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PubMed2004

The role of current product release criteria for identification of human islet preparations suitable for clinical transplantation.

BACKGROUND: Alloimmunity, autoimmunity, and nonspecific inflammation are known to be potential determinants for long-term islet survival and insulin independence. Sufficient islet mass is a key determinant. But islet engraftment and posttransplant survival may also depend on functional characteristics of the graft. This study investigated the significance of current product release criteria for the transplantation outcome. METHODS: Fourty five consecutive transplanted human islet preparations and their functional outcomes were analyzed. Islet mass was determined according to standard criteria: purity by light microscopy, viability by dye exclusion and Insulin secretory response to static glucose incubation. Islet graft function was monitored for > or = 1 year. Islet function was defined as full (FF), partial (PF), or nonfunction (NF) based on serum C-peptide levels and insulin independence. RESULTS: All islet grafts displayed primary function. Islet mass [IEQ/kg BW]: 7331.3 +/- 679.7 (FF), 5821.3 +/- 546.7 (PF), 6468.6 +/- 658.5 (NF), (FF vs PF p = .032) Purity [%] 86.9 +/- 3.1 (FF), 76.0 +/- 2.87 (PF), 88.2 +/- 2.3 (NF) (FF vs PF P =.045, PF vs NF, P = 0.01). (4) Viability [%]:89.2 +/- 2 (FF), 86.2 +/- 1.7 (PF), 87.3 +/- 1.8 (NF) (ns). Stimulation index (SI): 20 +/- 6.3 (FF), 80.2 +/- 28.2 (PF), 21.6 +/- 3.5 (NF) (ns) No correlation was observed between SI and any other parameter nor between SI and C-peptide levels. Islet mass significantly correlated with C-peptide levels at 6 and 12 months after transplantation for functioning grafts. CONCLUSIONS: Stringent product release criteria allow identification of islet preparations suitable for clinical transplantation. However, currently used parameters are not predictive of long-term graft function, indicating that further refined quality assessments including apoptosis and resistance to early inflammation, are required to assess the primary engrafted islet mass.

Automation↗
PubMed2001

Material parameter estimation with terahertz time-domain spectroscopy.

Imaging systems based on terahertz (THz) time-domain spectroscopy offer a range of unique modalities owing to the broad bandwidth, subpicosecond duration, and phase-sensitive detection of the THz pulses. Furthermore, the possibility exists for combining spectroscopic characterization or identification with imaging because the radiation is broadband in nature. To achieve this, we require novel methods for real-time analysis of THz waveforms. This paper describes a robust algorithm for extracting material parameters from measured THz waveforms. Our algorithm simultaneously obtains both the thickness and the complex refractive index of an unknown sample under certain conditions. In contrast, most spectroscopic transmission measurements require knowledge of the sample's thickness for an accurate determination of its optical parameters. Our approach relies on a model-based estimation, a gradient descent search, and the total variation measure. We explore the limits of this technique and compare the results with literature data for optical parameters of several different materials.

Algorithms↗
PubMed2004

Detection of coronary artery disease with MCG.

The diagnosis of cardiac ischemia related to coronary artery disease (CAD) is a clinical challenge. Despite many methods clinically available, the predictive value of each is still limited. Magnetocardiography (MCG) offers new insights in the electrogenesis of the disease. In the last decade a number of studies using biomagnetometers have dealt with the identification of CAD patients using coronary angiography as a gold standard. As the availability of these systems is limited, studies have focused either on exercise-induced ischemia or on chronic ischemia and the infarct scar at rest. Different parameters have been developed based on signal morphology, time intervals, source parameters or magnetic field map analysis. Concerning signal morphology, main work concentrates on ST-depression, ST-T signal amplitude as well as QRS and ST-T integrals. Dealing with time intervals, most studies focus on the QT interval. The evaluation of of QT dispersion spatially in the MCG, reflecting regional heterogeneity of repolarization, improved the identification of CAD patients. Besides the calculation of the equivalent current dipole during de- and repolarization, parameters of the magnetic field orientation were used to identify CAD patients and localize exercise-induced ischemic regions. Heart rate adjusted alteration in the magnetic field orientation allowed the quantification of ischemia-induced changes in MCG. The estimation of current density (CDV) further enabled to separate healthy subjects from CAD patients at rest. In the course of interventional therapy CDV maps returned toward that of healthy subjects.Thus, there is justification for routine clinical use of the MCG in the diagnosis of CAD.

Coronary Artery Disease↗
PubMed2002

Structural characterization of chondroitin/dermatan sulfate oligosaccharides from bovine aorta by capillary electrophoresis and electrospray ionization quadrupole time-of-flight tandem mass spectrometry.

An analytical approach based on high-performance capillary electrophoresis (CE) in conjunction with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) has been developed for providing the basis to obtain new insights into the domain structure of the glycosaminoglycan (GAG) moiety of proteoglycans. The feasibility and performance of the off-line CE/ESI-QTOF-MS approach in GAG oligosaccharide analysis were assessed by screening a chondroitin/dermatan sulfate (DS) oligosaccharide mixture obtained from bovine aorta by enzymatic depolymerization by chondroitin B lyase. The CS/DS mixture was analyzed by CE using 50 mM ammonium acetate, pH 12.0, dissolved in aqueous methanol (2:3; v/v), as a CE carrier. Structural identification of the GAG components was achieved using off-line CE/nanoESI-QTOF-MS and-MS/MS experiments. ESI-QTOF instrumental parameters were found to play an important role in the MS screening of the CE-separated GAG species. By optimizing the ESI conditions, oligosaccharides differing in chain length and degree of sulfation could be detected. The building block composition, the size of the carbohydrate chain, as well as structural features of the repeating HexA-GalNAc, HexA-GalNAc(S) units, have been determined using MS/MS by applying collision-induced dissociation at low energies. Cleavage of GAG chains by chondroitin B lyase occurs with formation of structural markers useful for identification of IdoA-containing domains.

Animals↗
PubMed2001

An impairment in sniffing contributes to the olfactory impairment in Parkinson's disease.

Although the presence of an olfactory impairment in Parkinson's disease (PD) has been recognized for 25 years, its cause remains unclear. Here we suggest a contributing factor to this impairment, namely, that PD impairs active sniffing of odorants. We tested 10 men and 10 women with clinically typical PD, and 20 age- and gender-matched healthy controls, in four olfactory tasks: (i) the University of Pennsylvania smell identification test; (ii and iii) detection threshold tests for the odorants vanillin and propionic acid; and (iv) a two-alternative forced-choice detection paradigm during which sniff parameters (airflow peak rate, mean rate, volume, and duration) were recorded with a pneomatotachograph-coupled spirometer. An additional experiment tested the effect of intentionally increasing sniff vigor on olfactory performance in 20 additional patients. PD patients were significantly impaired in olfactory identification (P < 0.0001) and detection (P < 0.007). As predicted, PD patients were also significantly impaired at sniffing, demonstrating significantly reduced sniff airflow rate (P < 0.01) and volume (P < 0.002). Furthermore, a patient's ability to sniff predicted his or her performance on olfactory tasks, i.e., the more poorly patients sniffed, the worse their performance on olfaction tests (P < 0.009). Finally, increasing sniff vigor improved olfactory performance in those patients whose baseline performance had been poorest (P < 0.05). These findings implicate a sniffing impairment as a component of the olfactory impairment in PD and further depict sniffing as an important component of human olfaction.

Adult↗
PubMed1996

[Lymph node dissections in malignant melanoma].

Elective lymph node dissection and its potential as a staging procedure, the prognosis of established lymph node metastases and the sentinel lymph node identification procedure are the most important aspects of lymph node dissection in malignant melanoma. It is widely accepted that subgroups of patients benefit from elective lymph node dissection. The question of which parameters identify the relevant patients properly is still under discussion. pT-categories are the most important prognostic factor; however, localisation and type of tumour and the sex of the patients are additional parameters influencing patient selection. Recently, the first studies have identified subgroups of nodal positive patients who would profit from adjuvant chemo-/immunotherapy. Therefore, lymph node dissection as a staging procedure has to be discussed in the future. Identification of the sentinel lymph node is receiving increasing attention because of its potential influence on the reassessment of elective lymph node dissection. However, this method needs further evaluation. If lymph node metastases have occurred, the prognosis of malignant melanoma decreases by 20%-50%, depending on the extent of metastasis in the individual case. The relevant topics and results are discussed on the basis of data of the Surgical Department of the University Hospital of Erlangen-Nuremberg.

Female↗
PubMed2000

Analysis of bisphosphonates by capillary electrophoresis-electrospray ionization mass spectrometry.

Capillary electrophoresis-electrospray ionization mass spectrometry (CE-ESI-MS) was applied to the direct identification and quantitation of clodronate and its four common impurities. The coaxial interface technique and negative ion mode were used in the detection. Ion source parameters and sheath liquid composition were optimized to produce maximum abundance of singly charged deprotonated molecules used in monitoring. In addition, the effects of electrolyte composition and instrumental parameters of CE on separation were studied. The developed method provides high separation power and specificity to bisphosphonate analysis. In quantitative analysis, the method showed good linearity (r=0.9946-0.9989), satisfactory repeatability (migration time variation: RSD=0.43-1.0%, peak area variation: RSD=2.2-9.4%) and sufficient sensitivity (detection limits: 0.08-0.22 mg ml(-1)) for identification of bisphosphonates from bulk material.

Diphosphonates↗
PubMed1991

Modeling the cost and performance of early identification protocols.

This is the first in a series of three papers concerned with the early identification of hearing loss. In this paper, a simple model is presented that permits the calculation of the performance and cost of early identification protocols. In the second paper (Turner, in press), this model is used to compare four early identification protocols that differ in hearing screening strategies. The third paper (Turner, in press) examines the factors that influence the early identification protocol. The model described in this paper is sufficiently general to accommodate most early identification strategies including those that meet the goal of identification and habilitation by 6 months. The model measures protocol performance using hit rate, false alarm rate, and selected posterior probabilities. The model also calculates two measures of the financial cost. One measure reflects the cost of implementing the protocol; the other reflects the cost-effectiveness of the protocol. The parameters required by the model are also specified and are based on published clinical data. The model is provided to help audiologists design and select early identification protocols that are optimum for their particular clinical situation.

Clinical Protocols↗
PubMed1991

Overtraining in athletes. An update.

Overtraining appears to be caused by too much high intensity training and/or too little regeneration (recovery) time often combined with other training and nontraining stressors. There are a multitude of symptoms of overtraining, the expression of which vary depending upon the athlete's physical and physiological makeup, type of exercise undertaken and other factors. The aetiology of overtraining may therefore be different in different people suggesting the need to be aware of a wide variety of parameters as markers of overtraining. At present there is no one single diagnostic test that can define overtraining. The recognition of overtraining requires the identification of stress indicators which do not return to baseline following a period of regeneration. Possible indicators include an imbalance of the neuroendocrine system, suppression of the immune system, indicators of muscle damage, depressed muscle glycogen reserves, deteriorating aerobic, ventilatory and cardiac efficiency, a depressed psychological profile, and poor performance in sport specific tests, e.g. time trials. Screening for changes in parameters indicative of overtraining needs to be a routine component of the training programme and must be incorporated into the programme in such a way that the short term fatigue associated with overload training is not confused with the chronic fatigue characteristic of overtraining. An in-depth knowledge of periodisation of training theory may be necessary to promote optimal performance improvements, prevent overtraining, and develop a system for incorporating a screening system into the training programme. Screening for overtraining and performance improvements must occur at the culmination of regeneration periods.

Adaptation, Physiological↗
PubMed2006

Parameter-based assessment of spatial and non-spatial attentional deficits in Huntington's disease.

A major challenge for neuropsychological research on Huntington's disease is the identification of biomarkers for the disease at the level of cognitive functions. Given that cortical-striatal-thalamic circuits are particularly vulnerable, possible markers loading functionally on these brain regions should be particularly significant. We investigated whether parametric values derived from a 'theory of visual attention' (TVA) can serve that purpose. They are derived as mathematically independent, quantitative measures of attentional components, and the tasks require only non-speeded vocal responses. As such, the methodology seems well suited for testing patients with motor problems and general cognitive decline. Accumulating neuroanatomical evidence suggests that striatal atrophy in Huntington's disease is asymmetrical with a more pronounced left-sided degeneration. We applied a partial-report paradigm to analyse whether this results in a pathological (leftward) bias of the spatial distribution of attention. In partial report, red target letters are presented either alone or accompanied by either a second target or a green distractor letter presented in the same or in the opposite hemi-field. Since basal ganglia lesions have also been shown to cause spatially non-lateralized impairments, that is, reduced perceptual processing speed and visual working memory (WM) storage capacity within both hemi-fields, we tested possible reductions in these parameters with a whole-report paradigm. Here, columns of five red or green letters are briefly presented and the subject has to report as many as possible. Eighteen patients and 18 matched control subjects performed a partial- and a whole-report task with briefly presented letter displays. In partial report, Huntington's disease patients demonstrated a pathological bias, indicating increased attentional weighting to the left hemi-field. The extent of lateralization was strongly related to age at onset and to the number of cytosine-adenine-guanine (CAG) triplet repeats on gene IT15. In contrast, the extent of lateralization was not related to disease progression as reflected by the duration of the disease since onset of the first symptoms. In whole report, the non-lateralized attentional parameters processing speed and visual WM storage capacity were reduced bilaterally in both hemi-fields. The extent of the reduction was related to the disease duration since onset, whereas no significant correlation with CAG repeats or age at onset was found. Laterality of attentional weighting may, therefore, represent a possible trait marker reflecting the intensity of the pathogenic mechanisms, while the reduction of visual processing speed and storage capacity may be state markers for the stage of disease progression.

Adult↗
PubMed1998

Cocoa fermentations conducted with a defined microbial cocktail inoculum.

Cocoa fermentations were performed in wooden boxes under the following four experimental regimens: beans naturally fermented with wild microflora; aseptically prepared beans with no inoculum; and beans inoculated with a defined cocktail containing microorganisms at a suitable concentration either at zero time or by using phased additions at appropriate times. The cocktail used consisted of a yeast, Saccharomyces cerevisiae var. chevalieri, two lactic acid bacterial species, Lactobacillus lactis and Lactobacillus plantarum, and two acetic acid bacterial species, Acetobacter aceti and Gluconobacter oxydans subsp. suboxydans. The parameters measured were cell counts (for yeasts, filamentous fungi, lactic acid bacteria, acetic acid bacteria, and spore formers, including reisolation and identification of all residual cell types), sugar, ethanol, acetic acid, and lactic acid contents (and contents of other organic acids), pH, and temperature. A cut test for bean quality and a sensorial analysis of chocolate made from the beans were also performed. The natural fermentation mimicked exactly the conditions in 800-kg boxes on farms. The aseptic box remained largely free of microflora throughout the study, and no significant biochemical changes occurred. With the zero-time inoculum the fermentation was almost identical to the natural fermentation. The fermentation with the phased-addition inoculum was similar, but many changes in parameters were slower and less pronounced, which led to a slightly poorer end product. The data show that the nearly 50 common species of microorganisms found in natural fermentations can be replaced by a judicious selection and concentration of members of each physiological group. This is the first report of successful use of a defined, mixed starter culture in such a complex fermentation, and it should lead to chocolate of more reliable and better quality.

Acetic Acid↗
PubMed1995

The effects of random element loss on letter identification: implications for visual acuity loss in patients with retinitis pigmentosa.

The hypothesis that reductions in Snellen acuities in patients with retinitis pigmentosa are due solely to losses of photoreceptors was tested by measuring the effects of random losses of sampling elements on letter identification. Sampling element losses were mimicked by setting the luminance of randomly selected pixels equal to the luminance of the surround. The amount of pixel blanking ranged from 0 to 90%. Letters varying in retinal subtense from 5 to 17 min arc were presented for 500 msec. Although letter identification accuracy decreased with increasing pixel blanking for all letter sizes, performance remained relatively high even when a majority of the pixels was blanked. The data suggest that unless the loss of cone photoreceptors in greater than 80%, loss of sampling elements alone can not account for letter acuities poorer than 20/40. In addition to loss of cone photoreceptors in patients with RP, there are histological reports of photoreceptor abnormalities and psychophysical studies of visual sensory deficits. It is conceivable that these alone, or in combination with losses of photoreceptors, could account for decreased visual acuity. In a series of experiments, stimulus parameters were manipulated in order to mimic the effects of some of these abnormalities and deficits and the effects on letter identification were examined. The results of these experiments demonstrated that sampling element loss interacts with sensory factors (e.g. luminance and contrast sensitivity) and perceptual factors (e.g. set size and letter orientation) to reduce letter identification accuracy. The implication of these results is that decreases in letter acuity observed in patients with retinitis pigmentosa cannot be attributed solely to a random loss of sampling elements in the underlying retina, but may be due to the combination of photoreceptor degeneration and other sensory and perceptual factors.

Adult↗
PubMed2001

The power of the transmission disequilibrium test (TDT) with both case-parent and control-parent trios.

The transmission disequilibrium test (TDT) customarily uses affected children and their parents (often case-parent trios, TDTD). Control-parent trios are necessary to guard against spurious significant results due to segregation distortion but are not generally utilized in the identification of disease susceptibility loci (DSL). Controls are often easy to recruit and the TDT can easily be extended to include control-parent trios into the analyses with unrelated case-parent trios. We present an extension of the TDT (TDTDC) that incorporates unrelated cases and controls and their parents into a single analysis. We develop a simple and accurate analytical method for computing the statistical power of various TDT (e.g. the TDTD, TDTDC, TDTDC and TDTC that employ control-parent trios only) under any genetic model. We investigated the power of these TDT, and particularly compared the relative power of the TDTD and TDTDC. We found that the TDTDC is almost always more powerful than the TDTC and TDTD. The relative power of the TDTDC and TDTD depends largely upon a number of parameters identified in the study. This study provides a basis for efficient use of control-parent trios in DSL identification.

Case-Control Studies↗
PubMed2001

A what-and-where fusion neural network for recognition and tracking of multiple radar emitters.

A neural network recognition and tracking system is proposed for classification of radar pulses in autonomous Electronic Support Measure systems. Radar type information is considered with position-specific information from active emitters in a scene. Type-specific parameters of the input pulse stream are fed to a neural network classifier trained on samples of data collected in the field. Meanwhile, a clustering algorithm is used to separate pulses from different emitters according to position-specific parameters of the input pulse stream. Classifier responses corresponding to different emitters are separated into tracks, or trajectories, one per active emitter, allowing for more accurate identification of radar types based on multiple views of emitter data along each emitter trajectory. Such a What-and-Where fusion strategy is motivated by a similar subdivision of labor in the brain. The fuzzy ARTMAP neural network is used to classify streams of pulses according to radar type using their functional parameters. Simulation results obtained with a radar pulse data set indicate that fuzzy ARTMAP compares favorably to several other approaches when performance is measured in terms of accuracy and computational complexity. Incorporation into fuzzy ARTMAP of negative match tracking (from ARTMAP-IC) facilitated convergence during training with this data set. Other modifications improved classification of data that include missing input pattern components and missing training classes. Fuzzy ARTMAP was combined with a bank of Kalman filters to group pulses transmitted from different emitters based on their position-specific parameters, and with a module to accumulate evidence from fuzzy ARTMAP responses corresponding to the track defined for each emitter. Simulation results demonstrate that the system provides a high level of performance on complex, incomplete and overlapping radar data.

Algorithms↗
PubMed2005

A historical overview of the heterologous expression of mammalian UDP-glucuronosyltransferase isoforms over the past twenty years.

UDP-Glucuronosyltransferases (UGTs) are actively involved in detoxification of xenobiotics and endogenous compounds and are a major source of drug inactivation and drug-drug interactions. UGTs are membrane-bound enzymes mostly localized in the endoplasmic reticulum (ER) and inner and outer nuclear membranes. UGT activities are totally dependent on the phospholipid content of the membrane and, as a result, are usually inactive when isolated from the ER in the presence of detergent. Several UGT expression systems have been described by different laboratories. They include expression in mammalian cells such as COS, V79 and HEK293. Also, baculovirus-infected insect cells systems have been developed and allow the expression of UGT isoforms with or without histidine molecule tags (His-tags). Moreover, as for CYP450, UGT isoforms have been expressed in E.coli. This review concentrates on a detailed description of all these expression systems in terms of their use for substrate specificity studies and the preparation of pure UGT proteins for active site identification and other structural studies. The effect of detergents and alamethicin on UGT catalytic activity in different expression systems will be discussed. Moreover, extensive comparative studies on the characterization of recombinant UGTs in terms of substrate specificity, evaluation of kinetic parameters, and the effect of inhibitors will be presented in this review. An overall picture of the use of different UGT expression systems will help in selecting the best one for identification of the individual UGT isoforms involved in the glucuronidation of drugs, environmental pollutants and physiologically important endogenous compounds. Especially important is an expression system where UGTs are biosynthesized with His-tags. UGTs expressed in this system can be easily purified to homogeneity, which will result in significant development of structure-function relationship studies, including the identification of substrate active sites and eventual crystallization. These are underdeveloped areas of UGT research and the availability of these recombinant UGTs will allow these gaps to be filled.

Animals↗
PubMed1981

Identification of prepositus neurons projecting to the oculomotor nucleus in the alert cat.

A population of prepositus hypoglossi nucleus neurons with discharges correlated to gaze parameters and antidromically activated by stimulation of the ipsilateral oculomotor nucleus has been recorded in the alert cat. The latency for antidromic invasion was of 0.6-0.8 msec. Neuronal firing rate encoded eye position and eye velocity in the horizontal plane, showing in all cases ipsilateral 'on' direction.

Animals↗
PubMed1996

Partial identification of underdetermined compartmental models: a method based on positive linear Lyapunov functions.

A class of models is considered in which the number of unknown parameters exceeds the number of independent equations that are derived from the input/observation configuration. It is shown that, under certain circumstances, if the number of unknown parameters is sufficiently decreased by setting some of the exit parameters to zero, then the fallaciously derived model has the following interesting properties. The functions of time that give the amounts in the compartments are constant multiples of their counterparts in the fallacious model. A subset of the fallacious fractional transfer coefficients have the same values as their counterparts in the true model whereas others yield interval bounds. These and related results are obtained from a method based on positive linear Lyapunov functions.

Humans↗
PubMed2001

Identification of an invasive, N-cadherin-expressing epithelial cell type in endometriosis using a new cell culture model.

Studies of molecular, cellular, and pathophysiological parameters in endometriosis are primarily hampered by a lack of in vitro model systems, such as endometriotic cell lines. To overcome this we successfully established cell lines from peritoneal endometriotic biopsies and characterized them at the molecular and cellular level. Two types of cells could be transformed: one exhibiting stromal cell features (cytokeratin/E-cadherin-negative), the other epithelial-like (cytokeratin-positive/E-cadherin-negative, invasive in vitro). Using a Matrigel assay the epithelial-like cell lines proved as invasive as metastatic carcinoma cells, possibly through the influence of N-cadherin implicated as a path-finding cadherin allowing cellular invasion and migration in both normal and pathophysiological processes. Our results support the idea that endometriosis, although not neoplastic, shares features with malignant cells and that metastasis in endometriosis may include mechanisms proposed for micrometastasis in cancer. Thus our cell lines will not only be useful tools for analyzing molecular and cellular events relating to endometriosis, but may also represent a paradigm for invasion and metastasis in general.

Biocompatible Materials↗

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