Assessing Formability and Failure of UHMWPE Sheets through SPIF: A Case Study in Medical Applications

This work presents a comprehensive investigation of an experimental study conducted on ultra-high molecular weight polyethylene (UHMWPE) sheets using single point incremental forming (SPIF). The analysis is performed within a previously established research framework to evaluate formability and failure characteristics, including necking and fracture, in both conventional Nakajima tests and incremental sheet forming specimens. The experimental design of the SPIF tests incorporates process parameters such as spindle speed and step down to assess their impact on the formability of the material and the corresponding failure modes. The results indicate that a higher step down value has a positive effect on formability in the SPIF context. The study has identified the tool trajectory in SPIF as the primary influencing factor in the twisting failure mode. Implementing a bidirectional tool trajectory effectively reduced instances of twisting. Additionally, this work explores a medical case study that examines the manufacturing of a polyethylene liner device for a total hip replacement. This investigation critically analyses the manufacturing of plastic liner using SPIF, focusing on its formability and the elastic recovery exhibited by the material.

Multiomics reveals multilevel control of renal and systemic metabolism by the renal tubular circadian clock

Circadian rhythmicity in renal function suggests rhythmic adaptations in renal metabolism. Todecipher the role of the circadian clock in renal metabolism, we studied diurnal changes in renal metabolic pathways using integrated transcriptomic, proteomic, and metabolomic analysisperformed on control mice and mice with inducible deletion of the circadian clock regulator Bmal1 in the renal tubule (cKOt). With this unique resource, we demonstrated that ~30% RNAs, ~20% proteins and ~20% metabolites are rhythmic in kidneys of control mice. Several key metabolic pathways including NAD+ biosynthesis, fatty acid transport, carnitine shuttle,and b-oxidation displayed impairments in kidneys of cKOt, resulting in a perturbedmitochondrial activity. Carnitine reabsorption from the primary urine was one of the mostimpacted processes with a ~50% reduction in plasma carnitine levels and a parallel systemicdecrease in tissues carnitine content. This suggests that the circadian clock in the renal tubule controls both kidney and systemic physiology.

Renal tubular peroxisomes are dispensable for normal kidney function

Peroxisomes are specialized cellular organelles involved in a variety of metabolic processes. In humans, mutations leading to complete loss of peroxisomes cause multiorgan failure (Zellweger’s spectrum disorders, ZSD), including renal impairment. However, the (patho)physiological role of peroxisomes in the kidney remains unknown. We addressed the role of peroxisomes in renal function in mice with conditional ablation of peroxisomal biogenesis in the renal tubule (cKO mice). Functional analyses did not reveal any overt kidney phenotype in cKO mice. However, infant male cKO mice had lower body and kidney weights, and adult male cKO mice exhibited substantial reductions in kidney weight and kidney weight/body weight ratio. Stereological analysis showed an increase in mitochondria density in proximal tubule cells of cKO mice. Integrated transcriptome and metabolome analyses revealed profound reprogramming of a number of metabolic pathways, including metabolism of glutathione and biosynthesis/biotransformation of several major classes of lipids. Although this analysis suggested compensated oxidative stress, challenge with high-fat feeding did not induce significant renal impairments in cKO mice. We demonstrate that renal tubular peroxisomes are dispensable for normal renal function. Our data also suggest that renal impairments in patients with ZSD are of extrarenal origin.

Dysfunction of the circadian clock in the kidney tubule leads to enhanced kidney gluconeogenesis and exacerbated hyperglycemia in diabetes

The circadian clock is a ubiquitous molecular time-keeping mechanism which synchronizes cellular, tissue, and systemic biological functions with 24-hour environmental cycles. Local circadian clocks drive cell type- and tissue-specific rhythms and their dysregulation has been implicated in pathogenesis and/or progression of a broad spectrum of diseases. However, the pathophysiological role of intrinsic circadian clocks in the kidney of diabetics remains unknown. To address this question, we induced type I diabetes with streptozotocin in mice devoid of the circadian transcriptional regulator BMAL1 in podocytes (cKOp mice) or in the kidney tubule (cKOt mice). There was no association between dysfunction of the circadian clock and the development of diabetic nephropathy in cKOp and cKOt mice with diabetes. However, cKOt mice with diabetes exhibited exacerbated hyperglycemia, increased fractional excretion of glucose in the urine, enhanced polyuria, and a more pronounced kidney hypertrophy compared to streptozotocin-treated control mice. mRNA and protein expression analyses revealed substantial enhancement of the gluconeogenic pathway in kidneys of cKOt mice with diabetes as compared to diabetic control mice. Transcriptomic analysis along with functional analysis of cKOt mice with diabetes identified changes in multiple mechanisms directly or indirectly affecting the gluconeogenic pathway. Thus, we demonstrate that dysfunction of the intrinsic kidney tubule circadian clock can aggravate diabetic hyperglycemia via enhancement of gluconeogenesis in the kidney proximal tubule and further highlight the importance of circadian behavior in patients with diabetes.

Renal tubular arginase-2 participates in the formation of the corticomedullary urea gradient and attenuates kidney damage in ischemia-reperfusion injury in mice

AIM

Arginase 2 (ARG2) is a mitochondrial enzyme that catalyses hydrolysis of l-arginine into urea and l-ornithine. In the kidney, ARG2 is localized to the S3 segment of the proximal tubule. It has been shown that expression and activity of this enzyme are upregulated in a variety of renal pathologies, including ischemia-reperfusion (IR) injury. However, the (patho)physiological role of ARG2 in the renal tubule remains largely unknown.

METHODS

We addressed this question in mice with conditional knockout of Arg2 in renal tubular cells (Arg2^lox/lox /Pax8-rtTA/LC1 or, cKO mice).

RESULTS

We demonstrate that cKO mice exhibit impaired urea concentration and osmolality gradients along the corticomedullary axis. In a model of unilateral ischemia-reperfusion injury (UIRI) with an intact contralateral kidney, ischemia followed by 24 hours of reperfusion resulted in significantly more pronounced histological damage in ischemic kidneys from cKO mice compared to control and sham-operated mice. In parallel, UIRI-subjected cKO mice exhibited a broad range of renal functional abnormalities, including albuminuria and aminoaciduria. Fourteen days after UIRI, the cKO mice exhibited complex phenotype characterized by significantly lower body weight, increased plasma levels of early predictive markers of kidney disease progression (asymmetric dimethylarginine and symmetric dimethylarginine), impaired mitochondrial function in the ischemic kidney but no difference in kidney fibrosis as compared to control mice.

CONCLUSION

Collectively, these results establish the role of ARG2 in the formation of corticomedullary urea and osmolality gradients and suggest that this enzyme attenuates kidney damage in ischemia-reperfusion injury.

On the Determination of Forming Limits in Polycarbonate Sheets

By proposing an adaptation of the methodology usually used in metal forming, this paper aims to provide a general procedure for determining the forming limits, by necking and fracture, of polymeric sheet. The experimental work was performed by means of Nakajima specimens with different geometries to allow to obtain strains in the tensile, plane, biaxial and equibiaxial states for Polycarbonate sheet with 1 mm of thickness. The application of the time-dependent and flat-valley approaches used in metals has been revealed appropriate to characterize the onset of necking and obtain the forming limits of polycarbonate, despite the stable necking propagation typical of polymeric sheets. An analysis of the evolution of the strain paths along a section perpendicular to the crack allowed for a deeper understanding of the steady necking propagation behaviour and the adoption of the methodology of metals to polymers. The determination of the fracture strains was enhanced with the consideration of the principal strains of the DIC system in the last stage, just before fracture, due to the significant elastic recovery typical of polymeric sheets. As a result of this analysis, accurate formability limits by necking and fracture are obtained for polycarbonate sheet, together with the principal strain space, providing a general framework for analysing incremental sheet forming processes where the knowledge of the fracture limits is relevant.

Prospective study of five-year outcomes and postoperative complications after total temporomandibular joint replacement with two stock prosthetic systems

To evaluate and compare outcomes and complications associated with reconstruction of the temporomandibular joint (TMJ), we prospectively analysed the data of 70 patients who had their joints replaced with stock prostheses during the period 2004-14 and who had been followed up for five years. We used two types of stock prostheses: the metal-on-metal Christensen system (CS), and the ultra-high-molecular-weight-polyethylene-on-metal Biomet® system (BS). Data were collected at 3, 6, 12, 24, 36, 48, and 60 months postoperatively and compared with preoperative measurements. Five years after the replacement there was an increase in mean (SD) mouth opening from 2.0 (0.6) to 4.0 (0.5cm) (p=0.012) in the CS, and from 2.5 (1.0) cm to 4.1 (0.6) cm (p=0.018) in the BS. The mean (SD) reductions in visual analogue pain scores were from 6.9 (1.6) to 2.0 (1.4) (p=0.001) in the CS, and 6.5 (1.4) to 1.5 (1.1) (p=0.001) in the BS. There were no significant differences in improvements in mouth opening or reduction in pain between the two groups. However, there were differences in the number of implants that failed, which led to removal and replacement of 2/14 prostheses in the CS group and 3/77 in the BS group (p=0.06). The results supported the placement of stock prostheses, as evidenced by a low incidence of complications and adverse events, and a long-term improvement in function and reduction in pain in the TMJ. The BS group had significantly fewer prosthetic failures than the CS group.

The intrinsic circadian clock in podocytes controls glomerular filtration rate

Glomerular filtration rate (GFR), or the rate of primary urine formation, is the key indicator of renal function. Studies have demonstrated that GFR exhibits significant circadian rhythmicity and, that these rhythms are disrupted in a number of pathologies. Here, we tested a hypothesis that the circadian rhythm of GFR is driven by intrinsic glomerular circadian clocks. We used mice lacking the circadian clock protein BMAL1 specifically in podocytes, highly specialized glomerular cells critically involved in the process of glomerular filtration (Bmal1^lox/lox/Nphs2-rtTA/LC1 or, cKO mice). Circadian transcriptome profiling performed on isolated glomeruli from control and cKO mice revealed that the circadian clock controls expression of multiple genes encoding proteins essential for normal podocyte function. Direct assessment of glomerular filtration by inulin clearance demonstrated that circadian rhythmicity in GFR was lost in cKO mice that displayed an ultradian rhythm of GFR with 12-h periodicity. The disruption of circadian rhythmicity in GFR was paralleled by significant changes in circadian patterns of urinary creatinine, sodium, potassium and water excretion and by alteration in the diurnal pattern of plasma aldosterone levels. Collectively, these results indicate that the intrinsic circadian clock in podocytes participate in circadian rhythmicity of GFR.

Optimization of Hole-Flanging by Single Point Incremental Forming in Two Stages

Single point incremental forming (SPIF) has been demonstrated to accomplish current trends and requirements in industry. Recent studies have applied this technology to hole-flanging by performing different forming strategies using one or multiple stages. In this work, an optimization procedure is proposed to balance fabrication time and thickness distribution along the produced flange in a two-stage variant. A detailed analytical, numerical and experimental investigation is carried out to provide, evaluate and corroborate the optimal strategy. The methodology begins by analysing the single-stage process to understand the deformation and failure mechanisms. Accordingly, a parametric two-stage SPIF strategy is proposed and evaluated by an explicit Finite Element Analysis to find the optimal parameters. The study is focused on AA7075-O sheets with different pre-cut hole diameters and considering a variety of forming tool radii. The study exposes the relevant role of the tool radius in finding the optimal hole-flanging process by the proposed two-stage SPIF.

Redox-Dependent Bone Alkaline Phosphatase Dysfunction Drives Part of the Complex Bone Phenotype in Mice Deficient for Memo1

Mediator of ErbB2-driven cell Motility 1 (MEMO1) is an intracellular redox protein that integrates growth factors signaling with the intracellular redox state. We have previously reported that mice lacking Memo1 displayed higher plasma calcium levels and other alterations of mineral metabolism, but the underlying mechanism was unresolved and the bone phenotype was not described. Here, we show that Cre/lox-mediated MEMO1 deletion in the whole body of C57Bl/6 mice (Memo cKO) leads to severely altered trabecular bone and lower mineralization, with preserved osteoblast and osteoclast number and activity, but altered osteoblast response to epidermal growth factor (EGF) and FGF2. More strikingly, Memo cKO mice display decreased alkaline phosphatase (ALP) activity in serum and in bone, while ALPL expression level is unchanged. Bone intracellular redox state is significantly altered in Memo cKO mice and we inferred that ALP dimerization was reduced in Memo cKO mice. Indeed, despite similar ALP oxidation, we found increased ALP sensitivity to detergent in Memo cKO bone leading to lower ALP dimerization capability. Thus, we report a severe bone phenotype and dysfunctional bone ALP with local alteration of the redox state in Memo cKO mice that partially mimics hypophosphatasia, independent of ALPL mutations. These findings reveal Memo as a key player in bone homeostasis and underline a role of bone redox state in controlling ALP activity.

Evaluation of total alloplastic temporo-mandibular joint replacement with two different types of prostheses: A three-year prospective study

BACKGROUND

Temporo-Mandibular Joint (TMJ) replacement has been used clinically for years. The objective of this study was to evaluate outcomes achieved in patients with two different categories of TMJ prostheses.

MATERIAL AND METHODS

All patients who had a TMJ replacement (TMJR) implanted during the study period from 2006 through 2012 were included in this 3-year prospective study. All procedures were performed using the Biomet Microfixation TMJ Replacement System, and all involved replacing both the skull base component (glenoid fossa) and the mandibular condyle.

RESULTS

Fifty-seven patients (38 females and 19 males), involving 75 TMJs with severe disease requiring reconstruction (39 unilateral, 18 bilateral) were operated on consecutively, and 68 stock prostheses and 7 custom-made prostheses were implanted. The mean age at surgery was 52.6±11.5 years in the stock group and 51.8±11.7 years in the custom-made group. In the stock group, after three years of TMJR, results showed a reduction in pain intensity from 6.4±1.4 to 1.6±1.2 (p<0.001), and an improvement in jaw opening from 2.7±0.9 cm to 4.2±0.7 cm (p<0.001). In the custom-made group, after three years of TMJR, results showed a reduction in pain intensity from 6.0±1.6 to 2.2±0.4 (p<0.001), and an improvement in jaw opening from 1.5±0.5 cm to 4.3±0.6 cm (p<0.001). No statistically significant differences between two groups were detected.

CONCLUSIONS

The results of this three-year prospective study support the surgical placement of TMJ prostheses (stock prosthetic, and custom-made systems), and show that the approach is efficacious and safe, reduces pain, and improves maximum mouth opening movement, with few complications. As such, TMJR represents a viable technique and a stable long-term solution for cranio-mandibular reconstruction in patients with irreversible end-stage TMJ disease. Comparing stock and custom-made groups, no statistically significant differences were detected with respect to pain intensity reduction and maximum mouth opening improvement.

Renal Fanconi Syndrome and Hypophosphatemic Rickets in the Absence of Xenotropic and Polytropic Retroviral Receptor in the Nephron

Tight control of extracellular and intracellular inorganic phosphate (Pi) levels is critical to most biochemical and physiologic processes. Urinary Pi is freely filtered at the kidney glomerulus and is reabsorbed in the renal tubule by the action of the apical sodium-dependent phosphate transporters, NaPi-IIa/NaPi-IIc/Pit2. However, the molecular identity of the protein(s) participating in the basolateral Pi efflux remains unknown. Evidence has suggested that xenotropic and polytropic retroviral receptor 1 (XPR1) might be involved in this process. Here, we show that conditional inactivation of Xpr1 in the renal tubule in mice resulted in impaired renal Pi reabsorption. Analysis of Pi transport in primary cultures of proximal tubular cells or in freshly isolated renal tubules revealed that this Xpr1 deficiency significantly affected Pi efflux. Further, mice with conditional inactivation of Xpr1 in the renal tubule exhibited generalized proximal tubular dysfunction indicative of Fanconi syndrome, characterized by glycosuria, aminoaciduria, calciuria, and albuminuria. Dramatic alterations in the renal transcriptome, including a significant reduction in NaPi-IIa/NaPi-IIc expression, accompanied these functional changes. Additionally, Xpr1-deficient mice developed hypophosphatemic rickets secondary to renal dysfunction. These results identify XPR1 as a major regulator of Pi homeostasis and as a potential therapeutic target in bone and kidney disorders.

Nephron-Specific Deletion of Circadian Clock Gene Bmal1 Alters the Plasma and Renal Metabolome and Impairs Drug Disposition

The circadian clock controls a wide variety of metabolic and homeostatic processes in a number of tissues, including the kidney. However, the role of the renal circadian clocks remains largely unknown. To address this question, we performed a combined functional, transcriptomic, and metabolomic analysis in mice with inducible conditional knockout (cKO) of BMAL1, which is critically involved in the circadian clock system, in renal tubular cells (Bmal1lox/lox/Pax8-rtTA/LC1 mice). Induction of cKO in adult mice did not produce obvious abnormalities in renal sodium, potassium, or water handling. Deep sequencing of the renal transcriptome revealed significant changes in the expression of genes related to metabolic pathways and organic anion transport in cKO mice compared with control littermates. Furthermore, kidneys from cKO mice exhibited a significant decrease in the NAD+-to-NADH ratio, which reflects the oxidative phosphorylation-to-glycolysis ratio and/or the status of mitochondrial function. Metabolome profiling showed significant changes in plasma levels of amino acids, biogenic amines, acylcarnitines, and lipids. In-depth analysis of two selected pathways revealed a significant increase in plasma urea level correlating with increased renal Arginase II activity, hyperargininemia, and increased kidney arginine content as well as a significant increase in plasma creatinine concentration and a reduced capacity of the kidney to secrete anionic drugs (furosemide) paralleled by an approximate 80% decrease in the expression level of organic anion transporter 3 (SLC22a8). Collectively, these results indicate that the renal circadian clocks control a variety of metabolic/homeostatic processes at the intrarenal and systemic levels and are involved in drug disposition.

Escherichia coli endotoxin increases cytosolic free Ca2+ by mobilizing intracellular calcium stores in cultured endothelial cells

The effects of bacterial lipopolysaccharide (Escherichia coli 0111:B4; LPS) on cytosolic free calcium were examined in cultured bovine endothelial cells. The effect of LPS on the cellular calcium response to vasopressin was also investigated. Intracellular calcium [Ca2+]i was determined using the fluorescent probe Fluo-3/AM and confocal microscopy. LPS caused a dose-dependent increase in [Ca2+]i. The calcium response to LPS was of the same magnitude when cells were studied in the absence of extracellular calcium suggesting that the effect of LPS is due mainly to a mobilisation of intracellular calcium stores. The cellular calcium response to vasopressin was completely abolished by LPS and vice versa. These results show that LPS evokes a rapid increase in intracellular free calcium in endothelial cells. This observation may contribute to an explanation for the early initial phase of the LPS-induced vascular hyporesponsiveness.

Two-year prospective study of outcomes following total temporomandibular joint replacement

The purpose of this 2-year prospective study was to investigate outcomes achieved with a stock temporomandibular joint (TMJ) replacement system in the management of end-stage TMJ disorders. Fifty-two patients requiring reconstruction (36 unilateral/16 bilateral) were operated on during the period 2006-2012; 68 total prostheses were implanted (Biomet Microfixation TMJ Replacement System). The mean age at surgery was 52.6±11.5 years. Changes in the values of inclusion diagnostic criteria at entry were assessed. These included persistent and significant TMJ pain, functional impairment after failure of other surgical therapies, and imaging evidence consistent with advanced TMJ disease of more than 1-year duration. Subjects were excluded if they presented insufficient quantity/quality of bone to support the TMJ replacement, severe hyperfunctional habits, active infectious disease, or an inability to follow postoperative instructions. Over the 2 years of postoperative follow-up, mean pain intensity was reduced from 6.4±1.4 to 1.6±1.2 (P<0.001), and jaw opening was improved from 2.7±0.9cm to 4.2±0.7cm (P<0.001). During the study period, three of 68 implants (4%) were explanted and new TMJ replacements fitted. The results of this study support the view that the surgical placement of stock TMJ prostheses provides significant long-term improvements in pain and function, with few complications.

Local renal circadian clocks control fluid-electrolyte homeostasis and BP

The circadian timing system is critically involved in the maintenance of fluid and electrolyte balance and BP control. However, the role of peripheral circadian clocks in these homeostatic mechanisms remains unknown. We addressed this question in a mouse model carrying a conditional allele of the circadian clock gene Bmal1 and expressing Cre recombinase under the endogenous Renin promoter (Bmal1(lox/lox)/Ren1(d)Cre mice). Analysis of Bmal1(lox/lox)/Ren1(d)Cre mice showed that the floxed Bmal1 allele was excised in the kidney. In the kidney, BMAL1 protein expression was absent in the renin-secreting granular cells of the juxtaglomerular apparatus and the collecting duct. A partial reduction of BMAL1 expression was observed in the medullary thick ascending limb. Functional analyses showed that Bmal1(lox/lox)/Ren1(d)Cre mice exhibited multiple abnormalities, including increased urine volume, changes in the circadian rhythm of urinary sodium excretion, increased GFR, and significantly reduced plasma aldosterone levels. These changes were accompanied by a reduction in BP. These results show that local renal circadian clocks control body fluid and BP homeostasis.

α-Ketoglutarate regulates acid-base balance through an intrarenal paracrine mechanism

Paracrine communication between different parts of the renal tubule is increasingly recognized as an important determinant of renal function. Previous studies have shown that changes in dietary acid-base load can reverse the direction of apical α-ketoglutarate (αKG) transport in the proximal tubule and Henle's loop from reabsorption (acid load) to secretion (base load). Here we show that the resulting changes in the luminal concentrations of αKG are sensed by the αKG receptor OXGR1 expressed in the type B and non-A-non-B intercalated cells of the connecting tubule (CNT) and the cortical collecting duct (CCD). The addition of 1 mM αKG to the tubular lumen strongly stimulated Cl(-)-dependent HCO(3)(-) secretion and electroneutral transepithelial NaCl reabsorption in microperfused CCDs of wild-type mice but not Oxgr1(-/-) mice. Analysis of alkali-loaded mice revealed a significantly reduced ability of Oxgr1(-/-) mice to maintain acid-base balance. Collectively, these results demonstrate that OXGR1 is involved in the adaptive regulation of HCO(3)(-) secretion and NaCl reabsorption in the CNT/CCD under acid-base stress and establish αKG as a paracrine mediator involved in the functional coordination of the proximal and the distal parts of the renal tubule.

Circadian expression of H,K-ATPase type 2 contributes to the stability of plasma K⁺ levels

Maintenance by the kidney of stable plasma K(+) values is crucial, as plasma K(+) controls muscle and nerve activity. Since renal K(+) excretion is regulated by the circadian clock, we aimed to identify the ion transporters involved in this process. In control mice, the renal mRNA expression of H,K-ATPase type 2 (HKA2) is 25% higher during rest compared to the activity period. Conversely, under dietary K(+) restriction, HKA2 expression is ∼40% higher during the activity period. This reversal suggests that HKA2 contributes to the circadian regulation of K(+) homeostasis. Compared to their wild-type (WT) littermates, HKA2-null mice fed a normal diet have 2-fold higher K(+) renal excretion during rest. Under K(+) restriction, their urinary K(+) loss is 40% higher during the activity period. This inability to excrete K(+) "on time" is reflected in plasma K(+) values, which vary by 12% between activity and rest periods in HKA2-null mice but remain stable in WT mice. Analysis of the circadian expression of HKA2 regulators suggests that Nrf2, but not progesterone, contributes to its rhythmicity. Therefore, HKA2 acts to maintain the circadian rhythm of urinary K(+) excretion and preserve stable plasma K(+) values throughout the day.

The circadian clock modulates renal sodium handling

The circadian clock contributes to the control of BP, but the underlying mechanisms remain unclear. We analyzed circadian rhythms in kidneys of wild-type mice and mice lacking the circadian transcriptional activator clock gene. Mice deficient in clock exhibited dramatic changes in the circadian rhythm of renal sodium excretion. In parallel, these mice lost the normal circadian rhythm of plasma aldosterone levels. Analysis of renal circadian transcriptomes demonstrated changes in multiple mechanisms involved in maintaining sodium balance. Pathway analysis revealed the strongest effect on the enzymatic system involved in the formation of 20-HETE, a powerful regulator of renal sodium excretion, renal vascular tone, and BP. This correlated with a significant decrease in the renal and urinary content of 20-HETE in clock-deficient mice. In summary, this study demonstrates that the circadian clock modulates renal function and identifies the 20-HETE synthesis pathway as one of its principal renal targets. It also suggests that the circadian clock affects BP, at least in part, by exerting dynamic control over renal sodium handling.

Identification of corticosteroid-regulated genes in cardiomyocytes by serial analysis of gene expression

Corticosteroids (aldosterone, cortisol/corticosterone) exert direct functional effects on cardiomyocytes. However, gene networks activated by corticosteroids in cardiomyocytes, as well as the involvement of the mineralocorticoid receptor (MR) vs the glucocorticoid receptor (GR) in these effects, remain largely unknown. Here we characterized the corticosteroid-dependent transcriptome in primary culture of neonatal mouse cardiomyocytes treated with 10(-6) M aldosterone, a concentration predicted to occupy both MR and GR. Serial analysis of gene expression revealed 101 aldosterone-regulated genes. The MR/GR specificity was characterized for one regulated transcript, namely ecto-ADP-ribosyltransferase-3 (Art3). Using cardiomyocytes from GR(null/null) or MR(null/null) mice we demonstrate that in GR(null/null) cardiomyocytes the response is abrogated, but it is fully maintained in MR(null/null) cardiomyocytes. We conclude that Art3 expression is regulated exclusively via the GR. Our study identifies a new set of corticosteroid-regulated genes in cardiomyocytes and demonstrates a new approach to studying the selectivity of MR- vs GR-dependent effects.

Mineralocorticoid effects in the kidney: correlation between alphaENaC, GILZ, and Sgk-1 mRNA expression and urinary excretion of Na+ and K+

Aldosterone exerts its effects through interactions with two types of binding sites, the mineralocorticoid (MR) and the glucocorticoid (GR) receptors. Although both receptors are known to be involved in the anti-natriuretic response to aldosterone, the mechanisms of signal transduction leading to modulation of electrolyte transport are not yet fully understood. This study measured the Na(+) and K(+) urinary excretion and the mRNA levels of three known aldosterone-induced transcripts, the serum and glucocorticoid-induced kinase (Sgk-1), the alpha subunit of the epithelial Na(+) channel (alphaENaC), and the glucocorticoid-induced-leucine-zipper protein (GILZ) in the whole kidney and in isolated cortical collecting tubules of adrenalectomized rats treated with low doses of aldosterone and/or dexamethasone. The resulting plasma concentrations of both steroids were close to 1 nmol/L. Aldosterone, given with or without dexamethasone, induced anti-natriuresis and kaliuresis, whereas dexamethasone alone did not. GILZ and alphaENaC transcripts were higher after treatment with either or both hormones, whereas the mRNA abundance of Sgk-1 was increased in the cortical collecting tubule by aldosterone but not by dexamethasone. We conclude the increased expression of Sgk-1 in the cortical collecting tubules is a primary event in the early antinatriuretic and kaliuretic responses to physiologic concentrations of aldosterone. Induction of alphaENaC and/or GILZ mRNAs may play a permissive role in the enhancement of the early and/or late responses; these effects may be necessary for a full response but do not by themselves promote early changes in urinary Na(+) and K(+) excretion.

Pulmonary tuberculosis in children in a developing country

OBJECTIVE

We evaluated the clinical and epidemiologic characteristics of Peruvian children presenting with pulmonary tuberculosis (PTB) to determine whether features predictive of confirmed PTB could be identified.

STUDY DESIGN

This was a cross-sectional study of 135 children (mean age: 6.8 years) presenting to the Hospital del Niño in Lima, Peru, with presumptive diagnosis of PTB. Clinical, epidemiologic, and laboratory findings were compared between 3 groups of pediatric patients with a presumptive diagnosis of PTB: those with positive Mycobacterium tuberculosis (MTB) cultures, those likely to have PTB based on clinical criteria but with negative cultures, and those who did not meet clinical diagnostic criteria or have positive cultures.

RESULTS

A total of 50 (37%) patients were diagnosed with definitive PTB based on positive sputum culture. Another 55 (47%) patients were classified as having probable PTB based on meeting at least 2 of the following criteria: cough lasting for at least 2 weeks, typical chest radiograph changes, purified protein derivative (PPD) >/=10 mm, or history of tuberculosis family contact. Patients with definitive or probable PTB were significantly older than patients without clinical PTB, and those with symptomatic disease were significantly older than those with asymptomatic disease. Patients with PTB diagnosed by culture were significantly more likely than those diagnosed using clinical criteria to have cough lasting >/=2 weeks, fever, and a PPD >/=10 mm.

CONCLUSIONS

The typical presentation of PTB in Peruvian children includes symptoms of active pulmonary disease similar to those seen in adults. This presentation differs significantly from that reported in developed countries, where many children have minimal or no symptoms at the time of presentation. The diagnostic criteria for pediatric PTB must be modified in hyperendemic developing country environments where features may differ from those described in the United States. The triad of cough lasting >/=2 weeks, fever, and a PPD >/=10 mm was highly predictive for culture-positive PTB among children in this low-income Peruvian population.

Insulinoma associated with a case of multiple endocrine neoplasia type I: Functional somatostatin receptors and abnormal glucose-induced insulin secretion

A sporadic case of multiple endocrine neoplasia type I with coexisting insulinoma and hyperparathyroidism was investigated in vivo and in vitro. The insulinoma was localized by somatostatin receptor scintigraphy and these receptors were functionally active. Octreotide administration decreased the basal insulin and glucagon secretion by 90 and 46%, respectively. Immunocytochemistry of the insulinoma tissue was positive for insulin, chromogranin A and neuropeptide Y. The insulinoma cells were also isolated and cultured in vitro. Incubation experiments revealed that a low glucose concentration (1 mmol/l) was sufficient to increase cytosolic free calcium and to produce a maximal glucose-induced insulin release. Northern blot analysis of RNA obtained from the tumor showed a high abundance of the low Km glucose transporter GLUT1 but no transcript for the high Km glucose transporter GLUT2. The abnormal distribution of glucose transporters probably relates to the abnormal glucose sensing of insulinoma cells, and explains their sustained insulin secretion at low glucose concentrations. Whether these abnormalities share a pathogenetic link with the presence of functionally active somatostatin receptors remains to be elucidated.

Effect of endotoxin on the angiotensin II receptor in cultured vascular smooth muscle cells

1. In some tissues, a decrease in the number of cell surface receptors and alterations of the receptor coupling have been proposed as possible mechanisms mediating the deleterious effects of bacterial endotoxin in septic shock. 2. The effects of bacterial lipopolysaccharide (Escherichia coli 0111-B4; LPS) on vascular angiotensin II and vasopressin receptors have been examined in cultured aortic smooth muscle cells (SMC) of the rat by use of radioligand binding techniques. 3. In vascular SMC exposed to 1 micrograms ml-1 endotoxin for 24 h, a significant increase in angiotensin II binding was found. The change in [125I]-angiotensin II binding corresponded to an increase in the number of receptors whereas the affinity of the receptors was not affected by LPS. In contrast, no change in [3H]-vasopressin binding was observed. 4. The pharmacological characterization of angiotensin II binding sites in control and LPS-exposed cells demonstrated that LPS induced an increase in the AT1 subtype of the angiotensin II receptors. Receptor coupling as evaluated by measuring total inositol phosphates was not impaired by LPS. 5. The effect of LPS on the angiotensin II receptor was dose-, time- and protein-synthesis dependent and was associated with an increased expression of the receptor gene. 6. The ability of LPS to increase angiotensin II binding in cultured vascular SMC was independent of the endotoxin induction of NO-synthase. 7. These results suggest that, besides inducing factors such as cytokines and NO-synthase, endotoxin may enhance the expression of cell surface receptors. The surprising increase in angiotensin II binding in LPS exposed VSM cells may represent an attempt by the cells to compensate for the decreased vascular responsiveness. It may also result from a non-specific LPS-related induction of genes.

Confocal microscopy to analyze cytosolic and nuclear calcium in cultured vascular cells

With the development of calcium-sensitive fluorescent dyes and videomicroscopic imaging, several investigators have located the changes in intracellular calcium in the cytoplasm, in the perinuclear region, and possibly in the nucleus. However, the presence of calcium in the nucleus is often difficult to ascertain because the fluorescence derived from the perinuclear area interferes with that of the nucleus. We have used confocal microscopy together with two calcium-sensitive dyes [acetoxymethyl esters of fluo 3 (fluo 3-AM) and rhod 2 (rhod 2-AM)] to analyze the cytosolic and nuclear calcium distribution in vascular smooth muscle and endothelial cells studied at rest and after stimulation with receptor-dependent (angiotensin, vasopressin) and receptor-independent (KCl) stimuli. With fluo 3-AM, the baseline fluorescence was located in the cytoplasm but was slightly higher in the nucleus. With all stimuli, the fluorescence intensity increased in both compartments but remained more pronounced within the nucleus. Yet, after calibration, the cytosolic calcium concentration was greater than that of the nucleus at rest and was equally high after stimulation, suggesting different properties of fluo 3 in the cytosol and in the nucleus. With rhod 2-AM, baseline fluorescence was low in the nucleus and high in the cytosol. Cell stimulation caused an initial increase in cytosolic calcium with no change in the nucleus followed by a rise in both compartments. Thus the stimulation of vascular cells is associated with marked increases in cytosolic and nuclear calcium. Fluo 3-AM seems to be a better indicator of nuclear calcium than rhod 2-AM. The increases in nuclear calcium induced by angiotensin II and vasopressin may contribute to their cell proliferative effect.

In vitro effects of DuP 753, a nonpeptide angiotensin II receptor antagonist, on human platelets and rat vascular smooth muscle cells

These experiments were designed to assess the ability of the new nonpeptide angiotensin II antagonist DuP 753 to inhibit the binding and, particularly, to antagonize the cellular response to angiotensin II in human platelets and primary cultures of rat aortic smooth muscle cells (SMC). The binding of 125I-angiotensin II was competitively inhibited by DuP 753 with a 50% binding inhibition (IC50) of 5 to 6 x 10(-8) mol/L in platelets and 1 x 10(-8) mol/L in vascular SMC as compared to an IC50 of 5 to 7.5 x 10(-9) mol/L with nonlabeled angiotensin II. In vascular SMC, DuP 753 completely abolished the effects of angiotensin II on 45CaCl2 efflux and 45CaCl2 uptake. Moreover, in these latter cells, DuP 753 prevented the angiotensin II but not the vasopressin induced increase in cytosolic calcium. These results demonstrate that DuP 753 competes with angiotensin II binding to its receptor in both animal and human cells and selectively blocks the cellular response to angiotensin II.