Biomedical subjects

P H C Eilers

Publications and source records attributed to P H C Eilers.

6 recordsLinked to original sources

PubMed2006

A comparison of three algorithms for chromatograms alignment.

In this paper the performance of three alignment algorithms, correlation optimized warping, parametric time warping and semi-parametric time warping, is compared on real chromatograms. Among these, parametric time warping is the simplest and fastest; generally less than 1s is required to align two chromatograms. It does not require the optimization of input parameters and allows the alignment of peak shifts in only one direction, or non-complex peak shifts in both directions. With correlation optimized warping and semi-parametric time warping complex peak shifts in both directions can be corrected but at the expense of the optimization of two input parameters. Semi-parametric time warping requires the selection of the proper number of B-splines in the warping function and, if necessary, the optimization of the penalty parameter. Often the default values can be used to obtain aligned signals. The optimization of the input parameters for correlation optimized warping (section length, slack) is not easy and time-consuming. Moreover, dependent on the input parameters, the computation time of the correlation optimized warping algorithm can be twice as long as for semi-parametric time warping for which computation times up to 23 s are required. However, the performance of both algorithms is equally good considering the improvement of the precision of the peak retention times and correlation coefficients between the chromatograms, after alignment. For the data aligned in this study, the average retention time precision and the lowest correlation before warping were 14 and 0.17, and were improved to three and 0.83, and six and 0.87 after warping, with correlation optimized warping and semi-parametric time warping, respectively.

Algorithms↗

PubMed2006

The absence of CCL2 expression in cervical carcinoma is associated with increased survival and loss of heterozygosity at 17q11.2.

To determine whether CCL2 mRNA expression is beneficial or detrimental for cervical cancer patients, the association between the expression of this molecule by cervical tumour cells, the number of tumour-associated macrophages, and clinicopathological parameters such as recurrence, relapse-free survival, and overall patient survival was investigated. In cervical cancer samples from 93 untreated cervical cancer patients, the CCL2 mRNA expression level was quantified using RNA in situ hybridization and verified using real-time quantitative RT-PCR. The number of tumour-associated macrophages was determined using immunohistochemistry. Furthermore, the study investigated whether lack of CCL2 expression was due to genetic alterations near the 17q11.2 (CCL2 genomic) region. CCL2 mRNA expression by cervical tumour cells was associated with the number of tumour-associated macrophages (p < 0.001). Lack of CCL2 mRNA expression (15 samples; 16%) was associated with increased cumulative relapse-free survival (log rank test, p = 0.030), increased cumulative overall survival (log rank test, p = 0.024), less post-operative surgery, reduced local and distant recurrence, reduced vascular invasion, and smaller tumour size (<40 mm). The absence of CCL2 mRNA expression corresponded with loss of heterozygosity (LOH) at 17q11.2 in five of six samples. The increased cumulative relapse-free survival and cumulative overall survival of cervical cancer patients lacking tumour cell-associated CCL2 mRNA suggest that the tumour-associated macrophages support tumour progression, presumably by promoting angiogenesis and production of growth factors.

Biomarkers, Tumor↗

PubMed2004

Modeling and correction of digit preference in tuberculin surveys.

SETTING: Human observers generally have a strong tendency to round analog measurements or estimates to 'nice' ending digits, such as 0, 5, or even numbers. This is known as digit preference; it is a well-known phenomenon in frequency distributions of indurations collected in tuberculin surveys. Digit preference can distort estimates of prevalence and other statistical parameters. METHODS: We have developed a statistical model that combines smoothing by penalized likelihood and the transfer of counts from non-preferred to preferred digits, to obtain estimates of: 1) the smooth underlying distribution and 2) the amount of digit preference. RESULTS: To illustrate the validity of the model, it was applied to data from several countries. CONCLUSION: With the proposed model, digit preference can be quantified and frequency distributions of indurations can be corrected for it.

Algorithms↗

PubMed2003

External rotation in the glenohumeral joint during elevation of the arm.

OBJECTIVE: To describe patterns of external rotation during humeral elevation, and to compare motion patterns.Design. Patterns of external rotation during forward flexion, scapular abduction and abduction in the frontal plane are described with P-spline curves with an approximately 95% confidence interval. BACKGROUND: External rotation of the humerus is an essential part of humeral elevation. Standard clinical assessment of external rotation provides insufficient information to describe external rotation patterns which may be essential for insight in shoulder disorders.Methods. The dominant and non-dominant arms of thirty subjects are measured, using a three-dimensional electromagnetic movement recording system. RESULTS: Overall group patterns demonstrate that humeral elevation in all planes is accompanied by about 55 degrees of external rotation, and each elevation plane has its own typical pattern. The dominant and non-dominant sides are comparable and can be combined. CONCLUSIONS: There are specific external rotation patterns for each elevation plane. Curves representing the approximately 95% confidence intervals make comparison between groups possible. This method can therefore possibly be used to study the external rotation patterns in groups with certain shoulder disorders to evaluate the results of before and after treatment. RELEVANCE: The method presented in this paper can be used to study external rotation patterns in healthy shoulders and in shoulders with a specific disorders to gain more insight, to define functional treatment, and to evaluate the results of treatment.

Adult↗

PubMed2003

Anticonvulsant drugs differentially suppress individual ictal signs: a pharmacokinetic/pharmacodynamic analysis in the cortical stimulation model in the rat.

Antiepileptic drugs can suppress seizures completely, but they may also modify the appearance of drug-resistant seizures. In this study, the effects of three antiepileptic drugs on a seizure pattern were assessed by means of population pharmacokinetic/pharmacodynamic (PK/PD) modeling, yielding estimates of baseline response, EC50, and Hill slope. Lamotrigine did not affect eye closure, although it did suppress the other ictal signs in a concentration-dependent fashion. Midazolam suppressed forelimb clonus less potently than the other ictal signs; the same was observed for tiagabine with respect to eye closure. This study shows that ictal component analysis (ICA) in combination with PK/PD modeling may facilitate drug selection and dose optimization. The application of ICA is not restricted to a single seizure type or anticonvulsant drug and can be used to identify drug combinations that have a complementary action.

Animals↗

PubMed2002

Measurement of three dimensional shoulder movement patterns with an electromagnetic tracking device in patients with a frozen shoulder.

OBJECTIVE: To compare three dimensional movement patterns of the affected and non-affected shoulder in patients with a frozen shoulder before and after physical therapy. METHODS: Patients with a unilateral frozen shoulder were assessed before and after three months of treatment. Three dimensional movement analysis was performed with the "Flock of Birds" electromagnetic tracking device while the patient raised their arms in three directions. Slopes of the regression lines of glenohumeral joint rotation versus scapular rotation, reflecting the scapulohumeral rhythm, were calculated. All assessments were made for both the affected and the unaffected side. Additional assessments included conventional range of motion (ROM) measurements and visual analogue scales (VAS) (0-100 mm) for shoulder pain at rest, during movement, and at night. RESULTS: Ten patients with a unilateral frozen shoulder were included. The slopes of the curves of the forward flexion, scapular abduction, and abduction in the frontal plane of the affected and the unaffected side were significantly different in all three movement directions. Mean differences were 0.267, 0.215, and 0.464 (all p values <0.005), respectively. Mean changes of the slopes of the affected side after treatment were 0.063 (p=0.202), 0.048 (p=0.169), and 0.264 (p=0.008) in forward flexion, scapular abduction, and abduction in the frontal plane, respectively. All patients showed significant improvement in active ROM (all p<0.005), and the VAS for pain during movement and pain at night (p<0.05). CONCLUSIONS: With a three dimensional electromagnetic tracking system the abnormal movement pattern of a frozen shoulder, characterised by the relatively early laterorotation of the scapula in relation to glenohumeral rotation during shoulder elevation, can be described and quantified. Moreover, the system is sufficiently sensitive to detect clinical improvements. Its value in other shoulder disorders remains to be established.

Adult↗