Combined functional magnetic resonance imaging and skin conductance to detect localized neural response to psychological stress: a pilot study.

OBJECTIVE: This preliminary study aims at investigating the neural correlates of the stress response, intended as an emotional and cognitive response, through the description of the activation of the autonomic nervous system in a problem-solving task and central functional data; in particular, we recorded skin conductance level (SCL) and response (SCR) and observed the correlation with fMRI data. MATERIALS AND METHODS: The results obtained from 6 healthy subjects, 3 males and 3 females, aged between 18 and 45 (average = 27, SD = 7.08) who voluntarily offered to participate in the study were examined. They were previously subjected to a brief clinical psychological assessment (MMPI-2) and then to a psychophysiological evaluation. The real experiment consisted in subjecting the participants to an adapted version of the Raven's Coloured Progressive Matrices 47 (CPM 47) test to evaluate some consequences on brain activity of attention, orientation, reflex and response to stress during fMRI data acquisition and SCL-SCR recording. RESULTS: SCR changes were found to be related to the activity of different brain regions such as bilateral precentral gyrus, right inferior frontal gyrus, right medial frontal gyrus, bilateral superior frontal gyri and left anterior cingulate suggesting a specific relationship between attentive processing and autonomic arousal. CONCLUSION: The association of SC measurement with neuroimaging allows to highlight the interaction between emotional and cognitive processes: although preliminary, these results partially confirm what previously found in literature on the neural correlates of psychological stress and underline the interaction between cognitive function and autonomic arousal system during a stressful problem-solving task.

Immunological fingerprint of 4CMenB recombinant antigens via protein microarray reveals key immunosignatures correlating with bactericidal activity.

Serogroup B meningococcus (MenB) is a leading cause of meningitis and sepsis across the world and vaccination is the most effective way to protect against this disease. 4CMenB is a multi-component vaccine against MenB, which is now licensed for use in subjects >2 months of age in several countries. In this study, we describe the development and use of an ad hoc protein microarray to study the immune response induced by the three major 4CMenB antigenic components (fHbp, NHBA and NadA) in individual sera from vaccinated infants, adolescents and adults. The resulting 4CMenB protein antigen fingerprinting allowed the identification of specific human antibody repertoire correlating with the bactericidal response elicited in each subject. This work represents an example of epitope mapping of the immune response induced by a multicomponent vaccine in different age groups with the identification of protective signatures. It shows the high flexibility of this microarray based methodology in terms of high-throughput information and minimal volume of biological samples needed.

Glycogen Synthase Kinase-3ß Inhibition Links Mitochondrial Dysfunction, Extracellular Matrix Remodelling and Terminal Differentiation in Chondrocytes.

Following inflammatory stimuli, GSK3 inhibition functions as a hub with pleiotropic effects leading to cartilage degradation. However, little is known about the effects triggered by its direct inhibition as well as the effects on mitochondrial pathology, that contributes to osteoarthritis pathogenesis. To this aim we assessed the molecular mechanisms triggered by GSK3ß inactivating stimuli on 3-D (micromass) cultures of human articular chondrocytes. Stimuli were delivered either at micromass seeding (long term) or after maturation (short term) to explore "late" effects on terminal differentiation or "early" mitochondrial effects, respectively. GSK3ß inhibition significantly enhanced mitochondrial oxidative stress and damage and endochondral ossification based on increased nuclear translocation of Runx-2 and ß-catenin, calcium deposition, cell death and enhanced remodelling of the extracellular matrix as demonstrated by the increased collagenolytic activity of supernatants, despite unmodified (MMP-1) or even reduced (MMP-13) collagenase gene/protein expression. Molecular dissection of the underlying mechanisms showed that GSK3ß inhibition achieved with pharmacological/silencing strategies impacted on the control of collagenolytic activity, via both decreased inhibition (reduced TIMP-3) and increased activation (increased MMP-10 and MMP-14). To conclude, the inhibition of GSK3ß enhances terminal differentiation via concerted effects on ECM and therefore its activity represents a tool to keep articular cartilage homeostasis.

Hydroxytyrosol modulates the levels of microRNA-9 and its target sirtuin-1 thereby counteracting oxidative stress-induced chondrocyte death.

OBJECTIVE: Nutraceutical compounds, such as hydroxytyrosol (HT), have been found to exert protective effects in osteoarthritis (OA) by affecting a variety of key molecular and cellular processes in chondrocytes. However, to our knowledge, no relationship has been reported between nutraceuticals and microRNA (miR) network in OA models. Here, we identified a miR that is implicated in HT-mediated chondroprotection following oxidative stress condition by targeting sirtuin-1 (SIRT-1). METHODS: Human primary and C-28/I2 chondrocytes were pre-treated with 100 µM HT 30 min before 100 µM H2O2 addition. In silico analyses were exploited to select putative candidate miRs able to target SIRT-1 mRNA. Luciferase-based gene reporter assay was employed to demonstrate the direct link between miR-9 and its putative mRNA target. Transient transfection approach was performed to examine the effects of miR-9 levels on caspase activity, cell viability and expression of OA-related genes. RESULTS: MiR-9 was identified and confirmed as a post-transcriptional regulator of SIRT-1. MiR-9 and SIRT-1 levels showed opposite changes in chondrocytes following H2O2 and HT treatment. Moreover mir-9 silencing inhibited cell death induced by H2O2 partly through down-regulation of SIRT-1, whereas miR-9 overexpression markedly reduced the protective effect of HT. The manipulation of miR-9 levels also resulted in the modulation of OA-related gene expression, including MMP-13, VEGF and RUNX-2. CONCLUSIONS: These results show that miR-9 is a critical mediator of the deleterious and OA-related effects of oxidative stress in chondrocytes and that modulation of miR expression may be a crucial mechanism underlying the protective action of HT.

Cell death in human articular chondrocyte: a morpho-functional study in micromass model.

Chondrocyte death and loss of extracellular matrix are the central features in articular cartilage degeneration during osteoarthritis pathogenesis. Cartilage diseases and, in particular, osteoarthritis are widely correlated to apoptosis but, chondrocytes undergoing apoptosis "in vivo" more often display peculiar features that correspond to a distinct process of programmed cell death termed "chondroptosis". Programmed cell death of primary human chondrocyte has been here investigated in micromasses, a tridimensional culture model, that represents a convenient means for studying chondrocyte biology. Cell death has been induced by different physical or chemical apoptotic agents, such as UVB radiation, hyperthermia and staurosporine delivered at both 1 and 3 weeks maturation. Conventional electron microscopy was used to analyse morphological changes. Occurrence of DNA fragmentation and caspase involvement were also investigated. At Transmission Electron Microscopy, control cells appear rounding or slightly elongated with plurilobated nucleus and diffusely dispersed chromatin. Typically UVB radiation and staurosporine induce chromatin apoptotic features, while hyperthermia triggers the "chondroptotic" phenotype. A weak TUNEL positivity appears in control, correlated to the well known cell death patterns occurring along cartilage differentiation. UVB radiation produces a strong positivity, mostly localized at the micromass periphery. After hyperthermia a higher number of fluorescent nuclei appears, in particular at 3 weeks. Staurosporine evidences a diffuse, but reduced, positivity. Therefore, DNA fragmentation is a common pattern in dying chondrocytes, both in apoptotic and "chondroptotic" cells. Moreover, all triggers induce caspase pathway activation, even if to a different extent, suggesting a fundamental role of apoptotic features, in chondrocyte cell death.

Doubly Labelled Water analysis: preparation, memory correction, calibration and quality assurance for δ2H and δ18O measurements over four orders of magnitudes.

RATIONALE: The Doubly Labelled Water (DLW) method is an established way of determining the metabolic rate in humans and animals, with the advantage that the subjects need not be confined. The method, however, needs accurate determination of both the δ(2)H and the δ(18)O isotope values over a wide range of enrichments. METHODS: In this paper we describe a number of crucial steps in the process of isotope determination in body fluids. These steps include micro-distillation, correction of the measurements for sample-to-sample memory and calibration of the isotope scales over many orders of magnitudes. In contrast to several published protocols and guidelines, we also take highly enriched samples into account, as they are required for studying the metabolic rate of birds and small mammals. For our isotope scale calibration, we made a set of gravimetrically prepared, double labelled waters with known isotope values. Our quality assurance includes a scheme for easy calculation of the error propagation, leading to a reliable estimate of the analytical error in the metabolic rate. RESULTS: Our memory correction algorithm assumes the existence of three water "pools" that have different sizes and exchange rates with the injected samples. We show that the method can correct even huge memory signals, without the need for "true" values. CONCLUSIONS: With the presented building blocks, we show how to assure a reliable and accurate isotope analysis for the DLW method, both for human and for animal applications. Although our measurements have been performed using isotope ratio mass spectrometry, most of the procedures are also useful for laser spectrometry.

Stress distribution in a post-restored tooth using the three-dimensional finite element method.

Clinicians are opting ever more frequently for restorative materials which have an elastic modulus similar to that of dentin when reconstructing endodontically treated teeth. Metallic posts, which are capable of causing dangerous and non-homogenous stresses in root dentin, are slowly being abandoned. Ideal posts may be those made of various types of fibre (carbon, mineral and glass) and which are adhesively luted into the canal. Among the different methods for evaluating the mechanical behaviour of posts in root canals (progressive loads and photo-elastic technique) the finite element method (FEM) presents many advantages. The aim of this paper is to evaluate, utilizing three-dimensional analysis of the finite elements, what the effect of material rigidity, depth of insertion and post diameter could be on the stress distribution in the different components of the single tooth-post-core reconstruction unit. The results of the FEM analyses, expressed as the distribution of Von Mises stress values, has allowed us to conclude that (i) fibreglass-reinforced composite distributes stress better than titanium alloy or stainless steel; (ii) fibreglass-reinforced composite posts should be inserted as deeply as possible (but maintaining 5-6 mm of gutta-percha apical seal); (iii) fibreglass-reinforced composite post diameter does not affect stress distribution, therefore, as much radicular dentin as possible should be preserved.

Interleukin-1 gene polymorphisms and gastric cancer risk in a high-risk Italian population.

OBJECTIVES: Host genetic factors, including the IL1 gene cluster, play a key role in determining the long-term outcome of Helicobacter pylori infection. The aim of the study was to investigate the relationship between selected IL1 loci polymorphisms and gastric cancer risk in an Italian population. METHODS: In a case-control study we compared the IL1B-31 and IL1B+3954 biallelic and IL1RN pentaallelic variable number of tandem repeats (VNTR) polymorphisms in 185 gastric cancer patients and 546 controls randomly sampled from the general population of an area at high gastric cancer risk (Tuscany, Central Italy). RESULTS: Genotype frequencies of the IL1B-31 T/C, IL1B+3954 C/T, and IL1RN polymorphisms among our population controls were in Hardy-Weinberg equilibrium. In multivariate analyses, no increase in gastric cancer risk was observed for the IL1B-31*C- and IL1B+3954*T- carriers; a significant 50% increase emerged for IL1RN*2 allele carriers (OR = 1.49; 95% CI: 1.01-2.21). Analyses based on combined genotypes showed also that the association with IL1RN*2 allele was limited to two-variant allele carriers who were also homozygous for the IL1B-31*T allele (OR = 2.23; 95% CI: 1.18-4.23) with a statistically significant interaction between these two genotypes (p= 0.043). Haplotype analysis showed an increased risk for the haplotype IL1RN*2/IL1B-31*T. CONCLUSIONS: Our results suggest that host genetic factors (such as the IL1RN and the IL1B-31 polymorphisms) interact in the complex process of gastric carcinogenesis in this high-risk Italian population. Overall, this effect appears more modest than previously reported in other populations, supporting the hypothesis that other still-to-be-defined factors are important in gastric carcinogenesis. These findings might be due to a haplotype effect.

Functional neuroanatomy of the cognitive process of mapping during discourse comprehension.

We used functional magnetic resonance imaging (fMRI) to identify brain regions involved in the process of mapping coherent discourse onto a developing mental representation. We manipulated discourse coherence by presenting sentences with definite articles (which lead to more coherent discourse) or indefinite articles (which lead to less coherent discourse). Comprehending connected discourse, compared with reading unrelated sentences, produced more neural activity in the right than left hemisphere of the frontal lobe. Thus, the right hemisphere of the frontal lobe is involved in some of the processes underlying mapping. In contrast, left-hemisphere structures were associated with lower-level processes in reading (such as word recognition and syntactic processing). Our results demonstrate the utility of using fMRI to investigate the neural substrates of higher-level cognitive processes such as discourse comprehension.

Pulmonary artery occlusion and lung collapse depletes rabbit lung adenosine triphosphate.

BACKGROUND: Although the bronchial circulation has traditionally been thought to provide adequate blood flow for the lung when the pulmonary artery is obstructed, recent studies have demonstrated that pulmonary artery occlusion results in lung injury. We hypothesized that after pulmonary artery occlusion, aerobic lung metabolic function is altered. We studied the changes in the concentration of adenine nucleotides as markers of injury in the intact rabbit lung after pulmonary artery occlusion in the presence and absence of pneumothorax. METHODS: A thoracotomy was performed on the rabbits, and on occlusive microvascular clamp was placed on the left pulmonary artery. The rabbit lungs were studied after 24 h of in vivo left pulmonary artery occlusion (n = 5), 24 h of left pulmonary artery occlusion with the lung collapsed by pneumothorax (n = 6), or 24 h of lung collapse alone (n = 5). RESULTS: Adenosine triphosphate concentrations of the occluded left lung decreased dramatically at 24 h in the group with pulmonary artery occlusion and collapse (adenosine triphosphate concentration 196 +/- 32 ng/g for the left lung and 1,479 +/- 197 ng/g for the right lung; P < 0.001). There were no differences between the lungs in the rabbits undergoing occlusion alone or collapse alone. CONCLUSIONS: After pulmonary artery occlusion or lung collapse, adenine nucleotides are preserved if ventilation is continued. The increased permeability of rabbit lungs after 24 h of left pulmonary artery occlusion alone cannot be explained on the basis of depletion of high-energy phosphates. In the absence of ventilation due to lung collapse, pulmonary artery occlusion results in decreased adenosine triphosphate concentrations, demonstrating that the residual circulations (bronchial and pulmonary venous flow) are inadequate to support normal lung aerobic metabolism.

[2D TOF angio-MR of the thoraco-abdominal aorta. Technique and clinical applications]. / Angio-RM 2D TOF dell'aorta toraco-addominale. Tecnica e applicazinoni cliniche.

The diagnostic role of Magnetic Resonance Angiography (MRA) was investigated in the study of the thoracic and abdominal aorta. Thirty-two patients with different conditions were examined: the thoracic aorta was affected in 7 cases (3 aneurysms, 2 dissections, 2 tumors) and the abdominal aorta in 25 cases (21 aneurysms, 3 stenoses and 1 dissection). Moreover, 2 kinkings and 1 dextroposition of the thoracic aorta were observed as occasional findings, together with 15 abdominal aorta kinking cases. A 1.5-T superconductive magnet (Magnetom, Siemens) with circular polarization body coil and the 2D TOF (FL 18 degrees, TR 30 ms, TE 10 ms, ST 5 mm, 1-mm overlap) technique were used. The images acquired on the coronal and sagittal or parasagittal planes were rotated from -45 degrees to 45 degrees and from 60 degrees to 120 degrees during post-processing, according to MIP. Digital angiography was the gold standard in all cases, angiography and CT were the gold standards for aneurysms, and surgery for the lesions reaching the thoracic aorta. The 2D TOF technique allowed excellent visualization of both the thoracic and the abdominal aorta. In thoracic aorta conditions, MRA always identified aneurysms and assessed their relationship to epiaortic branchings. Moreover, MRA identified 2 cases of thoracic aorta dissection. In one case (1/2) MRA failed to depict aortic wall infiltration by tumor. In 21 abdominal aorta aneurysms, MRA always correctly demonstrated both the extent of the aneurysm and its relationships to renal and iliac arteries. Moreover, the thrombotic aneurysmal component was demonstrated, together with left renal vein course, which was retroaortic in 4 cases. Abnormal course, stenoses (2 cases) and dissection of the abdominal aorta were always identified by MRA.

Pulmonary artery occlusion is sufficient to increase pulmonary vascular permeability in rabbits.

Unilateral pulmonary artery obstruction (PAO) for 24-48 h, followed by reperfusion, results in pulmonary edema and lung inflammation. We hypothesized that lung injury actually occurred during the period of PAO but, because of low microvascular pressures during the period of occlusion, was not detected until perfusion was reestablished. To test this hypothesis, we studied 14 rabbits divided into three groups: group I rabbits underwent sham occlusion of the left pulmonary artery for 24 h; group II rabbits underwent PAO but were not reperfused; and group III rabbits were subjected to PAO and then reperfused for 4 h. The fluid filtration coefficient measured during a zone 3 no-flow hydrostatic stress (pulmonary arterial pressure = pulmonary venous pressure, both greater than alveolar pressure) in group I lungs was less than that of lungs in either group II or III [0.52 +/- 0.02 (SE) ml.min-1.cmH2O.100 g wet wt-1 vs. 0.94 +/- 0.11 and 0.86 +/- 0.13 for groups II and III, respectively, P less than 0.05]. The wet-to-dry weight ratio of the left lung measured after the zone 3 stress was applied for 20 min was 6.90 +/- 0.09 in group I rabbits and 9.21 +/- 0.75 and 11.75 +/- 0.44 in groups II and III, respectively (P less than 0.05). Radiolabeled microspheres demonstrated that flow to the left lung was diminished after the period of PAO (38 +/- 4, 9 +/- 5, and 2 +/- 1% of cardiac output in groups I, II, and III, respectively; P less than 0.05 for group I vs. groups II and III).(ABSTRACT TRUNCATED AT 250 WORDS)

Antibody against neutrophil adhesion improves reperfusion and limits alveolar infiltrate following unilateral pulmonary artery occlusion.

Relief of unilateral pulmonary arterial occlusion results in bilateral lung injury and results in only partial restoration of pulmonary blood flow distal to the site of occlusion. We hypothesized that the "no reflow" phenomenon was in part due to neutrophil adherence and aggregation in the pulmonary vasculature. The study was carried out in two phases. First, we studied the effect of neutrophil depletion on left lung blood flow following 24 hr of left pulmonary artery occlusion. Hydroxyurea was used to deplete circulating neutrophils to 77 +/- 18/mm3 (means +/- sem) (n = 6) as compared to 708 +/- 165/mm3 in control rabbits (n = 8). In both groups left lung blood flow immediately following reperfusion was markedly reduced at 6.4 +/- 2.2% of cardiac output in control rabbits and 7.3 +/- 2.3 in treated rabbits. However, at 4 hr, neutrophil-depleted animals had significantly greater flow (18.7 +/- 3.6 vs 8.4 +/- 2.3% for control rabbits, P less than 0.05). In both groups, flow remained substantially below the normal rabbit left lung blood flow of 39.8 +/- 2.2%. To test whether the improved reflow was due to decreased numbers of neutrophils limiting aggregation, or whether active neutrophil adherence played a role, we tested the effect of a monoclonal antibody that interferes with neutrophil adhesiveness (MoAb 60.3) on reflow and on neutrophil emigration into the alveoli. We found that MoAb 60.3 did not affect initial reflow.(ABSTRACT TRUNCATED AT 250 WORDS)

Complement activation is a secondary rather than a causative factor in rabbit pulmonary artery ischemia/reperfusion injury.

We have previously demonstrated that reperfusion of a rabbit lung in vivo after 24 h of unilateral pulmonary artery occlusion results in edema, transient leukopenia, and intravascular leukocyte aggregation. We hypothesized that complement was activated by reperfusion and that this in turn contributed to lung injury. In the preliminary phase of the study, we found that ischemia followed by reperfusion resulted in a drop in C3 to 15 +/- 10% (mean +/- SEM) of the prereperfusion value as compared with no change in a group of control animals that had undergone an identical thoracotomy but without pulmonary artery occlusion and reperfusion (p less than 0.05). We then studied three groups of animals to determine if complement depletion with cobra venom factor (CVF) prior to ischemia and reperfusion would prevent the injury. Rabbits treated with CVF but without occlusion and reperfusion did not develop significant lung edema, with left and right lung wet/dry ratios of 5.32 +/- 0.11 and 5.26 +/- 0.12, respectively. For rabbits that were not treated with CVF but underwent ischemia and reperfusion, the comparable numbers were 6.15 +/- 0.36 and 5.19 +/- 0.32 (p less than 0.05 for right versus left). For CVF-treated rabbits that underwent ischemia and reperfusion, the right/left difference persisted (6.77 +/- 0.48 versus 5.35 +/- 0.14, p less than 0.01). Immunocytochemistry documented C3 deposition in non-CVF rabbits that underwent ischemia and reperfusion but not in CVF-treated rabbits. We conclude that ischemia/reperfusion of the lung results in complement activation, but it is not a complement-dependent injury.

Bronchial circulation in pulmonary artery occlusion and reperfusion.

Obstruction of pulmonary arterial blood flow results in minimal biochemical and/or morphological changes in the involved lung. If the lung is reperfused, a syndrome of leukopenia and lung edema occurs. We used the radiolabeled microsphere technique to measure the response of the bronchial circulation in rabbits to acute pulmonary artery occlusion (PAO) and to pulmonary artery reperfusion. We found that the bronchial blood flow (Qbr) decreased from a base line of 0.37 +/- 0.10 to 0.09 +/- 0.04 (SE) ml.min-1.g dry lung-1 (P less than or equal to 0.05) after 4 h of PAO. In a separate group of animals, Qbr 24 h after PAO remained low (0.20 +/- 0.07 ml.min-1.g dry lung-1, P = 0.06). Qbr during PAO was inversely correlated with the wet-to-dry ratio after reperfusion (r = -0.68, P = 0.06). Qbr did not change during 4 h of reperfusion. We speculate that a critical level of Qbr may be necessary during PAO to prevent ischemia/reperfusion injury from occurring.

Salicylic acid causes a diuresis and natriuresis in normal and common bile-duct-ligated cirrhotic miniature swine.

In patients with liver disease, or in normal subjects who are sodium-depleted, the administration of either a nonsteroidal anti-inflammatory drug or acetylsalicylate (aspirin) has a detrimental effect on the kidney; profound renal vasoconstriction and the retention of sodium and water may occur. We observed recently that salicylate (SA), in contrast to meclofenamate (MECLO) or aspirin, caused a diuresis and natriuresis in the sodium-depleted dog. To determine if SA would similarly affect the kidneys in a cirrhotic subject, the effects of SA (40 mg/kg) and subsequent MECLO treatment (2 mg/kg) were evaluated in five normal and six common bile-duct-ligated (CBDL) miniature swine. All six CBDL animals showed signs of biliary cirrhosis and four of the six were ascitic at the time of study. SA did not significantly alter renal blood flow or glomerular filtration rate in either the normal or CBDL animals. In both groups, SA caused a significant diuresis and natriuresis. MECLO, given after SA, caused a reduction in renal blood flow in the normal but not in the CBDL animals, but did not alter glomerular filtration rate in either group. In the CBDL animals, when MECLO was given alone a significant decrease in renal blood flow occurred. MECLO abolished the SA-induced diuresis and natriuresis in the normal swine but only affected the SA-mediated natriuresis in the CBDL animals. SA significantly reduced renal prostaglandin E2 excretion in both groups. With MECLO, prostaglandin E2 excretion was reduced further in the normals but not in the CBDL animals. These data demonstrate that SA does not produce detectable renal vasoconstriction in the cirrhotic pig.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal prostaglandin E2 and F2 alpha synthesis during exercise: effects of indomethacin and sulindac.

To assess the effects of acute exercise on renal prostaglandins E2 (PGE2) and F2 alpha (PGF2 alpha) synthesis, urine collections were obtained from six women before and after 30 min of treadmill exercise at approximately 80% of their maximal oxygen consumption. After receiving a placebo for 3 days, with acute exercise, there was a significant increase only in recovery urine PGE2 concentration. Due to a decline in urine volume, PGF2 excretion was unchanged and PGF2 alpha excretion was significantly decreased by exercise. Subjects repeated the tests after 3 d of indomethacin treatment (150 mg X d-1), a known renal prostaglandin (PG) inhibitor, and 3 d of sulindac (300 mg X d-1), a non-steroidal anti-inflammatory drug which may not inhibit renal PG synthesis. Pre-exercise urine PGE2 concentrations were decreased by indomethacin but not by sulindac, whereas, PGF2 alpha concentrations were decreased by both drugs. When compared to the control test, indomethacin and sulindac had different effects on pre-exercise urine/plasma osmolality ratios and free water clearances. Neither indomethacin nor sulindac influenced the decreases in free water clearances, which were observed during the placebo tests. Exercise proteinuria was significantly increased by indomethacin but not by sulindac. In conclusion, these data demonstrate that acute exercise may stimulate renal PGE2 synthesis. During exercise, renal PG synthesis attenuates protein excretion. There also appear to be differences between indomethacin and sulindac with regard to the effects on renal PG synthesis and kidney function.

On the enzymatic basis for mutagenesis by manganese.

The effects of manganese on DNA synthesis fidelity are measured using T4 DNA polymerase. When the nucleotide analogue 2-aminopurine deoxyribonucleoside triphosphate competes against dATP at thymine sites on template DNA, the aminopurine misincorporation frequency increases from 6.3% in the presence of Mg2+ to 29.2% in the presence of Mn2+. The major cause of the increased error rate is an approximate 4-fold increase in the frequency of aminopurine misinsertions. Exonucleolytic proofreading of aminopurine is similar in the presence of Mn2+ and Mg2+. However, the excision frequency of the correct nucleotide, dAMP, is increased 2-fold with Mn2+. In experiments in which insertion and incorporation velocities of aminopurine and adenine are measured independently of each other, a 5- to 10-fold decrease in the Michaelis constant for aminopurine is observed in the presence of Mn2+ compared to a 2-fold decrease in the Km for adenine. In contrast to the marked differential reduction in the ratio of aminopurine to adenine Km values, the maximum insertion velocities of both nucleotides are reduced by similar amounts (40-fold). We suggest that the mutagenic action of Mn2+ can be attributed primarily to a significant differential increase in binding of mispaired relative to correctly paired nucleotides to the polymerase-template complex. The resulting increase in the ratio of residence times for mispaired compared with correctly paired nucleotides on the complex results in their increased frequency of misinsertion. A smaller contributing factor to Mn2+-induced mutagenesis is a loss of proofreading specificity. We propose that the losses in both the specificities of nucleotide insertion and excision (proofreading) share a common molecular origin in which nucleotides are bound in the presence of Mn2+ in distorted configurations at the polymerase insertion and excision active sites resulting in increased nonspecific enzyme-substrate binding forces at the expense of template-substrate base pair specific hydrogen bonds.

Multiple myeloma in cosmetologists.

In an hypothesis-generating activity, data in a population-based cancer registry were analyzed according to occupation and industry. The number of cases of multiple myeloma was found to be excessive for females in the occupation "cosmetologists, hairdressers and manicurists." Race did not explain the excess. People in this occupation have potential exposure to a number of chemicals that produce mutations in bacteria. Studies should be done to investigate the hypothesis that these chemicals cause multiple myeloma in cosmetologists.