Biomedical subjects

H Christensen

Publications and source records attributed to H Christensen.

At least 91 records · Page 5Linked to original sources

PubMed2000

The influence of experimental muscle pain on motor unit activity during low-level contraction.

In the present study we compared motor unit (MU) activity in a painful extensor carpi ulnaris (ECU) muscle to that of a pain-free control. According to the pain adaptation model the activity of the painful ECU muscle may be inhibited and its antagonist activity increased during wrist extension performed as a pre-defined low-force ramp. The pre-defined low force may then be maintained by increased activity in the pain-free synergist muscles such as the extensor carpi radialis (ECR) muscle. Nine females (31-47 years old) participated in the study. Maximal voluntary contraction (MVC) of the wrist extensors was performed. A catheter was inserted into the ECU muscle to allow the injection of hypertonic saline to evoke muscle pain, and a concentric needle was inserted for the recording of MU activity. Surface electromyograms were recorded from a synergist and an antagonist (ECR and flexor carpi radialis) to the painful ECU muscle. A force ramp of isometric wrist extensions up to 10% MVC, with a force increase of 1% MVC x s(-1), were performed followed by 60 s of sustained contraction at 10% MVC. The number of MUs recruited was almost identical for baseline and with pain, and no effect of experimental muscle pain was found on the properties of the MUs (amplitude, area) or their firing characteristics (mean firing rate, firing variability) during low-force ramp contraction. During the sustained 10% MVC, no effect of pain was found for concentric or surface EMG of the forearm muscles. At low force levels no pain-induced modulations were found in MU activity, when the mechanical condition was similar to that of a control situation.

Adult↗

PubMed2000

Experimental muscle pain modulates muscle activity and work performance differently during high and low precision use of a computer mouse.

The aim was to investigate the influence of experimental muscle pain on performance and upper extremity muscle activity during occupational work requiring different levels of precision. Experimental muscle pain was induced by infusing hypertonic saline (0.3 ml, 5% NaCl) into the extensor carpi ulnaris (ECU) muscle. The same amount of isotonic saline was infused on a separate day to act as a control. Tasks requiring use of a computer mouse with high and low levels of precision were performed during the two sessions. Electromyographic (EMG) activity was measured from the ECU, the flexor carpi radialis (FCR) and the trapezius muscles. A group of 13 men participated in the study. Performance measured as work cycle time, cursor movements on the screen, and velocity of cursor movement were unaffected by muscle pain. The ECU muscle pain did not modulate EMG profiles of either the trapezius or FCR muscles either during high or during low precision work. During the low precision work the painful ECU muscle showed lower EMG activity in specific phases of the work cycle (highest activity phases) compared to the control session (P<0.05), whereas during the high precision work, experimental pain had no effect on the activity of the ECU muscle. In conclusion experimental muscle pain seems to modulate motor control differently depending on the precision level of the task. This may be of importance for our understanding of why some tasks lead to chronic musculoskeletal disorders.

Adult↗

PubMed2000

Non-linear relationships in associations of depression and anxiety with alcohol use.

BACKGROUND: Many studies have demonstrated co-morbidity of alcohol abuse/dependence with mood and anxiety disorders but relatively little is known about anxiety and depression across the full continua of alcohol consumption and problems associated with drinking. METHODS: Participants from a general population sample (N = 2725) aged 18-80 years completed the Alcohol Use Disorders Identification Test (AUDIT) and four measures of negative affect (two depression and two anxiety symptom scales) included in a self-completion questionnaire. RESULTS: High consumption, AUDIT total score, and AUDIT problems score were associated with high negative affect scores in participants under 60 years old (ORs in the range 1.80-2.83). Graphical and statistical analyses using continuous measures of alcohol use/problems and negative affect identified non-linear relationships where abstainers and occasional drinkers, as well as heavy and problem drinkers, were at risk of high anxiety and depression levels. This pattern, however, was not found in those aged > or = 60 years. The U-shaped relationship was not an artefact of abstainers being typical of the general population in their distribution of negative affect. CONCLUSIONS: Studies of co-morbidity should acknowledge the possibility of non-linear associations and employ both continuous and discrete measures. Abstainers, as well as heavy drinkers, are at increased risk of symptoms of depression and anxiety disorders. Psychosocial factors may play a role in the U-shaped relationship between alcohol consumption and mortality.

Adolescent↗

PubMed2000

Informant ratings of cognitive decline in old age: validation against change on cognitive tests over 7 to 8 years.

BACKGROUND: Informant questionnaires on cognitive decline are increasingly used as screening tests for dementia. Informants can provide a longitudinal perspective that is not possible with cognitive screening tests administered at one point in time. However, there are limited data on the validity of such questionnaires when judged against longitudinal change on cognitive tests. METHODS: A community sample of elderly people aged > or = 70 was assessed on cognitive tests at baseline and after a follow-up of 7-8 years. The participants were given the Mini-Mental State Examination and tests of episodic memory and mental speed. At follow-up, the short-form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) was completed by informants for 287 of the participants. RESULTS: Elderly people who were rated by informants as having moderate or severe decline had declined significantly on cognitive tests. The IQCODE correlated as highly with cognitive test change scores as these change scores correlated with each other. CONCLUSIONS: The IQCODE is a valid way of assessing cognitive decline when assessment can be carried out only at one point in time.

Age Factors↗

PubMed2000

Predicting anxiety and depression from personality: is there a synergistic effect of neuroticism and extraversion?

In a longitudinal study of college students, B. S. Gershuny and K. J. Sher (1998) found that high neuroticism and low extraversion had a synergistic effect in predicting anxiety and depression 3 years later. This article attempted to replicate their finding using data from 2 community samples: (a) a cross-sectional survey of 2,677 persons aged 18-79 years, and (b) a longitudinal study in which 441 persons aged 70 or older were followed over 3-4 years. Both studies found that neuroticism predicted anxiety and depression, but there were no Neuroticism x Extraversion interaction effects. These results cast doubt on the generalizability of the original findings.

Adolescent↗

PubMed2000

Risk factors for depression and anxiety in abstainers, moderate drinkers and heavy drinkers.

AIMS: To identify risk factors for depression and anxiety that are more prevalent in abstainers than in moderate drinkers and to estimate their contribution to U-shaped relationships of depression and anxiety with alcohol consumption. DESIGN: Cross-sectional general population sample. SETTING: Canberra, Australia. PARTICIPANTS: 2725 subjects completed questionnaires, including 1128 men and 1258 women aged 18-59 years. MEASUREMENTS: Consumption categories from AUDIT quantity/frequency items: (1) non-drinkers (no alcohol in the past year), (2) occasional drinkers (monthly or less), (3) lower-level drinkers (up to 14 standard drinks per week for men and seven for women), (4) higher-level drinkers (up to 28 and 14 standard drinks per week, respectively), and (5) those drinking at hazardous or harmful levels (over 28 and 14 standard drinks per week, respectively). Goldberg and DSSI/sAD depression and anxiety scales. A range of demographic, socio-economic, socio-environmental and personality factors. FINDINGS: Non-drinkers were more likely than lower-level drinkers to have low status occupations, poor education, current financial hardship, poor social support and recent stressful life events, and scored lower on extraversion, fun-seeking and drive. Many of these characteristics also applied to hazardous/harmful drinkers. In multivariate models, these risk factors accounted for a substantial part of the higher depression and anxiety scores of non-drinkers and occasional drinkers relative to lower-level drinkers. CONCLUSIONS: Abstainers have a range of characteristics known to be associated with anxiety, depression and other facets of ill health, and these factors may contribute significantly to their elevated levels of depression and anxiety.

Adolescent↗

PubMed2000

16S to 23S rRNA spacer fragment length polymorphism of Salmonella enterica at subspecies and serotype levels.

The variation in the lengths of the internal transcribed spacer (ITS) between 16S and 23S rRNA genes of 101 strains representing 58 serotypes of Salmonella enterica (used for Salm. choleraesuis) subsp. enterica (I), salamae (II), arizonae (IIIa), diarizonae (IIIb), houtenae (IV) and indica (VI) was used for typing by PCR amplification. Ten fragment lengths were observed by denaturing polyacrylamide gel electrophoresis on an automatic DNA sequencer resulting in 21 unique fragment patterns. Ten out of the 58 serotypes showed specific patterns but 48 serotypes were not fully differentiated. More than one ITS pattern was observed in seven serotypes. Five of the 21 fragment patterns contained representatives of more than one subspecies. Under non-denaturing electrophoresis conditions, serotype specificity was obtained but precise ITS fragment length determination was not possible. DNA sequence comparison between ITSs of individual rrn operons is needed to further interpret ITS diversity within Salm. enterica at serotype and subspecies levels.

Bacterial Typing Techniques↗

PubMed2000

Growth hormone treatment increases transmural colonic growth in GH-deficient dwarf rats.

Growth hormone (GH) has been implicated as an important factor in the growth regulation of several visceral organs including the gastrointestinal tract. Our aim was to study the effects of GH administration on colonic growth in dwarf rats with an isolated GH deficiency. Dwarf rats were treated with recombinant human growth hormone (rhGH; 2.0 mg/kg/day) for four weeks and compared with saline treated dwarf rats and rats with normal pituitary function. The colonic wall composition was measured by means of stereological techniques. RhGH treatment of the dwarf rats increased body weight by 80% and proximal and distal colon weight by 63% and 90%, when compared with placebo treated dwarf rats (P< 0.01). The weight of the proximal colonic mucosa increased by 83% (P< 0.01), submucosa by 78% (P< 0.05), and the muscularis propria by 51% (P< 0.001) in rhGH treated dwarf rats compared with dwarf controls. The weight of the distal colonic mucosa increased by 88% (P< 0.01), submucosa by 88% (P< 0.05) and the muscularis propria by 58% (P< 0.05) compared with dwarf controls. The growth of mucosa involved all mucosal layers, with a 73 and 92% increase in the proximal and distal colon luminal surface area respectively (P< 0.001, P< 0.01). The food consumption, expressed as g/day/100 g BW was 13% higher in dwarf rats receiving rhGH than in placebo treated rats (P< 0.05) and normal control rats (P< 0.05). When weights of the GI tract compartments are corrected for the increase in body weight the effects of GH treatment were small or non-significant. RhGH administration in GH deficient dwarf rats induces visceral growth with a pronounced increase in colonic luminal surface area and growth of all layers of the colonic wall. These findings confirm the important role of GH in the regulation of intestinal growth.

Animals↗

PubMed2000

The Internet and mental health literacy.

OBJECTIVE: This paper describes the informational and treatment opportunities offered by the Worldwide Web (WWW) and comments on the advantages, disadvantages and potential dangers of its role in mental health and mental health research. METHOD: Two perspectives are taken: (i) the impact of the Web from the point of view of the clinician (the practitioner view) and (ii) the impact of the Web on the public's knowledge of mental health (mental health literacy; the community or public health view). These perspectives are applied to two areas of impact: (i) information and knowledge; and (ii) treatment and self-help. RESULTS: The Web, due to its accessibility, has advantages in providing access to information, online therapy and adjunctive therapy in mental health. Problems include information overload, poor information quality, potential harm and lack of scientific evaluation. CONCLUSIONS: Issues of overload and quality of information, the potential for harm and the need to evaluate interventions are not unique to the Internet. However, the Internet has special features which make these issues more prominent. The Internet is likely to increase the general public's access to information and to decrease unmet need. Sites and interventions on the Internet need to be formally evaluated.

Austria↗

PubMed2000

Attitudes towards people with depression: effects on the public's help-seeking and outcome when experiencing common psychiatric symptoms.

OBJECTIVE: To determine whether people's attitudes towards a person who has experienced depression influence them in (i) the types of actions they take to help themselves if they experience common psychiatric symptoms, and (ii) the degree to which their symptoms improve. METHOD: A postal survey was carried out with 3,109 adults to assess attitudes and symptoms of anxiety and depression. Attitudes were assessed by questions on a depressed person's likely long-term outcome in various areas of life and whether the respondents thought the depressed person was likely to experience discrimination. A follow-up survey was carried out 6 months later with 422 persons who had a high level of symptoms at baseline. These individuals were asked about whether they had taken various actions to relieve their symptoms. RESULTS: The attitude measures did not predict use of actions which involved someone else having to know that the person had psychiatric symptoms, nor use of actions which did not. The attitude measures also did not predict change in anxiety and depression symptoms. CONCLUSIONS: The attitude measures did not predict patterns of help-seeking or outcome for people with common psychiatric symptoms. However, attitudes towards depression were quite benign and the situation could be different for people with severe mental disorders.

Adult↗

PubMed2000

Public beliefs about the helpfulness of interventions for depression: effects on actions taken when experiencing anxiety and depression symptoms.

OBJECTIVE: Previous research has shown that the public have different beliefs to mental health professionals about the helpfulness of interventions for mental disorders. However, it is not known whether the public's beliefs actually influence their behaviour when they develop psychiatric symptoms. METHOD: A postal survey of 3,109 Australian adults was used to assess beliefs about the helpfulness of a broad range of interventions for depression, as well as respondents' current level of anxiety and depression symptoms and any history of treated depression. A follow-up survey of 422 persons who had a high level of symptoms at baseline was conducted 6 months later. These people were asked which interventions they had used to reduce their symptoms. An analysis was carried out to see whether beliefs and other factors at baseline predicted subsequent use of interventions. RESULTS: There were some major discrepancies between the ranking of interventions as likely to be helpful and the ranking of how frequently they were actually used. Interventions involving mental health professionals were often rated as likely to be helpful, but were rarely used in practice. Other simple, cheap and readily available interventions were used the most frequently, but were not the most likely to be rated as helpful. The most consistent predictors across all interventions used were gender, history of treatment, current symptoms and belief in a particular intervention. Of particular interest was the finding that beliefs in the helpfulness of antidepressants predicted their use. However, beliefs were not predictors of use for all interventions. CONCLUSIONS: Beliefs about the helpfulness of an intervention did not always predict actual use of that intervention, although beliefs did predict use of antidepressants. Therefore, campaigns that change public beliefs about effective treatments may also influence actual use of treatments. Interventions preferred by professionals are not frequently used at present. Most people with anxiety and depression symptoms rely primarily on simple self-help interventions, the effectiveness of which has been little researched.

Adult↗

PubMed2000

Association of a functional polymorphism of the monoamine oxidase A gene promoter with personality and psychiatric symptoms.

A functional polymorphism in the promoter of the monoamine oxidase gene has recently been described by Sabol et al. This polymorphism is a strong candidate for associations with personality traits and psychiatric symptoms. We report relevant data from a general population sample of 850 Caucasian Australians. We found no associations with anxiety and depression symptoms, with personality traits that predispose to anxiety (neuroticism, behavioral inhibition, negative affect) or to a personality trait related to antisocial behavior (psychoticism).

Adult↗

PubMed2000

Description of Paralactobacillus selangorensis gen. nov., sp. nov., a new lactic acid bacterium isolated from chili bo, a Malaysian food ingredient.

Paralactobacillus selangorensis gen. nov., sp. nov. is described. This organism, isolated from a Malaysian food ingredient called chili bo, is an obligatory homofermentative, rod-shaped lactic acid bacterium. The G+C content is 46.1-46.2+/-0.3 mol%. Earlier 16S rRNA studies showed that this organism constitutes a new taxon distantly related to the Lactobacillus casei-Pediococcus group. A phenotypic description that distinguishes Paralactobacillus selangorensis from other genera of lactic acid bacteria is presented. The type strain of Paralactobacillus selangorensis is LMG 17710T.

Acetic Acid↗

PubMed2000

DNA-DNA hybridization determined in micro-wells using covalent attachment of DNA.

The present study was aimed at reducing the time and labour used to perform DNA-DNA hybridizations for classification of bacteria at the species level. A micro-well-format DNA hybridization method was developed and validated. DNA extractions were performed by a small-scale method and DNA was sheared mechanically into fragments of between 400 and 700 bases. The hybridization conditions were calibrated according to DNA similarities obtained by the spectrophotometric method using strains within the family Pasteurellaceae. Optimal conditions were obtained with 300 ng DNA added per well and bound by covalent attachment to NucleoLink. Hybridization was performed with 500 ng DNA, 5% (w/w) of which was labelled with photo-activatable biotin (competitive hybridization) for 2.5 h at 65 degrees C in 2 x SSC followed by stringent washing with 2 x SSC at the same temperature. The criteria for acceptance of results were a maximum of 15% standard deviation, calculated as a percentage of the mean for four replicate micro-wells, and that DNA similarities were not significantly different in at least two independent experiments. The relationship between DNA similarities obtained by the micro-well method (y) and by the spectrophotometric method (x) was y = 0.534x+30.6, when these criteria had been applied to 23 pairs of strains of Actinobacillus species, avian [Pasteurella] haemolytica-like bacteria and Mannheimia species. The correlation (Pearson) between DNA similarities obtained by interchange of strains used for covalent binding and hybridization was 0.794. Significantly lower DNA similarities were observed by the spectrophotometric compared with the micro-well method for three pairs of hybridizations. After removal of these data, the relationship between DNA similarities obtained by the micro-well and spectrophotometric methods improved to y = 0.855x + 11.0. It was found that the accuracy and precision of the micro-well method was at the same level as that of the spectrophotometric method, but the labour and analysis time were reduced significantly. The use of hybridization in the micro-well format will allow DNA-DNA hybridizations to be carried out between all strains selected for a particular taxonomic study, in order to construct complete data matrices and improve species definition.

Animals↗

PubMed2000

Polyphasic taxonomic approach in the description of Alishewanella fetalis gen. nov., sp. nov., isolated from a human foetus.

A taxonomically unique bacterium is described on the basis of a physiological and biochemical characterization, fatty acid profiling and sequence analyses of 16S rRNA and gyrase B (gyrB) genes. This non-motile, non-fermentative bacterium was isolated from a human foetus in Uppsala, Sweden, and originally misidentified as a Shewanella putrefaciens by conventional biochemical testing. The bacterium grew well at mesophilic temperatures with optimum growth at 37 degrees C. It was facultatively anaerobic and utilized various electron acceptors (trimethylamine oxide, nitrate, nitrite and thiosulphate). The dominant fatty acids were 17:1B, 16:1 cis9, 17:0 and 16:0. Fatty acids 13:0 iso and 15:0 iso, which have been found to be typical of Shewanella species were not detected. The G+C content of the DNA was 50.6 mol%. Phylogenetic analysis of the 16S rRNA gene sequence revealed a clear affiliation with members of the gamma subclass of the Proteobacteria. No relationship was seen with any of the established genera in the gamma subclass of the Proteobacteria, although a distinct relationship with Vibrionaceae was observed. That the bacterium represents a novel bacterial genus distinct from Vibrionaceae was also supported by gyrB sequence analysis. Considering the source and close proximity to the genus Shewanella, the name Alishewanella fetalis gen. nov., sp. nov. is proposed, for which the type strain is strain CCUG 30811T.

Autopsy↗

PubMed2000

Sites for depression on the web: a comparison of consumer, professional and commercial sites.

OBJECTIVE: To provide information on the range of treatments for depression provided by commercial, professional and consumer web sites. METHODS: An audit of the 21 most popular depression sites on the world wide web undertaken from March 1999 to July 1999, in Canberra, ACT. Treatment types and categories of treatment were compared among commercial, professional and consumer web sites. RESULTS: A total of 53 treatments or treatment types were mentioned. The number of treatments mentioned per site ranged from 2 to 38. Antidepressant medication and psychotherapy were noted by almost all sites. Consumer sites mentioned psychological therapies less frequently but did not mention dietary supplements or complementary treatments more frequently. CONCLUSIONS AND IMPLICATIONS: Consumer web sites provide a point of comparison to those from commercial or professional sources. They provide a voice to inform psychiatrists and GPs about preferred treatments and side effects and to alert researchers to areas that need formal investigation.

Analysis of Variance↗

PubMed2000

Acute response to precision, time pressure and mental demand during simulated computer work.

OBJECTIVES: The electromyographic (EMG) activity of shoulder and forearm muscles was recorded during a standardized computer task with different combinations of time pressure, precision demands, and mental demands to study the interaction of these factors and their effect on muscular response during simulated computer work. METHODS: The computer task lasted 5 minutes, and it was performed by 14 female computer-aided design (CAD) operators during 8 exposure combinations that differed with respect to time pressure, precision demand, and mental demand. Performance (number of produced drawings, mouse clicks, and errors) were recorded. The EMG activity was recorded from the trapezius, infraspinatus, deltoid, and extensor digitorum muscles. An electrogoniometer was used to measure wrist postures and movements. RESULTS: High time pressure (combined with low precision and low mental demands) resulted in higher EMG activity for all the muscles and in a small increase in the number of produced drawings. High precision demands caused a large reduction in the number of produced drawings, but not always a change in EMG activity. High precision demands and high mental demands led to no change or a reduction in muscle activity because the number of drawings was greatly reduced. CONCLUSIONS: The interaction between work pace and other exposure factors must be taken into account when the effects of changes in exposure demands on muscular response are predicted. Only then can it be predicted whether changing demands will constitute a risk of developing musculoskeletal disorders.

Adult↗

PubMed2000

Extensive metabolism of diltiazem and P-glycoprotein-mediated efflux of desacetyl-diltiazem (M1) by rat jejunum in vitro.

The objective of this in vitro study was to investigate both the intestinal metabolism and transport of diltiazem (DTZ) and its major metabolites in rat jejunum. Metabolism experiments were performed with everted sacs, whereas sheets mounted in a symmetrical twin chamber system were used in transport studies. DTZ was rapidly desacetylated by the rat jejunum to the principle metabolite desacetyl-diltiazem (M1). In addition, minor amounts of N-demethyl-diltiazem and desacetyl-N-demethyl-diltiazem were formed. Due to the rapid desacetylation, it proved difficult to study the transport of DTZ in this model. However, the primary metabolite M1 was shown to be subjected to P-glycoprotein (Pgp)-mediated efflux. The flux rate of M1 was 6- to 7-fold higher from the serosal to the luminal compartment than in the opposite direction. Both coadministration of verapamil and Pgp monoclonal antibody dose dependently increased luminal-to-serosal flux and decreased serosal-to-luminal flux. In conclusion, rat jejunum metabolizes DTZ extensively in vitro, and the major primary metabolite M1 is subjected to Pgp-mediated efflux.

ATP Binding Cassette Transporter, Subfamily B↗