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H Christensen

Publications and source records attributed to H Christensen.

At least 73 records · Page 4Linked to original sources
PubMed2001

The "common cause hypothesis" of cognitive aging: evidence for not only a common factor but also specific associations of age with vision and grip strength in a cross-sectional analysis.

A prominent hypothesis in cognitive aging is the existence of a common factor that is responsible for age-related deterioration in cognitive and noncognitive processes. A multiple indicators, multiple causes model was used to examine the nature of this common factor and its relationship to age, gender, and the apolipoprotein E (APOE) genotype. The common factor was modeled by using 10 indicator variables with 374 participants aged between 77.4 and 98.7 years. A latent factor was identified, with all indicators except blood pressure loading significantly. This factor could be established in 2 age strata within the sample. After controlling for the effects of gender, APOE, and level of education, direct effects of age were seen on visual functioning and grip strength. APOE was significantly associated with memory but not with the common factor. The findings suggest that a number of specific processes may operate concurrently with any common cause factor.

Aged↗
PubMed2001

Studies on the prevalence of Riemerella anatipestifer in the upper respiratory tract of clinically healthy ducklings and characterization of untypable strains.

A total of 44 bacterial strains obtained from 49 clinically healthy ducklings of different ages originating from four different farms were identified as members of the species Riemerella anatipestifer (RA) using conventional biochemical test methods. Numerical analysis of the whole-cell fatty acid patterns of these isolates resulted in two different clusters, one of which showed a similar pattern to that of the type strain of RA. Strains having a different fatty acid methyl esters (FAME)-profile (cluster II) were designated R. anatipestifer-like (RA-like). Sequencing of 16S rRNA genes of RA-like field isolates revealed 99% identity to RA. The significance of these observations are discussed. The present findings document for the first time that RA seems to represent a normal part of the pharyngeal flora of healthy Pekin ducks.

Animals↗
PubMed2001

What cognitive changes can be expected with normal ageing?

BACKGROUND: This paper briefly summarizes recent evidence on the nature of cognitive decline, the variability in individual responses to ageing, and risk factors known to affect the rate of cognitive decline. METHOD: Data from the Canberra Longitudinal Study were used to examine the course and diversity of cognitive decline. The sample consisted of 887 participants aged 70-93 years, who were examined in 1991 and followed up in 1994 and 1998. Data summarizing significant risk factors for cognitive decline were based on a review of 34 studies that examined the following predictors: education, the APOE epsilon4 allele, health, activity and blood pressure. RESULTS: Using data from participants living in the community, there is evidence that cognitive speed and memory performance decline with age, but that crystallized abilities remain largely intact in those who survive for long-term follow-up. Variability in test scores for memory and speed increases with age. There is evidence that poor health, fewer years of education, lower activity, the presence of the APOE epsilon4 allele, and blood pressure predict faster cognitive decline. CONCLUSIONS: The diversity in cognitive ageing suggests that more than one process may be operating to produce the observed cognitive outcomes. Education, good health, absence of the APOE epsilon4 allele, and activity may be protective of cognitive decline. Preventative strategies for sustaining high intellectual performance in later life may therefore be possible. These findings also speak to the need to extend analysis beyond examining mean changes in cognitive performance to an analysis based on individual differences in change.

Aged↗
PubMed2001

Fixed-dosed risperidone in mania: an open experimental trial.

The purpose of the study was to assess the efficacy and tolerance of risperidone in mania. Fourteen inpatients with a DSM-IV manic episode were treated with risperidone at a fixed daily dose of 6 mg for 4 weeks. Compliance was assured by weekly determinations of serum concentrations of risperidone. Ten out of the 14 patients completed all 4 weeks of treatment, and all of these achieved at least a 75% reduction on the Bech-Rafaelsen Mania Scale (MAS). On the other applied measures, a substantial improvement was also seen in most patients, and no worsening in any of the rating scales was observed in any patient. Five patients continued concomitant treatment with a mood stabilizer. When the results were compared with the results from a similar historic control group treated with the middle-potency typical antipsychotic zuclopenthixol at a daily dose of 20 mg under the same experimental conditions, a between group difference in mean percentage change (baseline versus endpoint) on the MAS was 34.7% (95% confidence interval = 7.9-61.6%) in favour of risperidone. Side-effect profiles were rather similar in the two treatment groups. Despite design limitations, these findings may justify the conduction of randomized controlled trials to investigate the use of risperidone in mania.

Administration, Oral↗
PubMed2001

Renal function outcome in unilateral hydronephrosis in newborn pigs. II. Function and volume of contralateral kidneys.

PURPOSE: We evaluated the compensatory response of contralateral kidney growth and function in pigs with unilateral hydronephrosis. MATERIALS AND METHODS: Unilateral partial ureteral obstruction causing severe hydronephrosis was induced at age 2 days in 12 piglets, while 10 underwent sham operation. At ages 4, 12 and 24 weeks single kidney function was assessed using 99mtechnetium diethylenetriaminepentaacetic acid differential uptake on renography combined with the glomerular filtration rate estimated from the plasma clearance of 99mtechnetium diethylenetriaminepentaacetic acid. Kidney size was measured in parallel by magnetic resonance imaging. RESULTS: At 4 weeks the glomerular filtration rate and volume of the contralateral kidneys did not differ from those in controls, although obstructed kidney function was significantly decreased. At 12 weeks the mean glomerular filtration rate plus or minus standard error of mean of the contralateral kidneys significantly increased to 1.60 +/- 0.11 versus 1.33 +/- 0.11 ml. per minute per kg. (p <0. 05), whereas kidney volume did not differ from that in sham operated controls. At 24 weeks the glomerular filtration rate and volume of the contralateral kidneys did not differ from those in controls. Glomerular filtration rate and volume of the contralateral kidneys did not correlate at 4 weeks but they correlated at 12 and 24 weeks (r = 0.94 and 0.89, respectively). CONCLUSIONS: Initially kidneys contralateral to obstructed kidneys with decreased function had no increased growth or function. Furthermore, function and volume of the contralateral kidneys were not associated at the early age. Thus, the results of our study imply that determining the size (growth) or function of the contralateral kidney at an early age does not predict function decrease in a partially obstructed kidney in this pig model.

Animals↗
PubMed2001

Is characterization of a single isolate sufficient for valid publication of a new genus or species? Proposal to modify recommendation 30b of the Bacteriological Code (1990 Revision).

From 1990 to 2000, the number of published named taxa based upon new isolates at species and genus levels in International Journal of Systematic and Evolutionary Microbiology, formerly International Journal of Systematic Bacteriology, have increased by approximately four- and sevenfold, respectively. New taxa based upon characterization of only a single isolate remained at around 40% for both categories. The Bacteriological Code (1990 Revision) has no recommendations on the number of strains required for definition of new taxa. For a few groups, a minimum number of 5-10 strains has been suggested in minimal standards. Since an exponential increase in new taxa can be expected in the future, the authors discuss problems related to naming new species and genera based upon descriptions of a single isolate and suggest that this practice is re-evaluated. It is proposed that the following should be added to Recommendation 30b of the Bacteriological Code: 'Descriptions should be based on as many strains as possible (minimum five), representing different sources with respect to geography and ecology in order to be well characterized both phenotypically and genotypically, to establish the centre (from which the type strain could be chosen) and the extent of the cluster to be named. In addition, comparative studies should be performed, including reference strains that represent neighbouring species and/or genera, in order to give descriptions that are sufficiently detailed to allow differentiation from these neighbours.'

Bacteria↗
PubMed2001

Specific detection of Pasteurella multocida in chickens with fowl cholera and in pig lung tissues using fluorescent rRNA in situ hybridization.

A Pasteurella multocida species-specific oligonucleotide probe, pmhyb449, targeting 16S rRNA was designed and evaluated by whole-cell hybridization against 22 selected reference strains in animal tissues. It differentiated P. multocida from other bacterial species of the families Pasteurellaceae and Enterobacteriaceae and also from divergent species of the order Cytophagales (except biovar 2 strains of Pasteurella avium and Pasteurella canis, which have high 16S rRNA similarity to P. multocida). The potential of the probe for specific identification and differentiation of P. multocida was further detected in formalin-fixed paraffin-embedded lung tissues from experimental fowl cholera in chickens and infections in pigs. In chicken lung tissues P. multocida cells were detected singly, in pairs, as microcolonies, and as massive colonies within air capillaries (septa and lumen), parabronchial septa, and blood vessels (wall and lumen). In pig lung, postmortem-injected P. multocida was detected in the alveoli (lumen and wall), and in both animals the bacterial cells were seen in the bronchi. The results showed that with the oligonucleotide probe pmhyb449, fluorescent in situ hybridization is a suitable and fast method for specific detection of P. multocida in histological formalin-fixed tissues. The test was replicable and reproducible and is recommended as a supplementary test for diagnosis and as a tool in pathogenesis studies of fowl cholera and respiratory tract infections in pigs due to P. multocida.

Animals↗
PubMed2001

Stroke severity determines body temperature in acute stroke.

BACKGROUND AND PURPOSE: Several studies have claimed that temperature on admission is of prognostic significance in acute stroke. Experimental studies showing that hyperthermia increases infarct size have lent credibility to this assumption. The aim of the present study was to test the hypothesis that initial body temperature is of importance for stroke outcome. METHODS: This prospective study included 725 consecutive patients, 584 with cerebral infarcts and 141 with intracerebral hemorrhages, admitted to an acute stroke unit within 6 hours of stroke onset. Time of stroke onset and time of admission were recorded. Body temperature was measured on admission and every 2 hours during the first 24 hours. Patients were divided into 2 groups on the basis of stroke severity on admission: Scandinavian Stroke Scale Score (SSS) </=25 was defined as major stroke, and SSS >25 was defined as mild to moderate stroke. RESULTS: On admission, mean body temperature was normal. In the major stroke patients, body temperature started to rise 4 to 6 hours after stroke onset. At 10 to 12 hours after stroke onset, increased body temperature was found to be related to poor outcome. In mild to moderate stroke, there was no significant rise in temperature. Initial temperature >37.5 degrees C was not related to stroke severity or stroke outcome. CONCLUSIONS: In major stroke, a significant rise in temperature occurred hours after stroke onset. Severe infarcts and intracerebral hemorrhages caused temperature to rise, whereas initially increased temperature had no influence on stroke severity. Elevated body temperature on admission within 6 hours of stroke onset had no prognostic influence on stroke outcome at 3 months.

Acetaminophen↗
PubMed2001

Memory complaints as a precursor of memory impairment in older people: a longitudinal analysis over 7-8 years.

BACKGROUND: There is considerable dispute about the validity of memory complaints. While some studies find that complaints are an early indicator of dementia or cognitive decline, there are also many studies showing that complaints are more closely associated with negative affect (depression, anxiety and neuroticism). The present paper used three-wave longitudinal data to test three hypotheses: (1) that memory complaints reflect an evaluation of present and past memory performance; (2) that memory complaints predict future memory performance; and (3) that memory complaints predict current and future negative affect. METHODS: A longitudinal study was carried out with a community sample of people aged 70 and over. Participants were assessed for memory complaints, memory performance and negative affect at three waves separated by 3.6 years and 4.0 years. There were 331 persons with data on all relevant variables. The data were analysed using structural equation modelling. RESULTS: Significant paths in the structural model were found from memory performance to future memory complaints, as well as from memory complaints to future memory performance, supporting hypotheses 1 and 2. Memory complaints were associated with current negative affect, but did not predict future negative affect. CONCLUSIONS: Memory complaints do reflect perceptions of past memory performance and are also an early manifestation of memory impairment. However, current negative affect (anxiety and depression symptoms) shows the greatest association with memory complaints.

Affect↗
PubMed2001

An analysis of motor unit firing pattern during sustained low force contraction in fatigued muscle.

In the present study motor unit (MU) firing pattern was analysed during long-term static contraction in order to see if fatigue would induce rotation of activity between different MU. Surface as well as intramuscular EMG were obtained from ten subjects during a sustained hand lift for 5 minutes after performance of a 30% MVC fatiguing contraction of the extensor carpi radialis muscle. A newly developed decomposition program constituted a powerful tool to obtain detailed knowledge of long term activity pattern of MU during low force contractions. Although the muscle was highly fatigued the majority of MU showed a continuous firing pattern after recruitment and no clear incidences of rotation were found for any of the subjects. Therefore, long term, low force contractions, as performed during many occupational work tasks, may involve continuous activation of the low threshold MU and this could have mechanical as well as metabolic implications for these muscle fibers.

Action Potentials↗
PubMed2001

Doublets in motor unit activity of human forearm muscle during simulated computer work.

Motor unit firing pattern and characteristics were analyzed during voluntary contractions as they occur during computer work. For comparison controlled standard ramp contractions were performed. Highly diverse firing patterns were identified while the MU characteristics were similar. Of special notice is the frequent occurrence of double discharges during computer like work but not during ramp contractions.

Computers↗
PubMed2000

Quality of web based information on treatment of depression: cross sectional survey.

OBJECTIVES: To evaluate quality of web based information on treatment of depression, to identify potential indicators of content quality, and to establish if accountability criteria are indicators of quality. DESIGN: Cross sectional survey. DATA SOURCES: 21 frequently accessed websites about depression. MAIN OUTCOME MEASURES: (i) Site characteristics; (ii) quality of content-concordance with evidence based depression guidelines (guideline score), appropriateness of other relevant site information (issues score), and subjective rating of site quality (global score); and (iii) accountability-conformity with core accountability standards (Silberg score) and quality of evidence cited in support of conclusions (level of evidence score). RESULTS: Although the sites contained useful information, their overall quality was poor: the mean guideline, issues, and global scores were only 4.7 (range 0-13) out of 43, 9.8 (6-14) out of 17, and 3 (0.5-7. 5) out of 10 respectively. Sites typically did not cite scientific evidence in support of their conclusions. The guideline score correlated with the two other quality of content measures, but none of the content measures correlated with the Silberg accountability score. Content quality was superior for sites owned by organisations and sites with an editorial board. CONCLUSIONS: There is a need for better evidence based information about depression on the web, and a need to reconsider the role of accountability criteria as indicators of site quality and to develop simple valid indicators of quality. Ownership by an organisation and the involvement of a professional editorial board may be useful indicators. The study methodology may be useful for exploring these issues in other health related subjects.

Cross-Sectional Studies↗
PubMed2000

Association of smoking and personality with a polymorphism of the dopamine transporter gene: results from a community survey.

In studies that used mixed volunteer samples, Lerman et al. [1999: Health Psychol 18:14-20] and Sabol et al. [1999: Health Psychol 18:7-13] reported on an association of smoking with a polymorphism of the dopamine transporter gene. We attempted to replicate this association in a nonvolunteer community sample of 861 Caucasians. No associations were found with either smoking initiation or smoking cessation. Sabol et al. [1999] also reported on an association of the dopamine transporter polymorphism with the personality trait of novelty seeking. However, we failed to find any associations with a range of personality traits, including a scale of fun seeking that correlates with novelty seeking. These negative findings suggest that either the original associations are not replicable or that any association is very small.

Adult↗
PubMed2000

COMT and DRD3 polymorphisms, environmental exposures, and personality traits related to common mental disorders.

In a community sample of 2,327 Caucasians, we tested the hypotheses that polymorphisms in the COMT and DRD3 genes are associated with personality traits conferring vulnerability to anxiety, depression, or alcohol misuse, or with current symptoms of these; and that the association is stronger in persons who also have been exposed to stressor experiences. To conserve resources and to allow replication, the genetic analysis was undertaken in two stages. For the COMT polymorphism, no statistically significant associations were found in the first sample of 862 persons. The remainder of the sample was therefore not analysed for that gene. For the DRD3 polymorphism, those in the first sample with at least one of the Ser(9) alleles had significantly higher scores in neuroticism (p=0.006) and behavioral inhibition (p=0.003). There was a trend, failing to meet the 1% significance criterion, for those with this genotype also to have higher depression and anxiety. The groups did not differ in alcohol use. In persons with the Ser(9) allele who were also exposed to stressors, there was a higher level of depression at the 5% level; and the depression level was higher in homozygotes. But when the remainder of the sample (1,465) was analysed, none of the associations reached statistical significance. We conclude that neither the COMT nor DRD3 polymorphisms are associated with anxiety, depression, or alcohol abuse. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:102-107, 2000

Catechol O-Methyltransferase↗
PubMed2000

Public belief systems about the helpfulness of interventions for depression: associations with history of depression and professional help-seeking.

BACKGROUND: Previous research has found that there are major differences between public and professional beliefs about the helpfulness of interventions for depression. The public appear to be guided by general belief systems about the helpfulness of medical, psychological and lifestyle interventions rather than by specific knowledge about what interventions are effective for depression. The present paper examines the effect that experiencing depression and receiving treatment might have on these beliefs. METHOD: The study involved a postal survey of 3109 adults from a region of New South Wales, Australia. Respondents were presented with a vignette describing a person with depression. They were asked to rate the likely helpfulness of various types of professional and non-professional help and of pharmacological and non-pharmacological interventions for the person described in the vignette. Respondents also completed the Goldberg Depression Scale and were asked whether they had ever had an episode of depression and whether they had seen a counsellor or a doctor for it at the time. Structural equation modelling was used to investigate the associations of history of depression and professional help-seeking with belief systems. RESULTS: A three-factor model was found to fit the helpfulness ratings, with factors reflecting beliefs in medical, psychological and lifestyle interventions. People who had sought help for depression were less likely to believe in the helpfulness of lifestyle interventions and more likely to believe in medical interventions. As well as these general associations with belief systems, having sought help for depression had a number of specific associations with beliefs. Controlling for general belief systems, those who had sought help were more likely to rate antidepressants, holidays, massage and new recreational pursuits as helpful, and were less likely to rate ECT and family as helpful. Those who had a history of depression but had not sought help were more likely to rate counselling as helpful, and less likely to rate family as helpful. Those with current depressive symptoms were less likely to rate telephone counselling, family and friends as helpful. CONCLUSION: Having sought help for depression is associated with general belief systems about the helpfulness of lifestyle and medical interventions and also has some associations with specific beliefs that may reflect experiences with treatment (e.g. the helpfulness of antidepressants). Those currently depressed or with a history of depression are less likely to regard family as helpful, possibly due to poorer social support. Generally speaking, having sought help is associated with beliefs closer to those of professionals.

Adult↗
PubMed2000

CYP2D6 is involved in O-demethylation of diltiazem. An in vitro study with transfected human liver cells.

OBJECTIVE: In a previous study of diltiazem (DTZ) pharmacokinetics in renal transplant patients, we speculated that a polymorphic enzyme could be involved in O-demethylation of diltiazem. The aim of this in vitro study was to investigate whether O-demethylation of DTZ is mediated by cytochrome P450-2D6 (CYP2D6). METHODS: DTZ was incubated with transfected human liver epithelial (THLE) cells expressing CYP2D6 (T5-2D6 clone). Metabolism of DTZ was studied over a concentration range of 12.5-400 microM and in the presence of quinidine (a CYP2D6 inhibitor) or erythromycin (a CYP3A4 inhibitor). THLE cells lacking CYP2D6 activity (T5-neo clone) were used as control. The culture medium of the cells, in which DTZ was dissolved, was analysed for DTZ and metabolites prior to and after 8 h of incubation using high-performance liquid chromatography (HPLC, UV detection). Authentic O-demethyl-DTZ (Mx) was not available, and this metabolite was therefore not identifiable. RESULTS: Desacetyl-O-demethyl-DTZ (M4) was exclusively produced during incubations of DTZ with THLE cells expressing CYP2D6. The rate of M4 formation was described using Michaelis Menten kinetics in the concentration range of DTZ used. Production of M4 was inhibited by quinidine, but not erythromycin. An unidentified chromatographic peak, which was interpreted to be Mx, showed the same pattern of formation as M4 both in absence and presence of inhibitors. N-demethylated metabolites, formed by CYP3A4, were not observed in any of the cell lines. CONCLUSION: Evidence was provided in vitro that O-demethylation of DTZ is mediated by the polymorphic isoenzyme CYP2D6. Involvement of CYP2D6 in the metabolism of DTZ may have clinical implications regarding pharmacokinetic variability and interactions.

Acetylation↗