Biomedical subjects

H Christensen

Publications and source records attributed to H Christensen.

At least 19 recordsLinked to original sources

PubMed2002

Evaluation of essential parameters in the chromatographic determination of cyclosporin A and metabolites using a D-optimal design.

The extensive use of routine monitoring of cyclosporin A (INN, ciclosporin) whole blood levels of patients undergoing such therapy has resulted in a wide variety of chromatographic conditions for analysing this drug. The aim of this study was to evaluate the importance of essential parameters in the chromatographic determination of cyclosporin A and its main metabolites, AM1, AM9 and AM4N. A D-optimal design was used to evaluate the effect of type and amount of organic modifier, temperature, flow rate, pH and gradient steepness. The optimal chromatographic conditions were determined by multi-linear regression. In the final chromatographic method separation of the compounds was carried out on a reversed phase C(8) column maintained at 80 degrees C. The mobile phase consisted of a linear gradient with two mobile phases containing acetonitrile and water. The flow rate was set at 0.8 ml/min. UV detection was carried out at 214 nm. Validation of the analytical method showed linearity over the range 25-1000 ng/ml (r>0.997). The detection limits of cyclosporin A, AM1, AM9 and AM4N were 1.3 pmol on column. The within-day and between-day relative standard deviations were <15% for cyclosporin A at all concentrations and for the metabolites at 250 and 1000 ng/ml, and <21% for the metabolites at limit of quantification (25 ng/ml).

Chromatography, High Pressure Liquid↗

PubMed2002

The course of blood pressure in acute stroke is related to the severity of the neurological deficits.

OBJECTIVES: To evaluate how soon after stroke the diagnosis of hypertension could be established. METHODS: In a prospective study including 1192 patients with acute stroke within 6 h, blood pressure was measured serially at 2-h intervals during the first 24 h. Results are presented as mean arterial blood pressure (MAP). The Scandinavian Stroke Scale (SSS) assessed the neurological deficit. RESULTS: In 779 patients with mild to moderate ischaemic stroke or transient ischaemic attack (TIA) and SSS > 25, MAP was 118 mmHg (CI 95%: 116-119 mmHg) on admission and 109 mmHg (CI 95%: 108-110 mmHg) 4 h later (paired t-test, P < 0.001). No such early decrease was observed in 228 patients with severe cerebral infarction (CI). In mild to moderate ischaemic stroke or TIA, MAP at 24 h was not different from MAP at 3 months in paired t-test. CONCLUSIONS: Blood pressure 24 h after admission in patients with mild to moderate CI or TIA was representative of the patient's blood pressure 3 months after stroke. A diagnosis of arterial hypertension can be established a few days after stroke.

Aged↗

PubMed2002

Patterns of association between alcohol consumption and symptoms of depression and anxiety in young adults.

AIMS: Recent epidemiological findings indicate that non-drinkers as well as hazardous/harmful drinkers experience higher levels of distress than moderate drinkers. Little is known about the age at which this develops. This paper examines levels of affect, depression and anxiety over the full range of alcohol consumption in young adults. DESIGN: Cross-sectional findings from the first wave of a prospective, longitudinal study are presented. PARTICIPANTS: The general population sample comprised of 2404 young adults (aged 20-24 years). living in the Canberra region. Measures included: the Goldberg Depression and Anxiety scales, the Positive and Negative Affect Schedule, and the Alcohol Use Disorders Identification Test. FINDINGS: For men, both non/occasional and hazardous/harmful consumption were associated with lower levels of positive affect and higher levels of anxiety and depression. The higher levels of distress evident for male abstainers were related to being less extroverted and less healthy and not to past hazardous/harmful alcohol consumption, current tobacco or marijuana use. For women, only hazardous/harmful drinkers were found to have higher levels of depression and negative affect. Hazardous/harmful consumption was related to using marijuana, tobacco and recent stressful events in both men and women. CONCLUSIONS: Higher levels of distress are already evident in male non-drinkers in early adulthood. The findings counter theories that distress in non-drinkers is due to past hazardous/harmful alcohol consumption, marijuana or tobacco use, or characteristics in common with hazardous/harmful drinkers. Alcohol use disorders and mental health problems are pertinent issues for young adults. However, more understanding is needed of the experiences of non-drinkers in an alcohol consuming culture.

Adult↗

PubMed2002

Sensory, chemical and bacteriological changes during storage of iced squid (Todaropsis eblanae).

AIMS: To relate sensory shelf-life of iced whole and gutted squid to bacterial growth and chemical changes. METHODS AND RESULTS: Cooked mantles from whole and gutted individuals were rejected after 10 and 12 days of storage, respectively, due to ammoniacal off-odours. Rate of production of both ammonia and trimethylamine was highest in the whole lot. Agmatine, which was only present in trace amounts in freshly-caught squid, increased rapidly in both lots. The main microflora at the time of sensory rejection of iced whole squid included Gram-negative, motile and non-fermentative rods, which were psychrophilic and had a requirement for NaCl. 16S rDNA sequence analyses identified the strains as belonging to the genus Pseudoalteromonas. Shewanella putrefaciens, Pseudoalteromonas sp. and Pseudomonas sp. dominated in spoiled gutted squid. Identification of strains from the stomach and digestive gland of recently-captured squid showed that the main flora consisted of Photobacterium phosphoreum. CONCLUSIONS: Spoilage of iced squid is likely to result from a combination of autolytic and bacterial changes. Agmatine seems to be an excellent freshness indicator. Photobacterium phosphoreum may contribute to spoilage through activity in the digestive gland, followed by diffusion of volatile compounds and amines to the mantle. SIGNIFICANCE AND IMPACT OF THE STUDY: Due to the psychrophilic nature of P. phosphoreum and Pseudoalteromonas sp., spread-plating and low temperature incubation are recommended for bacteriological evaluation of iced squid.

Animals↗

PubMed2002

Blood glucose increases early after stroke onset: a study on serial measurements of blood glucose in acute stroke.

The aim of this study was to evaluate if blood glucose levels change within the first 12 h after stroke onset and to investigate if the degree of change is related to stroke severity, type of stroke, or prognosis. This was a retrospective, descriptive trial based on 445 stroke patients with two blood glucose tests within 12 h of stroke onset and no history of diabetes mellitus. Blood glucose increased in the first 12 h after stroke onset; in mild to moderate stroke from 5.8 to 6.1 mmol/l (P < 0.001) and in severe stroke from 6.2 to 6.7 mmol/l (P < 0.001). In patients who died within 7 days of stroke onset, blood glucose increased from 6.8 to 7.1 mmol/l (P < 0.001). In conclusion, blood glucose increases after the onset of acute stroke and the increase is related to the severity of the stroke.

Acute Disease↗

PubMed2002

Bowel cleansing methods prior to CT colonography.

PURPOSE: To compare the cleansing effect, ease of preparation and side-effects of two cleansing regimens containing either polyethylene glycol solution (PEG) or phospho-soda (Na-P) solution prior to CT colonography in a prospective, randomized, radiologist-blinded design. MATERIAL AND METHODS: Fifty persons were randomized to receive either a PEG preparation or a Na-P preparation prior to CT colonography. On axial 2D images, the rectum, the sigmoid, the descending, the transverse and the cecum/ascending colon were scored semiquantitatively as to cleanness by two radiologists blinded to the bowel preparation regimen. Quality scores in the two groups were compared. Ease of preparation and side-effects were assessed by a questionnaire. RESULTS: The overall quality of the bowel preparation with the Na-P preparation was better than with the PEG preparation with significantly better cleansing scores for the rectum, the sigmoid, the descending and the transverse colon. The Na-P preparation was significantly better tolerated than the PEG preparation with significantly less nausea and significantly less fecal incontinence. CONCLUSION: The quality of the bowel preparation was better with the Na-P preparation than with the PEG preparation prior to CT colonography. Moreover, the Na-P preparation was better tolerated and with fewer side-effects.

Aged↗

PubMed2002

Intake of grapefruit juice alters the metabolic pattern of cyclosporin A in renal transplant recipients.

OBJECTIVE: The aim of the present study was to investigate the effect of grapefruit juice on the pharmacokinetics of cyclosporin A (CsA), as Sandimmun Neoral, and its main metabolites, M1, M9 and M4N, in renal transplant recipients. METHODS: Ten renal transplant recipients, on CsA-based immunosuppressive therapy, were included in this open, randomized crossover study. Patients were given their individualized morning dose of CsA, administered with either 250 ml water or 250 ml grapefruit juice and 12-hour CsA pharmacokinetic investigations were performed. The 2 investigation days were separated by at least 7 days. RESULTS: Administration of CsA with grapefruit juice compared with water significantly increased the area under the whole blood concentration versus time curve in the interval from 0-12 hours (AUC(0-12)) of CsA, by an average of 25 +/- 19% (p = 0.002). Intake of grapefruit juice did not have any significant influence on maximum whole blood concentration (Cmax) or time to Cmax (tmax) of CsA. AUC(0-12) and Cmax of M9 decreased significantly with intake of grapefruit juice, on average 22 +/- 11% (p = 0.0007) and 36 +/- 6% (p = 0.0001), respectively. AUC(0-12) of M1, however, was on average 13 +/- 14% (p = 0.02) higher upon co-administration of CsA with grapefruit juice as compared with water. The level of M4N was below the limit of quantification in most samples, and an effect of co-administration of CsA with grapefruit juice could not be determined for this metabolite. CONCLUSION: The present study shows that co-administration of grapefruit juice with CsA compared with water affects the formation and/or elimination of the 2 metabolites M1 and M9 differently. In addition, administration of CsA with grapefruit juice compared with water induced a moderate, but significant increase in systemic exposure of CsA in renal transplant recipients.

Adolescent↗

PubMed2002

Acceptable agreement between tympanic and rectal temperature in acute stroke patients.

Major concerns remain about the reliability of tympanic thermometers. The aim of this study was to investigate the agreement between rectal and tympanic thermometry and compare this with the repeatability of each method in patients with acute stroke. Tympanic temperature readings were from 0.7 degrees C below to 0.8 degrees C above rectal readings. As to repeatability, we found second rectal readings to be between 0.3 degrees C below and 0.4 degrees C above first readings, and second tympanic readings to be between 0.4 degrees C below and 0.5 degrees C above first readings. The agreement between the two methods is acceptable in clinical practice. Tympanic thermometry is useful in serial measurements, whereas, for a single accurate measurement, rectal mercury thermometry remains the method of choice.

Acute Disease↗

PubMed2001

Muscle activity and cardiovascular response during computer-mouse work with and without memory demands.

Computer-mouse work is characterized by repetitive movements combined with mental demands. The present purpose was to study how the body responded to simulated Computer Aided Design (CAD) work without memory demand and when a high short-term memory demand was introduced. Nine female subjects repetitively performed a task which involved 15 s of elevation of the right index and middle fingers followed by 6 s of rest. Every second time the fingers rested, the left index finger was required to type a six-figure number, either '123456' (without memory demand) or a random number shown half a minute before (with memory demand). After 7 min of performing the task without memory demand, the memory demand was introduced and continued for 1 h. Introduction of memory demand resulted in increased heart rate (77-->84 beats/min), blood pressure (systolic 129-->140 mmHg; diastolic 72-->79 mmHg) and forearm extensor muscle activity (wrist, 2.7-->4.5% EMGmax; finger, 5.6-->7.5% EMGmax) and finger flexor muscle activity (0.7-->1.2% EMGmax) indicating increased co-contraction. Hereafter, muscle activity and cardiovascular response tended to decrease. Self-reported stress and rating of perceived exertion (RPE) for the right shoulder increased throughout the period. Two additional sub-studies were inlcuded, which focused on adaptation to the physical load, showing a decrease in muscle activity and arousal, and reintroduction of the memory load, showing a lower response as compared to the initial response. The practical consequences of the findings suggest that job content should have variable mental demands.

Adult↗

PubMed2001

Random amplification of polymorphic DNA and phenotypic typing of Zimbabwean isolates of Pasteurella multocida.

Eighty-one isolates presumptively identified as Pasteurella multocida from a variety of diseases in animals in Zimbabwe were subjected to biochemical characterization, capsular typing and RAPD analysis. The majority of isolates (over 80%) were assigned into named taxa and were predominantly P. multocida subsp. multocida and P. multocida subsp. septica, whilst the remainder were unassigned. Serogroup A was predominant among the three capsular types (A, B and D) of P. multocida detected. Three main RAPD clusters and three subclusters were observed among the majority of isolates (93.8%), whilst the remainder was found to be weakly related. Nine different groups of strains with similar RAPD profiles (100% similarity) were also observed. The reference strain of capsular serogroup F clustered with the reference strain of P. multocida subsp. septica, whilst all other serogroups clustered with reference strains of subsp. multocida and gallicida. Notably, serogroups A and D were observed to be closely related to the reference strain of subsp. multocida. The relationship between biotype, capsular type, host origin and disease manifestation was not clear-cut. However, most pig isolates of subsp. multocida clustered together as did most cattle isolates of subsp. multocida. RAPD tended to separate subsp. multocida from septica.

Animals↗

PubMed2001

The cognitive decline scale of the psychogeriatric assessment scales (PAS): longitudinal data on its validity.

OBJECTIVE: The Cognitive Decline scale of the Psychogeriatric Assessment Scales (PAS)1 uses informant data to assess retrospectively change from earlier in life. Data from a 7-8-year longitudinal study were used to assess the validity of this scale against changes in cognitive performance and mortality. DESIGN AND MEASURES: PAS data were collected on three occasions, with gaps of 3.6 and 4.1 years between the waves. The Cognitive Decline score at Wave 3 was validated retrospectively against actual change on a brief test of current cognitive status (the PAS Cognitive Impairment scale) over the three waves, while the Cognitive Decline score at Wave 1 was assessed for predictive validity against future mortality and cognitive change. SETTING: A community survey in the Australian cities of Canberra and Queanbeyan. PARTICIPANTS: Participants were aged 70+ at the beginning of the study. The sample size varied from 729 to 279, depending on the number of waves involved. RESULTS: Participants with scores of 4+ on the Cognitive Decline scale at Wave 3 showed substantial deterioration over the previous 7-8 years. Scores of 4+ at Wave 1 predicted mortality and further cognitive deterioration. CONCLUSIONS: The Cognitive Decline scale allows a valid retrospective assessment of change and has predictive validity for subsequent cognitive deterioration and increased mortality.

Aged↗

PubMed2001

An investigation of how acute muscle pain modulates performance during computer work with digitizer and puck.

The purpose was to investigate the influence of muscle pain on work performance during computer work with digitizer and puck. Muscle pain was induced by infusion of hypertonic saline in the trapezius and the extensor carpi ulnaris (ECU) muscles on two separate days. Twelve healthy subjects participated. A computer task was performed in three 6 min sessions: baseline, pain, after pain. The computer task comprised production of drawings at maximal work pace. One drawing was defined as a work cycle. Work cycle time, number of puck button clicks, and screen pixels the cursor had moved per cycle were assessed. Shoulder pain did not influence these variables. Cycle time decreased from 13.8 (SD 2.2) to 13.0 s (SD 1.9) compared to baseline (p < 0.05) during ECU muscle pain. The increased or unchanged performance suggests that acute moderate muscle pain has minor influence on performance during computer work with digitizer and puck.

Adult↗

PubMed2001

Aerobic power and muscle strength among young and elderly workers with and without physically demanding work tasks.

The aim of the study was to investigate the effect of waste collection on the physical capacity of the workers. A total of 19 young and 28 elderly male waste collectors and two age-matched control groups participated. The aerobic power was estimated. The maximal isometric muscle strength was measured for back extension and flexion, shoulder elevation and abduction, and handgrip. The aerobic power was lower among the elderly workers compared with the young workers of both groups. No differences were found between waste collectors and control groups. A general tendency to larger muscle strength was found for both young and elderly waste collectors compared with the control groups. Waste collectors generally have a higher physical capacity than the control groups which is an indication of an early selection of the young waste collectors. With respect to the elderly waste collectors, the job seems to have a training effect especially for the shoulder muscles. No training effect is found for the aerobic power, and a discrepancy between work demand and individual aerobic capacity may occur among elderly workers resulting in a negative health effect unless the work task is evaluated according to age dependent criteria.

Adult↗

PubMed2001

A comparison of 'Early' and 'Late' stage brain activation during brief practice of a simple motor task.

This research study addresses the question: does the neural circuit implementing a motor task undergo change as a function of even limited practice? To detect potential neural changes associated with limited practice we compared brain activation at the early and late stages of motor performance on a simple task over one relatively brief session. Single-finger opposition served as cognitive stimulation during collection of BOLD fMRI signal. We predicted prefrontal cortex activation would be prominent early, with basal ganglia activation becoming prominent during late stage performance. Results revealed that both early and late performance involve areas in the cerebellum, prefrontal, mid-temporal, extrastriate, and parietal cortices, but that the particular regions within these broad areas differed for the two points of performance. The strongest dissociation between early and late performance involved the corpus striatum, thalamus, and cingulate gyrus. The findings suggested the neural circuit implementing this simple task varied over a relatively brief window of practice. Implications for defining the neurocognitive function of the structures involved, particularly the cerebellum, are discussed.

Adult↗

PubMed2001

Motor unit activity during stereotyped finger tasks and computer mouse work.

Motor unit (MU) activity pattern was examined in the right-hand extensor digitorum communis muscle (EDC) during standardised finger movements simulating actual computer mouse tasks. Intramuscular recordings were performed with a quadripolar needle electrode. Nine women performed four lifts of their right-hand index finger, middle finger or both as well as a number of double clicks. Additionally, the subjects performed contra lateral activity with their left-hand fingers and for three subjects recordings were also obtained during an interview with no physical activity. Besides the expected close coupling of MU activity with finger movement, activity was observed in three different situations with no physical requirements. Attention related activity was found before or after performance of the finger movement task, contra lateral activity in right EDC during left-hand finger tasks, and activity during mental activity without any finger movements involved. A relatively large number of doublet occurrences suggest they are a natural part of the activation pattern during performance of the rapid finger movement required to perform an efficient double click on the computer mouse.

Action Potentials↗

PubMed2001

Influence of memory demand and contra lateral activity on muscle activity.

Computer mouse work often includes memory demands and contra lateral activity. This study simulated video display unit (VDU) mouse-work and the focus was on forearm muscle activity as a result of standardised postural loads, memory demands and contra lateral activity. Surface and intramuscular electromyography (EMG) were recorded from the right forearm muscles during finger elevation and rest with and without memory demands and with and without contra lateral activity i.e. activity of the left hand. In most situations, memory demand increased activity in the m. extensor carpi radialis brevis and m. flexor digitalis superficialis. Also contra lateral activity increased activity in situations with and without memory demands. While surface EMG level of the m. extensor digitorum communis did not increase during memory demands, intramuscular EMG level increased when memory demands and contra lateral activity was combined. Influence of memory demands and contra lateral activity were most pronounced, in situations where activity levels were small. We presume that it is not only prolonged time of active computer mouse use that is a risk for development of musculoskeletal disorders, but also the time when people interact with the computer mentally or with the 'non-mouse hand', while resting their 'mouse-hand' on the mouse.

Adult↗

PubMed2001

Age is no kinder to the better educated: absence of an association investigated using latent growth techniques in a community sample.

BACKGROUND: Higher education has been posited to protect against cognitive decline, either because the rate of decline is slower in the more highly educated or the start of decline is delayed. Latent growth models provide improved methodology to examine this issue. METHODS: The sample consisted of 887 participants aged 70-93 years in 1991 and followed up in 1994 and 1998. Latent growth models and standard regression techniques were used to examine the rate of cognitive decline in four cognitive measures while controlling for health status and sex. A delayed start model was examined by incorporating interaction effects in a regression model. RESULTS: Neither the latent growth models nor the regression techniques revealed a slower rate of decline for the more highly educated. The proportion of the highly educated showing no change was no larger than the proportion of the less well educated. There were no significant age by education interaction effects, no chronologically later accelerations in the rate of change as a function of education, and no differences in rate of decline between the first measurement interval and the second. CONCLUSIONS: Education may not protect against cognitive decline although it is associated with long-term individual differences in level of functioning. The discrepancy between our study and others may be attributable to attrition effects, follow-up length, sample age, scaling artefacts and negative publication bias. Most importantly, practice effects may favour the better educated and hence account for the supposed protective effect in many longitudinal studies of cognitive change.

Activities of Daily Living↗

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↗