Resolving the challenges of producing small-bore tubing

Experience shows that sufficient time and resources must be allocated to writing a specification. It is essential to be clear about the intended use of the tubing. Once the preliminary specification has been compiled, trial and error is often a necessary part of the process of making a successful product. Finally, all polymers are affected by the environment and their previous history.

Nuclear insertions help and hinder inference of the evolutionary history of gorilla mtDNA

Numts are fragments of mitochondrial DNA (mtDNA) that have been translocated to the nucleus, where they can persist while their mitochondrial counterparts continue to rapidly evolve. Thus, numts represent 'molecular fossils' useful for comparison with mitochondrial variation, and are particularly suited for studies of the fast-evolving hypervariable segment of the mitochondrial control region (HV1). Here we used information from numts found in western gorillas (Gorilla gorilla) and eastern gorillas (Gorilla beringei) to estimate that these two species diverged about 1.3 million years ago (Ma), an estimate similar to recent calculations for the divergence of chimpanzee and bonobo. We also describe the sequence of a gorilla numt still possessing a segment lost from all contemporary gorilla mtDNAs. In contrast to that sequence, many numts of the HV1 are highly similar to authentic mitochondrial organellar sequences, making it difficult to determine whether purported mitochondrial sequences truly derive from that genome. We used all available organellar HV1 and corresponding numt sequences from gorillas in a phylogenetic analysis aimed at distinguishing these two types of sequences. Numts were found in several clades in the tree. This, in combination with the fact that only a limited amount of the extant variation in gorillas has been sampled, suggests that categorization of new sequences by the indirect means of phylogenetic comparison would be prone to uncertainty. We conclude that for taxa such as gorillas that contain numerous numts, direct approaches to the authentication of HV1 sequences, such as amplification strategies relying upon the circularity of the mtDNA molecule, remain necessary.

Rivers influence the population genetic structure of bonobos (Pan paniscus)

Bonobos are large, highly mobile primates living in the relatively undisturbed, contiguous forest south of the Congo River. Accordingly, gene flow among populations is assumed to be extensive, but may be impeded by large, impassable rivers. We examined mitochondrial DNA control region sequence variation in individuals from five distinct localities separated by rivers in order to estimate relative levels of genetic diversity and assess the extent and pattern of population genetic structure in the bonobo. Diversity estimates for the bonobo exceed those for humans, but are less than those found for the chimpanzee. All regions sampled are significantly differentiated from one another, according to genetic distances estimated as pairwise FSTs, with the greatest differentiation existing between region East and each of the two Northern populations (N and NE) and the least differentiation between regions Central and South. The distribution of nucleotide diversity shows a clear signal of population structure, with some 30% of the variance occurring among geographical regions. However, a geographical patterning of the population structure is not obvious. Namely, mitochondrial haplotypes were shared among all regions excepting the most eastern locality and the phylogenetic analysis revealed a tree in which haplotypes were intermixed with little regard to geographical origin, with the notable exception of the close relationships among the haplotypes found in the east. Nonetheless, genetic distances correlated with geographical distances when the intervening distances were measured around rivers presenting effective current-day barriers, but not when straight-line distances were used, suggesting that rivers are indeed a hindrance to gene flow in this species.

Association between a deletion/insertion polymorphism in the alpha2B-adrenergic receptor gene and insulin secretion and Type 2 diabetes. The Finnish Diabetes Prevention Study

AIMS/HYPOTHESIS

Impaired insulin secretion has a strong genetic component. In this study we investigated whether the 12Glu9 polymorphism in the gene encoding the alpha2B-adrenergic receptor ( ADRA2B) is associated with insulin secretion and/or the incidence of Type 2 diabetes in individuals with impaired glucose tolerance.

METHODS

We investigated a total of 506 subjects with impaired glucose tolerance participating in the Finnish Diabetes Prevention Study (DPS). Participants were randomly assigned to an intervention group or a control group. Anthropometric measurements and an oral glucose tolerance test were performed at baseline and at annual follow-up. In a subgroup of patients (n=83), a frequently sampled intravenous glucose tolerance test (FSIGT) was performed at baseline.

RESULTS

All patients had similar anthropometric measurements and insulin and glucose levels at baseline. Multiple logistic regression analysis revealed significant interaction (p=0.003) between study group and genotype across the entire study population. In the control group, subjects with the Glu9 allele had an increased risk of developing Type 2 diabetes compared with subjects with the Glu12/12 genotype (odds ratio [OR]=2.68, 95% CI 1.02-7.09, p=0.047 for Glu12/12, and OR=5.17, 95% CI 1.76-15.21, p=0.003 for Glu9/9). This increased risk was not observed in the intervention group, who showed significant weight loss during the trial. In the subgroup who underwent the FSIGT, subjects with the Glu9/9 genotype showed the lowest acute insulin response (p=0.005 for trend).

CONCLUSIONS/INTERPRETATION

The 12Glu9 polymorphism of ADRA2B is associated with impaired first-phase insulin secretion and may predict the development of Type 2 diabetes in subjects with impaired glucose tolerance who are not subjected to a lifestyle intervention.

Common polymorphisms in the genes regulating the early insulin signalling pathway: effects on weight change and the conversion from impaired glucose tolerance to Type 2 diabetes. The Finnish Diabetes Prevention Study

AIMS/HYPOTHESIS

Type 2 diabetes is a complex disorder with strong heritability. The aim of our study was to investigate whether common polymorphisms in the genes regulating the early insulin signalling pathway (insulin; A-23T, insulin-like growth factor 1 receptor [IGF-1R]; GAG1013GAA, plasma cell membrane glycoprotein 1 [PC-1]; K121Q, insulin receptor substrate [IRS-1]; G972R, insulin receptor substrate 2 [IRS-2]; G1057D and phosphatidylinositol 3-kinase p85 alpha [PI3K]; M326I) affect the weight change and development of Type 2 diabetes in the Finnish Diabetes Prevention Study.

METHODS

We screened for the polymorphisms in 490 overweight subjects with impaired glucose tolerance whose DNA was available from the Finnish Diabetes Prevention Study. These subjects were randomly allocated into a control group and an intervention group characterised by intensive, individualised diet and exercise.

RESULTS

In carriers of the GAA1013GAA genotype of IGF-1R, the R972 allele of IRS-1 and the D1057D genotype of IRS-2, lifestyle intervention did not lead to significant differences in weight loss between the intervention and control groups, implying a role of these risk genotypes in the regulation of body weight. We observed a statistically significant difference in the conversion rate from IGT to diabetes between the genotypes of the IGF-1R gene (GAG1013GAG: 18.6%, GAG1013GAA: 10.4%, GAA1013GAA: 19.5%, p=0.033). Common polymorphisms in the insulin, PC-1 and PI3K genes did not regulate weight change or conversion to diabetes.

CONCLUSIONS/INTERPRETATION

The common polymorphisms of the IGF-1R, IRS-1 and IRS-2 genes may modify the weight change response to a lifestyle intervention but not the conversion from IGT to Type 2 diabetes, whereas IGF-1R may also regulate the risk of developing Type 2 diabetes.

The effects of the Pro12Ala polymorphism of the PPARgamma-2 gene on lipid metabolism interact with body size at birth

Body size at birth is an indicator of the intrauterine environment. The effects of the Pro12Pro genotype and the 12Ala allele of the PPARgamma-2 gene on glucose and insulin metabolism in adult life depend on body size at birth. A low birth weight is associated with insulin resistance and type 2 diabetes. The peroxisome proliferator-activated receptor-gamma (PPARgammas) are also regulators of adipocyte differentiation, and the PPARgamma-2 gene could also contribute to the development of dyslipidemia. Therefore, the effects of the Pro12Ala polymorphisms of the PPARgamma-2 gene on lipid metabolism were measured in 476 elderly persons whose birth weight was known. The Ala12 allele was associated with increased serum total, low-density lipoprotein (LDL), and non-high-density lipoprotein (non-HDL) cholesterol concentrations but only among those who had birth weights below 3000 g. These interactions between the effects of the PPARgamma-2 gene on adult traits and the effects of birth weight may be interpreted as examples of gene-environmental interactions, which underlie plasticity during development.

Obesity from cradle to grave

BACKGROUND

Obesity is known to track from early life into adult life.

OBJECTIVE

To examine the relation of obesity in adult life to growth and living conditions during childhood.

DESIGN

Birth cohort study.

PARTICIPANTS

A total of 4515 people (2135 men and 2380 women) who were born at Helsinki University Central Hospital between 1934 and 1944, who attended child welfare clinics and were still resident in Finland in the year 2000.

MEASUREMENTS

Incidence of obesity based upon lifetime maximum body mass index (BMI) ascertained from a postal questionnaire and defined as a BMI>or=30 kg/m(2). The main explanatory measurements were size at birth, childhood growth, and socioeconomic status in childhood and in adult life.

RESULTS

The cumulative incidence of obesity was 33.8% in men and 32.4% in women. The incidence rose with increasing body size at birth. From birth the mean weight and BMI of people who later became obese exceeded the average and remained above average at a statistically significant level at all ages from 6 months to 12 y. Childhood BMI was a stronger predictor of adult obesity than body size at birth. A higher maternal BMI in pregnancy was associated with a more rapid childhood growth and an increased risk of becoming obese in adult life. Higher socioeconomic status and better educational attainment were associated with a lower prevalence of obesity. There was no association between the duration of breastfeeding and later obesity.

CONCLUSIONS

These results emphasize the importance of early life factors in the pathogenesis of adult obesity.

A Comparative Study of Surfactant Adsorption on Model Surfaces Using the Quartz Crystal Microbalance and the Ellipsometer

The nature of hexaethylene glycol mono-n-tetradecyl ether (C(14)EO(6)) layers adsorbed onto different model surfaces was systematically investigated by means of QCM-D (quartz crystal microbalance-dissipation) and ellipsometry. The amount of non-ionic surfactant adsorbed is determined both at hydrophilic and hydrophobic surfaces. In particular, the substrates employed were hydrophilic silica, hydrophobized silica (using dimethyldichlorosilane), and hydrophobized gold surfaces (using 10-thiodecane and 16-thiohexadecane). It was shown that the frequency shift obtained from the QCM-D experiments results in an overestimation of the adsorbed mass. This is attributed to two different effects, viz. water that is coupled to the adsorbed layer due to hydration of the polar region of the surfactant and second water that for other reasons is trapped within the adsorbed layer. Furthermore, from the ellipsometry data the adsorbed layer thickness is determined. By combining the thickness information and the dissipation parameter (obtained from the QCM-D experiments), we note that the dissipation parameter is insufficient in describing the viscoelastic character of thin surfactant films.

Size at birth, fat-free mass and resting metabolic rate in adult life

Resting metabolic rate is an important predictor of obesity and is closely related to fat-free mass. There is evidence that fat-free mass may be partly determined during critical periods of growth before and after birth. The objective of this study was to examine the relationship between size at birth, childhood growth and fat-free mass and resting metabolic rate in adult life. 318 men and women with detailed records of body size at birth and growth during school years participated in the study. Fat-free mass correlated positively with birth weight among both sexes (r = 0.264, p < 0.001). Those having a higher birth weight had a higher fat-free mass at any adult BMI. Fat-free mass among men increased by 2.2 kg (95 % Cl 0.5 to 3.9; p = 0.01) for every kg increase in birth weight and by 1.5 kg (95 % Cl 1.3 to 1.7, p < 0.0001) for every kg/m(2) BMI in adult life. In women, fat-free mass increased by 2.7 kg (95 % Cl 1.6 - 3.9; p < 0.001) for every kg increase in birth weight and by 0.8 kg (95 % CI 0.7 to 1.0, p < 0.001) for every kg/m(2) of BMI in adult life. Height, weight and body mass index at each age from 7 to 15 years were also strongly, positively associated with fat-free mass. A negative correlation between birth weight and resting metabolic rate expressed per unit of fat-free mass (r = - 0.158; p < 0.001) was found. Fat-free mass may be determined during critical periods of muscle growth in utero and during childhood. The muscle tissue of people who had a lower birth weight is more metabolically active than those with a higher birth weight. This may protect them from the increased risk of obesity associated with low fat-free mass.

International online support to process optimisation and operation decisions

The information level at all technical facilities has developed from almost nothing 30-40 years ago to advanced IT--Information Technology--systems based on both chemical and mechanical on-line sensors for process and equipment. Still the basic part of information is to get the right data at the right time for the decision to be made. Today a large amount of operational data is available at almost any European wastewater treatment plant, from laboratory and SCADA. The difficult part is to determine which data to keep, which to use in calculations and how and where to make data available. With the STARcontrol system it is possible to separate only process relevant data to use for on-line control and reporting at engineering level, to optimise operation. Furthermore, the use of IT makes it possible to communicate internationally, with full access to the whole amount of data on the single plant. In this way, expert supervision can be both very local in local language e.g. Polish and at the same time very professional with Danish experts advising on Danish processes in Poland or Sweden where some of the 12 STARcontrol systems are running.

2,2',6,6'-Tetrachloro-4,4'-propane-2,2-diyldiphenol, 2,2',6-tribromo-4,4'-propane-2,2-diyldiphenol and 2,2',6,6'-tetrabromo-4,4'-propane-2,2-diyldiphenol

Three flame retardants with very similar molecular structures showing three different packing patterns have been studied. The crystal structure of 2,2',6,6'-tetrachloro-4,4'-propane-2,2-diyldiphenol, C(15)H(12)Cl(4)O(2), can be described as a packing of sheets. The packing shows a very short intermolecular Cl.Cl contact distance of 3.094 (2) A between pairs of molecules inside each sheet. The crystal structure of 2,2',6-tribromo-4,4'-propane-2,2-diyldiphenol, C(15)H(13)Br(3)O(2), can be described as a packing of doubly stranded helical square tubes. These square helices are interconnected through Br...Br contacts between different helices. Finally, a previously known structure, 2,2',6,6'-tetrabromo-4,4'-propane-2,2-diyldiphenol [Simonov, Cheban, Rotaru & Bels'skii (1986). Kristallografiya, 31, 397-399], C(15)H(12)Br(4)O(2), which is the most commonly used flame retardant and which has twofold rotational symmetry, has been refined in the correct absolute configuration. The structure shows large differences from the chloro analogue with regard to packing, van der Waals distances and hydrogen-bond distances.

Binding of 2,4,6-trinitrotoluene and its degradation products in a soil organic matter two-phase system

The widely used explosive 2,4,6-trinitrotoluene (TNT) and its degradation products are of large environmental concern because of their toxic properties and high concentrations encountered in contaminated soils. Batch experiments were used to study TNT* (the sum of TNT and its degradation products) bonding to dissolved (DOM) and particulate (POM) soil organic matter. Reversed-phase high performance liquid chromatography (RP-HPLC) was used as a separation technique in combination with 14C-labeled TNT to determine free TNT and TNT* bound to DOM. By use of dialysis we showed that DOM did not interfere with the HPLC analysis of free TNT. Depending on pH and total TNT concentration, the relative distribution of TNT* among water, POM, and DOM varied between 60 to 90, 10 to 30, and 0.5 to 6%, respectively, after 22 h of equilibration. The association of TNT* to DOM was strongly pH dependent and followed a nonlinear Langmuir isotherm. The association of TNT* to POM was less pH dependent and data were equally well fitted by linear and nonlinear isotherms. Particulate organic matter had 6.4 (pH 6.2) to 22 (pH 5.2) times greater capacity to bind TNT* than DOM, but the binding strength (the slope of the isotherm) was greater for DOM. The TNT degradation was enhanced with increasing concentration of soil organic matter, resulting in a stronger bonding of TNT* to DOM and POM. Based on our results, combined with other recent findings, we suggest that it is mainly the degradation products of TNT that associate with DOM and POM, and that the association with DOM is mainly of ionic character involving specific DOM sites. The greater binding capacity and a weaker, linear type of isotherm suggests a nonspecific type of partitioning in POM, possibly of hydrophobic character.

Combinations of beta cell specific autoantibodies at diagnosis of diabetes in young adults reflects different courses of beta cell damage

To explore the natural course of beta cell function in recent onset diabetes, a subgroup (n=157) of all incident cases (n=879) 15-34 years old, 1992-1993 in Sweden, and with positivity for at least one autoantibody of islet cell antibodies (ICA), glutamic acid decarboxylase antibodies (GADA) or tyrosine phosphatase antibodies (IA-2A) were followed prospectively for the first four years with annual analysis of C-peptide. The aim was to relate the course of beta cell function, measured as C-peptide, in early diabetes with the presence of different islet autoantibodies at diagnosis. We found that patients positive for ICA alone (n=11) had significantly higher C-peptide levels both at diagnosis and during the first three years compared with the other patients (n=146; p=0.022, p<0.001, p=0.004 and p=0.0022). Patients positive for GADA alone or in combination with other antibodies (n=125) had significantly lower C-peptide during the first three years after diagnosis compared with the other patients (n=32, p<0.001, p=0.0011 and p=0.0136). Patients with two or three autoantibodies had C-peptide levels similar to levels found in patients positive only for GADA. However, after four years, there were no significant differences between any of the groups of different autoantibody combinations. At diagnosis, 55% (86/157) of the patients had C-peptide levels above the lower normal range of 0.25 nmol/l, but the frequency of patients with beta cell function above this level decreased after two years to 41% (65/157; p=0.035) and after four years to 22% (35/157; p=0.0041). It is concluded that young adult diabetic patients positive only for ICA at diagnosis have a better preserved beta cell function with higher levels of C-peptide during the first three years compared with patients positive for GADA alone or in combinations with other autoantibodies.

Method for real-time detection of inorganic pyrophosphatase activity

A sensitive and simple method for real-time detection of inorganic pyrophosphatase (PPase) (EC 3.6.1.1) activity has been developed. The method is based on PPase-induced activation of the firefly luciferase activity in the presence of inorganic pyrophosphate (PPi). PPi inhibits the luciferase activity, but in the presence of PPase the luciferase activity is restored and the luminescence output increases. The assay yields linear responses between 8 and 500 mU. The detection limit was found to be 8 mU PPase. The method was used to detect the hydrolytic activity of PPases from Saccharomyces cerevisiae, Escherichia coli, and Bacillus stearothermophilus. As substrate for the luciferase, adenosine 5'-phosphosulfate can replace ATP, which is an advantage for detection of PPase activity in crude extracts containing ATP-hydrolyzing activities. The method can be used for kinetic and inhibition studies as well as for detection of PPase activity during different purification procedures.

Size at birth, childhood growth and obesity in adult life

BACKGROUND

Several studies have shown tracking of obesity from childhood to adult life. People who develop obesity in adult life may therefore have had a particular path of growth from birth through childhood.

OBJECTIVE

To examine the relationship of obesity to size at birth and childhood growth.

DESIGN

Birth cohort study.

PARTICIPANTS

A total of 5210 individuals alive and living in Finland in 1997, who were born at the Helsinki University Central Hospital between 1924 and 1933 and who went to school in Helsinki were sent a questionnaire in order to get information about adult weight and height. Detailed birth and school health records were available for all subjects. In all, 3847 responded and 3659 (1552 men and 2107 women) with adequate data are included in the present study.

MEASUREMENTS

Incidence of obesity based upon lifetime maximum body mass index (BMI) ascertained from a postal questionnaire and defined as a BMI>30 kg/m(2). The main explanatory measurements were size at birth and childhood growth in height, weight and BMI.

RESULTS

The cumulative incidence of obesity was 34.2% in men and 33.9% in women. The incidence rose with increasing birth weight and ponderal index (birthweight/length(3); P=0.01 and P=0.04, respectively). These associations were statistically significant only among males. By the age of 7 y the mean weights, heights and BMI of people who later became obese exceeded the average and remained above average at all ages from 7 to 15 y. In both men and women there was a 3-fold increase in obesity associated with a BMI>16 kg/m(2) at age 7 compared with a BMI<14.5 kg/m(2) (P<0.0001). Boys and girls whose mothers had a high BMI in pregnancy had more rapid childhood growth and an increased risk of becoming obese. This effect was stronger among boys (P=0.008).

CONCLUSIONS

Obesity is initiated early in life. These results emphasise the importance of early preventive measures for its treatment.

Heritability of leptin levels and the shared genetic effects on body mass index and leptin in adult Finnish twins

OBJECTIVES

Leptin is involved in the regulation of body weight, but the relative role of genetic and environmental influences on inter-individual variation in leptin levels is unknown.

DESIGN AND SUBJECTS

To investigate the genetic and environmental contributions to the association of body mass index (BMI) with serum leptin levels, 58 monozygotic (MZ, 27M, 31F), and 74 like-sexed dizygotic (DZ, 32M, 42F) Finnish twin pairs aged 50--76 y were studied.

MEASUREMENTS

Serum leptin levels, weight, height, hip and waist measurements.

RESULTS

Women had higher mean leptin levels (16.8+/-9.5 ng/ml), and more overall variability in leptin levels than men (6.4+/-3.5 ng/ml; P<0.0001). Leptin levels correlated highly with BMI in men and women. Among women, the MZ and DZ pairwise correlations for leptin were 0.41 (P=0.009) and 0.07 (P=0.32), respectively. Among men the MZ and DZ pairwise correlations for leptin were 0.47 (P=0.006) and 0.23 (P=0.10). Univariate twin analysis indicated that, among women, 34% and, among men, 45% of the variance in leptin can be attributed to additive genetic effects, and the remainder to unique environmental effects. Significant non-additive genetic or shared familial effects could not be demonstrated. A bivariate twin analysis of leptin and BMI indicated that the correlation between additive genetic effects on leptin and BMI was 0.79 (95% CI 0.68--0.86) in women, and 0.68 (0.51--0.80) in men. The correlation between environmental effects on leptin and BMI was 0.77 (95% CI 0.66--0.85) in women, and 0.48 (0.26--0.66) in men.

CONCLUSION

Leptin levels are moderately heritable in older adults, and a substantial proportion of genetic effects are in common on leptin levels and obesity in both women and men. International Journal of Obesity (2001) 25, 132-137

Glutamic acid decarboxylase antibodies (GADA) is the most important factor for prediction of insulin therapy within 3 years in young adult diabetic patients not classified as Type 1 diabetes on clinical grounds

BACKGROUND

Differentiation between Type 1 and Type 2 diabetes in adults is difficult at diagnosis. In this study we tested the hypothesis that autoantibodies at diagnosis are predictive for insulin treatment within 3 years in patients initially not classified as Type 1 diabetes.

METHODS

In a nationwide population-based study, blood samples were obtained from 764 patients, all diagnosed with diabetes during a 2-year period. At diagnosis, 583 (76%) were classified as Type 1, 110 (14%) as Type 2 and 71 (9.3%) could not be classified.

RESULTS

Among patients not classified as Type 1 diabetes, 52 (47%) of Type 2 and 42 (59%) of unclassified patients were positive for islet cell antibodies (ICA), glutamic acid decarboxylase antibodies (GADA) or tyrosine phosphatase antibodies (IA-2A). These patients (n=94) had lower body mass index (BMI) (p<0.001) and lower C-peptide (p<0.001) compared to the autoantibody negative patients (n=87). Compared to clinically classified Type 1 diabetes patients positive for autoantibodies (n=477), they have higher BMI (p<0.001), higher C-peptide (p<0.001) and the same levels of ICA, GADA and IA-2A. After 3 years, 93% of autoantibody positive patients initially not classified as Type 1 were on insulin. When ICA, GADA, IA-2A, BMI and C-peptide were tested in a multiple logistic regression, only GADA was significant for insulin treatment within 3 years (OR=18.8; 95% CI 1.8-191) in patients treated with diet or oral drugs at diagnosis.

CONCLUSIONS

A correct classification is difficult in adult diabetic patients. The presence of pancreatic autoantibodies, especially GADA, at diagnosis of diabetes are highly predictive for insulin therapy within 3 years from diagnosis.

Fetal and childhood growth and hypertension in adult life

The association between low birth weight and raised blood pressure has been extensively replicated. Little is known about the way childhood growth modifies the effects of low birth weight. We report on the fetal and childhood growth of 1958 men and women who received treatment for hypertension and belong to a cohort of 7086 people born in Helsinki, Finland, during 1924-1933. As expected, the men and women who developed hypertension had low birth weight (P=0.002). They were also shorter in body length at birth (P=0.02). After birth they experienced accelerated growth, so that by 7 years their heights and weights were approximately average. In a simultaneous regression, both birth length and tall height had statistically significant although opposing effects on hypertension (P=0.003 for birth length and 0.009 for height at 7 years). Accelerated postnatal growth was associated with better childhood living conditions. Children who later developed both hypertension and type 2 diabetes, rather than hypertension alone, had small placental size as well as small body size at birth, and their accelerated postnatal growth continued beyond 7 years. We suggest that hypertension may originate through retarded growth in utero followed by accelerated postnatal growth as a result of good living conditions. Retarded fetal growth leads to permanently reduced cell numbers in the kidney and other tissues, and subsequent accelerated growth may lead to excessive metabolic demand on this limited cell mass.

Tinnitus and cognitive interference: a stroop paradigm study

The aim of this study was to investigate cognitive interference caused by tinnitus by means of a modified version of the Stroop color-word test. In a mixed-design study, the performances of tinnitus patients (n = 23) and healthy controls with normal hearing (n = 23) were compared on three versions of the Stroop test: the original version, a modified version including physical-threat words, and a tinnitus version for which tinnitus words (descriptors of tinnitus; e.g., peep) were derived empirically. Matched control conditions (words) were included for all three versions, yielding a total of six screens that were presented on a computer. Participants in the control group were matched with the patients for age and gender. Main dependent measures were performance on the Stroop tests in terms of total time for completing each test. Also included were the Tinnitus Questionnaire (TQ), the Beck Depression Inventory (BDI), the state version of the Spielberger Trait State Anxiety Inventory (STAI-S), and a subtest from the Wechsler Adult Intelligence Scale measuring verbal ability. Results showed that tinnitus patients performed significantly slower on all six test conditions. The classical Stroop color-word interference was replicated in both groups. Also, an effect for physical-threat words was found for both groups. Our expected tinnitus word interference could not be established. Patients scored significantly higher than controls on the BDI and the STAI, but these measures did not correlate with the Stroop results. In conclusion, the results indicate that tinnitus patients have impaired cognitive performance overall, as measured by these variations of the Stroop paradigm, but hearing impairment cannot be excluded as a possible confounder.