Do we need education in metrology in chemistry?
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Use of solid-phase extraction to eliminate interferences in the determination of mercury by flow-injection CV AAS.
Solid-phase extraction with two-step elution has been developed for effective elimination of copper and iron interference with mercury determination by flow-injection cold vapour atomic absorption spectrometry (CV AAS). Sodium tetrahydroborate(III) was used as reducing agent. Cation-exchanger Dowex 50Wx4 was applied for the sorption of mercury and both interfering ions. In the first step elution of Cu(II) and Fe(III) was performed using 0.5 mol L(-1) KF solution. Then mercury was eluted with 0.1% thiourea in 8% HCl. The detection limit (3 delta) for Hg(II) was 27 ng L(-1). The expanded uncertainty estimated for the whole procedure was about 6%. The accuracy of the proposed method was evaluated by determination of the recovery of known amount of mercury added to mineral, spring, and tap waters, and by analysis of a certified reference material BCR-144R (sewage sludge).
Journal Article↗
Molecularly-imprinted polypyrrole-modified stainless steel frits for selective solid phase preconcentration of ochratoxin A.
A molecularly-imprinted polymer (MIP) was prepared by electropolymerization of pyrrole (Py) onto a stainless steel frit, using ochratoxin A (OTA) as the template, in order to make a micro solid phase preconcentration (microSPP) device. The OTA template was removed with 1% triethylamine (TEA) in methanol. Compared to non-imprinted polypyrrole (PPy), the molecularly-imprinted polypyrrole (MIPPy) enhanced the selective binding of OTA. The percentage recovery improved from 0 to 40% when the OTA sample solution was acidified with 1 M HCl (1% by volume). At a flow rate of 0.2 mL/min, maximum OTA binding was reached in 6 min after a total loading of 3.2 ng OTA. Final elution of the OTA was analyzed by high performance liquid chromatography (HPLC) with fluorescence detection, using 20:80 v/v acetonitrile-ammonia buffer (NH4Cl/NH3, 20 mM, pH 9.2) as the mobile phase. The MIPPy-microSPP-HPLC results clearly demonstrated that the MIPPy-microSPP device afforded selective preconcentration of OTA from red wine samples, at OTA concentration levels as low as 0.05 ppb, prior to HPLC analysis.
Biosensing Techniques↗
Good oral presentation of scientific work.
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ABCs of teaching analytical sciences. Tips for effective poster presentations.
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Journal Article↗
Understanding the contribution of binocular vision to the control of adaptive locomotion.
Abstract. Although the contribution of binocular vision to reach-to-grasp movements has been extensively studied, it has been largely ignored in locomotion. The aim of these studies was to explore the role of binocular vision during the approach phase and step over the obstacle and the contribution of head movements to acquisition of depth information under monocular vision. Binocular and monocular vision was manipulated in different phases using either an eye patch or liquid crystal glasses. Head movement relative to the trunk was restricted in the first experiment by a modified Ferno Universal Head Immobilizer attached to a rigid board strapped to the participant's back. Whole body kinematics were collected by placing infrared diodes on anatomical landmarks and using an Optotrak imaging system. Several measures related to head and limb movement were analyzed. Three major findings emerged from these studies. First, binocular vision is important for the acquisition of accurate information about the surrounding environment: accuracy but not precision of limb elevation over the obstacle was adversely affected when binocular vision was unavailable. Second, motion parallax due to self-motion provides the most critical depth information and it can be used to partially compensate for the loss of binocular vision. Although head movement is not essential to augment depth information, it is important for reorientation of the visual field to obtain the necessary information about the moving limbs when visual field is suddenly limited under monocular vision. Third, step over the obstacle is pre-planned based on visual information acquired during the approach phase: changes in visual condition during the adaptive step do not influence the limb trajectory. Collectively these three studies provide unique insights into the contribution of binocular vision during adaptive locomotion.
Adaptation, Psychological↗
Obstacle avoidance during locomotion using haptic information in normally sighted humans.
The goal of the study was to examine the accuracy and precision of control of adaptive locomotion using haptic information in normally sighted humans before and after practice. Obstacle avoidance paradigm was used to study adaptive locomotion; individuals were required to approach and step over different sizes of obstacles placed in the travel path under three sensory conditions: full vision (FV); restricted lower visual field (RLVF) using blinders on custom glass frames; and no vision (NV) using haptic information only. In the NV condition, individuals were a given an appropriate-sized cane to guide their locomotion. Footfall patterns were recorded using the GAITRite system, and lead and trail limb trajectories were monitored using the OPTOTRAK system, which tracked infrared diodes placed on the toes and the cane. Approach step lengths were reduced for the haptic condition: this slowed the forward progression and allowed greater time for haptic exploration, which ranged from 2.5 to 4 s and consisted of horizontal cane movements (to detect the width and relative location of the obstacle) and vertical cane movements (to detect the height of the obstacle). Based on feed-forward and on-line sensory (under both vision and haptic conditions) information about location of the obstacle relative to the individual, variability of foot placement reduced as the individual came closer to the obstacle, as has been shown in the literature. The only difference was that the reduction in variability of foot placement under haptic condition occurred in the last step compared with earlier under vision. Considering that the obstacle is detected only when the cane comes in contact, as opposed to vision condition when it is visible earlier, this difference is understandable. Variability and magnitude of lead and trail limb elevation for the haptic condition was higher than the RLVF and FV conditions. In contrast, only the magnitude of lead and trail limb elevation was higher in the RLVF condition when compared with the FV condition. This suggests that it is the inability of the haptic sense to provide accurate information about obstacle characteristics compared with the visual system, and not simple caution that lead to higher limb elevation. In the haptic and RLVF condition when vision was unavailable for on-line monitoring of lead limb elevation, kinesthetic information from lead limb elevation was used to fine-tune trail limb elevation. Both the control of approach phase and limb elevation findings held up even after sufficient practice to learn haptic guidance of adaptive locomotion in the second experiment. These results provide a clear picture of the efficacy of the haptic sensory system to guide locomotion in a cluttered environment.
Adaptation, Psychological↗
MRI of a family with leukoencephalypathy with vanishing white matter.
Leukoencephalopathy with vanishing white matter (VWM) is a newly described entity with characteristic MRI features. We report the cranial MRI findings in three sisters with slowly progressive neurological deterioration. The MRI showed symmetrical diffuse abnormalities of cerebral white matter with hypointensity on FLAIR images. The diagnosis of leukoencephalopathy with VWM was made on the basis of genetic analysis.
Adolescent↗
Biotransformation of 6,7-epoxygeraniol by fungi.
The biotransformation of 6,7-epoxygeraniol by resting cells of selected fungi was investigated. The main product obtained from the transformation in Rhodotorula glutinis and R. marina cultures was 6,7-epoxynerol (5-48% of chloroform extracts), whereas Saccharomyces cerevisiae, Candida parapsilosis and C. kefyr reduced this substrate to 6,7-epoxycitronellol (30-33% of chloroform extracts). Cultures of Yarrowia lipolytica, Botrytis cinerea and S. cerevisiae promoted the cyclisation of 6,7-epoxygeraniol to 2-methyl-2-(2-hydroxyethyl)-5-(2-hydroxyprop-2-yl)tetrahydrofuran (11-99% of chloroform extracts). The biotransformation of 6,7-epoxynerol was also investigated. However, none of the tested micro-organisms converted this compound.
Acyclic Monoterpenes↗
Use of fluorescence spectroscopy to differentiate yeast and bacterial cells.
This study focuses on the characterization of bacterial and yeast species through their autofluorescence spectra. Lactic acid bacteria (Lactobacillus sp.), and yeast (Saccharomyces sp.) were cultured under controlled conditions and studied for variations in their autofluorescence, particularly in the area representative of tryptophan residues of proteins. The emission and excitation spectra clearly reveal that bacterial and yeast species can be differentiated by their intrinsic fluorescence with UV excitation. The possibility of differentiation between different strains of Saccharomyces yeast was also studied, with clear differences observed for selected strains. The study shows that fluorescence can be successfully used to differentiate between yeast and bacteria and between different yeast species, through the identification of spectroscopic fingerprints, without the need for fluorescent staining.
Fluorescence↗
Assessment of prokaryotic collagen-like sequences derived from streptococcal Scl1 and Scl2 proteins as a source of recombinant GXY polymers.
Collagen triple helix, composed of the repeating Gly-Xaa-Yaa (GXY) sequence, is a structural element found in all multicellular animals and also in some prokaryotes. Long GXY polymers are highly regarded components used in food, cosmetic, biomedical, and pharmaceutical industries. In this study, we explore a new concept for the production of recombinant GXY polymers which are based on the sequence of "prokaryotic collagens", the streptococcal collagen-like proteins Scl1 and Scl2. Analysis of 50 Scl variants identified the amino acid distribution and GXY-repeat usage that are involved in the stabilization of the triple helix in Scls. Using circular dichroism spectroscopy and electron microscopy, we show that significantly different recombinant rScl polypeptides form stable, unhydroxylated homotrimeric triple helices that can be produced both intra- and extracellularly in the Escherichia coli. These rScl constructs containing 20 to 129 GXY repeats had mid-point melting temperatures between 32 and 39 degrees C. Altogether, Scl-derived collagens, which are different from the mammalian collagens, can form stable triple helices under physiological conditions and can be used for the production of recombinant GXY polymers with a wide variety of potential applications.
Bacterial Proteins↗
Clinical usefulness of 99mTc-EDDA/HYNIC-TOC scintigraphy in oncological diagnostics: a preliminary communication.
This study assessed the clinical usefulness of a new technetium-99m labelled somatostatin analogue from the standpoint of oncological diagnostics. The study group comprised 40 patients in whom malignant neoplasms (32 primary and 8 metastatic) had been diagnosed. Among the primary tumours there were 21 cases of lung cancer (2 small cell and 19 non-small cell), seven pituitary adenomas (five hormonally active and two inactive), one liposarcoma, two carcinoids and one breast carcinoma. The metastatic tumours consisted of three malignant melanomas, one phaeochromocytoma, one prostatic cancer, one leiomyosarcoma, one pancreatic carcinoma ectopically secreting ACTH and one carcinoid of the thymus. The radiopharmaceutical 99mTc-EDDA/HYNIC-Tyr3-octreotide was administered i.v. at an activity of 740-925 MBq. The imaging comprised a whole-body scan and a single-photon emission tomography acquisition. Positive scintigrams were obtained in all cases of small cell and non-small cell lung cancer, four out of five hormonally active pituitary adenomas, one out of two cases of carcinoid, the liposarcoma and the breast cancer. Neoplastic metastases were visualised in two out of three patients with melanoma and in patients with phaeochromocytoma, ACTH-secreting pancreatic carcinoma and thymic carcinoid. Scintigrams were negative in both hormonally inactive pituitary adenomas, in one case of metastatic malignant melanoma, in the leiomyosarcoma and in the case of metastasis from prostatic carcinoma. The results of this pilot study indicate that 99mTc-EDDA/HYNIC-TOC is a potentially useful radiopharmaceutical for imaging of a wide range of primary and metastatic tumours. Special attention should be paid to the successful imaging of all cases of non-small cell lung cancer.
Adult↗
Diagnosis and staging of children's lymphoma using the technetium-labelled somatostatin analogue, 99mTc-depreotide.
Somatostatin receptor scintigraphy (SRS) is useful in diagnosing tumours with increased expression of somatostatin receptors. Lymphoma cells are known to express somatostatin receptors; however, the application of indium-labelled analogues in children is limited. The aim of this study was to investigate whether the technetium-labelled somatostatin analogue, depreotide, may be useful in diagnosing and staging malignant lymphoma in children. Fifteen children (mean age 13.8 years) with malignant lymphoma were studied (eight with Hodgkin's lymphoma and seven with non-Hodgkin's lymphoma). All children were investigated for verification of staging established by other modalities. Imaging was performed 3-5 h after administration of 300-550 MBq (99m)Tc-depreotide. All patients underwent whole-body scan and single-photon emission tomography of the chest and/or abdomen. Images were assessed visually. In all patients, foci of increased tracer uptake were found. The neck and thorax were the most frequent lesion localisations. Abdominal lesions were found in four patients, and bone lesions in three. In two patients, diffusely increased uptake was observed throughout the skeleton (verified as representing bone marrow involvement). In 11 patients, the number of abnormal sites detected by SRS was greater than that detected by CT. Based on radionuclide examination, three children were upstaged and none were downstaged. It is concluded that (99m)Tc-depreotide shows increased accumulation in pathological sites in malignant lymphoma in children. SRS with (99m)Tc-depreotide provides a single-day imaging method with high sensitivity in lymphoma and with all the advantages of a technetium-labelled compound. Further studies are required on the specificity and the possible value of (99m)Tc-depreotide in the follow-up of these patients.
Adolescent↗
Beneficial effects of atorvastatin on myocardial regions with initially low vasodilatory capacity at various stages of coronary artery disease.
PURPOSE: The aim of this study was to analyse non-invasively the regional effect of therapy with an HMG-CoA reductase inhibitor on myocardial blood flow in patients with coronary artery disease (CAD) with special reference to segments with initially substantially impaired vasodilation. METHODS: The study included 26 patients with untreated hypercholesterolaemia. Coronary angiography revealed CAD in nine patients with stenosis >50% and wall irregularities or minimal stenosis <30% in 17 patients. Before and 4.6+/-1.8 months after atorvastatin therapy, ( 13)N-ammonia positron emission tomography (PET) studies were performed at rest and under pharmacological stress. Minimum coronary vascular resistance (MCR) and coronary flow reserve (CFR) were determined. Segments were divided into those with normal or near-normal (MBF during adenosine > or =2.0 ml/min/g) and those with abnormal (MBF<2.0 ml/min/g) vasodilator flow response. In CAD patients, 156 segments were analysed, 85 of which had abnormal MBF; in the non-obstructive group, 59 of 297 segments had abnormal MBF. RESULTS: LDL cholesterol decreased after atorvastatin therapy from 186+/-43 mg/dl to 101+/-26 mg/dl (p<0.001). In normal segments no significant changes in MBF, CFR and MCR were found. However, initially abnormal segments showed significant improvements in MCR (15%, p<0.0001) and MBF during adenosine (30%, p<0.0001) after therapy. CONCLUSION: The improvement in regional coronary vasodilator function after atorvastatin in patients with coronary atherosclerosis may be caused, at least in part, by increased flow-mediated (endothelium-dependent) dilation of the total arteriolar and arterial vascular system. These data further support the concept of non-invasive management of stable CAD by statin therapy and life-style modification guided by PET.
Aged↗
Primary hyperparathyroidism revisited in menopausal women with serum calcium in the upper normal range at population-based screening 8 years ago.
Population-based screening showed 2.1% prevalence of primary hyperparathyroidism (pHPT) in postmenopausal women. Individuals with total serum (s)-calcium levels of 2.55 mmol/L or more at screening were diagnosed with pHPT when subsequent analysis supported inappropriately elevated intact parathormone (PTH) levels in relation to even normal s-calcium levels. The arbitrary diagnostic criteria were validated by parathyroidectomy. Herein we reinvestigated biochemical signs of pHPT in women not diagnosed with pHPT due to s-calcium 2.50 to 2.54 mmol/L (group A, n = 160) at screening or due to appropriate PTH levels on two occasions after screening (group B, n = 70). Altogether, 99 women in group A and 47 in group B underwent reinvestigation 8.8 years after screening when they were 65 to 84 years old. The s-calcium levels averaged 2.56 mmol/L and had increased in group A (mean 0.04 mmol/L) and decreased in group B (mean 0.05 mmol/L). A total of 48 and 18 females (48%, 38%), respectively, met the previously validated criteria of pHPT. Altogether 21% of them were hypercalcemic (range 2.60-3.12 mmol/L). Subgroup analysis showed that PTH had not increased with time (n = 47) and that atherogenic blood lipids, but not glucose levels, were similar in pHPT patients and matched controls (n = 37). Assuming the existence of pHPT already at screening, the prevalence of pHPT could be adjusted to 3.4%. Even the most liberal diagnostic criteria utilized at pHPT screening seemed to underdiagnose the disease by inefficient cutoff limits for s-calcium and PTH. Because one-fifth of the women with pHPT progressed to hypercalcemia, long-term follow-up is advocated for those with s-calcium in the upper normal range.
Aged↗
Neutropenic enterocolitis: a serious complication during the treatment of acute leukemias.
Neutropenic enterocolitis (NE) is a severe gastrointestinal complication in patients who undergo aggressive chemotherapy. It is a necrotizing inflammation of the cecum, colon, and the terminal part of the ileum. The serious clinical state of NE patients requires very frequent surgical consultations; however, in a few particular cases of NE, e.g., perforation of the bowels, a surgical intervention is necessary. Here, we report on six cases of NE in patients with acute leukemias. The patients were all women aged 21-55 years. Two of them had acute myeloid leukemia and four had lymphoblastic leukemia. NE occurred 7-10 days after the completion of chemotherapy, during the neutropenic phase. They represented a typical picture of NE: two of them died because of septic shock; five patients had subileus with irritation of the peritoneum; and one had hepatosplenic abscesses confirmed 6 months later by post-mortem examination. In each case, a surgical opinion was required. None of these patients were operated on. We present a report summarizing our experience and problems with six patients who had a clinical picture of NE and offer a short review of the current literature on the subject.
Abdominal Neoplasms↗
Successful treatment of refractory autoimmune thrombocytopenia with rituximab and cyclosporin A in a patient with chronic granulomatous disease.
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Adolescent↗
P-glycoprotein expression does not change the apoptotic pathway induced by curcumin in HL-60 cells.
PURPOSE: One of the mechanisms responsible for the multidrug resistance (MDR) phenotype of cancer cells is overexpression of so-called ATP-dependent drug efflux proteins: the 170-kDa P-glycoprotein (P-gp) encoded by the MDR1 gene and the 190-kDa multidrug resistance-associated protein 1 encoded by the MRP1 gene. The purpose of the present study was to verify the hypothesis postulating that P-gp expression, apart from enabling drug efflux, confers on the cells resistance to apoptosis by inhibiting caspase-8 and caspase-3. MATERIALS AND METHODS: Human HL-60 cells, either drug-sensitive or with the MDR phenotype caused by overexpression of P-gp (HL-60/Vinc) or MRP1 (HL-60/Adr), were treated with the natural dye curcumin at 50 micro M or with UVC to induce apoptosis. Symptoms of cell death were assessed by morphological observation after Hoechst staining, DNA fragmentation was measured by flow cytometry and the TUNEL method, and caspase-8 and caspase-3 activation and cytochrome c release from mitochondria were measured by Western blotting. RESULTS: Curcumin induced cell death in HL-60 cells, both sensitive and with the MDR phenotype, which could be classified as caspase-3-dependent apoptosis, together with cytochrome c release, activation of caspase-3 and oligonucleosomal DNA fragmentation. No active caspase-8 was detected. Also UVC caused caspase-3 activation in both the sensitive and the MDR HL-60 cells. CONCLUSIONS: Our findings show that there was no correlation between P-gp expression and resistance to caspase-3-dependent apoptosis induced by curcumin and UVC, at least in HL-60 cells. However, we cannot exclude the possibility of parallel P-gp expression and caspase-3 inhibition in some other cell lines, as cancer cells can acquire many different apoptosis-resistance mechanisms.
ATP Binding Cassette Transporter, Subfamily B, Mem↗