, and normalized protein catabolic rate (nPCR)). In 42 PD patients, serum urea was the only significant independent predictor of CarbHb (r=-0.51, P:=0.001). No relationship was found between CarbHb and Kt/V, corrected creatinine clearance (CrCl) or nPCR in PD patients.

CONCLUSIONS

Serum urea is the most consistent independent predictor of CarbHb in dialysis patients. This association in combination with the lack of a relationship with conventional measures of dialysis dose and a positive relationship with serum albumin suggest that a single measurement of CarbHb is unlikely to be a useful indicator of the adequacy of dialysis.

Lipopolysaccharide-induced MCP-1 gene expression in rat tubular epithelial cells is nuclear factor-kappaB dependent

BACKGROUND

Endotoxin is an important factor in the development of acute renal failure related to infection and in acceleration of chronic nephritis. Lipopolysaccharide (LPS; the major component of endotoxin) is one of the most potent triggers for renal cells to produce monocyte chemoattractant protein-1 (MCP-1), a key cytokine involved in immune cell recruitment into the renal interstitium in acute and chronic renal diseases. Knowledge about the transcriptional regulation of MCP-1 in renal tubular epithelial cells in response to LPS is incomplete.

METHODS

Transcriptional regulation of MCP-1 was investigated in rat proximal tubule cells (PTCs) in primary culture and was exposed to LPS using electromobility shift assay and supershift analysis for nuclear factor-kappaB (NF-kappaB) and Western blot for the NF-kappaB inhibitory protein IkappaB. To prove the role for NF-kappaB, activator protein (AP-1), and sequence-specific transcription factor (Sp1), mutation and deletion analysis was performed using a 3.5 kb fragment of rat MCP-1 5'-flanking region inserted into a luciferase reporter construct transfected into tubular epithelial cell line (NRK-52E).

RESULTS

LPS increased NF-kappaB in a dose- and time-dependent manner, which paralleled that of MCP-1 mRNA expression. IkappaBalpha decreased within 30 minutes of LPS treatment, but returned to basal levels by two hours. IkappaBbeta levels were depressed within one hour and remained low throughout the culture period after LPS stimulation. The activity of the transfected 5'-flanking region of the MCP-1 gene increased nearly threefold after LPS stimulation. Mutation or deletion of NF-kappaB binding sites, located in the enhancer region of the 5'-flanking region, resulted in a total loss of LPS-induced increase in luciferase activity. Mutation of putative AP-1 and Sp1 sites, located in the proximal promoter region of MCP-1, reduced basal luciferase activity in unstimulated cells, but had no effect on LPS-stimulated luciferase activity.

CONCLUSIONS

These studies prove that NF-kappaB is critical for LPS-induced MCP-1 transcription, and AP-1 and Sp1 are essential for basal expression of MCP-1 in rat tubule cells. The species-specific nature of transcriptional regulation of MCP-1 has important implications for the delineation of treatment to prevent endotoxin-mediated renal injury.

Predictive value of 72-hour blastomere cell number on blastocyst development and success of subsequent transfer based on the degree of blastocyst development

OBJECTIVE

To determine the predictive value of 72-hour blastomere cell number on blastocyst development and to compare success rates of subsequent transfer based on the degree of blastocyst development.

DESIGN

Retrospective clinical study.

SETTING

Private assisted reproductive technology center.

PATIENT(S)

Ninety-three women aged 32.0 +/- 5.1 years undergoing oocyte retrieval for IVF.

INTERVENTION(S)

Bipronucleate oocytes obtained from IVF were grown for up to 168 hours after fertilization and subsequently transferred at the blastocyst stage.

MAIN OUTCOME MEASURE(S)

Percentages of embryos developing to blastocyst from 72-hour embryos by blastomere cell number and subsequent implantation and pregnancy rates of transferred blastocysts.

RESULT(S)

Rates of blastocyst formation and expansion increased as cell numbers at 72 hours increased. Implantation rates were 43% for embryos transferred to women receiving only expanded blastocysts and 17% for embryos transferred to women receiving one or more less developed blastocysts. Pregnancy rates were higher for women receiving only expanded blastocysts than for women receiving one or more less developed blastocysts, although the difference was not significant.

CONCLUSION(S)

More developed 72-hour embryos are more likely to become blastocysts and expand. Implantation rates are greater for the transfer of expanded rather than unexpanded blastocysts.

Identification of a fourth cheY gene in Rhodobacter sphaeroides and interspecies interaction within the bacterial chemotaxis signal transduction pathway

The Escherichia coli chemotaxis signal transduction pathway has: CheA, a histidine protein kinase; CheW, a linker between CheA and sensory proteins; CheY, the effector; and CheZ, a signal terminator. Rhodobacter sphaeroides has multiple copies of these proteins (2 x CheA, 3 x CheW and 3 x CheY, but no CheZ). In this study, we found a fourth cheY and expressed these R. sphaeroides proteins in E. coli. CheA2 (but not CheA1) restored swarming to an E. coli cheA mutant (RP9535). CheW3 (but not CheW2) restored swarming to a cheW mutant of E. coli (RP4606). R. sphaeroides CheYs did not affect E. coli lacking CheY, but restored swarming to a cheZ strain (RP1616), indicating that they can act as signal terminators in E. coli. An E. coli CheY, which is phosphorylated but cannot bind the motor (CheY109KR), was expressed in RP1616 but had no effect. Overexpression of CheA2, CheW2, CheW3, CheY1, CheY3 and CheY4 inhibited chemotaxis of wild-type E. coli (RP437) by increasing its smooth-swimming bias. While some R. sphaeroides proteins restore tumbling to smooth-swimming E. coli mutants, their activity is not controlled by the chemosensory receptors. R. sphaeroides possesses a phosphorelay cascade compatible with that of E. coli, but has additional incompatible homologues.

Inhibition of NFkappaB activation with antioxidants is correlated with reduced cytokine transcription in PTC

We recently reported that inhibition of the transcription factor nuclear factor-kappaB (NFkappaB) with pyrrolidinedithiocarbamate (PDTC) reduced interstitial monocyte infiltration in rats with proteinuric tubulointerstitial disease, whereas N-acetylcysteine (NAC) was not effective. Here we investigate the effects of antioxidants (PDTC, NAC, and quercetin) on NFkappaB activation and cytokine transcription in primary cultured rat proximal tubular epithelial cells (PTC) stimulated with lipopolysaccharide. Antioxidant-mediated inhibition of NFkappaB activation (PDTC, 20-100 microM; NAC, 100 mM; and quercetin, 50 microM) diminished the induction of both pro- [interleukin (IL)-1beta, tumor necrosis factor-alpha, monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-1alpha, and MIP-2] and anti-inflammatory (IL-10, transforming growth factor-beta1) cytokine transcription in PTC (RT-PCR analysis). PDTC and quercetin did not affect PTC viability, but NAC (100 mM) caused a threefold increase in lactate dehydrogenase leakage (P < 0.001). We conclude that NAC is unable to suppress NFkappaB activation in PTC at subtoxic and physiologically relevant concentrations. Furthermore, antioxidant-mediated inhibition of NFkappaB is correlated with the nonselective reduction of cytokine transcription in activated tubular cells. These data might explain the protective effects of PDTC-mediated NFkappaB inhibition in tubulointerstitial disease in vivo.

Inhibition of nuclear factor-kappaB activation reduces cortical tubulointerstitial injury in proteinuric rats

BACKGROUND

Protein-induced chemokine expression in proximal tubular cells is mediated by the transcription factor nuclear factor-kappa B (NF-kappaB). We hypothesized that in vivo inhibition of renal NF-kappaB activation would reduce interstitial monocyte infiltration in a rat model of nonimmune proteinuric tubulointerstitial inflammation.

METHODS

Male Wistar rats received a single intravenous injection of doxorubicin hydrochloride [adriamycin (ADR), 7.5 mg/kg] and were studied 7, 14, 21, and 28 days later. In a second study, inhibitors of NF-kappaB [N-acetylcysteine (NAC; 150 mg/kg, b.i.d., i.p.), pyrrolidine dithiocarbamate (PDTC, 50 mg/kg, b. i.d., i.p.)] or vehicle were commenced on day 14 after the onset of proteinuria and were continued until day 30.

RESULTS

Rats injected with ADR had increased proteinuria (UpV, day 28, 474 +/- 57; control, 18 +/- 2 mg/day; P < 0.01) and cortical tubulointerstitial injury [tubule cell atrophy, interstitial volume, and monocyte/macrophage (ED-1) infiltration]. Electrophoretic mobility shift assay of nuclear extracts from whole cortex of ADR rats demonstrated that NF-kappaB activation (p50/65, p50/c-Rel) increased from day 7 (4.7 +/- 0.2 fold-increase above control; P < 0.01) was maximal at day 28 (6.2 +/- 0.7; P < 0.01) and correlated with UpV (r = 0.63; P < 0.05) and interstitial ED-1 infiltration (r = 0.67; P < 0.01). Chronic treatment of ADR rats with PDTC suppressed NF-kappaB activation (by 73%; P < 0.05) without any effect on UpV. NF-kappaB inhibition with PDTC was accompanied by a reduction in tubule cell atrophy (59%; P < 0.01), interstitial volume (49%; P < 0.05) and ED-1 infiltration (48%; P < 0.01), and cortical lipid peroxidation (41%; P < 0.05) compared with vehicle-treated ADR rats. In contrast NAC had no effect on NF-kappaB activation, tubulointerstitial injury, or UpV in ADR rats.

CONCLUSION

The activation of NF-kappaB may have an important role in mediating cortical interstitial monocyte infiltration and tubular injury in nonimmune proteinuric tubulointerstitial inflammation.

Induction of monocyte chemoattractant protein-1 by albumin is mediated by nuclear factor kappaB in proximal tubule cells

The transcription and translation of monocyte chemoattractant protein-1 (MCP-1), a CC chemokine, are increased in proximal tubule epithelial cells (PTC) stimulated with pathophysiologically relevant concentrations of albumin. The purpose of this study was to investigate whether nuclear factor kappaB (NFkappaB)/Rel proteins play a role in albumin-induced MCP-1 transcription. Confluent monolayers of rat PTC in primary culture were stimulated with delipidated bovine serum albumin. NFkappaB, the NFkappaB inhibitory protein (IkappaB), and MCP-1 transcription were assessed using electrophoretic mobility shift assays, Western immunoblotting, semiquantitative reverse transcription-PCR, and ribonuclease protection assays. Activation of NFkappaB by delipidated bovine serum albumin (15 mg/ml) was detectable within 2 h, maximal after 8 h, and maintained for at least 16 h of continuous exposure. Supershift analysis showed that the activated proteins were composed of p50/p50, p50/p65, and p50/c-Rel dimers. dimers. Cytoplasmic IkappaBalpha levels were decreased 30 min after stimulation and returned to unstimulated levels by 4 to 8 h. IkappaBbeta levels were decreased at 2 h and there was no recovery until 8 h. Inhibition of NFkappaB with pharmacologic agents (N-tosyl-phenylalanine chloromethyl ketone and dexamethasone) and an antisense oligonucleotide to the rat p65 subunit of NFkappaB significantly reduced MCP-1 transcription. The 3.6-kb 5' flanking region of the rat MCP-1 gene was cloned and sequenced, and two putative kappaB binding sites were identified within the enhancer region. Therefore, albumin increased NFkappaB and reduced IkappaB levels in PTC, and MCP-1 expression was dependent on NFkappaB activation. It is concluded that the activation of NFkappaB/Rel proteins modulates chemokine production in PTC in response to albumin and is likely to have an important role in the mediation of tubulointerstitial injury in proteinuric renal disease.

Evidence suggesting that nitric oxide mediates iron-induced toxicity in cultured proximal tubule cells

The potential role of nitric oxide (NO) in iron-induced toxicity was studied in proximal tubule cells in primary culture. NO production (NO2-/NO3-) was significantly increased in iron-treated compared with control cells (3.43 +/- 0.08 vs. 1.56 +/- 0.08 nmol/dish, P < 0.01). NO synthase (NOS) activity was also induced by iron treatment (16.2 +/- 2.0 vs. 0.4 +/- 0.2 nmol of [3H]citrulline/mg protein, P < 0.01). L-Arginine, a substrate for NOS, augmented iron-induced NO production and cell damage [lactate dehydrogenase (LDH) leakage], whereas aminoguanidine, an inhibitor of NOS, reduced iron-induced NO production and LDH leakage. Sodium nitroprusside, an exogenous NO donor, induced LDH leakage in a dose-dependent manner, but no effect on lipid peroxidation (malo-ndialdehyde bis[dimethyl acetal] (MDA) production) was observed. Superoxide dismutase and catalase decreased iron-induced MDA production but did not affect LDH leakage or NO production. Dimethylpyrroline N-oxide and desferal prevented MDA production, LDH leakage, and NO production. We concluded that NO is one of the mediators of iron-induced toxicity in proximal tubule cells. NO-induced toxicity is not dependent on lipid peroxidation. This may explain the variable effect of different antioxidants on cell damage and lipid peroxidation in iron-induced cytotoxicity.

Toxicity of holotransferrin but not albumin in proximal tubule cells in primary culture

Proteinuria has been invoked as a cause of tubulointerstitial injury in chronic renal disease, and in vivo studies have suggested indirectly the particular nephrotoxicity of one urinary protein holotransferrin (Tf-Fe). However, to date there has been no direct evidence for the nephrotoxicity of Tf-Fe. To examine the potential cytotoxicity of Tf-Fe and the mechanism involved, and to compare this to another urinary protein albumin, rat proximal tubule cells were studied in primary culture. Tf-Fe at pH 6.0 caused functional and ultrastructural injury, but no cytotoxicity was seen with cells exposed to albumin, apotransferrin (transferrin), or Tf-Fe at pH 7.4. The influence of pH on Tf-Fe-induced cytotoxicity was not due to pH per se, but could be explained by an effect on Tf-Fe uptake. At pH 6.0, uptake of 125I-Tf-Fe (3.55 +/- 0.05 versus 1.25 +/- 0.10 fmol/dish, P < 0.01) and intracellular iron concentration (1.14 +/- 0.25 versus 0.46 +/- 0.23 nmol/dish, P < 0.01) were increased compared with values at pH 7.4. In contrast, pH 6.0 did not increase iron uptake from FeCl3. Lysine (100 mM) inhibited Tf-Fe uptake, decreased intracellular iron concentration, and attenuated Tf-Fe-induced cytotoxicity. The iron chelator des-ferrioxamine (200 microM) and hydroxyl radical scavenger dimethylpyrroline N-oxide (32 mM) abolished lactate dehydrogenase leakage induced by Tf-Fe at pH 6.0. Lipid peroxidation, as assessed by production of malondialdehyde, preceded lactate dehydrogenase leakage. In summary, holotransferrin, but not albumin, is toxic to rat proximal tubule cells, a pH-dependent effect involving its uptake into tubule cells, its iron moiety, and its lipid peroxidation.

Mitochondrial function in rat renal cortex in response to proteinuria and iron

1. Proximal tubular cell dysfunction in chronic glomerular disease (CGD) has been ascribed, in part, to reabsorption of transferrin-iron from tubular fluid and subsequent cytosolic peroxidative injury. To investigate a possible role for altered mitochondrial function in tubular cell injury in CGD, renal cortical mitochondrial respiratory function was examined in rats with adriamycin nephrosis. 2. State 4 (resting) respiration was increased in adriamycin nephrosis in comparison with control (51 +/- 2 vs 43 +/- 2 ng atoms oxygen (O)/min per mg protein, respectively; P < 0.02). 3. Mitochondrial iron concentration was increased in nephrotic rats compared with control (9.52 +/- 0.70 vs 5.97 +/- 0.26 nmol Fe/mg protein, respectively; P < 0.001) and rates of state 3, state 4 and uncoupled respiration and the severity of proteinuria correlated with mitochondrial iron concentration. 4. To further define the relationship between mitochondrial iron accumulation and altered respiratory function, rats were loaded with iron. 5. In comparison with control, acute iron loading of normal rats impaired creatinine clearance (1.48 +/- 0.02 vs 0.40 +/- 0.29 mL/min), increased kidney weight (1.33 +/- 0.07 vs 1.74 +/- 0.14 g) and impaired mitochondrial enzyme activity (e.g. cytochrome oxidase 185.0 +/- 46.6 vs 362.0 +/- 32.8 delta log [cytochrome C]/min per mg protein; P < 0.05), but had no significant effect on rates of mitochondrial respiration or on mitochondrial fragility. 6. Mitochondrial iron concentration was not increased by iron loading, despite a similar increment in cytoplasmic iron to that seen in rats with adriamycin nephrosis. 7. In summary, resting mitochondrial respiration is increased in nephrotic rats in proportion to mitochondrial iron accumulation. Changes in mitochondrial oxygen consumption do not appear to be a primary event in the tubular cell injury of iron loading.

Proteinuria and tubulointerstitial injury

These studies have demonstrated pathways whereby one urinary protein, holotransferrin, may alter proximal tubular cell function and cause tubular cytotoxicity, and at least two urinary proteins, albumin and transferrin, may mediate the development of interstitial inflammation in proteinuric renal disease.

Induction of monocyte chemoattractant protein-1 in proximal tubule cells by urinary protein

Cytokines play a pivotal role in synthesis and deposition of extracellular matrix in chronic renal failure (CRF). The proinflammatory properties of monocyte chemoattractant protein (MCP)-1 make it an ideal candidate cytokine for the production of interstitial inflammation in CRF. To investigate the possible role of proteinuria in inducing proximal tubular (PT) MCP-1, MCP-1 mRNA levels were measured by Northern blot and reverse transcription PCR in confluent monolayers of PT cells in primary culture in media containing a variety of proteins. PT cells produced MCP-1 mRNA in response to bovine serum albumin (BSA), delipidated BSA (dBSA; 0.5 to 30 mg/ml), holotransferrin, and apotransferrin (1 to 8 mg/ml). Unstimulated PT cells expressed very low levels of MCP-1 mRNA, detectable by reverse transcription PCR but not by Northern blot. The expression of MCP-1 mRNA reached a peak (sixfold greater than control) within 4 h of exposure to dBSA and was maintained for at least 24 h with continued exposure. Removal of dBSA from the media led to a rapid decline in MCP-1 mRNA expression. dBSA-induced MCP-1 expression was inhibited by lysine, an inhibitor of protein uptake, and reproduced by dBSA purified by gel and size-selective filtration. dBSA influenced MCP-1 expression at the level of transcription and probably translation, as evidenced by abrogation of MCP-1 by actinomycin D and superinduction with the protein synthesis inhibitor cycloheximide. The concentration of MCP-1 protein in response to dBSA added to the apical surface of PT cells was 2.4-fold greater in basolateral than in apical media, indicating basolateral secretion of MCP-1 protein. In summary, PT cell MCP-1 mRNA and protein expression are upregulated by albumin and transferrin, in concentrations similar to those of proteinuric urine. This effect could explain the link between proteinuria and interstitial inflammation in CRF.

A review of quality of life in chronic renal failure

The quality of life of patients with end-stage renal disease (ESRD) has become an area of intensive investigation because of the high costs of renal-replacement therapy (dialysis or renal transplantation) and the rising prevalence of renal failure. Studies comparing quality of life of patients using different forms of renal-replacement therapy are flawed by deficiencies in study design, such as lack of randomisation. Nevertheless, in both retrospective and prospective studies, transplantation has been shown to offer the highest levels of functional ability, employment and subjective quality of life. After case-mix adjustment, there is little difference between peritoneal dialysis and haemodialysis in terms of quality-of-life (QOL) outcomes. Vocational rehabilitation is an important aim of therapy; for patients below retirement age, pre-dialysis education and counselling are important in maintaining employment. The elderly comprise the fastest-growing group of dialysis recipients; multiple comorbidities add to functional impairment in these patients. Subjective quality of life remains surprisingly high in many elderly patients, despite poor objective quality of life. The quality of life of patients with diabetes mellitus and ESRD is lower than that of nondiabetic patients with ESRD. For selected patients with insulin-dependent diabetes mellitus, combined renal and pancreatic transplantation offers the advantage of freedom from insulin injections. Unfortunately, available evidence suggests only small improvements in quality of life with combined transplantation versus kidney-only transplantation, probably because many patients have developed multiple diabetic complications by the time of transplantation. Epoetin alfa (erythropoietin) has been shown to improve quality of life in a number of trials. The optimal target haematocrit is a subject of controversy, but on current evidence, a target of 34 to 37% is reasonable. The degree of improvement in quality of life must be balanced against the additional costs of achieving a higher haematocrit. Further study is necessary to clarify the optimal target haematocrit for epoetin alfa therapy, as well as the possible effects of nutritional support, growth hormone in paediatric patients, and combined renal and pancreatic transplantation in improving quality of life.

Twin- versus single-bag disconnect systems: infection rates and cost of continuous ambulatory peritoneal dialysis

Although twin-bag disconnect fluid-transfer systems for continuous ambulatory peritoneal dialysis (CAPD) have a lower rate of catheter-related infection than single-bag systems, their greater monetary purchase cost has prevented universal adoption. Therefore, a single-center randomized study was performed in 63 adult patients to compare the efficiency and total cost of Freeline Solo (FS, twin-bag) and Basic Y (BY, single-bag) systems. Patients were new to CAPD (N = 39), or had a new CAPD catheter, or had had no episodes of peritonitis or exit-site infection in the previous 12 months (N = 24). Total follow-up was 631 patient months (pt.mon), and 53 patients were still on the trial at its termination. Patients rated FS as easier to use than BY (P < 0.001). Peritonitis occurred on 23 occasions in 12 out of 30 patients using BY, and on seven occasions in five of 33 patients using FS. Time to first infection was less with BY than FS (hazard ratio, 2.4; 95% confidence interval (CI), 1.0 to 5.3; P < 0.04). Cumulative incidence of peritonitis was 1 per 14.0 pt.mon with BY and 1 per 46.5 pt.mon with FS (odds ratio, 3.6; 95% CI 1.5 to 8.5; P = 0.004). Length of hospitalization for peritonitis or exit-site infection was 98 days in six patients with BY, versus 17 days in two patients with FS. With BY, four catheters were removed because of infection, but none with FS (P < 0.05). With BY, the total cost of infection was $AUD127,079 ($5033 per pt.yr) versus $19,250 ($704 per pt.yr) with FS, which offset the higher purchase cost of FS. The total cost of CAPD was $AUD956 per pt.yr less with FS than BY. In conclusion, the higher purchase cost of the FS twin-bag system is more than offset by savings from its lower incidence of peritonitis.

Correcting acidosis in hemodialysis: effect on phosphate clearance and calcification risk

Control of uremic acidosis by hemodialysis carries the potential risks of reducing phosphate clearance and worsening metastatic calcification; modeling bicarbonate delivery has been proposed to adequately correct acidosis without impairing phosphate removal. To test the efficacy and safety of different methods for controlling acidosis, nine stable adults received in random order standard (S; dialysate HCO3- 30 to 34 mmol/L), high (H; 40 mmol/L) or modeled (M; 28 mmol/L, rising exponentially to 35 mmol/L at 3 h, 40 mmol/L at 4 h) bicarbonate dialysis for 4 wk each, and were tested during the last two dialyses of each treatment. More oral bicarbonate capsules were required with M than H (2.8 +/- 0.4 versus 1.4 +/- 0.4/day, P = 0.04) to maintain predialysis HCO3- at 24 to 26 mmol/L. Plasma HCO3- was significantly higher with H than M during dialysis, and than S before, during, and after dialysis. Plasma inorganic phosphate, phosphate rebound, clearance of phosphate from plasma (80 to 90 mL/min) and mass transfer of phosphate into dialysate (12 to 13 mmol/4 h dialysis) were no different among the three treatments. Similarly, there were no differences in plasma concentration of urea, total calcium, estimated ionized calcium, lipids, and potassium, clearance and mass transfer of urea, blood pressure, and symptoms with the three treatments. Estimated levels of tribasic inorganic phosphate, the phosphate component of hydroxyapatite, were very similar before and after each treatment. Plasma calcium x phosphate product was less than 3.5 mmol2/L2 at all times with each treatment. A risk factor for metastatic calcification was calculated from the relative saturation ratio of its principle component, hydroxyapatite (Ca5 (PO4)3 OH); this was no different among each of the treatments, and was not altered significantly by dialysis. Uremic acidosis can be fully corrected by high or modeled bicarbonate dialysis without any reduction of phosphate clearance or increased risk of metastatic calcification. The added cost of modeling technology is not justified by the criterion of phosphate clearance alone.

Crystal structure of histidyl-tRNA synthetase from Escherichia coli complexed with histidyl-adenylate

The crystal structure at 2.6 A of the histidyl-tRNA synthetase from Escherichia coli complexed with histidyl-adenylate has been determined. The enzyme is a homodimer with a molecular weight of 94 kDa and belongs to the class II of aminoacyl-tRNA synthetases (aaRS). The asymmetric unit is composed of two homodimers. Each monomer consists of two domains. The N-terminal catalytic core domain contains a six-stranded antiparallel beta-sheet sitting on two alpha-helices, which can be superposed with the catalytic domains of yeast AspRS, and GlyRS and SerRS from Thermus thermophilus with a root-mean-square difference on the C alpha atoms of 1.7-1.9 A. The active sites of all four monomers are occupied by histidyl-adenylate, which apparently forms during crystallization. The 100 residue C-terminal alpha/beta domain resembles half of a beta-barrel, and provides an independent domain oriented to contact the anticodon stem and part of the anticodon loop of tRNA(His). The modular domain organization of histidyl-tRNA synthetase reiterates a repeated theme in aaRS, and its structure should provide insight into the ability of certain aaRS to aminoacylate minihelices and other non-tRNA molecules.

Mechanisms of iron-induced proximal tubule injury in rat remnant kidney

The proposition that proximal tubule (PT) iron accumulation may cause PT injury by lysosomal destabilization or reactive oxygen species generation in human and animal chronic renal disease was examined in partially nephrectomized [remnant kidney (RK)] and sham-operated (SO) Wistar rats. Electron microscopic histochemistry with horseradish peroxidase indicated iron uptake into and release from lysosomes. PT cytoplasmic iron was seen in RK but not in SO by energy-dispersive X-ray spectrometry. Total (9.66 +/- 1.89 vs. 3.30 +/- 0.31 nmol/mg protein; P < 0.01), low-molecular-weight (1.39 +/- 0.09 vs. 0.91 +/- 0.07; P < 0.001), and catalytic iron (1.88 +/- 0.27 vs. 1.28 +/- 0.09; P = 0.05) were higher in RK cytoplasm than in SO. Lysosomal enzyme activity was greater in RK than in SO [e.g., N-acetyl-beta-D-glucosaminidase (NAG): 0.75 +/- 0.05 vs. 0.57 +/- 0.06 mumol p-nitrophenol.h-1.mg protein-1; P < 0.05] and was increased further by chronic iron loading (e.g., RK and NAG: 0.84 +/- 0.04 vs. 0.60 +/- 0.07; P < 0.05). There was no enzymatic evidence of lysosomal fragility, and chronic iron loading of RK decreased fragility as assessed by NAG release (1.36 +/- 0.14 vs. 2.17 +/- 0.14; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Iron depletion in the remnant kidney

Urinary and proximal tubular iron are increased after subtotal nephrectomy, and iron depletion has been shown to be beneficial in proteinuric models of chronic renal disease in rats. In this study, iron depletion by low iron pair-fed diet and periodic phlebotomy was induced for 6 months in rats with partial (5/6) nephrectomy, resulting in a reduction in hematocrit and serum iron in all iron-deficiency subgroups. Tubular iron, assessed by energy dispersive analysis and electron microscopy, was reduced in quantity but not number of iron-containing lysosomes only within 1 subgroup of severe iron deficiency (p < 0.05). There was no improvement in serial isotopic glomerular filtration rate measurements, urinary protein and transferrin excretion, tubular damage scores, serum creatinine, or measures of reactive oxygen species (ROS) generation. In a subgroup of rats with no supplementation of sulfhydryl amino acids (cysteine and methionine) which can act as ROS scavengers, iron deficiency increased urinary protein excretion (213.3 +/- 23.0 mg/24 h, mean +/- SEM, vs. 87.4 +/- 16.1, p < 0.001), urinary transferrin excretion (p < 0.05), kidney weight (p < 0.05) and tissue malondialdehyde, a lipid peroxidation product (0.78 +/- 0.16 nmol/mg protein vs. 0.57 +/- 0.19, p < 0.05), consistent with increased ROS generation. Hence, no beneficial effect of iron-deficiency was demonstrated by any measure of structure of function in the remnant kidney, and it may enhance damage if sulfhydryl repletion is not provided.

Anti-Nform antibody in hemodialysis patients

The anti-Nform antibody is produced by dialysis patients following reuse of dialyzers sterilized with formaldehyde and it has been implicated as a cause of hemolytic anemia. Formaldehyde is one of the common disinfectants used for reprocessing capillary hemodialyzers. The safety of formaldehyde and the clinical significance of anti-Nform antibody need further evaluation. Amongst 45 patients practising dialyzer reuse, anti-Nform antibody was detected in 5 (11.1%), but not amongst 111 patients not reusing their dialyzer (p < 0.005). The presence of anti-Nform was not related to the sex, or duration of dialysis with positive anti-Nform antibody. Direct Coombs' test was positive amongst 80% of all tested patients with anti-Nform antibody, and in 38% of patients reusing dialyzers but without anti-Nform antibody. No tests of hemolysis (including direct Coombs' test) discriminated between anti-Nform antibody-positive and -negative patients, nor between anti-Nform antibody patients with and without overt hemolysis. The best diagnostic test for hemolysis in anti-Nform antibody-positive patients was hematocrit rise after cessation of dialyzer reuse. It appears that despite the induction of anti-Nform antibody, hemolysis is rarely a serious consequence of dialyzer reuse.

Crystal structure of human chorionic gonadotropin

The three-dimensional structure of human chorionic gonadotropin shows that each of its two different subunits has a similar topology, with three disulphide bonds forming a cystine knot. This same folding motif is found in some protein growth factors. The heterodimer is stabilized by a segment of the beta-subunit which wraps around the alpha-subunit and is covalently linked like a seat belt by the disulphide Cys 26-Cys 110. This extraordinary feature appears to be essential not only for the association of these heterodimers but also for receptor binding by the glycoprotein hormones.

Dietary protein alters tubular iron accumulation after partial nephrectomy

Reactive oxygen species (ROS) have been implicated in progression of disease in the rat remnant kidney (RK) model of chronic renal failure. Substantial amounts of iron accumulate in proximal tubular lysosomes of RK and could damage tubules by ROS generation. The effect of dietary protein intake on ROS, tubular damage and iron accumulation assessed by energy dispersive analysis was determined in RK (5/6 nephrectomy, N = 12) and sham-operated kidneys (SO, N = 10). In RK, mean lysosomal iron concentration, urinary iron and protein excretion and morphological damage were increased and GFR decreased. Dietary protein loading (40% vs. 12%) increased the number of iron-containing lysosomes (P < 0.05) and the mean lysosomal iron (P < 0.02) in proximal tubular cells after four weeks. In RK, high protein diet increased renal weight (P < 0.01), numerical density of iron-containing lysosomes and tubular damage (both P < 0.05). ROS generation, assessed by tissue and plasma malondialdehyde (MDA), was also increased (both P < 0.05). Plasma MDA correlated with tubular iron accumulation (r = 0.75). In RK fed a high protein diet (N = 18) treatment with the iron-chelator desferrioxamine reduced serum iron, urinary volume, and tubular iron accumulation and damage compared to controls (P < 0.01). In summary, in RK dietary protein manipulation altered urinary iron and protein excretion, proximal tubular iron accumulation, renal cortical ROS generation and ultrastructural damage. Desferrioxamine treatment reduced tubular lysosomal iron and ultrastructural damage. These results suggest a role for tubular iron as a determinant of tubular injury associated with dietary protein loading in rats with partial nephrectomy.

The role of tubular iron accumulation in the remnant kidney

Iron has been implicated in the pathophysiology of several models of acute and chronic renal disease. In this study, energy-dispersive x-ray spectrometry was used to quantify and localize iron in rat remnant kidneys (RK) and normal kidneys (NK) and to determine its pathophysiologic significance. Substantial iron accumulation occurred in proximal tubular cell secondary lysosomes of RK (P < 0.001 versus NK) and reached a plateau at 8 wk after partial nephrectomy. In NK, minor increases of iron also occurred with aging (P < 0.02). Proximal tubular iron accumulation correlated independently with protein excretion (r = 0.90) and impairment of GFR (r = 0.70) and was associated with tubular damage and phosphate accumulation (both P < 0.001). Iron nitrilotriacetate (1 mg/kg ip) increased tubular lysosomal iron accumulation and tubular damage (P < 0.001 versus nitrilotriacetate) in NK, comparable to levels seen in untreated RK, and increased cortical cytosolic malondialdehyde, consistent with reactive oxygen species generation. The iron chelator deferoxamine (30 mg/kg per day ip) significantly reduced iron accumulation and tubular damage in RK at 4 wk, compared with deferoxamine chelated to iron and untreated RK. These results suggest that filtered iron enters the remnant tubular lysosomes across the brush border membrane by endocytosis and may produce tubular damage in chronic renal disease by the generation of reactive oxygen species.

Increased nephron oxygen consumption: potential role in progression of chronic renal disease

We have previously reported that remnant kidneys demonstrate marked increases in oxygen consumption (QO2) when normalized for sodium transport as compared with normal kidneys. This increase in oxygen consumption could be attenuated by dietary maneuvers such as protein restriction and phosphate restriction and also by calcium channel blockers. The basis of this enhanced metabolic activity, however, has not been fully defined. Furthermore, circumstances of increased oxygen consumption are associated with enhanced oxygen radical generation. These oxygen radicals could lead to renal tissue lipid peroxidation if the remnant kidney contains insufficient oxygen radical scavengers. This review summarizes available evidence for increased nephron oxygen consumption as a cause of tubulointerstitial injury and its relationship to progression of chronic renal disease.

Lysosomal iron accumulation and tubular damage in rat puromycin nephrosis and ageing

1. Energy dispersive X-ray spectrometry was used to examine the relationship between proteinuria and increased urinary iron excretion, and structural and functional damage in puromycin nephrosis. 2. After 11-12 days rats treated with puromycin (10 mg/100 g, i.v.i.) had greater proteinuria (211.6 +/- 35.7 mg/day, mean +/- s.e.m.) and urinary iron excretion (15.4 +/- 2.2 micrograms/day) than saline-treated controls (14.5 +/- 1.4 mg/day and 1.1 +/- 0.2 micrograms/day, respectively, both P < 0.001). 3. On day 13, mean lysosomal iron concentration of proximal tubular cells (306.6 +/- 64.5 vs 11.9 +/- 8.6 mg%, P < 0.001), and proximal tubular cell damage assessed semi-quantitatively (1.17 +/- 0.10 vs 0.62 +/- 0.10, P < 0.001) were higher and creatinine clearance (0.15 +/- 0.01 vs 0.29 +/- 0.02 mL/min per g kidney weight, P < 0.001) lower than in control rats. 4. At days 35, 60 and 360 there were no differences in any of the measured parameters between rats treated with puromycin or saline, and in both groups proteinuria, tissue damage and lysosomal iron concentration increased with time. 5. Lysosomal iron accumulation was the only independent predictor of both functional and structural damage. 6. In conclusion, the apparent association between proteinuria and tubulo-interstitial damage in puromycin nephrosis, and with ageing, is best explained by factors associated with accumulation of iron within lysosomes of proximal tubule cells.