NADP+ binding to the regulatory subunit of methionine adenosyltransferase II increases intersubunit binding affinity in the hetero-trimer

Mammalian methionine adenosyltransferase II (MAT II) is the only hetero-oligomer in this family of enzymes that synthesize S-adenosylmethionine using methionine and ATP as substrates. Binding of regulatory β subunits and catalytic α2 dimers is known to increase the affinity for methionine, although scarce additional information about this interaction is available. This work reports the use of recombinant α2 and β subunits to produce oligomers showing kinetic parameters comparable to MAT II purified from several tissues. According to isothermal titration calorimetry data and densitometric scanning of the stained hetero-oligomer bands on denatured gels, the composition of these oligomers is that of a hetero-trimer with α2 dimers associated to single β subunits. Additionally, the regulatory subunit is able to bind NADP(+) with a 1:1 stoichiometry, the cofactor enhancing β to α2-dimer binding affinity. Mutants lacking residues involved in NADP(+) binding and N-terminal truncations of the β subunit were able to oligomerize with α2-dimers, although the kinetic properties appeared altered. These data together suggest a role for both parts of the sequence in the regulatory role exerted by the β subunit on catalysis. Moreover, preparation of a structural model for the hetero-oligomer, using the available crystal data, allowed prediction of the regions involved in β to α2-dimer interaction. Finally, the implications that the presence of different N-terminals in the β subunit could have on MAT II behavior are discussed in light of the recent identification of several splicing forms of this subunit in hepatoma cells.

Dosimetry of a cone beam CT device for oral and maxillofacial radiology using Monte Carlo techniques and ICRP adult reference computational phantoms

OBJECTIVES

The aim of this study was to calculate organ and effective doses for a range of available protocols in a particular cone beam CT (CBCT) scanner dedicated to dentistry and to derive effective dose conversion factors.

METHODS

Monte Carlo simulations were used to calculate organ and effective doses using the International Commission on Radiological Protection voxel adult male and female reference phantoms (AM and AF) in an i-CAT CBCT. Nine different fields of view (FOVs) were simulated considering full- and half-rotation modes, and also a high-resolution acquisition for a particular protocol. Dose-area product (DAP) was measured.

RESULTS

Dose to organs varied for the different FOVs, usually being higher in the AF phantom. For 360°, effective doses were in the range of 25-66 μSv, and 46 μSv for full head. Higher contributions to the effective dose corresponded to the remainder (31%; 27-36 range), salivary glands (23%; 20-29%), thyroid (13%; 8-17%), red bone marrow (10%; 9-11%) and oesophagus (7%; 4-10%). The high-resolution protocol doubled the standard resolution doses. DAP values were between 181 mGy cm(2) and 556 mGy cm(2) for 360°. For 180° protocols, dose to organs, effective dose and DAP were approximately 40% lower. A conversion factor (DAP to effective dose) of 0.130 ± 0.006 μSv mGy(-1) cm(-2) was derived for all the protocols, excluding full head. A wide variation in dose to eye lens and thyroid was found when shifting the FOV in the AF phantom.

CONCLUSIONS

Organ and effective doses varied according to field size, acquisition angle and positioning of the beam relative to radiosensitive organs. Good positive correlation between calculated effective dose and measured DAP was found.

Recurrent membranoproliferative glomerulonephritis after second renal graft treated with plasmapheresis and rituximab

We present a case of a 45-year-old man who suffered from idiopatic membranoproliferative glomerulonephritis (MPGN) in the native kidney that relapsed after his first and second renal grafts. The patient was diagnosed in 1990 with lobular MPGN type I, receiving his first renal graft in 1996. In 2001, a biopsy showed recurrence of MPGN type I (rMPGN). He underwent a second renal graft in 2008. In January 2010, he experienced increased proteinuria and creatinine. Upon electron microscopy of a renal graft biopsy we diagnosed a new rMPGN. At the time of the biopsy, complement levels were normal, although C3 and C4 decreased further. We administered 12 plasmapheresis (PP) sessions and four doses of rituximab. Due to persistent renal impairment, we performed a new biopsy 3 months later, showing less severity of the acute lessions. He received a new cycle of treatment (PP+rituximab). One year later, his renal function was stable with a creatinine ranging between 2 and 2.5 mg/dL and a protein/creatinine ratio less than 1 mg/mg. We concluded that the treatment stopped the disease progression.

Impact of recurrent glomerulonephritis on renal graft survival

BACKGROUND

Glomerular disease causes graft loss in the intermediate and long term, especially recurrent primary renal disease, negatively impacting graft survival. Thus, it must be considered a differential diagnosis in the evaluation of chronic graft dysfunction.

METHODS

The objectives of our study were to compare the impacts of primary glomerular disease on graft survival and association with interstitial fibrosis/tubular atrophy (IFTA) or transplant glomerulopathy. We examined the influence of the relapse of glomerulonephritis (GN) on renal graft survival in a retrospective study of 1057 patients undergoing renal transplantations between March 1981 and October 2009. Among this group, 128 patients were diagnosed with pretransplant GN by renal biopsy. We examined graft survival on recurrence compared with IFTA and transplant glomerulopathy using Kaplan-Meier analysis.

RESULTS

We analyzed a cohort of 128 patients who were diagnosed with pretransplant GN by renal biopsy, including 28.9% (37) of whom were males. The mean age was 42.04 ± 13.82 years. The most frequent type was immunoglobulin A GN (IgAGN; 31.3%), followed by membranoproliferative GN (MPGN; 28.9%), rapidly progressive GN (RPGN; 16.4%), focal-segmental GN (FSGN; 13.3%), membranous GN (9.4%), and minimal change GN; (0.8%). Among the 16 cases (12.5%) of GN recurrence; MPGN was associated most frequently (n = 10, 28.9%), followed by FSGN (n = 4, 23.5%), RPGN (n = 1, 4.8%), and IgAGN (n = 1, 2.5%). We noted that 11.8% of subjects to be positive for hepatitis C virus; while 3.9% were hepatitis B virus(HBV)-positive. We observed no differences in hepatic serology between patients who experienced recurrence (HBV 6.3% vs hepatitis C virus [HCV] 18.8%) compared with IFTA (HBV 3.1% vs HCV 9.4%). Fifty-one patients (39.8%) were biopsied after transplantation due to impaired renal function: there were recurrences of GN in 12.5% (n = 16), IFTA in 25% (n = 32), and transplant glomerulopathy in 2.3% (n = 3) cases. The average graft survival in our cohort was 8.36 ± 0.59 years. The median patient survival among those who experienced a recurrence was 8.36 ± 1.79 years; 7.19 ± 1.01 years in IFTA patients; and 3.31 ± 0.91 years in patients with transplant glomerulopathy (log-rank P = .06). Upon multivariate analysis, recurrence of GN was not an independent predictor of renal loss.

CONCLUSIONS

MPGN was the type of GN that recurred most frequently followed by FSGN. No differences in graft survival were noted between long-term recurrence of GN and other causes of chronic graft dysfunction. The recurrence of primary disease did not worsen the renal graft prognosis versus other causes of chronic graft dysfunction.

Autonomic and metabolic effects of OSA in childhood obesity

This study investigates the effects of exposure to intermittent hypoxia on cardiovascular autonomic control and metabolic function in obese children with obstructive sleep apnea (OSA). Each subject underwent: (1) a polysomnography; (2) morning fasting blood samples and a subsequent FSIVGTT; (3) noninvasive measurement of respiration, arterial blood pressure, and heart rate during supine and standing postures. Assessment of adiposity was performed using a DEXA scan. From these measurements, we deduced the pertinent sleep parameters, Bergman minimal model parameters and the parameters characterizing a minimal model of cardiovascular variability. Results suggest that intermittent hypoxia in OSA contributes independently to insulin resistance and autonomic dysfunction in overweight children.

Continuous versus interrupted sutures for repair of episiotomy or second-degree perineal tears: a randomised controlled trial

OBJECTIVE

To evaluate the repair techniques of continuous and interrupted methods for episiotomy or perineal tears.

DESIGN

A randomised controlled trial.

SETTING

The Hospital Universitario Principe de Asturias, a state hospital belonging to the community of Madrid.

SAMPLE

Four hundred forty-five women who had undergone vaginal deliveries with episiotomies or second-grade tearing of the perineum between September 2005 and July 2007.

METHODS

One group was repaired with continuous, nonlocking sutures involving the vagina, perineum, and subcutaneous tissues. The other group had continuous, locking sutures of the vagina, interrupted sutures in the perineal muscles, and interrupted transcutaneous sutures. The threads used for stitching were identical in both groups.

MAIN OUTCOME MEASURES

The participants were questioned regarding the sensation of pain and the use of painkillers on the second and the tenth days, and 3 months postpartum.

RESULTS

When comparing the group with continuous suture to the group with interrupted sutures, the differences included less repair time (1 minute; P= 0.017) and less suture material used (relative risk [RR], 3.2, 95% CI: 2.6-4.0). The comparison of pain on the second and tenth days, and 3 months postpartum were not statistically different between the two techniques (RR, 1.08, 95% CI: 0.74-1.57; RR, 0.96, 95% CI: 0.59-1.55; and RR, 0.68, 95% CI: 0.19-2.46, respectively).

CONCLUSIONS

Although we did not demonstrate that one technique was better than the other in the incidence of pain in the short or long term, we showed that episiotomy and perineal tear repairs with continuous suturing were quicker and used less suture material without an increase in complication than interrupted suturing.

[Cardiovascular risk in subjects with high probability of metabolic syndrome and insulin resistance. DESIRE study]

INTRODUCTION AND OBJECTIVES

The metabolic syndrome is an association of closely related alterations. The main objective of this study is to know the frequency of the metabolic syndrome and insulin resistance, and their role as cardiovascular risk indicators in an adult population assigned to Primary Care centers in Spain.

METHODS

Subjects > or = 45 years with basal glycemia > or = 90 mg/dl and abdominal circumference > or = 94 cm (men) or > or = 80 cm (women). ATP III modified-criteria were used for the metabolic syndrome and HOMA index > 3.29 was used for insulin resistance. Cardiovascular risk was estimated by the Framingham and SCORE models.

RESULTS

A total of 2,341 subjects (62 +/- 10 years; 44.6% males) were included. Frequency of metabolic syndrome and insulin resistance was 54.6% (52.5; 56.8) and 56.6% (54.5; 58.7) respectively. Metabolic syndrome was associated to a higher cardiovascular risk score with both Framingham (16 [15; 16] vs 11 [11; 12] p < 0.0001) and SCORE (2.7 [2.4; 3] vs 2.4 [2.1; 2.8]; p = 0.006) models. The results were similar for the presence of insulin resistance.

CONCLUSIONS

Metabolic syndrome and insulin resistance are cardiovascular risk predictors. Early identification of metabolic syndrome by the use of simple clinical measures (basal glycemia and waist circumference) would make the intervention on the different disorders of metabolic syndrome possible.

Quantitative micro-analysis of metal ions in subcellular compartments of cultured dopaminergic cells by combination of three ion beam techniques

Quantification of the trace element content of subcellular compartments is a challenging task because of the lack of analytical quantitative techniques with adequate spatial resolution and sensitivity. Ion beam micro-analysis, using MeV protons or alpha particles, offers a unique combination of analytical methods that can be used with micrometric resolution for the determination of chemical element distributions. This work illustrates how the association of three ion beam analytical methods, PIXE (particle induced X-ray emission), BS (backscattering spectrometry), and STIM (scanning transmission ion spectrometry), allows quantitative determination of the trace element content of single cells. PIXE is used for trace element detection while BS enables beam-current normalization, and STIM local mass determination. These methods were applied to freeze-dried cells, following a specific cryogenic protocol for sample preparation which preserves biological structures and chemical distributions in the cells. We investigated how iron accumulates into dopaminergic cells cultured in vitro. We found that the iron content increases in dopaminergic cells exposed to an excess iron, with marked accumulation within distal ends, suggesting interaction between iron and dopamine within neurotransmitter vesicles. Increased iron content of dopaminergic neurons is suspected to promote neurodegeneration in Parkinson's disease.

Health-related quality of life in patients with osteoarthritis after total knee replacement: factors influencing outcomes at 36 months of follow-up

OBJECTIVES

(1) To evaluate health-related quality of life (HRQL) in patients with severe osteoarthritis (OA) undergoing total knee replacement (TKR) and (2) to identify the influence of sociodemographic, clinical, intra-operative and postoperative variables on HRQL at 36 months after TKR.

DESIGN

Prospective study with a 36-month follow-up. Preoperative interviews were carried out with 90 in-patients. The disease-specific Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire was used to measure the health status. Sociodemographic, clinical, intra-operative degree of difficulty, in-patient and postoperative data were collected. Associations were analyzed using linear regression models.

RESULTS

Of the 90 potentially eligible patients, 67 (54 females, mean age 74.83, standard deviation [SD] 5.57) completed follow-up assessment. There were significant differences between preoperative and postoperative WOMAC pain, stiffness and function scores (P<0.001, P=0.005 and P<0.001, respectively). Variables retained in each of the models explained between 15% and 23% (R(2) adjusted) of the variability of each WOMAC dimension. Higher preoperative WOMAC scores were associated with greater postoperative improvement (P<0.001). Chronic musculoskeletal pain unrelated to knee OA was associated with higher WOMAC pain, stiffness and function dimension scores (P=0.004, P=0.029 and P=0.005, respectively). Severe (Class III) obesity (body mass index [BMI] 35-39.9) was associated with more pain (P=0.049).

CONCLUSIONS

In patients with severe OA, HRQL significantly improved at 36 months after TKR, especially in the pain dimension. Lower preoperative WOMAC scores, chronic pain unrelated to knee OA, and severe obesity negatively influenced postoperative WOMAC scores. This disease-specific questionnaire may help to identify patients at increased risk of negative outcomes after surgery.

[Alterations in bone mineral metabolism in patients with calcium kidney stone disease and polymorphism of vitamin D receptor. Preliminary results]

Bone health, within calcium kidney stone disease is a matter of controversy. On the other hand, some genetic studies have shown an association between some Vitamin D receptor polymorphisms and calcium kidney stone disease.

MAIN OBJECTIVE

To study the possible association between calcium kidney stone disease with bone metabolism and some Vitamin D receptor polymorphisms.

PATIENTS AND METHODS

This is a case-control study, with seventy-two subjects of both genders divided into two groups: Group I: cases, composed by 51 patients suffering from calcium kidney stone disease. Twenty-four of them had no hypercalciuria, 16 had absortive hypercalciuria and 11 had renal hypercalciuria. Group II: controls, composed by 21 people, without either urolithiasis or hypercalciuria. We performed a complete study including biochemical markers of bone mineral remodelling, bone mineral density (BMD) was estimated both in the lumbar spine (L2-L4) and femoral neck, and also VDR polymorphism for the loci b, a and t.

RESULTS

Patients with urolithiasis had lower values of BMD both in the lumbar spine and femoral neck, compared to controls. Z-score were lower in the lumbar spine and femoral neck (p =0,045 y 0,031, respectively). Those patients with absorptive hypercalciuria had higher BMD in the femoral neck than those with renal hypercalciuria and non-hypercalciuria. Because they had more weight and height all the statistical study was performed alter adjusting by these two variables and statistical significance was then only stated between patients with hypercalciuria and without it. Patients with urolithiasis had higher values of 1,25 (OH)2 vitamin D (p=0,002), and lower of PTH (p=0,049), without any relationship to hypercalciuria and its subtypes. Seventy six percent of the patients had a daily calcium intake lower than 800 mg/day. The distribution of VDR alleles in patients with urolithiasis was similar to controls, although after grouping genotypes, a lower distribution of BB and tt polymorphisms were observed in patients suffering from urolithiasis.

CONCLUSIONS

Calcium kidney stone disease by itself produces a decrease in BMD, more intense in femoral neck, independently the presence or absence of hypercalciuria. Patients suffering from urolitihiasis have higher values of 1,25 (OH)2 vitamin D than non-hypercalciuric patients and lower values of PTH probably due to a low dietary calcium intake. In our population studied there is no relationship between VDR polymorphisms and the presence of calcium kidney stone disease. Because the reduced number of patients of our study, more studies are needed to obtain definitely conclusions.

Role of activator protein-1 on the effect of arginine-glycine-aspartic acid containing peptides on transforming growth factor-β1 promoter activity

While arginine-glycine-aspartic acid-based peptidomimetics have been employed for the treatment of cardiovascular disorders and cancer, their use in other contexts remains to be explored. Arginine-glycine-aspartic acid-serine induces Transforming growth factor-beta1 transcription in human mesangial cells, but the molecular mechanisms involved have not been studied extensively. We explored whether this effect could be due to Activator protein-1 activation and studied the potential pathways involved. Addition of arginine-glycine-aspartic acid-serine promoted Activator protein-1 binding to its cognate sequence within the Transforming growth factor-beta1 promoter as well as c-jun and c-fos protein abundance. Moreover, this effect was suppressed by curcumin, a c-Jun N terminal kinase inhibitor, and was absent when the Activator protein-1 cis-regulatory element was deleted. Activator protein-1 binding was dependent on the activity of integrin linked kinase, as transfection with a dominant negative mutant suppressed both Activator protein-1 binding and c-jun and c-fos protein increment. Integrin linked kinase was, in turn, dependent on Phosphoinositol-3 kinase activity. Arginine-glycine-aspartic acid-serine stimulated Phosphoinositol-3 kinase activity, and Transforming growth factor-beta1 promoter activation was abrogated by the use of Phosphoinositol-3 kinase specific inhibitors. In summary, we propose that arginine-glycine-aspartic acid-serine activates Integrin linked kinase via the Phosphoinositol-3 kinase pathway and this leads to activation of c-jun and c-fos and increased Activator protein-1 binding and Transforming growth factor-beta1 promoter activity. These data may contribute to understand the molecular mechanisms involved in the cellular actions of arginine-glycine-aspartic acid-related peptides and enhance their relevance as these products evolve into clinical therapeutic use.

Imaging and speciation of trace elements in biological environment

Mineral elements, often at the trace level, play a considerable role in physiology and pathology of biological systems. Metallogenomics, metalloproteomics, and metallomics are among the emerging disciplines which are critically dependent on spatially resolved concentration maps of trace elements in a cell or tissue, on information on chemical speciation, and on that on metal-binding coordination sites. The mini-review discusses recent progress in analytical techniques for element profiling on the genome scale, biological trace element imaging, and probing, identification and quantification of chemical species in the biological environment. Imaging of the element distribution in cells and tissue sections is becoming possible with sub-micrometer spatial resolution and picogram-level sensitivity owing to advances in laser ablation MS, ion beam and synchrotron radiation X-ray fluorescence microprobes. Progress in nanoflow chromatography and capillary electrophoresis coupled with element specific ICP MS and molecule-specific electrospray MS/MS and MALDI enables speciation of elements in microsamples in a complex biological environment. Laser ablation ICP MS, micro-SXRF, and micro-PIXE allow mapping of trace element distribution in 1D and 2D proteomics gels. The increasing sensitivity of EXAFS and XANES owing to the use of more intense synchrotron beams and efficient focusing optics provide information about oxidation state, fingerprint speciation of metal sites and metal-site structures.

Micro-chemical imaging of cesium distribution in Arabidopsis thaliana plant and its interaction with potassium and essential trace elements

Cesium as an alkali element exhibits a chemical reactivity similar to that of potassium, an essential element for plants. It has been suggested that Cs phytotoxicity might be due either to its competition with potassium to enter the plant, resulting in K starvation, or to its intracellular competition with K binding sites in cells. Such elemental interactions can be evidenced by chemical imaging, which determines the elemental distributions. In this study, the model plant Arabidopsis thaliana was exposed to 1 mM cesium in the presence (20 mM) or not of potassium. The quantitative imaging of Cs and endogenous elements (P, S, Cl, K, Ca, Mn, Fe, and Zn) was carried out using ion beam micro-chemical imaging with 5 microm spatial resolution. Chemical imaging was also evidenced by microfocused synchrotron-based X-ray fluorescence (microXRF) which presents a better lateral resolution (<1 microm) but is not quantitative. Cesium distribution was similar to potassium which suggests that Cs can compete with K binding sites in cells. Cesium and potassium were mainly concentrated in the vascular system of stems and leaves. Cs was also found in lower concentration in leaves mesophyll/epidermis. This late representing the larger proportion in mass, mesophyll/epidermis can be considered as the major storage site for cesium in A. thaliana. Trichomes were not found to accumulate cesium. Interestingly, increased Mn, Fe, and Zn concentrations were observed in leaves at high chlorosis. Mn and Fe increased more in the mesophyll than in veins, whereas zinc increased more in veins than in the mesophyll suggesting a tissue specific interaction of Cs with these trace elements homeostasis. This study illustrates the sensitivity of ion beam microprobe and microfocused synchrotron-based X-ray fluorescence to investigate concentrations and distributions of major and trace elements in plants. It also shows the suitability of these analytical imaging techniques to complement biochemical investigations of metallic stress in plants.

Attention-deficit hyperactivity disorder involves differential cortical processing in a visual spatial attention paradigm

OBJECTIVE

Inattention is undoubtedly one of the main characteristics of Attention-deficit hyperactivity disorder (ADHD). Nevertheless, a growing corpus of evidence shows that not all attentional processes are affected in this condition. This study aimed to explore the distribution of attentional resources in children with ADHD via a spatially shifted double-oddball visual task.

METHODS

We recorded event-related potentials (ERPs) for all visual stimuli. Subjects were instructed to allocate attention in a specific area of visual space while ignoring all stimuli presented outside. Ten male children (age: 9-14; mean = 11.6 +/- 2.1) who met DSM-IV criteria for the ADHD combined subtype participated in the study, along with ten age- and sex-matched healthy controls (9-14; mean = 11.2 +/- 2.3).

RESULTS

ADHD subjects showed late differential cortical responses to initially suppressed irrelevant stimuli. The amplitude of early N1-P1 components were mainly modulated by stimulus location and showed no significant differences between groups, but a late P300-like positivity was clearly evoked in the ADHD group by peripheral stimuli.

CONCLUSIONS

These results suggest that ADHD may not compromise the early attentional spatial filter but rather entails a different distribution of attentional resources at later stages of cortical processing. Perhaps these differences may be attributable to individual differences in attentional mechanisms.

SIGNIFICANCE

ADHD may not affect initial focusing of visual attention but rather the allocation of processing resources in later stages.

An interdisciplinary approach to investigate the impact of cobalt in a human keratinocyte cell line

Since in nuclear power plants, risks of skin contact contamination by radiocobalt are significant, we focused on the impact of cobalt on a human cutaneous cell line, i.e. HaCaT keratinocytes. The present paper reports an interdisciplinary approach aimed at clarifying the biochemical mechanisms of metabolism and toxicity of cobalt in HaCaT cells. Firstly, a brief overview of the used instrumental techniques is reported. The following parts present description and discussion of results concerning: (i) toxicological studies concerning cobalt impact towards HaCaT cells (ii) structural and speciation fundamental studies of cobalt-bioligand systems, through X-ray absorption spectroscopy (XAS), ab initio and thermodynamic modelling (iii) preliminary results regarding intracellular cobalt speciation in HaCaT cells using size exclusion chromatography/inductively coupled plasma-atomic emission spectroscopy (SEC/ICP-AES) and direct in situ analysis by ion beam micropobe analytical techniques.

Epileptic seizures caused by low valproic acid levels from an interaction with meropenem

A 55-year-old woman was diagnosed with pneumonia and was treated with meropenem; 5 days later she developed epileptic seizures. She had been treated with valproic acid for 16 years to control her epileptic seizures. Her serum valproic acid concentration was low during treatment with meropenem than previously recorded despite an increase of valproic dose. As soon as administration of meropenem was withdrawn, valproic acid concentration increased to previous levels and her seizures stopped. Meropenem decreases valproic acid concentration, and may promote the development of epileptic seizures in previously controlled epileptic patients. The acute lowering of serum valproate produced by meropenem probably precludes their concomitant use.